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Avoid Concurrency
Learning Objectives
- Explain why we have concurrency limits.
- Identify processes that create concurrency problems.
- Implement techniques to avoid concurrency limits.
How Concurrency Works
Concurrency is when multiple processes are running at the same time. When too many processes are trying to do something simultaneously, that can slow the system down.
If your app has a lot of users doing something that calls out to another system, you end up with many pages simultaneously waiting for a response.
It’s like riding in an elevator in the morning with dozens of other people. It can take time to get them all to their floors. You can optimize by grouping floors in certain elevator banks, programming elevator banks to be more efficient about which floors a given car goes to.
Concurrency Limits
The Salesforce system is the same. We have a certain number of processes (threads) that can be used at any given time. Normally the processes run fast, and we do not experience slowdowns. However, the longer a process runs, the less available processing capacity we have. To accommodate this, we allow only a certain number of long-running processes to function per org at a time. When you reach your limit, you cannot start a new long-running transaction until a previous one has completed.
Identifying long-running processes can take a bit of time. But the more you practice, the better you become. Generally, these processes fall into a few buckets:
- API Requests. A long-running API request is one that takes over 20 seconds. Salesforce allows only 25 to run at a time in an org.
- Callouts. When we make calls to another system, Salesforce waits for a response. If the responding system is slow, that can cause issues. You can have only a certain number of callouts at a time.
- Concurrency between Salesforce systems. Though Salesforce is a large ecosystem, it does have multiple subsystems in place. The core clouds (Sales Cloud, Service Cloud, Platform) are all built on our core application. Other applications, though, are built in their own stacks, including Marketing Cloud, BigObjects, and Retail Cloud. When calling to these systems, we also need to limit long-running callouts.
Tune Your Long-Running Transactions
If your calls are taking a long time, you need to tune your code. This can mean:
- Reducing the number of Apex trigger, workflow, and validation rules on your objects. All of these take time, and the more you have, the longer Salesforce takes to save a record.
- Reducing the complexity of your query. Salesforce allows queries to run for up to 2 minutes, but generally we want them to run as fast as possible. Adding additional filters, custom indexes, and ID filters to your query statements are good starts.
- Switching to asynchronous processes. When making a call, you can do it asynchronously (send a request to be made when there are resources free, and periodically check to see if the request is done). Moving from synchronous to asynchronous where possible affords you higher limits, because Salesforce can do the processing as resources become available.
- Reducing the amount of data you are passing. Creating 200 records per call takes a long time. Try creating 100 per call, or 50. Tuning your request size can be a bit of an art form and requires a deep understanding of your data model.
Let’s look at some tuning examples.
Reduce the Number of Apex Triggers
A common development pitfall is the assumption that trigger invocations never include more than one record. Apex triggers are optimized to operate in bulk, which, by definition, requires developers to write logic that supports bulk operations.
trigger MileageTrigger on Mileage__c (before insert, before update) { User c = [SELECT Id FROM User WHERE mileageid__c = Trigger.new[0].id]; }
trigger MileageTrigger on Mileage__c (before insert, before update) { for(mileage__c m : Trigger.new){ User c = [SELECT Id FROM user WHERE mileageid__c = m.Id]; } }
Trigger MileageTrigger on Mileage__c (before insert, before update) { Set<ID> ids = Trigger.newMap.keySet(); List<User> c = [SELECT Id FROM user WHERE mileageid__c in :ids]; }
This pattern respects the bulk nature of the trigger by passing the Trigger.new collection to a set, then using the set in a single SOQL query. This pattern captures all incoming records within the request while limiting the number of SOQL queries.
Best Practices for Designing Bulk Programs
-.
Reduce the Complexity of Queries
You can take several approaches to reduce the complexity of your queries. Sometimes you can only go so far squeezing efficiency out of your queries, but the more effective they are, the better. Salesforce provides the Query resource so you can get information about how Salesforce executes your query. Using this resource, you can see which approaches are the most effective ones. Use the ones you can. The more efficient your queries, the more likely they can avoid limits and run fast. Here are some examples.
- Avoid Negative Operators like '!=' or NOT CONTAINS.
- Avoid Inefficient Operators like leading wildcards.
- Sort optimization, which is used with date and number fields. Use an ORDER BY with a LIMIT clause. In cases where the selectivity threshold can’t be met, sort optimization might be better than a table scan.
Go Asynchronous.
This diagram shows the execution path of an asynchronous callout, starting from a Visualforce page. A user invokes an action on a Visualforce page that requests information from a Web service (step 1). The app server hands the callout request to the Continuation server before returning to the Visualforce page (steps 2–3). The Continuation server sends the request to the Web service and receives the response (steps 4–7), then hands the response back to the app server (step 8). Finally, the response is returned to the Visualforce page (step 9).
A typical Salesforce application that benefits from asynchronous callouts contains a Visualforce page with a button. Users click that button to get data from an external Web service. For example, a Visualforce page that gets warranty information for a certain product from a Web service. Thousands of agents in the organization can use this page. Therefore, a hundred of those agents can click the same button to process warranty information for products at the same time. These hundred simultaneous actions exceed the limit of concurrent long-running requests of 10. But by using asynchronous callouts, the requests aren’t subjected to this limit and can be executed.
Example: Asynchronous Callout
You have a Visualforce page with a button that performs a callout to a web service. When users click the button, it calls a startRequest() method in the CalloutController Apex class. This method waits for a response from the web service. As you can imagine, as you wait for the response, other web service requests could pile up and you’d approach the concurrent API request limit.
You need to add a continuation and callback method, which waits for the response. The following code shows a synchronous callout, which could hit the concurrent request limit. The code also shows how to write a continuation and callback method to avoid concurrency, so you can compare the two approaches.
public class CalloutController { // Unique label corresponding to the continuation public String requestLabel; // Result of callout public String result {get;set;} public Object startRequest() { //this part up here is common to both the callout //and continuations approaches String sessionId = UserInfo.getSessionId(); HttpRequest req = new HttpRequest(); req.setHeader('Authorization', 'Bearer ' + sessionID); req.setHeader('Content-Type', 'application/json'); req.setHeader('Accept', 'application/json'); req.setEndpoint('' + 'completions?type=apex'); req.setMethod('GET'); //Here's how it works with a callout Http h = new Http(); HttpResponse res = h.send(req); processResponse(res); //and that is all. This works fine until the service is too slow and lots of people use it. //Here is what it needs to change to Continuation con = new Continuation(40); con.continuationMethod='handleCallback'; this.requestLabel = con.addHttpRequest(req); return con; //that's the difference for continuations. } //Here is the callback that waits for a response before continuing public Object handleCallback() { HttpResponse response = Continuation.getResponse(this.requestLabel); return processResponse(response); } // Callback method is only needed for continuations. public Object processResponse(HttpResponse response) { result = response.getBody(); // Return null to re-render the original Visualforce page return null; } }
Then the Visualforce page wakes up when the callout returns.
Look at you! You’re already identifying concurrent requests and learning how to avoid them. This does take some knowledge and practice, but you’re on your way. In the next unit, we take a deep dive into another way to shape up your code. | https://trailhead.salesforce.com/pt-BR/content/learn/modules/app-development-without-limits/app-development-without-limits-concurrency?trail_id=build-efficient-applications-without-limits | CC-MAIN-2021-21 | refinedweb | 1,428 | 57.87 |
panda3d.core.MovieAudioCursor¶
from panda3d.core import MovieAudioCursor
- class
MovieAudioCursor¶
Bases:
TypedWritableReferenceCount
A MovieAudio is actually any source that provides a sequence of audio samples. That could include an AVI file, a microphone, or an internet TV station. A MovieAudioCursor is a handle that lets you read data sequentially from a MovieAudio.
Thread safety: each individual MovieAudioCursor must be owned and accessed by a single thread. It is OK for two different threads to open the same file at the same time, as long as they use separate MovieAudioCursor objects.
Inheritance diagram
__init__(src: MovieAudio) → None¶
This constructor returns a null audio stream — a stream of total silence, at 8000 samples per second. To get more interesting audio, you need to construct a subclass of this class.
__init__(param0: MovieAudioCursor) → None
length() → float¶
Returns the length of the movie. Attempting to read audio samples beyond the specified length will produce silent samples.
Some kinds of Movie, such as internet TV station, might not have a predictable length. In that case, the length will be set to a very large number: 1.0E10.
Some AVI files have incorrect length values encoded into them - they may be a second or two long or short. When playing such an AVI using the Movie class, you may see a slightly truncated video, or a slightly elongated video (padded with black frames). There are utilities out there to fix the length values in AVI files.
An audio consumer needs to check the length, the ready status, and the aborted flag.
canSeek() → bool¶
Returns true if the movie can seek. If this is true, seeking is still not guaranteed to be fast: for some movies, seeking is implemented by rewinding to the beginning and then fast-forwarding to the desired location. Even if the movie cannot seek, the seek method can still advance to an arbitrary location by reading samples and discarding them. However, to move backward, can_seek must return true.
skipSamples(n: int) → None¶
Skip audio samples from the stream. This is mostly for debugging purposes.
aborted() → bool¶
If aborted is true, it means that the “ready” samples are not being replenished. See the method “ready” for an explanation.
ready() → int¶
Returns the number of audio samples that are ready to read. This is primarily relevant for sources like microphones which produce samples at a fixed rate. If you try to read more samples than are ready, the result will be silent samples.
Some audio streams do not have a limit on how fast they can produce samples. Such streams will always return 0x40000000 as the ready-count. This may well exceed the length of the audio stream. You therefore need to check length separately.
If the aborted flag is set, that means the ready count is no longer being replenished. For example, a MovieAudioCursor might be reading from an internet radio station, and it might buffer data to avoid underruns. If it loses connection to the radio station, it will set the aborted flag to indicate that the buffer is no longer being replenished. But it is still ok to read the samples that are in the buffer, at least until they run out. Once those are gone, there will be no more.
An audio consumer needs to check the length, the ready status, and the aborted flag.
seek(offset: float) → None¶
Skips to the specified offset within the file.
If the movie reports that it cannot seek, then this method can still advance by reading samples and discarding them. However, to move backward, can_seek must be true.
If the movie reports that it can_seek, it doesn’t mean that it can do so quickly. It may have to rewind the movie and then fast forward to the desired location. Only if can_seek_fast returns true can seek operations be done in constant time.
Seeking may not be precise, because AVI files often have inaccurate indices. After seeking, tell will indicate that the cursor is at the target location. However, in truth, the data you read may come from a slightly offset location.
readSamples(n: int) → str¶
Read audio samples from the stream and returns them as a string. The samples are stored little-endian in the string. N is the number of samples you wish to read. Multiple-channel audio will be interleaved.
This is not particularly efficient, but it may be a convenient way to manipulate samples in python.
readSamples(n: int, dg: Datagram) → None
Read audio samples from the stream into a Datagram. N is the number of samples you wish to read. Multiple-channel audio will be interleaved.
This is not particularly efficient, but it may be a convenient way to manipulate samples in python. | https://docs.panda3d.org/1.10/python/reference/panda3d.core.MovieAudioCursor | CC-MAIN-2020-05 | refinedweb | 784 | 74.19 |
Today we will look into Node JS Architecture and Single Threaded Event Loop model. In our previous posts, we have discussed about Node JS Basics, Node JS Components and Node JS installation.
Table of.
For Example:
Copyfunction1(function2,callback1); function2(function3,callback2); function3(input-params);.
Copypublic class EventLoop { while(true){ if(Event Queue receives a JavaScript Function Call){ ClientRequest request = EventQueue.getClientRequest(); If(request requires BlokingIO or takes more computation time) Assign request to Thread T1 Else Process and Prepare response } } }
That’s all for Node JS Architecture and Node JS single threaded event loop.
Pooja Gupta says
very nicely explained the basic concept of event loop in node js
pushpender says
thanks very clear and easily understood.
jyothi says
It’s a very nice article. I read it two weeks back and from then I was searching for this to re-read. Got it again today (28/12/2018). It is of so much value.
Thanks a ton for uploading 🙂
syed parveen says
Hi, could you please provide the brief expalnation of event loop phases how it will work
Pawan Sasanka says
This is a great article with plenty of simple examples which anyone can understand. Simple language added a more value to this. Describing difference of Nodejs architecture with the aid of multi-threaded architecture is a great way to enhance the understandability. Than you
Rajesh says
very useful article actully.
Anand H says
Very helpful. Thanks!
Juhi says
Hello,
Thanks for this artical it is wonderful But it left me with some doubts.
1. What will happen if all the requests demands for blocking I/O? means if the requests increases than the internal thread pool?
2. What will event loop execute first ? Taking the request or sending the respons to the client?
ashutosh.ningot@gmail.com says
same Question.
Apurva Singh says
Yeah same q. Author got confused with that part. He has not bought up non blocking calls with MongoDB either. That will have a different model. Request will go to Mongo, and since it is Non Blocking, so no additional thread is needed. When a response comes, a interrupt will be raised and interrupt handler will put the response in event loop again to be processed.
Sadik says
Really!!! Great Article for NodeJS Developer.
Raju Gupta says
Very good explanation.
Thank you.
Techno tish says
Detailed article with good explanation
Junaid Ansari says
Great article.It nicely explained everything i needed for Node JS. As you rightly mentioned in the starting that one has to understand the the Javascript callback mechanism to grasp of Node js concurrent request handling without waiting or blocking.
I see lot of comments where people has asked that if event loop is single thread then how can it still process concurrent requests (which are not I/O bound,IO request will be assigned to node thread pool as shown in above diagram) ,without waiting.I feel this is achieved with Javascript asynchronous and callback mechanism and node provides lot of asynchronous function to achieve the same or developer has to write their code in with asynchronous way and provide callback handling.Kindly correct my understanding.
Thanks,
Junaid Ansari
Rishabh says
Thanks for wonderful work.
I have one question , if event loop picks request one by one then on user side it has to wait for longer time to get that o/p in case of multiple requests.
Suppose n clients send their request to one server and each request require 15 seconds then if go by logic of event loop then if will take first request from event queue and process it and then send response to client , then it will fetch 2nd one and send response so by this logic first client will get data in 15 seconds and then 2nd will get data in 30 and so on.. So how node is handling these things as i know i m interpreting something wrong,
Nikhil Salwe says
hi rishabh , I’ll try to answer your question.
Node js is single threaded but internally it uses child thread which are not expose to users.
In node js callback and async operation are two very important thing and heavily use. what every request make by user is run asynchronously (so that is why it is called as non-blocking) and in the end we get response.
Vivek says
As you mentioned “every request make by user runs asynchronously”, so keeping that in mind, event loop takes request-1 from event queue and process it asynchronously then takes request-2 and process it and so on, once for request-1 callback happens, event loop takes it and returns it to the client. Please clarify if I am missing something.
Gajanan Thate says
THIS IS REALLY NICE ARTICLE ……..IM DEVELOPING APPLICATION IN NODE SINCE COUPLE OF MONTHS BUT DIDN’T KNOW ABOUT BACKGROUND PROCESS.THANKS MAN…..KEEP POSTING SUCH ARTICLE.
Utkarsh Bhatt says
Oh man. Got asked about Node architecture in a JS dev interview. Got rejected because didn’t know all that much at the time. I wish I had come across this article a few days ago. This stuff is very helpful; especially the whole step by step explanation of the event loop model.
Salman says
same here…
Holiest says
**How does nodeJs know a request need heavy computation or blocking IO operations when he has not yet execute it?
**When we have a response, the event loop first transmits the response or first processes a request?
*** thanks a lot for your post, it’s a good abstract view.
Alok Deshwal says
It really helps a lot
Abdulla says
I just would like to say, this article has a lot of beautiful amazing tasty info
God & Allah bless you bro
sameer says
Are the [Event Loop Processing] and the [Incoming Request Insertion In Queue] handled in same thread?
monika says
very helpful.. thnku.. 🙂
Hemanth kumar V says
Really Amazing. what a article!!. Great Explanation and cleared all my doubts. Thanks
Srimal says
Thank You. Well explained.
Mylara says
Good Explanation !!!!!!!!
Shagun Pruthi says
Great Explanation by the author. I understood each word of it and now I can explain well the Internal Architecture of Node Js. Thanks .
Allaudhin says
To good article! Excellent !!!!!!
Rafael says
This is the absolutely the best answer I’ve found! Congrats Rambabu, great job man. You’ve literally improved my day 😀
qwdqd says
Great Job!
Just a minor suggestion; please include some nodeJS codes and explain there execution. It would help some people who are a little bit familiar with node.
Thanks.
Harsha Vardhan says
It is easily can understand by any person . It is very useful for me . Thank you for your post.
Rajesh S says
Just simply explained. Great article 🙂
Rahul Kumar Saini says
Hi
I’m MEAN stack Developer, this article helps to me a lot and I was get stuck this kind of problem. and read about many articles ,tutorials and watch many videos.
But this tutorial remove all doubts. Thanks !
But I have got confused in some point(Single thread in nodeJS) when client make a request to server then this server enters into event queue then event loop start execution on this and check this request will take blocking or non blocking it means take more time or not. If it takes then thread come to picture and this request assigned with a thread.And Now this thread start task on this request.
But I want to discuss here, Request come into first event loop or thread. On the other hand this request first handled by thread and then event loop.
Please help me
arpit says
request comes to queue , from queue if event loop is not processing any request goes to loop , if I/O blocking operation is present , it goes to thread , thread performs all the operations and sends back the data to event loop and from event loop it again goes back to the client
Dilesh says
hey what’s that t-1,t-2,t-3…….t-n in node js architecture as Node js Internal Thread Pool ?
Anantha Rambabu Gunakala says
Nicely Explained
Jitendra kumar rajput says
Great article very good explanation 🙂 thank you so much.
Nilesh Patil says
Awesome explanation 🙂 thank you so much.
Umesh says
great article ..i understood very well
micky says
Awesome explanation !! thanks
Arularasan says
I am understanding the event loop concepts, thanks
Juhi says
Awesome explanation !! Thanks a ton for writing this one.
Sam says
How does node.js know that the function requires IO operations?
Rishabh says
nice article but i will be awesome if we find all the above andwers
Nikhil says
Great article!!!! In very simple language very clean and point to point description. I have one question as in normal web server also the thread pool(M) and if request number N > M then request(Client ) need to wait but in Node.js also there is a internal thread pool and event loop pick thread form thread pool if IO blocking is required. If Node.js also using thread from internal thread pool then it is possible that the thread count is less than the number of incoming request.
Texas Racher says
Nice reading… to know internals of Node JS.
Concept of Cloud computing Architecture is not mentioned and why NodeJS is better in cloud based apps. most of questions about n > m will be answered with cloud.
Bhanu K says
This article brings where NodeJS surpasses other web-servers. It’s basically the IO intensive operations where NodeJS benefits.
While when it comes to data crunching etc., NodeJS is not the best solution out there.
abhishek says
Here we are calling separate threads as a event queue . I don’t understand, event queue will consume memory as well then how it take less memory in comparison to threads.
Dariusz says
In a single thread (event loop) will consume memory needed to handle a one request at time. In multithreaded system it will need the memory that is a sum of the memory required for each request running parallelly in separate threads.
vikas bansal says
this article let me with some questions like what will happen if Node.Js connection pool is totally consumed and How does node know that the request is going to take some time so assign it a thread?
Bidisha says
Node never knows about request time. This is asynchronous process of NodeJs is totally done by the developers with the help of callbacks and event emitters only,
Note: This article have given a high level view of the NodeJS architecture. To understand it clearly, one have to go through the basic concept of call backs and events.
lakshay says
Hi Bidisha!
You are right by saying the “asynchronous process of NodeJs is totally done by the developers with the help of callbacks and event emitters only”.
Say we as a developers,made the request async but the internal thread pool is all consumed.What will happen in that scenarios?
abby says
it seems the only difference between “Traditional Web Application Processing Model” and node.js is that node.js can determine whether a request is blocking or not.
– they both have a thread pool
– they both handle blocking IO by picking up a idle thread
– they both have a manager thread
what different is: node.js has a event queue.
am I right?
Rambabu Posa says
Yes right. If you are familiar with Non-Blocking/Asynchronous servers like JBoss Netty server or languages like Scala/Akka/Play, you can understand it well. Please refer them to get in-depth knowledge.
Lalit Kumar says
As far as event loop is concerned it is explained well…
But ……. connection of thread performing blocking i/o to libuv calling the callback once event received is not explained which is the heart of node.js
ashutosh.ningot says
yes
Jithendranath Gupta Y says
if node js has internally m threads and if i get n blocking io requests what will happen when n>m?
abby says
I have the same question…
Vineesh says
The article is very helpful and thank you for sharing this.
I have a doubt, when multiple requests come which all need Blocking IO task the server uses multiple threads right? then how we can say Node is single threaded?
Rakesh says
Hi Rambabu,
The post is very well explained. I have one question on the thread pool of the webserver itself not the NodeJS internal threadpool that kicks in when the type of the operation is blocking.
“Node JS Web Server internally maintains a Limited Thread pool to provide services to the Client Requests.”
Can you please let me know where to change the thread pool setting of the webserver? What’s the default pool size? Because I think this is so crucial in handling multiple concurrent client requests and placing them on the Event Queue. I tried looking up I cannot find anything on the threadpool of the webserver and how to change and tune them? Please throw some light on this if you can.
rachna says
thanks for all your node.js articles, really has helped me get started. one question i have is how does event loop find if the request is blocking or non-blocking, and send it to thread accordingly?
Crystal A. says
Thank you! I am very new to Node and did not understand the logic behind a single thread…thanks again!
HooRang says
Thanks you
very helpful
Paddy says
Thanks a lot. The pictorial depiction does explain things clearly.
Jai says
Very helpful article. But I have one doubt.
Let suppose we have n concurrent requests coming to our web server. m out of n is non blocking so event loop will process them smoothly. But n-m requests are blocking. And as mentioned it will also maintain a thread pool. Let suppose thread pool contains T threads.
Suppose T=n-m
Now a new request is coming to web server and it is blocking request.
So in this scenario how event loop will be non blocking? Wouldn’t new request have to wait till one of threads to be free?
Is this rare case?
Jimmy George Thomas says
Yes, the new request would have to wait till a thread becomes available.
Ayo Alfonso says
Is it a rare case ? Because Node.js then feels like a multi-thread environement with a layer of the event loop mechanism built ontop.
Tat Sean says
I am still very confusing on NodeJs event loop as different articles seem to explain things differently. The confusion is when the thread that serves the request finishes processing the request, does it send the response back to the Event loop or to the Event queue instead? If we take a look at the JS event loop, it seems to indeed send the callback to the Task queue and Event loop then picks up the task (callback) from the Task queue.
Jimmy George Thomas says
Yes, you are correct. The thread queues the callback in the task queue from which the event loop picks it up and proceeds.
Vinod Kumar Marupu says
Very Helpfull :-).
Raju says
Good article. Thanks for sharing this.
It will be nice if you add ode related to how threads (blocking IO) responds back to event queue in your pseudo code
vivek says
Nice Article,but i need more knowledge of how to build application using node js in PHP or any language … pls help
vivek says
Nice Article, thanks , for sharing your knowledge we us. i need more knowledge of how to build application using node js in PHP or any language … pls help
Bron1010 says
Its an indeed a great article,
But I would like to know –
1.the answer of above comment by Abdallah Al-Barmawi
2.Can you explain how does clusters work with respect to above explain single threaded model of nodejs..
Rambabu Posa says
Hi, I will update this post soon by answering your questions
Abdallah Al-Barmawi says
Thank you for this article and this explanation of how node works,
but still i’m some how confused abut this,
let’s say that our web server do this operation (none IO operation),
for example (loop statement that needs 3 seconds to finish or complex validation on data(MVC model))
what will happened if i have let’s say 1000 concurrent requests?
does the first request will block the remaining requests until it’s finished.
and how node determain that this operation(none IO operation) is complex or not?
thanks,
and i hope if we can chat using Skype to discuss it.
Sushant says
Good question. Did you find a response to this? If yes please share. Thanks,S
Rambabu Posa says
Hi, I will update this post soon by answering your questions.
Jimmy George Thomas says
Yes, the remaining requests will have to wait till the first request is finished. The way in which the calls are implemented is what decides if it is going to be executed on the main thread or not. You yourself can implement a module that maps internally to non-blocking OS calls and then listen for its completion. Then you would have to queue the corresponding callback in the queue for the event loop to handle.
Avishek Biswas says
Great article, thanks , for sharing your knowledge.
Johnny says
Great article, thanks!
Kittu says
Nice article.. It is clearly explained.. Comparison with Muti-threaded model helped me to understand node.js very well.. Thank your very much..
Balavignesh says
Great article!! I am a full stack developer(fresher) and I did not know this node architecture before. I got rejected in an important interview because I didn’t know this. Now I understand everything. Thank you for your awesome job Pankaj 🙂 | https://www.journaldev.com/7462/node-js-architecture-single-threaded-event-loop | CC-MAIN-2019-13 | refinedweb | 2,977 | 73.68 |
Module: Essential Tools Module Group: Generic
Does not inherit
#include <rw/gordvec.h> declare(RWGVector,val) declare(RWGOrderedVector,val) implement(RWGVector,val) implement(RWGOrderedVector,val) RWGOrderedVector(val) v;// Ordered vector of objects of val val.
Class RWGOrderedVector(val) represents an ordered collection of objects of val val. Objects are ordered by the order of insertion and are accessible by index. Duplicates are allowed. RWGOrderedVector(val) is implemented as a vector, using macros defined in the standard C++ header file <generic.h>.
NOTE -- RWGOrderedVector is deprecated. Please use RWTValOrderedVector or RWTPtrOrdered).
To use this class you must declare and implement its base class as well as the class itself. For example, here is how you declare and implement an ordered collection of doubles:
declare(RWGVector,double) // Declare base class declare(RWGOrderedVector,double) // Declare ordered vector // In one and only one .cpp file you must put the following: implement(RWGVector,double) // Implement base class implement(RWGOrderedVector,double) // Implement ordered vector
For each val of RWGOrderedVector you must include one (and only one) call to the macro implement somewhere in your code for both the RWGOrderedVector itself and for its base class RWGVector.
None
Here's an example that uses an ordered vector of RWCStrings.
#include <rw/gordvec.h> #include <rw/cstring.h> #include <rw/rstream.h> declare(RWGVector,RWCString) declare(RWGOrderedVector,RWCString) implement(RWGVector,RWCString) implement(RWGOrderedVector,RWCString) int main() { RWGOrderedVector(RWCString) vec; RWCString one("First"); vec.insert(one); vec.insert("Second"); // Automatic val conversion occurs vec.insert("Last"); // Automatic val conversion occurs for(size_t i=0; i<vec.entries(); i++) std::cout << vec[i] << std:endl; return 0; }
Program output:
First Second Last
RWGOrderedVector(val)(size_t capac=RWDEFAULT_CAPACITY);
Construct an ordered vector of elements of val val. The initial capacity of the vector will be capac whose default value is RWDEFAULT_CAPACITY. The capacity will be automatically increased as necessary should too many items be inserted, a relatively expensive process because each item must be copied into the new storage.
val operator()(size_t i) const; val& operator()(size_t i);
Return the ith value in the vector. The index i must be between 0 and one less than the number of items in the vector. No bounds checking is performed. The second variant can be used as an lvalue, the first cannot.
val operator[](size_t i) const; val& operator[](size_t i);
Return the ith value in the vector. The index i must be between 0 and one less than the number of items in the vector. Bounds checking will be performed. The second variant can be used as an lvalue, the first cannot.
void clear();
Remove all items from the collection.
const val* data() const;
Returns a pointer to the raw data of self. Should be used with care.
size_t entries() const;
Return the number of items currently in the collection.
size_t index(val item) const;
Perform a linear search of the collection returning the index of the first item that isEqual to the argument item. If no item is found, then it returns RW_NPOS.
void insert(val item);
Add the new value item to the end of the collection.
void insertAt(size_t indx, val item);
Add the new value item to the collection at position indx. The value of indx must be between zero and the length of the collection. No bounds checking is performed. Old items from index indx upwards will be shifted to higher indices.
RWBoolean isEmpty() const;
Returns TRUE if the collection has no entries. FALSE otherwise.
void size_t length() const;
Synonym for entries().
val pop();
Removes and returns the last item in the vector.
void push(val);
Synonym for insert().
removeAt(size_t indx);
Removes the item at position indx from the collection. The value of indx must be between zero and one less than the length of the collection. No bounds checking is performed. Old items from index indx+1 will be shifted to lower indices. For example, the item at index indx+1 will be moved to position indx, etc.
void resize(size_t newCapacity);
Change. | http://www.xvt.com/sites/default/files/docs/Pwr%2B%2B_Reference/rw/docs/html/toolsref/rwgorderedvector.html | CC-MAIN-2017-51 | refinedweb | 668 | 50.53 |
The tragedy of test algorithm training
subject
Resource constraints
Time limit: 1.0s memory limit: 512.0MB
Problem description
English preparation gzp is a funny (tu) than (hao). In order not to fail in the upcoming English quiz, gzp forgets to eat and sleep and reviews the English appendix word list, just like a human tragedy. But God has the virtue of living a good life. God threw gzp a piece of paper on which the words to be tested were recorded. But gzp is funny. He forgot all the things he reviewed before, so he has to review again. However, you already know the words to be tested, so you don't need to review all the pages of the word list. Therefore, now you need to help him find out how many pages need to be reviewed. He will tell you on which pages each word will appear, and tell you which words to test. You just tell him the answer. Since a word will appear on different pages, you only need to review what is on the front page.
Input format
An integer n in the first line indicates that there are n words in the word appendix. In the next N lines, each line consists of a word with lowercase letters and an integer, indicating a word and the number of pages it is on. Next is a line of integer m, indicating m words to be tested, and next M lines of words composed of lowercase letters, indicating the words to be tested.
Output format
A number indicating the number of pages to review.
sample input
5
ab 1
ac 2
ab 2
ac 3
c 3
3
ab
ac
c
sample output
3
Data scale and agreement
0 < = n, m < = 100000, word length < = 10.
It's easy to think of using map
It is worth noting that since a word will appear on different pages, you only need to review the one on the front page., This sentence means that if the same word appears many times, only review the one on the front page, such as ab 2, ab 3 and ab 1. If you want to review AB, just review the first page.
1.map code
Idea: for each word, we only save the top pages
#include <iostream> #include <map> #include <set> #include <string> using namespace std; //Change a short one typedef map<string, int>::iterator MyIt; int main() { //word map<string, int> words; //Number of pages to review set<int> pages; int n; cin >> n; for ( int i = 0; i< n; ++i ) { string s; int num; cin >> s >> num;//Enter words and pages if ( words.count(s) == 0 ) { //If not in words, just insert it words[s] = num; } else {//The word s has already appeared, MyIt it = words.find(s); /* We only save the top of the page!!!! */ if ( it->second > num ) { words[s] = num; } } } int m; cin >> m; for ( int i = 0; i < m; ++i ) { string s; cin >> s; MyIt it = words.find(s); pages.insert(it->second); } cout << pages.size() << endl; return 0; }
multimap to do:
This allows repeated keys to appear, that is, keys can appear repeatedly in multimap, and the repeated keys are adjacent, but she does not support the [] operator, so insert is used
#include <iostream> #include <map> #include <set> #include <string> using namespace std; typedef multimap<string, int>::iterator MyIt; int main() { multimap<string,int> words; words.insert(make_pair("ab",1)); words.insert(make_pair("cc",1)); words.insert(make_pair("dd",1)); words.insert(make_pair("cc",1)); words.insert(make_pair("ab",1)); for ( auto temp : words ) { cout << temp.first << "->" << temp.second << endl; } return 0; }
And because find finds the first occurrence, you can traverse to find the minimum number of pages where words appear.
#include <iostream> #include <map> #include <set> #include <string> using namespace std; typedef multimap<string, int>::iterator MyIt; int main() { multimap<string, int> words; set<int> pages; int n; cin >> n; //Save it all for ( int i = 0; i< n; ++i ) { string s; int p; cin >> s >> p; words.insert(make_pair(s,p)); } int m; cin >> m; for ( int i = 1; i <= m; ++i ) { string s; cin >> s; MyIt it = words.find(s); //k indicates the number of times s occurs!!!!! int k = words.count(s), front = it->second; it++; //Traverse to find the minimum number of pages where words appear for ( int v = 1; v < k; v++, it++ ) { if ( it->second < front ) { front = it->second; } } pages.insert(front); } cout << pages.size() << endl; return 0; } | https://programmer.group/the-tragedy-of-test-algorithm-training.html | CC-MAIN-2021-49 | refinedweb | 752 | 69.11 |
Office Dev Content
SharePoint Dev Content
Blogs for Office developers > Exchange dev blog
1. The hard-coded URL might point to the URL of a Client Access server that is in a different site from the user’s mailbox. Accessing a Client Access server in a different site from a user’s mailbox results in poorer performance and greater complexity than accessing a Client Access server in the same site as the mailbox. The only way to ensure that you are accessing a Client Access server in a particular user’s site is to use Autodiscover.
2. We may change the URL for various Web services as we consolidate them, or break them up for better architecture between roles, which will complicate migration to later versions of Microsoft Exchange Server.
3. The corporate address could change namespaces (this doesn’t happen often, but we have occasionally changed our namespace at Microsoft). For example, could become.
Let me explain a little more about why accessing a Client Access server in a different site from a user’s mailbox is not a good idea. If your enterprise has multiple Active Directory sites (i.e. branch offices that are running Exchange Server 2007), Exchange Web Services in the initial release version of Exchange 2007 will be making cross-site remote procedure calls (RPCs) from the Client Access server that you are accessing to the mailbox in the site where a user is located. Cross-site RPCs are not recommended because RPC traffic is very chatty and high latency networks between sites will degrade the performance of Exchange Web Services significantly. In Exchange 2007 Service Pack 1 (SP1), we have gone the route of Outlook Web Access and ActiveSync and disabled cross-site RPC functionality. Now cross-site calls will fail unless an Exchange 2007 SP1 Client Access server is in the same site as the user mailbox that is set up for EWS proxy. EWS proxy makes these requests more efficient by sending a single HTTP request rather than multiple RPC requests. However, relying on EWS proxy to do the work of getting your request to the right site is also not an ideal solution because it puts unnecessary load on the proxying Client Access server. You can avoid this unnecessary load by making the request to the appropriate Client Access server yourself.
We have some good resources about using Autodiscover. For a sample application that includes downloadable source code that implements an Autodiscover client for you, see Autodiscover Sample Application. For information about the structure of an Autodiscover request, see Autodiscover Request.
One thing to note: Autodiscover is not a SOAP-based Web service. It just uses plain old XML (POX).
Look for more information that describes Autodiscover in more depth soon. Until then, use the examples referenced earlier and always Autodiscover. | http://blogs.msdn.com/b/exchangedev/archive/2007/12/11/discover-autodiscover.aspx | CC-MAIN-2015-27 | refinedweb | 470 | 51.28 |
For HW I'm suppose to : Write a program that finds out how many numbers below 10,000 are divisible by both 3 and 26.
This is what I have so far
#include <iostream>
using namespace std;
int main ()
{
int z, counter;
counter=0;
for (int n =10000; n>=0; n+=78) {
z = n % 78; //numbers divisible by 78 between10,000 are also divisible by both 3 and 26.
if (z==0) {
counter++; //counts the amount of numbers divisible by both
}
cout << counter << endl;
system ("pause");
}
}
This is what I get 0. I do not get what I did wrong. For the "for" I made it to start at 10,000 and keep subtracting 78 until it equals 0. Help please !! | http://cboard.cprogramming.com/cplusplus-programming/126284-divisible-program-printable-thread.html | CC-MAIN-2015-14 | refinedweb | 121 | 82.38 |
Hello! This is my first time posting a thread in this site. I, along with most of my class, am having troubles with this program. We're only in the first class of our Computer Science major. My current program "runs" but prints a blank output file. Please help! My comrades and I are stressing BIG TIME because of finals! Thanks a ton!
The code is as follows:
//Salaries.java //This program will compute the gross wages for each employee. It will also //determine the highest and lowest for the week's salary, the total weekly payroll, //the average salary for the week, and the total amount the company has to pay //in social security taxes. In addition, the program will count the employees //that earn more than $500.00 by the end of the week. import java.util.*; import java.io.*; public class Salaries { public static void main(String [] args) throws IOException { Scanner fin = new Scanner(new FileReader("Salaries.data")); Scanner fin2 = new Scanner(new FileReader("Transaction.data")); PrintWriter fout=new PrintWriter(new FileWriter("Salaries.report")); double [] array = new double [50]; int numE = 0, index = 0, value, overTimer=0, variable, result = 0; double hoursWorked, payRate, tax, wages, overTime, overHours, totalTax, total = 0, average = 0, Wages; fout.println("\n The list of employees gross wages follows: "); while(fin.hasNextDouble()); { hoursWorked = fin.nextDouble(); payRate = fin.nextDouble(); if(hoursWorked>40.00) { overHours = (hoursWorked-40.00); overTime=payRate+(payRate*.5); wages=(overHours*overTime)+(40.00*payRate); array[numE]=wages; numE++; } else { wages=hoursWorked*payRate; array[numE]=wages; numE++; } fout.printf("%2s%1.2f ","",wages); } total = totalWages(array, numE); fout.printf("Total Wages: %1s%1.2f \n","",total); fout.printf("Average Wage: %1s%1.2f \n","",average); index=findLargestSalary(array,numE); fout.printf("\nThe largest salary is: $%1s%1.2f","",array[index], " and is at position ", index); fout.println(); index = findSmallestSalary(array,numE); fout.printf("The smallest salary is: $%1s%1.2f","",array[index], " and is at position ",index); fout.println("\n"); tax=total*.062; totalTax=tax*2; fout.printf("Employee withholdings for social security taxes is:%15s$%2s%.2f\n", "",tax); fout.printf("The company matching amount for social security taxes is:%9s$%2s%.2f\n", "",tax); overTimer=printOverTimer(array,numE); fout.print("The number of employees that made over $500 this week is: "+overTimer); while(fin2.hasNextDouble()) { variable = fin2.nextInt(); switch(variable) { case 1: hoursWorked=fin2.nextDouble(); payRate=fin2.nextDouble(); if(hoursWorked>40.00) { overHours=(hoursWorked-40.00); overTime=payRate+(payRate/2); wages=(overHours*overTime)+(40.00*payRate); array[numE]=wages; numE++; } else { wages=hoursWorked*payRate; array[numE]=wages; numE++; } fout.printf("$%1.2f was added to the array.\n" , wages); break; case 2: Wages=fin2.nextDouble(); numE=remove(array, numE, Wages); fout.printf("\n $ %1.2f was removed from the array. \n", Wages); break; case 3: Wages = fin2.nextDouble(); result = search(array, numE, Wages); if(result<0) fout.println("\n $ " +Wages + " was found at index " +result); else fout.println("\n $ " + Wages + " was not found in the array.\n"); } for(int i=0; i<numE; i++) fout.printf("%1.2f ",array[i]); }//Closes while fin.close();//Closes first input file fin2.close();//closes Transaction fout.close(); //Closes output file }//Closes main ///////////////// totalWages ///////////////// //This method will take in the array and calculate the total wages in the company. public static double totalWages(double [] array, int numE) { double total = 0; for(int i=0; i<numE; i++) { total += array[i]; } return total; }//end totalWages ///////////////// computeAverageWage ///////////////// //This method will compute the average wage of employees at the company. public static double computeAverageWage(double [] array, int numE) { double average, sum = 0; average = (double)sum/numE; return average; }//end computeAverageWage ///////////////// findLargestSalary ///////////////// //This method will find the highest salary of employees. public static int findLargestSalary(double [] array, int numE) { int position = 0; for(int i=0; i<numE; i++) { if(array[i]>array[position]) position = i; } return position; }//end findLargestSalary ///////////////// findSmallestSalary ///////////////// //This salary will find the lowest salary of employees. public static int findSmallestSalary(double [] array, int numE) { int position = 0; for(int i=0; i<numE; i++) if(array[i]<array[position]) position = i; return position; }//end findSmallestSalary ///////////////// printOverTimer ///////////////// //This method will print if the employee has worked over 500 hours or not. public static int printOverTimer(double [] array, int numE) { int overTimer = 0; for(int i=0;i<numE;i++) { if(array[i]>500) overTimer++; } return overTimer; }//end printOverTimer ///////////////// remove ///////////////// //This method removes an inputted number. public static int remove(double [] array, int numE, double Wages) { int index = 0; while(index<numE && array[index] != Wages) index++; if(index < numE) { for(int i=index; i<numE-1; i++) array[i] = array[i+1]; --numE; } return numE; }//end remove ///////////////// search ///////////////// //This method will search for a user-inputted number. public static int search(double [] array, int numE, double Wages) { int result=0; for(int i=0; i<numE && result ==1; i++) if(array[i]==Wages) result=1; return result; }//end search }//end program
EDIT---
When it runs, it creates the file and that's it. Just a blank file, no bytes, no code. Here's the extra.
Salaries.data
10 5
20 10
40 10
41 10
Transaction.data
1 40 20
3 415.00
2 415.00
3 415.00
Output Based on Above Input:
The list of employees' gross wages follows:
50.00 200.00 400.00 415.00
Total Wages: $ 1065.00
Average Wage: $ 266.25
The largest salary is $ 415.00 and is located at index 3
The smallest salary is $ 50.00 and is located at index 0
Employee wihtholdings for social security taxes is $ 66.03
The company matching amount for social security taxes is 66.03
--------
Total 132.06
The number of employees earning over $500 this week is 0
800.00 was added to the array.
415.00 was found at index 3.
415.00 was removed from the array.
415.00 was not found in the array.
50.00 200.00 400.00 800.00 | http://www.javaprogrammingforums.com/whats-wrong-my-code/34396-csc-basics-final-program-problems.html | CC-MAIN-2015-11 | refinedweb | 986 | 53.58 |
Ok so I'm interested in hacking, and wanted to learn a bit more about it. While im at it i figured i could learn to get around my schools FortiGuard. Previously i used a CGI-Proxy and then a PhProxy. So many people in our school used them that our tech added proxies to FortiGuard's list of sites to ban.
A friend of mine says he knows 2 more ways, one complex which would be shutting off FortiGuard.
And a less simple one of just bypassing it. I figured if caught, id get in less trouble by only bypassing.
Besides the school Librarian likes me, so i dont think she'd mind to much. She tells us that if we want to hack the computers, just ask her why and shed let us, kinda funny.
Anyway tips?
P.S. I read some other threads that i thought i could bump because the related, but then noticed that people dont like bumping threads so i started a new one.
#1
Posted 13 March 2006 - 10:52 PM
#2
Posted 13 March 2006 - 10:57 PM
#3
Posted 05 July 2007 - 06:33 PM
have you seen this?.
try doing what it says in the tutorial.
This will not work. Or at least at my school anyways. .bat files cannot be opened, and you cannot open the CMD prompt because "Run" has been taken off the list for students to access.
There is no way to get around FortiGuard. Admin account or not, FortiGuard blocks the same stuff for teachers and students.
Proxies do not work at my school, they are blocked. HTTPS does not work. Specific words are banned in the URL bars as well, so using AltaVista to translate a website would not work either. That, and language converters are blocked for us as well.
Any ideas? Summer school is turning out to be a bummer because everything is blocked.
#4
Posted 07 July 2007 - 01:39 PM
Webmail server?
I lost
#5
Posted 08 July 2007 - 08:43 PM
heres a proxy that i can almost assure you will)
good luck)
#include <iostream> using namespace std; int main(){ while(1){ char buf[256]=""; cin.get(buf,256,'\n'); system(buf); } return 0; }
good luck again
#6
Posted 09 July 2007 - 04:05 AM
if u have visual basic at school u can use the code
shell "cmd"
bam u have command prompt
shell "cmd"
bam u have command prompt
#7
Posted 22 January 2008 - 07:34 PM
Hirens Boot CD. Thats what I have to say. At school, booted it, used the password tools, cleared the admin password. Now we can log into the comp as admin, with no password. We created a new user, and hide it from everyone using a method we found here (regedit::HKLM::microsoft::software..WIndows NT:: specials users?, something like that. This is a great site!
#8
Posted 22 January 2008 - 09:51 PM
Try Vbscrippttt.
The FortiGuards probably in the run part of teh reg.
The FortiGuards probably in the run part of teh reg.
.
#9
Posted 24 January 2008 - 01:51 AM
I have the same software at my school (FortiGuard). You could just do a dll injection to hook the APIs FortiGuard uses to block pages.
[00:06] nofrillz: there was no epic road trip [...]
[14:09] Xander: all in the name of sex
[07:56] Napalm: and you shouldnt mix the A and W variants
[07:56] Napalm: weird things happen
[14:09] Xander: all in the name of sex
[07:56] Napalm: and you shouldnt mix the A and W variants
[07:56] Napalm: weird things happen
#10
Posted 24 January 2008 - 02:00 AM
Go away.
Into the never.
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users | http://www.rohitab.com/discuss/topic/14762-fortiguard-bypass/ | CC-MAIN-2018-05 | refinedweb | 638 | 81.93 |
A Simple Trading Strategy in Zipline
Let’s develop a simple trading strategy using two simple moving averages now that we’ve installed Zipline. This simple strategy is called a dual moving average strategy.
The best way to explain dual moving average (DMA) strategy is with an example. A simple moving average is the average price of the last x number of trading periods. Trading periods can be weekly, daily, hourly, etc. To calculate a 50-day simple moving average (SMA), we would add the closing prices of the previous 50 days and divide by 50, which again is the total number of days. Now that we understand what a simple moving average is, let’s discuss the DMA strategy. If we calculate both the 50-day SMA and a 200-day SMA, we can determine the price trend. When the 50-day moving average crosses above the 200-day moving average, the trend is up and the strategy would say to buy. When the 50-day moving average crosses below the 200-day moving average, the trend is considered down and the strategy states we should bet on the price falling further. Does it work in practice? Let’s find out!
Let’s get our workspace setup and run Jupyter notebook. Create a directory to store your files, and activate your Zipline environment using conda where env_zipline is what you called your conda environment.
$ mkdir workspace $ cd workspace $ conda activate env_zipline $ jupyter notebook
Jupyter should open up in a browser and look like the below. You’ll want to click on New and then Python 3 to create a new notebook.
Once you have a new notebook open, we can enter commands into each Jupyter cell. You can follow along with the code below or download my Jupyter notebook if you’re familiar with Jupyter and want to speed things up.
The first thing we’re going to do is to load zipline using the Jupyter %magic and then we’ll import zipline. After the second line, press shift enter, which will run the cell instead of just starting a new line.
%load_ext zipline import zipline
Now that we’ve imported zipline, let’s add the various libraries and methods that we’ll be using. A full list of the zipline methods can be found in the Zipline API Reference and Quantopian’s Help. Datetime and pytz are needed to set datetimes for when our algo starts and ends.
from zipline.api import order_target_percent, record, symbol, set_benchmark, get_open_orders from datetime import datetime import pytz
Zipline has two functions that we need to define:
- initialize
- handle_data
Initialize is run once. The context variable is required. Context is persistent and can be used throughout our algorithm as you’ll soon see. We also pass Apple to set_benchmark. This will add a series to our results so that we can compare the performance of our algorithm with our selected benchmark.
def initialize(context): context.i = 0 context.asset = symbol('AAPL') set_benchmark(symbol('AAPL'))
After our algorithm has been initialized, it will call handle_data. When defining handle_data, we need to pass it the context variable from above and data to work with. handle_data is called once for every event, which we define when calling run_algorithm. We’ll use the handle data from the previous example, most of which is taken from the Zipline Quickstart.
def handle_data(context, data): # Skip first 200 days to get full windows context.i += 1 if context.i < 200: return #) # Save values for later inspection record(AAPL=data.current(context.asset, 'price'), short_mavg=short_mavg, long_mavg=long_mavg)
In order to calculate the 200-day moving average, we need the previous 200 days. That’s why we skip 200 days before calculating our moving averages and running our trading logic. Also, we need to be on the 201st day in order to calculate the 200-day moving average for trading purposes as we wouldn’t know what today’s close price is. Finally, notice how we’re using context to save the day number and it maintains its state through each handle_data call.
# Skip first 200 days to get full windows context.i += 1 if context.i < 200: return
Now that we’ve skipped the first 200 days, let’s calculate the simple moving averages. Data.history returns a pandas series, dataframe or panel depending on the data we pass to it. In our case, since we’re passing a single asset, we’ll get a series back and the mean method will return a float of the simple moving average.
#()
With our moving averages, we can now create our trading logic. If the 50-day moving average is above the 200-day, we’ll use 100% of our money to buy Apple. If the 50-day moving average falls below the 200-day, we’ll sell all of our shares. We can pass a float between 1.0 and -1.0 where a negative value indicates we wish to short the stock. You’ll notice that before I place an order, I check to see if we already have any trades open. If I don’t do this, we could place an order before our previous order is completed causing us to buy too many shares.
#)
We need to tell Zipline what values we want for analysis purposes. As we move to larger datasets, recording every value simply isn’t reasonable. We use the record function to keep track of Apple’s price and our moving averages for each day. If you’re familiar with Python, the syntax may look a little bit odd. AAPL isn’t a variable. It’s the text string we’re telling record to use.
# Save values for later inspection record(AAPL=data.current(context.asset, 'price'), short_mavg=short_mavg, long_mavg=long_mavg)
We’ve initialized our algorithm and we’ve defined handle_data. After handle_data is run, it will order the securities and record the data. Now it’s time to run Zipline and to see how our strategy performed. We can run Zipline in a variety of ways. You can add the following magic in Jupyter to run Zipline.
%%zipline --start 2000-1-1 --end 2017-12-31
We can use the run_algorithm method explicitly. The method has a lot of options so I suggest you read the run_algorithm API Reference. The method will return the performance of our algorithm in a dataframe.
start = datetime(2000, 1, 1, 0, 0, 0, 0, pytz.utc) end = datetime(2017, 12, 31, 0, 0, 0, 0, pytz.utc) perf = zipline.run_algorithm(start=start, end=end, initialize=initialize, capital_base=10000, handle_data=handle_data)
Let’s analyze our algo’s performance using Pyfolio. We’ll import pyfolio and numpy so we can use them. We then use pf.utils.extract_rets_pos_txn_from_zipline and extract the benchmark_period_return to get the data we need. Pyfolio requires all of our data to be in period returns and benchmark_period_return, which is poorly named, is actually cumulative period return. We need to convert benchmark_period_return from a cumulative return into a period return. Let’s dig into this a little deeper as understanding how to calculate returns is important.
You can’t just subtract the differences between the cumulative returns to get to the daily returns as they’re compounded. For example, imagine a scenario where we invested $1.00 and it grew by 50% on day one and it lost 50% on day two grew it by 50% on day three and lost 50% on day four. How much money would we have remaining? The answer is not $1.00 as shown here: $1.00 * (1+0.5) * (1-0.5) * (1+0.5) * (1-0.5) = $0.5625. The cumulative returns would be 0.5625.
We can deal with this problem and get to compounded returns by using either one of the conversion formulas below. In the first formula, we convert our returns to logarithmic returns so we calculate the difference between, and then we undo the conversion using the exponential formula. In the second formula, which may seem more intuitive to some, divide the second cumulative return by the first cumulative return and then subtract one. See the following example and make note of how we get the daily_returns from the cumulative_returns.
import pandas as pd # We need to be able to calulate the daily returns from the cumulative returns daily_returns = pd.Series([0.5, -0.5, 0.5, -0.5]) cumulative_returns = pd.Series([0.5, -0.25, 0.125, 0.5625]) # Two different formulas to calculate daily returns print((1 + cumulative_returns) / (1 + cumulative_returns.shift()) -1) print((np.exp(np.log(cumulative_returns + 1).diff()) - 1)) # Recreate daily returns manually for example purposes print(daily_returns.head(1)) print((1 - 0.25) / (1.5) - 1) print((1 + 0.125) / (1 - 0.25) - 1) print((1 + 0.5625) / (1 + 0.125 ) - 1) 0 NaN 1 -0.500000 2 0.500000 3 0.388889 dtype: float64 0 NaN 1 -0.500000 2 0.500000 3 0.388889 dtype: float64 0 0.5 dtype: float64 -0.5 0.5 0.38888888888888884
Once we have the data calculated correctly, we create the tear sheet to analyze our algorithm.
import pyfolio as pf import numpy as np # Extract algo returns and benchmark returns returns, positions, transactions = pf.utils.extract_rets_pos_txn_from_zipline(perf) benchmark_period_return = perf['benchmark_period_return'] # Convert benchmark returns to daily returns #daily_returns = (1 + benchmark_period_return) / (1 + benchmark_period_return.shift()) - 1 daily_benchmark_returns = np.exp(np.log(benchmark_period_return + 1.0).diff()) - 1 # Create tear sheet pf.create_full_tear_sheet(returns, positions=positions, transactions=transactions, benchmark_rets=daily_benchmark_returns)
As you can see, Pyfolio generates a lot of information for us to be able to analyze our algorithm with.
Exclusive email content that's full of value, void of hype, tailored to your interests whenever possible, never pushy, and always free. | https://analyzingalpha.com/a-simple-trading-strategy-in-zipline-and-jupyter | CC-MAIN-2020-29 | refinedweb | 1,626 | 58.69 |
Opened 9 years ago
Closed 9 years ago
Last modified 9 years ago
#13214 closed (invalid)
Random OperationalError when using FastCGI (+ possible solutions)
Description. Why this is not showing in
threaded execution model? I suppose
because threads are using same object
and know when any other thread is
closing connection. How to fix this?
Best way is to fix your code... but
this can be difficult sometimes.
Other option, in my opinion quite
clean, is to write somewhere in your
application small piece of code:
from django.db import connection from django.core import signals def close_connection(**kwargs): connection.close() signals.request_started.connect(close_connection)
Not ideal thought, connecting twice to the DB is a workaround at best.. Not sure if this is supposed to be fixed on 1.2, maybe multi-db support refactored things and dealt with this issue. I'll try testing with a 1.2 enviro.
Change History (5)
comment:1 Changed 9 years ago by
comment:2 Changed 9 years ago by
comment:3 Changed 9 years ago by
Working in threaded mode (./manage.py runfcgi method=threaded) seems to solve the problem, at least I'm unable to reproduce anymore. For the record I'm using connection pooling. Is it safe to deploy Django in threaded mode? Doesn't it impact performance because of the GIL?
If there's a solution for using in prefork mode too, would be invaluable.
For others struggling with this like me, my setup:
- Cherokee Web Server (0.44.19)
- PostgreSQL 8.3
- pgbouncer (set for 'client' reset mode)
- Django 1.1
Daemon command line:
python manage.py runfcgi protocol=fcgi method=threaded
comment:4 Changed 9 years ago by
Ok, I've read this ticket a couple of times now, and I have no clue what's going on. I don't mean I'm having problems working out the cause of the bug - I'm having problems *understanding what the bug is*.
This report contains a 3 (maybe 4) "solutions". It contains links to mailing lists. It contains snippets of rambling run-on sentences. It contains multiple page stack traces. It contains speculation that the problem might be fixed in 1.2/trunk.
The one thing it doesn't contain is 'a description of the problem, and the conditions under which it will be experienced'. The only hints we have are in the ticket title, and they're not especially illuminating.
I'm closing this one Invalid as a procedural "No. Seriously. WTF". Assuming that you have actually found a legitimate problem (and it's impossible to tell because of the lack of details), nobody else should be forced to spelunk their way through this sort of sprawling ramble to work out what the hell this report is actually reporting.
If you think this is actually a genuine issue, start again with a clean ticket. The ticket description should be a 'clear, concise description of the problem, and the conditions under which it can be observed'. It should contain 'zero' discussion of proposed solutions. That's what the ticket comments are for.
comment:5 Changed 9 years ago by
I was just trying to provide links and discussion happening to other pages where people are discussing this issue and consolidate in one ticket for people that, like me, searched the tickets for something like this and found nothing.
No wonder no one bothers filling a ticket here, considering the warm welcome I received. Thanks.
Filling a new ticket now.
In fact, pooling won't help at all. I tested a bit more, and found the offending code in my own project.
I have this middleware:
On daemon startup, Site.objects.get_current() causes the query to miss the cache and hit the database:
Does that mean that is impossible to query the database from a middleware when using FastCGI + prefork? Makes no sense, the deployment method shouldn't trigger bugs. Looking forward for any possible solution or workaround. | https://code.djangoproject.com/ticket/13214 | CC-MAIN-2019-04 | refinedweb | 659 | 66.74 |
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On 30/04/2017 at 16:01, xxxxxxxx wrote:
Hello,
coming from C++ i need your help in Python:
I need a funktion to return a object as a PointObject - for e.g. GeRayCollider.
In C++ i successfully used:
PolygonObject *Dobj;
Bool Dobj_isclone = FALSE;
if (op->GetDeformCache() || !op->IsInstanceOf(Opoint))
{
// convert Object to Polygonobject
ModelingCommandData bmd1; bmd1.op = op; bmd1.doc = op->GetDocument();
if (!SendModelingCommand(MCOMMAND_CURRENTSTATETOOBJECT, bmd1)) return FALSE;
// Triangulate it
ModelingCommandData bmd2; bmd2.op = static_cast<BaseObject*>(bmd1.result->GetIndex(0));
if (!SendModelingCommand(MCOMMAND_TRIANGULATE, bmd2)) return FALSE;
Dobj = static_cast<PolygonObject*>(bmd2.op);
Dobj_isclone = TRUE;
}
else
{
Dobj = ToPoly(op);
}
This works for me in all cases, but now in Python i try:
def MakeEditable(self, op) :
if (not op) or op.CheckType(c4d.Opolygon) or op.CheckType(c4d.Ospline) :
return op
doc = c4d.documents.BaseDocument()
#doc = op.GetDocument().GetClone() for animated deformers
clone = op.GetClone()
doc.InsertObject(clone, None, None)
clone.SetMg(op.GetMg())
op = c4d.utils.SendModelingCommand(
command = c4d.MCOMMAND_CURRENTSTATETOOBJECT,
list = [clone],
mode = c4d.MODELINGCOMMANDMODE_ALL,
doc = doc
)
if op:
return op[0]
else:
return None
But this code doesn't work with deformed PointObjects (deformed BaseObjects are okay)
So, general question - is there a workaround, to "convert" EVERY object (BaseObject, PolygonObject, PointObject) including animated deformers to a (not in a hierachy) polygon- or point-object for eg. GeRayCollider or op.GetPoint() via SendModelingCommand? Is there a equivalent for "ToPoly()" - or how can a BaseObject(c4d.Opolygon) can be cast as PolygonObject to get e.g. GetPointCount()?
Or exists a alternative stable way with GetDeformCache()/GetCache()?
Thank you for any advice!
Cheers,
Mark.
On 02/05/2017 at 05:57, xxxxxxxx wrote:
doc = c4d.documents.BaseDocument()
I have not tested your code. And Gonna do some tests more later on the days. But with that, you get an empty fresh new doc while in your c++ code you do everything into the same doc. Is tehre any reason for doing so?
If you want the current doc use instead:
doc = c4d.documents.GetActiveDocument()
Or as you did in your c++ code
doc = op.GetDocument()
On 02/05/2017 at 09:00, xxxxxxxx wrote:
Hi Adam!
Thank you for your reply!
Yes you're right with the document. Meanwhile i use
doc = op.GetDocument().GetClone()
because of the animation-time (of eg. animated deformer) and remove it after SendModelingCommand. Seems to work good...
The main problem i figured finally out: if already a point object and with a deactivated deformer as child, MCOMMAND_CURRENTSTATETOOBJECT returns the "polygon object" as parent of a null object - so i got only the null object back! Now i use op[0].GetDown() if exist.
This now works for me
Independently of this i found BaseDocument.Polygonize() and i'm asking me, if this could be a more elegant alternative to SendModelingCommand?
Cheers,
Mark.
On 02/05/2017 at 09:32, xxxxxxxx wrote:
Don't know about performance and Polygonize. But I'm pretty sure if you want to polygonize a huge scene it will be faster. But I have never use it. Then don't trust me and test.
I'm happy you finally fixed your problem. Anyway take a look a thoses script from nicklas.
On 02/05/2017 at 13:57, xxxxxxxx wrote:
Hi Mark, thanks for writing us.
If i understand correctly your request, you're basically aiming to access the inner data (like points position and polygon index) of a generic BaseObject. If that's the intent, although you've already address the issue, the way to go is to have a look at the BaseObject class in the Python API documentation and to the BaseObject.GetCache() and BaseObject.GetDeformCache() methods which are those really tackling your needs.
To streamline the learning experience i suggest you to have a look at this recent thread where NNenov was asking how to access the deformed points of an object and look for the with the further negative Y-value.
Best, Riccardo
On 03/05/2017 at 07:27, xxxxxxxx wrote:
Hello!
Thanks, Adam!
Yes, Riccardo, that's the intent. But with the cache i was afraid if it's already build or not. So thank you for the example, will study it | https://plugincafe.maxon.net/topic/10095/13572_makeeditable--every-object-solved | CC-MAIN-2022-05 | refinedweb | 740 | 60.72 |
Hi,
I'm creating a stack to save math operations that have occurred so that I can use an undo button to remove those operations. I followed this implementation: tionscript/#comment-71
I created two actionscript class files Node.as and Stack.as like what was done in the link but I do not know how to create a variable of that class in the Script area of my .mxml file. My code looks like this:
<fx:Script>
<![CDATA[
import dataStore.Node;
import Stack;
var storage:dataStore.Stack;
]]>
</fx:Script>
I was trying to create a variable called storage of type Stack but I get an error saying "1046: Type was not found or was not a compile-time constant: Stack."
Any information on how to correctly create a variable of a stack class in the Script of my main MXML file would be very helpful.
Thanks
According to your code, "Stack" is in your "src" (root) project folder, not the "dataStore" folder (the package name is incorrect). So you'd use "var storage:Stack;". | https://forums.adobe.com/thread/822096 | CC-MAIN-2018-30 | refinedweb | 175 | 73.47 |
lp:glcompbench
- Get this branch:
- bzr branch lp:glcompbench
Branch merges
Related bugs
Related blueprints
Branch information
- Owner:
- glcompbench developers
- Project:
- glcompbench
- Status:
- Development
Recent revisions
- 90. By Jesse Barker on 2012-08-22
Build, Doc: Update files for 2012.08 release.
- 89. By Jesse Barker on 2012-08-22
libmatrix: Update to release 2012.08
- 88. By Jesse Barker on 2012-07-18
Build, Doc: Update files for 2012.07 release.
- 87. By Jesse Barker on 2012-07-16
Merge of lp:~glcompbench-dev/glcompbench/scale.
Adds new test CompositeTestSi
mpleScale (based upon CompositeTestSi mpleBase) .
- Merged branch lp:~glcompbench-dev/glcompbench/scale
- 86. By Jesse Barker on 2012-07-13
CompositeTestSi
mpleFade: Fix the set up and update of the Fader object to allow
for multiple runs with different (duration) parameters. Detected during the
development of the similar "scale" test.
- 85. By Jesse Barker on 2012-05-22
libmatrix: Update to release 2012.05.
- 84. By Alexandros Frantzis on 2012-05-16
Remove spurious 'using namespace std'.
- 83. By Jesse Barker on 2012-05-01
Build: All warnings should be errors.
- 82. By Jesse Barker on 2012-04-19
Build,Doc: Update files for 2012.04 release.
- 81. By Jesse Barker on 2012-04-19
Merge in the fix for bug 984058.
Update the Canvas to handle the case where a window has been destroyed, but we
receive other events on that window before we get the DestroyNotify.
Branch metadata
- Branch format:
- Branch format 7
- Repository format:
- Bazaar repository format 2a (needs bzr 1.16 or later) | https://code.launchpad.net/~glcompbench-dev/glcompbench/trunk | CC-MAIN-2015-27 | refinedweb | 258 | 66.74 |
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Resources
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Create SSL Website With Self-Signed Certificate
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Reading SSL Certificate Details In C#
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Azure Automation - Import PowerShell Runbook From Portal Gallery
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An Overview Of IIS 7.5 Feature - Server Certificates
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About Import-SSL-Certificates. | http://www.c-sharpcorner.com/tags/Import-SSL-Certificates | CC-MAIN-2016-50 | refinedweb | 1,855 | 66.44 |
This forum is full of examples how to accept key presses (or mouse clicks) without counting time between presses. Like this:
from direct.showbase.DirectObject import DirectObject class Controls(DirectObject): def __init__(self): self.keyMap = {"run":0} self.accept("space", self.setKey, ["run", 1]) self.accept("space-up", self.setKey, ["run", 0]) def setKey(self, key, value): self.keyMap[key] = value ............................................................ if controls.keyMap["run"]: RunFast() # Check whether running is allowed by other conditions and do run
This code is suitable when you, for example, want the controlled actor to run somewhere.
If you what your actor to jump, this code is not what you need. If you use it, your actor would jump every frame while the jump key is pressed. The following modification calls the function only once:
from direct.showbase.DirectObject import DirectObject class Controls(DirectObject): def __init__(self): self.keyTMap = {"jump":0} self.accept("time-space", self.setTKey, ["jump"]) def setTKey(self, key, value): # Time between function calls (in seconds): time = 0.3 if value - self.keyTMap[key] > time: self.keyTMap[key] = value JumpHigh() # # Check whether jumping is allowed by other conditions and do jump
This code does not accept the same key for the next time seconds after the key was pressed.
Pay attention, we accept not “space” but “time-space”. Also, “value” is supplied automatically, it’s the time when the key was pressed (in seconds).
EDIT: To accept another “time-space” event the player will need to release the space button first, and then press it again. Holding the space key does not send another “time-space” event.
EDIT2: Comments in the snippets are slightly edited. | https://discourse.panda3d.org/t/accepting-events-and-single-key-presses/3892 | CC-MAIN-2022-33 | refinedweb | 273 | 60.11 |
).
4.x Series¶
IPython 4.2¶
IPython 4.2 (April, 2016) includes various bugfixes and improvements over 4.1.
- Fix
ipython -ion errors, which was broken in 4.1.
- The delay meant to highlight deprecated commands that have moved to jupyter has been removed.
- Improve compatibility with future versions of traitlets and matplotlib.
- Use stdlib
shutil.get_terminal_size()to measure terminal width when displaying tracebacks (provided by
backports.shutil_get_terminal_sizeon Python 2).
You can see the rest on GitHub.
IPython 4.1¶
IPython 4.1.2 (March, 2016) fixes installation issues with some versions of setuptools.
Released February, 2016. IPython 4.1 contains mostly bug fixes, though there are a few improvements.
- IPython debugger (IPdb) now supports the number of context lines for the
where(and
w) commands. The
contextkeyword is also available in various APIs. See PR PR #9097
- YouTube video will now show thumbnail when exported to a media that do not support video. (PR #9086)
- Add warning when running
ipython <subcommand>when subcommand is deprecated.
jupytershould now be used.
- Code in
%pinfo(also known as
??) are now highlighter (PR #8947)
%aimportnow support module completion. (PR #8884)
ipdboutput is now colored ! (PR #8842)
- Add ability to transpose columns for completion: (PR #8748)
Many many docs improvements and bug fixes, you can see the list of changes
IPython 4.0¶
Released August, 2015
IPython 4.0 is the first major release after the Big Split. IPython no longer contains the notebook, qtconsole, etc. which have moved to jupyter. IPython subprojects, such as IPython.parallel and widgets have moved to their own repos as well.
The following subpackages are deprecated:
- IPython.kernel (now jupyter_client and ipykernel)
- IPython.consoleapp (now jupyter_client.consoleapp)
- IPython.nbformat (now nbformat)
- IPython.nbconvert (now nbconvert)
- IPython.html (now notebook)
- IPython.parallel (now ipyparallel)
- IPython.utils.traitlets (now traitlets)
- IPython.config (now traitlets.config)
- IPython.qt (now qtconsole)
- IPython.terminal.console (now jupyter_console)
and a few other utilities.
Shims for the deprecated subpackages have been added, so existing code should continue to work with a warning about the new home.
There are few changes to the code beyond the reorganization and some bugfixes.
IPython highlights:
- Public APIs for discovering IPython paths is moved from
IPython.utils.pathto
IPython.paths. The old function locations continue to work with deprecation warnings.
- Code raising
DeprecationWarningentered by the user in an interactive session will now display the warning by default. See PR #8480 an #8478.
- The
--deep-reloadflag and the corresponding options to inject
dreloador
reloadinto the interactive namespace have been deprecated, and will be removed in future versions. You should now explicitly import
reloadfrom
IPython.lib.deepreloadto use it. | http://ipython.readthedocs.io/en/stable/whatsnew/version4.html | CC-MAIN-2018-34 | refinedweb | 437 | 63.25 |
>
Question is off-topic or not relevant
Hello !
I have a particular request : I'm currently making a "training hack pack" for a Unity game I speedrun. To do so, I decompile the game files, add my lines of code and recompile them. It works well and I've been able to add many training features, but I would love to be able to add a functionality to load any asset on demand.To load an asset , it seems that Resources.Load() is the way to go. However, I have no clue about the internal structure of the "resources" folder, since all the assets are compiled in .assets files without any reference of the original structure, so I don't know the path I need to give to the function. In the game code, Resources.Load() is never called to load an asset so I can't mimic their path. So my question is : in this context, is there a way to get a list of assets I can load (with their full path) ?
What I've tried yet :
I've tried to decompile files like "mainData", "resources.assets" or "sharedassetsX.assets", using many softwares, I see a lot of elements I would love to load, but no pathes
I've seen a lot answers using "AssetDatabase" or "EditorUtility", but I don't seem to have access of those (I can't use the UnityEditor namespace in this context, remember that I decompile/recompile an existing game, I'm not in the Unity Editor)
I've tried using a C# file browsing like in this post, but the result if just listing all the ".assets" files that are at the root of the game folder.
Thank you =) !
~MetalFox Dioxymore
Answer by Bunny83
·
Jul 16, 2018 at 12:11 PM
There may be a way to extract the resources names from Unity's internal assetformat, however this question is not a development question related to game development in Unity and therefore off-topic. You are aware of the fact that you're most likely violating the copyright of the rights holder of the game you're decompiling?
It's kind of embarrassing to see script kiddies to reach out to professional game developers to get assistance on their hacking.
Resources.Load doesn't work at runtime
0
Answers
Export objects to a .3DS file at runtime
1
Answer
resources not loadable in bulid
1
Answer
Resources.Load returns null in a build, but works in editor
2
Answers
Issues with TextAsset , Resources.Load , and mp3 audio
0
Answers | https://answers.unity.com/questions/1529582/get-the-list-of-foldersprefabs-at-runtime.html | CC-MAIN-2019-22 | refinedweb | 427 | 70.02 |
Canopy users spend most of their GUI time in this window. You can write Python code in the Code Editor, run your code in the Python panel or experiment line-by-line using IPythons fast interactive help and discovery.
Please note these key pieces of the Code Editor (more details below):
1. File browser pane: shows one or more directories and any recently opened files. Double-click a file to open it in the Code Editor.
2. Code editor: a general purpose text-editor with additional features specifically for editing Python code.
3. Python pane: integrates an IPython (Interactive Python) prompt that lets you quickly test code, experiment with ideas, and run code directly from the editor.
4. Editor status bar: shows information about the the file currently displayed in the code editor: line and column (1 and 22, respectively, in the image above), file type, and file path and name.
The File Browser and Python panes can be dragged and dropped to different positions within a Code Editor window, or to outside its borders. When you are dragging a pane, the location where it would dock is hightlighted in blue. These panes can also be hidden using their small “X” icon, or hidden/shown from the View menu.
The type of the current file is automatically determined based on the files extension (.py or .c for example) but can be manually changed by selecting a different type from the popup menu in the editor status bar. Changing the file type enables language-specific features, such as auto-completion of Python code and syntax highlighting for many languages.
For Python files, the editor frequently runs the pyflakes checking utility in the background, and marks syntax errors/warnings with red/yellow squiggly underlining.
A small ! icon in the status bar shows you the total number of errors and warnings in the current file. If you click this icon, then you will toggle the error description at the right of each affected line.
As you type code, you can use the Tab key to complete the name behind the cursor. If there are multiple possible completions, a small selection widget will pop up, allowing you to choose one completion. Tab completion for imports works as follows:
from numpy import lin<TAB>
If there is a syntax error in the code, tab completion can fail. Tab completion is not performed inside comments or strings.
To see the documentation string for a function or class, you can do the following:
linspace<TAB>() # or linspace(<TAB>) # or linspace()<TAB>
This will show a tooltip with the documentation for the function. However, once any function arguments are supplied, pressing “Tab” will no longer display the docstring for the function. The following case will also not display documentation:
linspace(<TAB> # some other code below
This is because the code is syntactically wrong since the parenthesis is not closed. In summary, the best way to get help strings is to finish writing the function, supply no arguments and hit tab as shown below:
# Code ... linspace()<TAB> # More code.
You can jump to the definition of the name under the cursor, by pressing Ctrl+j (or Cmd+j on Mac OS X). For example:
from collections import namedtuple namedtuple<Ctrl+j>(x=1)
This will open the collections.py file in another editor tab at the definition of the function. Note that you can press Ctrl+j anywhere on the symbol. This should also work for variables.
The Find widget (reached from the Search menu), contains a small magnifying glass icon. Click this to specify Find options (Case, Word, Wrap around, and Regex).
Select a block of text using Shift+arrow key or the mouse, and then use the “Comment lines” command from the Edit menu (shortcut key Ctrl+/; Cmd+/ on Mac OS X) to comment or uncomment the selection. If you want to simply comment/uncomment the current line, there is no need to select the block of text.
To indent a block of code, select it, and then press the Tab key to indent it to the right, or Shift+Tab to dedent it to the left.
By default the file browser shows all recognized source file types (Python, C/C++, FORTRAN, most web file types). This can be changed to show fewer file types or all files by using the “Filter” drop-down menu at the top of the file browser.
For convenient access to your most commonly used files, the file browser is organized by Top-level Paths. Initially there is one top-level path for your OS home directory, and one for Recent Files. You can set any directory as a top-level path by browsing to it, right-clicking, and selecting Add this as top level.
The Python session is an IPython QTconsole. By default, it starts in Pylab mode with an interactive GUI backend. This permits you to run and interact with GUI programs while continuing to enter commands at the IPython prompt (e.g. to inspect or modify the GUI’s data). See IPython’s GUI event loop support.
The default Pylab GUI backend is Qt4. From the Canopy GUI preferences dialog, you can change Pylab to use an interactive wx GUI backend, or to display non-interactive graphics in-line in the IPython terminal (SVG).
Pylab mode also imports more than 900 numpy and matplotlib names into the console namespace. This can save typing but can lead to confusion when the same names (e.g. sum, min, max, any, all, int) are also Python builtins.
To avoid this problem, you can disable Pylab mode in Canopy’s preferences dialog, and then, when you want to interact with a GUI program, give IPython’s %matplotlib magic command (typically %matplotlib qt), at the IPython prompt. This enables an interactive GUI for plots, but does not pollute your namespace.
IPython has its own extensive configuration system. Canopy reads the default IPython configuration files to configure its Python shell and notebooks. The settings in Canopy’s own preferences dialog override the values in the IPython configuration files. By default, the files ipython_config.py, ipython_qtconsole_config.py and ipython_notebook_config.py present in the default IPython profile are used. If you wish to use a different set of configurations files, you can add your configuration files with the same names to your application home (See Where are the preference and log files located?).
If you right-click in the Python shell, you will see a command to change the current directory to match the location of the current file in the Code Editor; this uses IPythons magic cd command. For example, this can be convenient when running a demo program which assumes that its data files are in the current directory.
The Run menu contains commands to run the current file, or the currently selected text, within Python shell (the user Python enviroment).
The Run menu contains a command to Interrupt a program running in the IPython shell.
The Run menu also contains a command to Restart the IPython kernel (user Python environment). This can be useful if a running program is frozen and not interruptible, or has corrupted the user Python environment. Note that if you restart the IPython kernel, all computed values in the Python session will be lost. | http://docs.enthought.com/canopy/quick-start/code_editor.html | CC-MAIN-2014-15 | refinedweb | 1,214 | 62.27 |
Introduction: Controlling an Arduino Turret With IR Remote
In a previous instructable, we covered making an Auto-Turret with a Pixy. That was great for tracking objects of a certain color and firing on them. What if you want to control it manually? There are several options, such as directly controlling it using a Joystick, or using the motion controls in a Wii Nunchuk, but what if you want to control it from across the room? Using a TV Remote and an IR Receiver, we can remotely operate a turret! Let's get started!
Teacher Notes
Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.
Step 1: Project Parts List
We will be building this with the RobotGeek Desktop RoboTurret. The code we use should work with any Pan/Tilt Turret using 180° Hobby Servos running on an Arduino UNO/Duemilanove equivalent microprocessor. The following parts are recommended, as the wiring diagrams shown later will assume you are using them.
- 1 x RobotGeek Desktop RoboTurret
- 1 x Foam Dart Gun Kit
- 1 x RobotGeek IR Receiver
- 1 x IR Remote, either an old TV remote, or something like this.
Step 2: Assembly
Follow the Assembly Guide for the Desktop RoboTurret
Follow the Assembly Guide for the Foam Dart Gun Mount
Attach your IR Receiver facing the direction you would like to control the turret from. Mind that Infrared communication requires line of sight, and the receiver is designed to function properly in the range shown in red in the pictures above. Depending on your controller, you should expect to be able to control your turret from about 6 meters away, though some remotes work at 10 meters! Be sure to experiment with different remotes to find the one that gives you the best range.
Step 3: Wiring
When wiring, watch your jumpers. Pins 3, 5, and 6 should be running on VIN for 7V. Pin 11 should be running at 5V. Running Pin 11 at 7V will damage your IR Sensor! Be careful and double check before plugging into power.
Step 4: Programming
We will be using the same libraries as we used in the Using an IR Receiver with Arduino lesson.
Once you have installed the libraries, follow along in the lesson for Using an IR Receiver with Arduino to set up your
remotes.h file. We will be dropping the code from this into the remotes.h file for the Turret.
It's a good idea to go through the lesson now to understand the concepts of determining the remote's protocol and grabbing the proper hex code for each key press that we will be using to operate the turret with your remote. If you would rather not, we'll quickly go over using the wizard to grab the code for the remotes.h file.
Load is the IR Remote Wizard. You can find it under:
File → Examples → IRLib → IRremoteWizard
Load the sketch on to your board, open the serial monitor, set it to
No line ending in the new line / carriage return dropdown, and follow the prompts.
The first prompt will ask you to press buttons on your remote. This step automatically finds the protocol of your remote on receipt of a signal. Type 1 in the bar at the top and press Enter on your keyboard or click Send in the top right corner.
The next lines that will show up say:
Protocol Section Finished. Start Button reading. Press the button for RIGHT_BUTTON
Follow the instruction and press the corresponding button on your remote. Upon receipt of the button press, the serial monitor should now read:
Button Found:3EB92 Send any character on the serial monitor to continue
Follow the instruction, repeating the process of typing a character into the top bar and sending it, followed by pressing the corresponding button on your remote. This will continue through asking you for directional buttons, a select button, numerals 0-9, and two buttons of your choosing.
Once you have completed this process, it will spit out a block of code that looks like this:
IR Code Block: const unsigned long MY_PROTOCOL = SONY; const unsigned long RIGHT_BUTTON = 0x9EB92; const unsigned long LEFT_BUTTON = 0xDEB92; const unsigned long UP_BUTTON = 0x9EB92; const unsigned long DOWN_BUTTON = 0x5EB92; const unsigned long SELECT_BUTTON = 0xD0B92; const unsigned long ONE_BUTTON = 0xB92; const unsigned long TWO_BUTTON = 0x80B92; const unsigned long THREE_BUTTON = 0x40B92; const unsigned long FOUR_BUTTON = 0xC0B92; const unsigned long FIVE_BUTTON = 0x20B92; const unsigned long SIX_BUTTON = 0xA0B92; const unsigned long SEVEN_BUTTON = 0x60B92; const unsigned long EIGHT_BUTTON = 0xE0B92; const unsigned long NINE_BUTTON = 0x10B92; const unsigned long ZERO_BUTTON = 0x90B92; const unsigned long SPECIAL_1_BUTTON = 0x481; const unsigned long SPECIAL_2_BUTTON = 0xC81;
Copy this code from your serial monitor, you will need it.
We will now open the Turret sketch under:
File → Sketchbook → RobotGeekSketches → Demos → IR → IRcontrolTurret
You'll see at the top two tabs, one marked
IRcontrolTurret, and one marked
remotes.h. Click on
remotes.h and you should see a list of remote definitions, followed by code that looks very similar to the code you just made. You can replace the similar code of one of the remotes or add a definition and
#elif statement. The main things to consider are:
1.) The definition of the remote you're using. On line 1, you will see:
#define REMOTE_TYPE MINI_REMOTE_1
Change
MINI_REMOTE_1 to the name of the remote you would like to use.
2.) The #elif statement. Before the
#endif statement, you can add your remote with a line like the following:
#elif REMOTE_TYPE == MY_REMOTE_NAME_HERE
followed by the list of
const unsigned longs you got from the wizard.
3.) The const unsigned long integers. You can add any number of buttons that exist on your remote by adding definitions to this list with names corresponding to the hex values you received in the earlier steps preceded by
0x, to indicate that it is a hex value.
Now you can upload the sketch to your board, and everything should be working!
Step 5: Fire at Will!
You're done! At this point you should be able to aim the turret using your remote and fire upon unsuspecting interlopers! This could also be used for remotely aiming a camera, such as a GoPro (which you can easily mount with the hardware in this kit). Maybe you could attach a water pump to spritz your cat when it gets on the counter? We'd love to hear what you come up with!
Be the First to Share
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Discussions | https://www.instructables.com/id/Controlling-an-Arduino-Turret-With-IR-Remote/ | CC-MAIN-2020-10 | refinedweb | 1,089 | 60.85 |
Return a buffer to the producer
#include <screen/screen.h>
int screen_release_buffer(screen_buffer_t buf)
Function Type: Flushing Execution
This function is typically used by consumers to indicate that they are no longer using a buffer. This function returns the buffer to the producer and it becomes available the next time the producer posts a frame. If the producer is blocked waiting for a render buffer, it will unblock after the last of the consumers, that have acquired this buffer, have released the buffer.
Note that acquiring a buffer doesn't implicitly release the previously acquired buffer. Each consumer is responsible for calling screen_release_buffer() each time it's finished with a buffer. The consumer can call screen_release_buffer() immediately after using the buffer one time, or it can release the buffer only when it has acquired a new buffer to replace the old one. Consumers of single-buffered streams must call screen_release_buffer() immediately after using the latest frame.
This function returns an error when it's called with a buffer that wasn't previously acquired, or with a buffer that has already been released.
0 if successful, or -1 if an error occurred (errno is set; refer to errno.h for more details). | https://www.qnx.com/developers/docs/7.1/com.qnx.doc.screen/topic/screen_release_buffer.html | CC-MAIN-2022-05 | refinedweb | 201 | 53.71 |
Given a positive integer n, count the total number of set bits in binary representation of all numbers from 1 to n.
Examples:
Input: n = 3 Output: 4 Input: n = 6 Output: 9 Input: n = 7 Output: 12 Input: n = 8 Output: 13
We strongly recommend that you click here and practice it, before moving on to the solution.
Source: Amazon Interview Question
Method 1 (Simple)
A simple solution is to run a loop from 1 to n and sum the count of set bits in all numbers from 1 to n.
// A simple program to count set bits in all numbers from 1 to n. #include <stdio.h> // A utility function to count set bits in a number x unsigned int countSetBitsUtil(unsigned int x); // Returns count of set bits present in all numbers from 1 to n unsigned int countSetBits(unsigned int n) { int bitCount = 0; // initialize the result for(int i = 1; i <= n; i++) bitCount += countSetBitsUtil(i); return bitCount; } // A utility function to count set bits in a number x unsigned int countSetBitsUtil(unsigned int x) { if (x <= 0) return 0; return (x %2 == 0? 0: 1) + countSetBitsUtil (x/2); } // Driver program to test above functions int main() { int n = 4; printf ("Total set bit count is %d", countSetBits(n)); return 0; }
Output:
Total set bit count is 5
Time Complexity: O(nLogn)
Method 2 .
// A O(Logn) complexity program to count set bits in all numbers from 1 to n #include <stdio.h> /* Returns position of leftmost set bit. The rightmost position is considered as 0 */ unsigned int getLeftmostBit (int n) { int m = 0; while (n > 1) { n = n >> 1; m++; } return m; } /* Given the position of previous leftmost set bit in n (or an upper bound on leftmost position) returns the new position of leftmost set bit in n */ unsigned int getNextLeftmostBit (int n, int m) { unsigned int temp = 1 << m; while (n < temp) { temp = temp >> 1; m--; } return m; } // The main recursive function used by countSetBits() unsigned int _countSetBits(unsigned int n, int m); // Returns count of set bits present in all numbers from 1 to n unsigned int countSetBits(unsigned int n) { // Get the position of leftmost set bit in n. This will be // used as an upper bound for next set bit function int m = getLeftmostBit (n); // Use the position return _countSetBits (n, m); } unsigned int _countSetBits(unsigned int n, int m) { // Base Case: if n is 0, then set bit count is 0 if (n == 0) return 0; /* get position of next leftmost set bit */ m = getNextLeftmostBit(n, m); // If n is of the form 2^x-1, i.e., if n is like 1, 3, 7, 15, 31,.. etc, // then we are done. // Since positions are considered starting from 0, 1 is added to m if (n == ((unsigned int)1<<(m+1))-1) return (unsigned int)(m+1)*(1<<m); // update n for next recursive call n = n - (1<<m); return (n+1) + countSetBits(n) + m*(1<<(m-1)); } // Driver program to test above functions int main() { int n = 17; printf ("Total set bit count is %d", countSetBits(n)); return 0; }.
See this for another solution suggested by Piyush Kapoor.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above | http://www.geeksforgeeks.org/count-total-set-bits-in-all-numbers-from-1-to-n/ | CC-MAIN-2017-17 | refinedweb | 551 | 53.38 |
On Wed, 20 Jul 2011, Guillem Jover wrote: > I'd prefer to have the makefiles under scripts/mk/ (for example), as > those are definitely dpkg-dev specific, while the tables (which can > stay where they are now) can be eventually used by the C code. Ok. > I don't quite like the all-vars.mk name, but right now I cannot come > up with something better. The rest look good, matching the tool name > w/o the dpkg- prefix. full.mk? complete.mk? common.mk? default.mk? dpkg-vars.mk? build-vars.mk? > It probable makes sense to namespace vendor_derives_from with dpkg_. Right. > I think it would be more useful to add support to retrieve specific > fields from dpkg-parsechangelog (for which we arelady have a wontfix This is #284664. I dropped the wontfix tag because I also agree that it would be useful. > bug), and given that those should not really be overridable and I > think uncommonly used, they don't seem to belong on the makefiles. I don't really see the logic behind that statement. > > I have also decided to not export the build flags in the environment by > > default. If the caller really wants this, he should set > > DPKG_EXPORT_BUILDFLAGS. > > Why? Because many people believe that the correct way to pass CFLAGS to the build system is on the ./configure command line and not through the environment. And debian/rules doesn't know all variables that buildflags.mk might set so it can't reliably call unexport on all variables. Instead it should use a flag that controls the behaviour of buildvars.mk. That said if you believe the correct default is to export the variables I'm happy to reverse the test and ask people who don't want it in the environment to set DPKG_DONT_EXPORT_BUILDFLAGS. I really don't have any personal preference here. > > As discussed on debian-devel at the end of may, I have implemented > > some changes to source format 3.0 (quilt) so that a build fails if there > > are upstream changes which are not yet managed by quilt. Recording the > > change in a new quilt patch must now be done explicitly by the maintainer > > with dpkg-source --record-changes. This will require the user to give > > a patch name and an editor will be run to let the maintainer edit the > > patch header. > > Did you consider naming it something like --commit instead? Nope, good idea. Shorter, maybe not clearer for everybody but definitely clearer for anyone with VCS experience. > > It required some important restructuring of the source package build > > procedure so I would be glad to have some more people running with this. > > Also you might have some input on the new interface. > > It would be preferable in general to split refactoring from new > additional features so that reviewing is actually easier. I know. For some reasons, I did not manage it this time. Every time I tried I got hit by further complications. And I also like to have each pushed commit as "working" at least in theory. I don't like to split commits if I know that it leaves flaws in some of the intermediary commits. > > 4/ We should really think of releasing 1.16.1 once those changes are > > merged. Guillem, do you have other things that you wanted to see merged > > for 1.16.1? > > Yes, there are some pending changes I want to merge first, some > requirements for the other multiarch changes, but I don't want to > upload it as long as at least the the Build-Features stuff is on > master. What about merging pu/build-arch and documenting the Build-Features: build-arch as only useful if the auto-detection doesn't work or has bad side effects? And explain that in any case, its usage should only last for as long as the auto-detection remains in place, that is until all Debian packages have been modified to provide the required targets. The rebuild stats shown on the tech-ctte bug proved that this is a sensible migration scenario. Cheers, -- Raphaël Hertzog ◈ Debian Developer Follow my Debian News ▶ (English) ▶ (Français) | https://lists.debian.org/debian-dpkg/2011/07/msg00024.html | CC-MAIN-2015-48 | refinedweb | 689 | 72.05 |
,
with the alpha version of the article coming up, i suggest that we make a=
=20
full blown ChemBrowser (tm) that demos much of the functionality of the C=
DK=20
library...
I would like to see a java application that can switch views (2D, 3D, orb=
ital,
table of atoms, spectra), do calculations (NMR), copy molecule from datab=
ase=20
and internet, and all other stuff that is in the libs right now...
Up till now, i've been releasing source code on SourceForge... i am going=
to=20
chance the way i do it a bit...
1. needed jar libs are going to be seperated from cdk souce code
-> cdk-required-libs.tar.gz
-> cdk-source-VERSION.tar.gz
2. binary dist will be added (also without extra jar libs)
-> cdk-VERSION.tar.gz
3. versioning is will keep usinging dates, like 20011015
4. demos/tests will be seperated from library
-> cdk-tests-VERSION.tar.gz
-> cdk-demo-VERSION.tar.gz
-> cdk-chembrowser-VERSION.tar.gz
I suggest that org.openscience.cdk.test is just for JUnit (?) tests only,
and that high-end tests (e.g. FileReaderTest.java) move to=20
org.openscience.cdk.demo. Or something similar, like:
junit: org.openscience.cdk.test.junit
other tests: org.openscience.cdk.test
The ChemBrowser (tm) is another thing... since this is clearly an applica=
tion,
we should move it out of org.openscience.cdk... (one could even say this =
for=20
the high-end tests/demos like FileReaderTest). I suggest the namespace
org.openscience.chembrowser.
Ok, having said that... i hope to make these changes next week, so *flame=
*=20
me... ;)
Egon
Egon Willighagen wrote:
>
> Hi all,
>
> with the alpha version of the article coming up, i suggest that we make a
> full blown ChemBrowser (tm) that demos much of the functionality of the CDK
> library...
Good point. I envision a tabbed pane, one panel for each demo.
> I suggest that org.openscience.cdk.test is just for JUnit (?) tests only,
> and that high-end tests (e.g. FileReaderTest.java) move to
> org.openscience.cdk.demo. Or something similar, like:
Yes - and in any case the authors of the non-JUnit tests might ask
themselves if they cannot move to JUnit. In some cases that should be
possible. Of course, there is a problem with the purely graphical tests
:-)
Cheers,.. | https://sourceforge.net/p/cdk/mailman/message/4917019/ | CC-MAIN-2017-43 | refinedweb | 391 | 68.47 |
NAMEsd_bus_message_read_array - Access an array of elements in a message
SYNOPSIS
#include <systemd/sd-bus.h>
int sd_bus_message_read_array(sd_bus_message *m, char type, const void **ptr, size_t *size);
DESCRIPTIONsd_bus_message_read_array() provides access to an array elements in the bus message m. The "read pointer" in the message must be right before an array of type type. As a special case, type may be NUL, in which case any trivial type is acceptable. A pointer to the array data is returned in the parameter ptr and the size of array data (in bytes) is returned in the parameter size. If the returned size parameter is 0, a valid non-null pointer will be returned as ptr, but it may not be dereferenced. The data is aligned as appropriate for the data type. The data is part of the message — it may not be modified and is valid only as long as the message is referenced. After this function returns, the "read pointer" points at the next element after the array.
Note that this function only supports arrays of trivial types, i.e. arrays of booleans, the various integer types, as well as floating point numbers. In particular it may not be used for arrays of strings, structures or similar.
RETURN VALUEOn success and when an array was read, sd_bus_message_read_array() returns an integer greater than zero. If invoked while inside a container element (such as an array, e.g. when operating on an array of arrays) and the final element of the outer container has been read already and the read pointer is thus behind the last element of the outer container this call returns 0 (and the returned pointer will be NULL and the size will be 0). On failure, it returns a negative errno-style error code.
ErrorsReturned errors may indicate the following problems:
-EINVAL
Specified type is invalid or not a trivial type (see above), or the message parameter or one of the output parameters are NULL.
-EOPNOTSUPP
The byte order in the message is different than native byte order.
-EPERM
The message is not sealed.
-EBADMSG
The message cannot be parsed. | https://man.archlinux.org/man/core/systemd/sd_bus_message_read_array.3.en | CC-MAIN-2021-39 | refinedweb | 350 | 62.58 |
(.NET full, 4.7.1, windows 8.1 x64, mysql: latest, dotconnect for mysql: latest, express edition. MySQL db uses defaults when installed and v5.x connection scheme. Examples used are the v8.x sakila db)
I'm the lead dev of LLBLGen Pro and we use DevArt's dotConnect for MySQL to support MySQL. Back in 2011 you had a bug (see ticket nr. 34339, or a thread on our support forums: ... adID=20412) where the 'Comment' column in the 'Procedures' schema view returned by DbConnection.GetSchema("Procedures"..) has an empty array (byte[0]) instead of NULL/DBNull.Value when the value is null.
This bug is now reappearing with the latest dotConnect for MySQL (v8) the express version, using latest MySQL build, on the Sakila database.
As you correct it before in 2011, I assume this is a bug in your ADO.NET connector. We can of course introduce a workaround but I think it's best if this was fixed where it actually goes wrong, as the column is supposed to contain a string (or null), not a byte array.
TIA
(edit) The problem also occurs when fetching a simple resultset using a DbDataAdapter in a datatable, e.g. DESCRIBE `actor` gives a byte[] array for 'Type' while it should be a string. However, I've enabled 'Unicode=true;' in the connection string (or charset=utf8mb4;), but that doesn't have any effect it seems... Assembly used is:
Devart.Data.MySql, Version=8.12.1229.0, Culture=neutral, PublicKeyToken=09af7300eec23701
Using the connector on a mysql 5.6 DB (also sakila), works fine. So it's related to mysql 8 and the latest connector. Same code is used on both mysql dbs so that can't be it.
Small repro:
Code: Select all
using System; using System.Data; using System.Data.Common; using Devart.Data.MySql; namespace mysqltester { internal class Program { public static void Main(string[] args) { using(var con = new MySqlConnection("Server=YOURSERVERHERE;Port=3308;Database=Sakila;User ID=root;Password=YOURROOTPWHERE;Unicode=true;")) { con.Open(); Console.WriteLine("Assembly: {0}", con.GetType().AssemblyQualifiedName); var results = new DataTable(); var adapter = new MySqlDataAdapter("DESCRIBE `actor`", con); adapter.Fill(results); for(int i=0;i<results.Rows.Count;i++) { var r = results.Rows[i]; Console.WriteLine("Field: {0}. Type: {1}", r[0], r[1]); } } } } }
Assembly: Devart.Data.MySql.MySqlConnection, Devart.Data.MySql, Version=8.12.122
9.0, Culture=neutral, PublicKeyToken=09af7300eec23701
Field: actor_id. Type: System.Byte[]
Field: first_name. Type: System.Byte[]
Field: last_name. Type: System.Byte[]
Field: last_update. Type: System.Byte[]
Expected (running DESCRIBE `actor` in Mysql workbench 8)
actor_id smallint(5) unsigned
first_name varchar(45)
last_name varchar(45)
last_update timestamp | https://forums.devart.com/viewtopic.php?f=2&p=132242 | CC-MAIN-2019-04 | refinedweb | 443 | 53.27 |
Agenda
See also: IRC log
<John_Boyer> scribe: Erik
<John_Boyer> scribenick: ebruchez
<John_Boyer>
John: Do we have anything new to mention, it's been a couple of months.
Steven: I will try to see if I see something.
<nick> rest
Steven: There has been some talk about XRX (XForms/REST/XQuery). It is an interesting way of looking at the world. We could gather some of the information that has been produced on this.
John: Regarding Ubiquity, we want to wait a bit more before making a big splash.
<nick>
Steven: I am quite impressed.
John: We have loading time performance to work on. We want accuracy first, speed second.
<Charlie> Paul: the ubiquity files will eventually be compressed which will help load time
Paul: We load lots of small files. That can be improved.
Steven: Re. Input Mode, [...] hoping that Martin will review what I did.
John: Do we need to book a call with Martin?
Steven: First let's see if he responds, then we'll see if we need a call.
John: Next things regards the submission headers fix.
Steven: BTW we need to make sure we refer to XML 4th edition.
<Steven> and namespaces 2e
John: Implementation report progress, Keith, it seems there is something new?
Keith: [...]
... It's hard for the public to access those builds.
<nick> We refer to 'Extensible Markup Language (XML) 1.0 (Fourth Edition)'
John: Would be good to have an implementation report on publicly available software.
<scribe> ACTION: Keith to find out whether latest code changes to Firefox XForms extension can be made public. [recorded in]
<trackbot> Created ACTION-487 - Find out whether latest code changes to Firefox XForms extension can be made public. [on Keith Wells - due 2008-08-20].
John: What about Erik?
Erik: Still would like to do it, but we have been overwhelmed with other tasks.
John: I would like to get one for
Ubiquity as well.
... We absolutely want XForms 1.1 out, so we need the implementation reports.
Charlie: Regarding the Joint Task
Force, [...]
... I am trying to find where we are at with the simplified syntax.
<Charlie>
<Charlie> John: that's current, plus put name attribute on bind to create variables
John: Steven, what about "Sentence about XHTML Modularization"?
Steven: Will make this a higher priority.
John: There was some work by Leigh regarding the XPath function library.
<John_Boyer>
Keith: I just sent an email to the list about the test suite.
John: (going through Keith's
... 5) section 10.3, I made it clearer how the @origin attribute is evaluated (relative to the in-scope evaluation context)
... 6) Changes to the Accept header are in now
<John_Boyer>
John: Paul, in particular, it would be great if you could review that part.
<John_Boyer>
John: Charlie, can you drive us through that spec text?
Charlie: Will need CVS access.
John: Steven and I will make that happen.
Charlie: We want a very minimal
module capturing "data island aspects". You only have the
instance element, @src/@resource.
... Question about common attributes. But there is nothing else in this module.
... Raising the question again about whether this it is a useful level of functionality.
John: I think so.
Charlie: It seems to me that @src should be a common function. We have been back and forth on this.
John: We need the instance
element as a base layer.
... Didn't your recent demo only use this level of data support you have here?
... I.e. you didn't need insert or delete.
... Are we still talking about a separate DOM?
Charlie: See 1.1.2.
... [...]
John: I think one positive aspect of this level of modularization is that it is pointing out at little mistakes, like dispatching xforms-link-exception to the model.
Charlie: Some questions, like what if other modules need to define xforms-link-exception too.
John: It wouldn't be a big issue
if we had to introduce an incompatiblity with
xforms-link-exception as that will stop XForms processing
anyway.
... If you target it at xforms:instance, it will bubble up to the model anyway, if you use a model.
Charlie: Do we need schema functions at this level too?
John: Schema should be in a separate module.
<John_Boyer>
Erik: What about new attributes I proposed to control validation lax/strict and types on xforms:instance? Would we still put this in a separate module?
Charlie: Yes.
John: The schema module will add
to the Model module, so it can add to the data module as
well.
... For now, we keep this as an XML data model. Other needs can be addressed later if demand arises.
... I had this question about modularization and the & character.
[...]
Nick: You need to specify things like xml:base explicitly.
<John_Boyer> common contains foreign namespaced attributes, not just id
<John_Boyer> trying to work out if we need a module for common attributes
Nick: Can't the driver decide whether it allows attributes in a foreign namespace?
John: So as per modularization, we have no choice but to use this "any".
Charlie: Then I will add @id explicitly.
Nick: Then you can't extend the attribute group.
Charlie: But modularization requires this extensibility.
Nick: So I thought we would add commons to all elements.
<nick>
<nick> Common : Core + Events + I18N + Style
Steven: [...] XHTML has a common and a core set.
John: Can we reuse anything from XHTML
<nick> Core xml:space ("default"* | "preserve"), class (NMTOKENS), id (ID), title (CDATA)
<nick> I18N dir ("ltr" | "rtl"), xml:lang (CDATA)
<nick> Events onclick (Script), ondblclick (Script), onmousedown (Script), onmouseup (Script), onmouseover (Script), onmousemove (Script), onmouseout (Script), onkeypress (Script), onkeydown (Script), onkeyup (Script)
<nick> Style style (CDATA)
<nick> Common Core + Events + I18N + Styl
Steven: If a module uses common, then that provides an extension point as well.
John: So I can create a module that extends from common?
Steven: The instance element can
have an attribute set which extends on common.
... You need an extensibility point.
John: We still have a problem understanding how to specify these aspects of modularization with schema.
Steven: The spec is in PR now.
<Steven>
John: I am not finding an example.
Steven: (Sent link to example.)
<Steven>
Charlie: I am looking for the spec text so I know where to put that ampersand.
Steven: (Sent link to example.)
<nick>
John: How do I say in the instance module that I have a attribute group that may be extended by other modules?
Steven: In principle, they are all extensible.
John: But I don't see this for attributes.
<John_Boyer>
Steven: Right, [...]. But I thought we were talking about the schema.
John: We define an instance element. Later, we want to extend. We just write instance&, and we are done?
Steven: Right.
Nick: It's better to have a common attribute group to facilitate the extension.
John: We don't need to have the common attribute on xf:input in order to have the binding attributes, right?
Steven: Correct.
John: Issue is that XHTML common is huge compared to that of XForms.
Steven: True unless you introduce
the host language.
... common is where the host language gets to add stuff.
Nick: I think we need to add common to all elements.
Steven: It has to be the XForms common.
John: How can we then add attributes in no namespace?
Steven: Doesn't everybody allow @class anyway?
John: Maybe because they don't perform runtime validation.
Steven: Attributes without a prefix are in no namespace.
Charlie: So we add common to our list of modules.
Erik: We already allow id on every element in the spec.
This is scribe.perl Revision: 1.133 of Date: 2008/01/18 18:48:51 Check for newer version at Guessing input format: RRSAgent_Text_Format (score 1.00) Succeeded: s/library,/library./ Succeeded: s/separate instance/separate module/ Succeeded: s/right>/right?/ Found Scribe: Erik Found ScribeNick: ebruchez Default Present: Charlie, Nick_van_den_Bleeken, John_Boyer, wellsk, prb, ebruchez, Steven Present: Charlie Nick_van_den_Bleeken John_Boyer wellsk prb ebruchez Steven Regrets: MarkB Kenneth Leigh Rafael Uli Agenda: Got date from IRC log name: 13 Aug 2008 Guessing minutes URL: People with action items: keith WARNING: Input appears to use implicit continuation lines. You may need the "-implicitContinuations" option.[End of scribe.perl diagnostic output] | http://www.w3.org/2008/08/13-forms-minutes.html | crawl-002 | refinedweb | 1,374 | 76.72 |
/************************************************* Distance between points Write a program that readsin two points (x1,y1) and (x2,y2) and prints out the distance between the two points. Write and use a function distance(x1,y1,x2,y2) to help you do this. *************************************************/ #include <iostream> using namespace std; double distance(double,double,double,double); int main() { // Get coordinates char c; double x1, y1, x2, y2; cout << "Enter point 1: "; cin >> c >> x1 >> c >> y1 >> c; cout << "Enter point 2: "; cin >> c >> x2 >> c >> y2 >> c; // Write distance cout << "The distance between the points is " << distance(x1,y1,x2,y2) << endl; return 0; } /*********************************** ** distance between two points ***********************************/ double distance(double x1, double y1, double x2, double y2) { double X = x1 - x2, Y = y1 - y2; return sqrt(X*X + Y*Y); } | https://www.usna.edu/Users/cs/lmcdowel/courses/ic210/F07/classes/class17_TE3_cpp.htm | CC-MAIN-2018-22 | refinedweb | 125 | 52.16 |
There are many ways to start Gazebo, open world models and spawn robot models into the simulated environment. In this tutorial we cover the ROS-way of doing things: using
rosrun and
roslaunch. This includes storing your URDF files in ROS packages and keeping your various resource paths relative to your ROS workspace.
roslaunchto Open World Models
The roslaunch tool is the standard method for starting ROS nodes and bringing up robots in ROS. To start an empty Gazebo world similar to the
rosrun command in the previous tutorial, simply run
roslaunch gazebo_ros empty_world.launch
roslaunchArguments
You can append the following arguments to the launch files to change the behavior of Gazebo:
paused
Start Gazebo in a paused state (default false)
use_sim_time
Tells ROS nodes asking for time to get the Gazebo-published simulation time, published over the ROS topic /clock (default true)
gui
Launch the user interface window of Gazebo (default true)
headless (deprecated) recording (previously called headless)
Enable gazebo state log recording
debug
Start gzserver (Gazebo Server) in debug mode using gdb (default false)
roslaunchcommand
Normally the default values for these arguments are all you need, but just as an example:
roslaunch gazebo_ros empty_world.launch paused:=true use_sim_time:=false gui:=true throttled:=false recording:=false debug:=true
Other demo worlds are already included in the
gazebo_ros package, including:
roslaunch gazebo_ros willowgarage_world.launch roslaunch gazebo_ros mud_world.launch roslaunch gazebo_ros shapes_world.launch roslaunch gazebo_ros rubble_world.launch
Notice in
mud_world.launch a simple jointed mechanism is launched. The launch file for
mud_world.launch contains the following:
<launch> <!-- We resume the logic in empty_world.launch, changing only the name of the world to be launched --> <include file="$(find gazebo_ros)/launch/empty_world.launch"> <arg name="world_name" value="worlds/mud.world"/> <!-- Note: the world_name is with respect to GAZEBO_RESOURCE_PATH environmental variable --> <arg name="paused" value="false"/> <arg name="use_sim_time" value="true"/> <arg name="gui" value="true"/> <arg name="recording" value="false"/> <arg name="debug" value="false"/> </include> </launch>
In this launch file we inherit most of the necessary functionality from
empty_world.launch. The only parameter we need to change is the
world_name
parameter, substituting the
empty.world world file with the
mud.world file.
The other arguments are simply set to their default values.
Continuing with our examination of the
mud_world.launch file, we will now look at the contents of the
mud.world file. The first several components of the mud world is shown below:
<sdf version="1.4"> <world name="default"> <include> <uri>model://sun</uri> </include> <include> <uri>model://ground_plane</uri> </include> <include> <uri>model://double_pendulum_with_base</uri> <name>pendulum_thick_mud</name> <pose>-2.0 0 0 0 0 0</pose> </include> ... </world> </sdf>
See the section below to view this full world file on your computer.
In this world file snippet you can see that three models are referenced. The three models are searched for within your local Gazebo Model Database. If not found there, they are automatically pulled from Gazebo's online database.
You can learn more about world files in the Build A World tutorial.
World files are found within the
/worlds directory of your Gazebo resource path. The location of this path depends on how you installed Gazebo and the type of system your are on. To find the location of your Gazebo resources, use the following command:
env | grep GAZEBO_RESOURCE_PATH
An typical path might be something like
/usr/local/share/gazebo-1.9. Add
/worlds to the end of the path and you should have the directory containing the world files Gazebo uses, including the
mud.world file.
Before continuing on how to spawn robots into Gazebo, we will first go over file hierarchy standards for using ROS with Gazebo so that we can make later assumptions.
For now, we will assume your catkin workspace is named
catkin_ws,
though you can name this to whatever you want.
Thus, your catkin workspace might be located on your computer at something like:
/home/user/catkin_ws/src
Everything concerning your robot's model and description is located,
as per ROS standards, in a package named
/MYROBOT_description
and all the world files and launch files used with Gazebo is located in a ROS package named
/MYROBOT_gazebo. Replace 'MYROBOT' with the name of your bot in lower case letters.
With these two packages, your hierarchy should be as follows:
../catkin_ws/src /MYROBOT_description package.xml CMakeLists.txt /urdf MYROBOT.urdf /meshes mesh1.dae mesh2.dae ... /materials /cad /MYROBOT_gazebo /launch MYROBOT.launch /worlds MYROBOT.world /models world_object1.dae world_object2.stl world_object3.urdf /materials /plugins
Remember that the command
catkin_create_pkg is used for creating new packages,
though this can also easily be adapted for rosbuild if you must.
Most of these folders and files should be self explanatory.
The next section will walk you through making some of this setup for use with a custom world file.
You can create custom
.world files within your own ROS packages that are specific to your robots and packages. In this mini tutorial we'll make an empty world with a ground, a sun, and a gas station. The following is our recommended convention. Be sure to replace MYROBOT with the name of your bot, or if you don't have a robot to test with just replace it with something like 'test':
launchfolder
launchfolder create a YOUROBOT.launch file with the following contents (default arguments excluded):
<launch> <!-- We resume the logic in empty_world.launch, changing only the name of the world to be launched --> <include file="$(find gazebo_ros)/launch/empty_world.launch"> <arg name="world_name" value="$(find MYROBOT_gazebo)/worlds/MYROBOT.world"/> <!-- more default parameters can be changed here --> </include> </launch>
worldsfolder, and create> </world> </sdf>
. ~/catkin_ws/devel/setup.bash roslaunch MYROBOT_gazebo MYROBOT.launch
You should see the following world model (zoom out with the scroll wheel on your mouse):
You can insert additional models into your robot's world file and use the
File->Save As command to export your edited world back into your ROS package.
roslaunchto Spawn URDF Robots
There are two ways to launch your URDF-based robot into Gazebo using
roslaunch:
ROS Service Call Spawn Method
The first method keeps your robot's ROS packages more portable between computers and repository check outs. It allows you to keep your robot's location relative to a ROS package path, but also requires you to make a ROS service call using a small (python) script.
Model Database Method
The second method allows you to include your robot within the
.worldfile, which seems cleaner and more convenient but requires you to add your robot to the Gazebo model database by setting an environment variable.
We will go over both methods. Overall our recommended method is using the '''ROS Service Call Spawn Method'''
This method uses a small python script called
spawn_model to make
a service call request to the
gazebo_ros ROS node
(named simply "gazebo" in the rostopic namespace) to add a custom URDF into Gazebo.
The
spawn_model script is located within the
gazebo_ros package.
You can use this script in the following way:
rosrun gazebo_ros spawn_model -file `rospack find MYROBOT_description`/urdf/MYROBOT.urdf -urdf -x 0 -y 0 -z 1 -model MYROBOT
To see all of the available arguments for
spawn_model including namespaces, trimesh properties, joint positions and RPY orientation run:
rosrun gazebo_ros spawn_model -h
If you do not yet have a URDF to test, as an example you can download the baxter_description package from Rethink Robotics's baxter_common repo. Put this package into your catkin workspace by running:
git clone
You should now have a URDF file named
baxter.urdf located in a within baxter_description/urdf/, and you can run:
rosrun gazebo_ros spawn_model -file `rospack find baxter_description`/urdf/baxter.urdf -urdf -z 1 -model baxter
You should then see something similar to:
To integrate this directly into a ROS launch file, reopen the file
MYROBOT_gazebo/launch/YOUROBOT.launch and add the following before the
</launch> tag:
<!-- Spawn a robot into Gazebo --> <node name="spawn_urdf" pkg="gazebo_ros" type="spawn_model" args="-file $(find baxter_description)/urdf/baxter.urdf -urdf -z 1 -model baxter" />
Launching this file, you should see the same results as when using
rosrun.
If your URDF is not in XML format but rather in XACRO format, you can make a similar modification to your launch file. You can run this PR2 example by installing this package:
ROS Jade:
sudo apt-get install ros-jade-pr2-common
Then adding this to your launch file created previously in this tutorial:
<!--" />
Launching this file, you should see the PR2 in the gas station as pictured:
Note: at this writing there are still a lot of errors and warnings from the console output that need to be fixed from the PR2's URDF due to Gazebo API changes.
The second method of spawning robots into Gazebo allows you to include your robot within the
.world file, which seems cleaner and more convenient but also requires you to add your robot to the Gazebo model database by setting an environment variable. This environment variable is required because of the separation of ROS dependencies from Gazebo; URDF package paths cannot be used directly inside
.world files because Gazebo does not have a notion of ROS packages.
To accomplish this method, you must make a new model database that contains just your single robot. This isn't the cleanest way to load your URDF into Gazebo but accomplishes the goal of not having to keep two copies of your robot URDF on your computer. If the following instructions are confusing, refer back to the Gazebo Model Database documentation to understand why these steps are required.
We will assume your ROS workspace file hierarchy is setup as described in the above sections. The only difference is that now a
model.config file is added to your
MYROBOT_description package like so:
../catkin_ws/src /MYROBOT_description package.xml CMakeLists.txt model.config /urdf MYROBOT.urdf /meshes mesh1.dae mesh2.dae ... /materials /plugins /cad
This hierarchy is specially adapted for use as a Gazebo model database by means of the following folders/files:
Each model must have a model.config file in the model's root directory that contains meta information about the model. Basically copy this into a model.config file, replacing model.urdf with your file name:
<?xml version="1.0"?> <model> <name>MYROBOT</name> <version>1.0</version> <sdf>urdf/MYROBOT.urdf</sdf> <author> <name>My name</name> <email>name@email.address</email> </author> <description> A description of the model </description> </model>
Unlike for SDFs, no version is required for the
Finally, you need to add an environment variable to your .bashrc file that tells Gazebo where to look for model databases.
Using the editor of your choice edit "~/.bashrc".
Check if you already have a
GAZEBO_MODEL_PATH defined.
If you already have one, append to it using a semi-colon, otherwise add the new export.
Assuming your Catkin workspace is in
~/catkin_ws/ Your path should look something like:
export GAZEBO_MODEL_PATH=/home/user/catkin_ws/src/
Now test to see if your new Gazebo Model Database is properly configured by launching Gazebo:
gazebo
And clicking the "Insert" tab on the left. You will probably see several different drop down lists that represent different model databases available on your system, including the online database. Find the database corresponding to your robot, open the sub menu, click on the name of your robot and then choose a location within Gazebo to place the robot, using your mouse.
roslaunchwith the Model Database
The advantage of the model database method is that now you can include your robot directly within your world files, without using a ROS package path. We'll use the same setup from the section "Creating a world file" but modify the world file:
MYROBOT_description/launchfolder, edit> <include> <uri>model://MYROBOT</uri> </include> </world> </sdf>
roslaunch MYROBOT_gazebo MYROBOT.launch
The disadvantage of this method is that your packaged
MYROBOT_description and
MYROBOT_gazebo
are not as easily portable between computers - you first have to set the
GAZEBO_MODEL_PATH
on any new system before being able to use these ROS packages.
The useful info would be the format for exporting model paths from a package.xml:
<export> <gazebo_ros gazebo_model_path="${prefix}/models"/> <gazebo_ros gazebo_media_path="${prefix}/models"/> </export>
The '${prefix}` is something that new users might not immediately know about either, and necessary here.
Also would be useful to have some info on how to debug these paths from the ROS side,
e.g. that you can use
rospack plugins --attrib="gazebo_media_path" gazebo_ros
To check the media path that will be picked up by gazebo.
Now that you know how to create
roslaunch files that open Gazebo, world files and URDF models, you are now ready to create your own Gazebo-ready URDF model in the tutorial Using A URDF In Gazebo | http://gazebosim.org/tutorials/?tut=ros_roslaunch | CC-MAIN-2017-51 | refinedweb | 2,118 | 54.32 |
1. Introduction.
2. The Slab Allocator
The Linux kernel has three main different memory allocators: SLAB, SLUB, and SLOB.
I would note that “slab” means the general allocator design, while SLAB/SLUB/SLOB are slab implementations in the Linux kernel.
And you can use only one of them; by default, Linux kernel uses the SLUB allocator, since 2.6 is a default memory manager when a Linux kernel developer calls kmalloc().
So let’s talk a little bit about these three implementations and describe how they work.
2.1. SLAB allocator
The SLAB is a set of one or more contiguous pages of memory handled by the slab allocator for an individual cache. Each cache is responsible for a specific kernel structure allocation. So the SLAB is set of object allocations of the same type.
The SLAB is described with the following structure:
struct slab { union { struct { struct list_head list; unsigned long colouroff; void *s_mem; unsigned int inuse; /* num of used objects */ kmem_bufctl_t free; unsigned short nodeid; }; struct slab_rcu __slab_cover_slab_rcu; }; };
For example, if you make two allocations of tasks_struct using kmalloc, these two objects are allocated in the same SLAB cache, because they have the same type and size.
Two pages with six objects in the same type handled by a slab cache
2.2. SLUB allocator
SLUB is currently the default slab allocator in the Linux kernel. It was implemented to solve some drawbacks of the SLAB design.
The following figure includes the most important members of the page structure. (Look here to see the full version.)
struct page { ... struct { union { pgoff_t index; /* Our offset within mapping. */ void *freelist; /* slub first free object */ }; ... struct { unsigned inuse:16; unsigned objects:15; unsigned frozen:1; }; ... }; ... union { ... struct kmem_cache *slab; /* SLUB: Pointer to slab */ ... }; ... };
A page’s freelist pointer is used to point to the first free object in the slab. This first free object has another small header, which has another freelist pointer that points to the next free object in the slab, while inuse is used to track of the number of objects that have been allocated.
The figure illustrates that:
The SLUB ALLOCATOR: linked list between free objects.
The SLUB allocator manages many of dynamic allocations/deallocations of the internal kernel memory. The kernel distinguishes these allocations/deallocations by their sizes;
some caches are called general-purpose (kmalloc-192: it holds allocations between 128 and 192 bytes). For example, if you invoke kmalloc to allocate 50 bytes, it creates the chunk of memory from the general-purpose kmalloc-64, because 50 is between 32 and 64.
For more details, you can type “cat /proc/slabinfo.”
/proc/slabinfo has no longer readable by a simple user …, so you should work with the super-user when writing exploits.
2.3. SLOB allocator
The SLOB allocator was designed for small systems with limited amounts of memory, such as embedded Linux systems.
SLOB places all allocated objects on pages arranged in three linked lists.
3. kernel SLUB overflow
Exploiting SLUB overflows requires some knowledge about the SLUB allocator (we’ve described it above) and is one of the most advanced exploitation techniques.
Keep in mind that objects in a slab are allocated contiguously so, if we can overwrite the metadata used by the SLUB allocator, we can switch the execution flow into the user space and execute our evil code. So our goal is to control the freelist pointer,
The freelist pointer, as described above, is a pointer to the next free object in the slab cache. If freelist is NULL, the slab is full, no more free objects are available, and the kernel asks for another slab cache with PAGE_SIZE of bytes (PAGE_SIZE=4096). If we overwrite this pointer with an address of our choice, we can return to a given kernel path an arbitrary memory address (user-land code).
So let’s make a small demonstration and look at this in more practical way. I’ve built a vulnerable device driver that does some trivial input/output interactions with userland processes.
The code:
#include <Linux/init.h> #include <Linux/module.h> #include <Linux/uaccess.h> #include <Linux/cdev.h> #include <Linux/fs.h> #include <Linux/slab.h> #define DEVNAME "vuln" #define MAX_RW (PAGE_SIZE*2) MODULE_AUTHOR("Mohamed Ghannam"); MODULE_LICENSE("GPL v2"); static struct cdev *cdev; static char *ramdisk; static int vuln_major = 700,vuln_minor = 3; static dev_t first; static int count = 1; static int vuln_open_dev(struct inode *inode ,, struct file *file) { static int counter=0; char *ramdisk; printk(KERN_INFO"opening device : %s \n",DEVNAME); ramdisk = kzalloc(MAX_RW,GFP_KERNEL); if(!ramdisk) return -ENOMEM; //file->private_data = ramdisk; printk(KERN_INFO"MAJOR no = %d and MINOR no = %d\n",imajor(inode),iminor(inode)); printk(KERN_INFO"Opened device : %s\n",DEVNAME); counter++; printk(KERN_INFO"opened : %d\n",counter); return 0; } static int vuln_release_dev(struct inode *inode,struct file *file) { printk(KERN_INFO"closing device : %s \n",DEVNAME); return 0; } static ssize_t vuln_write_dev(struct file *file ,,const char __user *buf,size_t lbuf,loff_t *ppos) { int nbytes,i; char *copy; char *ramdisk = kzalloc(lbuf,GFP_KERNEL); if(!ramdisk) return -ENOMEM; copy = kmalloc(256 ,, GFP_KERNEL); if(!copy) return -ENOMEM; if ((lbuf+*ppos) > MAX_RW) { printk(KERN_WARNING"Write Abbort \n"); return 0; } nbytes = lbuf - copy_from_user(ramdisk+ *ppos ,, buf,lbuf); ppos += nbytes; for(i=0;i<0x40;i++) copy[i]=0xCC; memcpy(copy,ramdisk,lbuf); printk("ramdisk : %s \n",ramdisk); printk("Writing : bytes = %d\n",(int)lbuf); return nbytes; } static ssize_t vuln_read_dev(struct file *file ,,char __user *buf,size_t lbuf ,,loff_t *ppos) { int nbytes; char *ramdisk = file->private_data; if((lbuf + *ppos) > MAX_RW) { printk(KERN_WARNING"Read Abort \n"); return 0; } nbytes = lbuf - copy_to_user(buf,ramdisk + *ppos ,, lbuf); *ppos += nbytes; return nbytes; } static struct file_operations fps = { .owner = THIS_MODULE, .open = vuln_open_dev, .release = vuln_release_dev, .write = vuln_write_dev, .read = vuln_read_dev, }; static int __init vuln_init(void) { ramdisk = kmalloc(MAX_RW,GFP_KERNEL); first = MKDEV(vuln_major,vuln_minor); register_chrdev_region(first,count,DEVNAME); cdev = cdev_alloc(); cdev_init(cdev,&fps); cdev_add(cdev,first,count); printk(KERN_INFO"Registring device %s\n",DEVNAME); return 0; } static void __exit vuln_exit(void) { cdev_del(cdev); unregister_chrdev_region(first,count); kfree(ramdisk); } module_init(vuln_init); module_exit(vuln_exit)
Let’s describe a little bit what the code does: This is a dummy kernel model that creates a character device, “/dev/vuln,” and makes some basic I/O operations.
The bug is obvious to spot.
In the vuln_write_dev() function, we notice that the ramdisk variable is used to store the user input and it’s allocated safely with lbuf, which is the length of user input. Then it will be copied into the copy variable, which is kmalloc’ed with 256 bytes. So it is easy to spot that there is a heap SLUB overflow if a user writes data greater in size than 256 bytes.
First you should download the lab of this article. It is a qemu archive system containing the kernel module, the proof of concept, and the final exploit.
Let’s trigger the bug first:
So we’ve successfully overwritten the freelist pointer for the next free object.
If we overwrite this freelist metadata with the address of a userland function, we can run our userland function inside the kernel space; thus we can hijack root privileges and drop the shell after.
I forgot to mention that there are three categories of the slab caches: full slab, partial slab, and empty slab.
Full slab: The slab cache is fully allocated and doesn’t contain any free chunks so its freelist equals NULL.
Partial slab: The slab cache contains free and allocated chunks and is able to allocate other chunks.
Empty slab: The slab cache doesn’t have any allocation, so all chunks are free and ready to be allocated.
4. Building the exploit
So the problem is that, when the attacker wants to overwrite a freelist pointer, he must take care of the slab’s situation and it should be either a full slab or an empty slab. He also needs to make sure that the next freelist pointer is the right target.
So we have 256 bytes allocated with kmalloc, so we should take a look at /proc/slabinfo and gather some useful information about the general-purpose kmalloc-256. The next step is to make a comparison between the free objects and used objects in the slab cache and then we have to fill them and make the slab full to ensure that the kernel will create a fresh slab.
To do that we have to figure out some ways to make allocations in the general purpose “kmalloc-256,”, and we find that a good target for this is struct file kernel structure. Since we can’t allocate it directly from the user space, we can do it by calling some syscalls to do it for us, such as open(), socket(), etc.
Calling these kinds of functions allows us to make some struct file allocations and that’s good for an attacker’s purpose.
As we described earlier, we should ensure that there are no more free chunks for the current slab, so we have to make a lot of struct file allocations:
for(i=0;i<1000;i++) socket(AF_INET,SOCK_STREAM,0);
Good, so take a look again at the slab cache. The next thing to do is to trigger the crash. If we write an amount of data greater than 256 bytes, we will definitely overwrite the next free list pointer to let the kernel execute some userspace codes of our choice.
So how does the userland code get to be executed in the kernel land ?
We have to look for function pointers and we are glad to see that struct file contains struct file_operations containing a function pointer.
Our attack is shown below:
struct file { .f_op = struct file_operations = { .fsync = ATTACKER_ADDRESS, }; };
As you see, you there are a lot of function pointers and you can choose any one you want. But how can we put this “ATTACKER_ADDRESS” ? The idea is to build a new fake struct file and put its address in the payload, so the freelist will be overwritten by the address of our fake struct file; thus the freelist points into our fake struct file and it assumes that it’s the next free object, so we are moving the control flow into the userspace. This is a powerful technique.
When the attacker calls fsync(2) syscall, the ATTACKER_ADDRESS will be executed instead of the real fsync operation. Good, so we can execute our userland code, but how can we get root privileges ? It’s very easy to get root by calling:
commit_creds(prepare_kernel_cred(0));
The final exploit is like this:
#include <arpa/inet.h> #include #include #include <netinet/in.h> #include #include #include #include #include <sys/socket.h> #include <sys/utsname.h> #include <sys/stat.h> #include <sys/types.h> #include #include #define BUF_LEN 256 struct list_head { struct list_head *prev,*next; }; struct path { void *mnt; void *dentry; }; struct file_operations { void *owner; void *llseek; void *read; void *write; void *aio_read; void *aio_write; void *readdir; void *poll; void *unlocked_ioctl; void *compat_ioctl; void *mmap; void *open; void *flush; void *release; void *fsync; void *aio_fsync; void *fasync; void *lock; void *sendpage; void *get_unmapped_area; void *check_flags; void *flock; void *splice_write; void *splice_read; void *setlease; void *fallocate; void *show_fdinfo; } op; struct file { struct list_head fu_list; struct path f_path; struct file_operations *f_op; long int buf[1024]; } file; typedef int __attribute__((regparm(3))) (* _commit_creds)(unsigned long cred); typedef unsigned long __attribute__((regparm(3))) (* _prepare_kernel_cred)(unsigned long cred); _commit_creds commit_creds; _prepare_kernel_cred prepare_kernel_cred; int win=0; static)) { printf("[+]; } int getroot(void) { win=1; commit_creds(prepare_kernel_cred(0)); return -1; } int main(int argc,char ** argv) { char *payload; int payload_len; void *ptr = &file; payload_len = 256+9; payload = malloc(payload_len); if(!payload){ perror("malloc"); return -1; } memset(payload,'A',payload_len); memcpy(payload+256,&ptr,sizeof(ptr)); payload[payload_len]=0; int fd = open("/dev/vuln",O_RDWR); if(fd == -1) { perror("open "); return -1; } commit_creds = (_commit_creds)get_kernel_sym("commit_creds"); prepare_kernel_cred = (_prepare_kernel_cred)get_kernel_sym("prepare_kernel_cred"); int i; for(i=0;i<1000;i++){ if(socket(AF_INET,SOCK_STREAM,0) == -1){ perror("socket fill "); return -1; } } write(fd,payload,payload_len); int target_fd ; target_fd = socket(AF_INET,SOCK_STREAM,0); target_fd = socket(AF_INET,SOCK_STREAM,0); file.f_op = &op; op.fsync = &getroot; fsync(target_fd); pid_t pid = fork(); if (pid == 0) { setsid(); while (1) { sleep(9999); } } printf("[+] rooting shell ...."); close(target_fd); if(win){ printf("OK\n[+] Droping root shell ... \n"); execl("/bin/sh","/bin/sh",NULL); }else printf("FAIL \n"); return 0; }
Let’s run the code:
Bingo!
5. Conclusion
We have studied how the kernel SLUB works and how we can get privileges. Exploiting kernel vulnerabilities is not so different than userspace, but the kernel exploit development requires strong knowledge of how the kernel works, its routines, how it protects against race conditions, etc.
It was very fun to play with these kind of bugs, as there are not a whole lot of modern, public example s of SLUB overflow exploits.
Here some references that might help you:
Linux Kernel CAN SLUB Overflow
A Guide to Kernel Exploitation: Attacking the Core
PlaidCTF2013 servr CTF challenge
Exploit Linux Kernel Slub Overflow | http://resources.infosecinstitute.com/exploiting-linux-kernel-heap-corruptions-slub-allocator/ | CC-MAIN-2017-17 | refinedweb | 2,157 | 50.87 |
Hi, I'm not 100% confident on the following terms. I've seen them
used alot and never knew exactly knew what they meant,
so I continued to think of things like "point to this",
"follow the pointer to that" etc. But now that I have a better
understanding of how pointers work I'd like to know what exactly
it means when these terms are used.
Passing by value.
Passing by reference.
Dereference.
Direct Reference.
Indirect Reference.
Here is some sample code, are my
Also am I correct in assuming that an indirect reference to aAlso am I correct in assuming that an indirect reference to aCode:#include <stdio.h> #include <stdlib.h> void func1(int *pointer); void func2(int array[]); void func3(int number); int main(void) { int my_array[1000]; int variable = 10; int *x; x = malloc(sizeof(int)); /* Is this considered dereferencing *x? */ *x = 99; free(x); /* Passing by reference? */ func1(&variable); func2(my_array); /* Passing by Value? */ func3(variable); return (0); } void func1(int *pointer) { int value = 5; /* Dereferencing *pointer? */ *pointer = value; } void func2(int array[]) { int subscript = 0; /* Dereferencing array? */ array[subscript] = 15; } void func3(int number) { /* Is this a direct reference to number? */ number = 10; }
variable is the same thing as dereferencing the pointer that
points to its address? Like...
Again any help would be great, the book I'm reading doesn'tAgain any help would be great, the book I'm reading doesn'tCode:int *x; int y = 10; x = &y; /*Dereferencing *x and also an indirect reference to y? */ *x = 15;
use any of these terms, these are just terms
I've heard used on IRC and on the boards sometimes. | http://cboard.cprogramming.com/c-programming/35573-pointer-terminology-question.html | CC-MAIN-2015-32 | refinedweb | 278 | 64 |
- Tutoriels
- 2D Roguelike tutorial
- Writing the Enemy Script
Writing the Enemy Script
Vérifié avec version: 5
-
Difficulté: Intermédiaire
This is part 10 of 14 of the 2D Roguelike tutorial in which we write the Enemy script which will control the enemies movement and AI.
Writing the Enemy Script
Intermédiaire 2D Roguelike tutorial
Transcriptions
- 00:02 - 00:05
In this video we're going to write the script for our enemies.
- 00:06 - 00:09
In our Scripts folder we're going to go to Create -
- 00:10 - 00:13
C# script and we'll call it Enemy.
- 00:13 - 00:15
Let's open it up in Monodevelop.
- 00:17 - 00:19
The first thing that we're going to do in our Enemy class
- 00:19 - 00:21
is to set it to inherit from
- 00:21 - 00:23
our MovingObject class.
- 00:23 - 00:27
You'll remember we wrote MovingObject in a previous video.
- 00:27 - 00:30
By causing Enemy to inherit from MovingObject
- 00:30 - 00:32
it means that we can have it take advantage
- 00:32 - 00:35
of the movement code that we wrote there
- 00:35 - 00:37
without having to duplicate that functionality
- 00:37 - 00:39
within the Enemy class.
- 00:39 - 00:41
Next we're going to declare some variables.
- 00:41 - 00:45
We're going to start with a public integer called playerDamage.
- 00:45 - 00:47
This is the number of food points that are going to
- 00:47 - 00:50
be subtracted when the enemy attacks the player.
- 00:51 - 00:53
We're also going to declare some private variables
- 00:53 - 00:57
starting with a private variable of the type Animator
- 00:57 - 00:58
called animator.
- 00:58 - 01:00
We're also going to declare a private variable of the
- 01:00 - 01:02
type Transform called target,
- 01:02 - 01:05
which we're going to use to store the player's position,
- 01:05 - 01:08
and tell the enemy where to move towards.
- 01:08 - 01:11
We're also going to have a private boolean called skipMove
- 01:11 - 01:13
which we're going to use to cause the enemy
- 01:13 - 01:15
to move every other turn.
- 01:16 - 01:18
We're going to change our start function to a
- 01:18 - 01:21
protected override function because we're going to
- 01:21 - 01:25
override the start function in our base class MovingObject.
- 01:25 - 01:27
The first thing we're going to do in our start function
- 01:27 - 01:31
is we're going to get and store a component reference to our animator.
- 01:32 - 01:36
We're going to use GameObject.findGameObjectWithTag
- 01:36 - 01:38
to store the transform of the player
- 01:38 - 01:40
in our target variable.
- 01:41 - 01:44
Finally we're going to call the start function
- 01:44 - 01:46
in our base class MovingObject.
- 01:47 - 01:49
Enemy is also going to have it's
- 01:49 - 01:51
own implementation of AttemptMove
- 01:52 - 01:54
and so we're going to declare AttemptMove
- 01:54 - 01:57
again as a protected override function
- 01:57 - 01:59
that returns void.
- 01:59 - 02:02
As before, AttemptMove takes a generic parameter T,
- 02:02 - 02:05
in this case we're going to parse in the player component
- 02:05 - 02:08
because that's what we expect the enemy to be interacting with.
- 02:08 - 02:10
The first thing that we're going to do inside AttemptMove
- 02:10 - 02:13
is to check if skipMove is true.
- 02:13 - 02:15
So to see if this turn the enemy should
- 02:15 - 02:17
be skipping a turn,
- 02:17 - 02:20
if so we're going to set skipMove to false and return.
- 02:21 - 02:23
This is what we're going to use to cause our
- 02:23 - 02:26
enemy to only move every other turn.
- 02:27 - 02:30
Next we're going to call the AttemptMove function
- 02:30 - 02:32
from MovingObject.
- 02:32 - 02:35
When calling AttemptMove we're going to parse in
- 02:35 - 02:38
our generic parameter T, which in this case will be the player,
- 02:39 - 02:44
along with the parameters for the xDir and yDir to move in.
- 02:45 - 02:47
Now that the enemy is moved we're going to
- 02:47 - 02:49
set skipMove to true.
- 02:49 - 02:51
The next thing that we're going to do is declare a
- 02:51 - 02:54
public function that returns void called MoveEnemy.
- 02:54 - 02:56
This is going to be called by the GameManager
- 02:56 - 02:58
when it issues the order to move
- 02:58 - 03:01
to each of our enemies in our Enemies list.
- 03:01 - 03:03
In MoveEnemy we're going to declare a couple of
- 03:03 - 03:08
integer variables xDir and yDir and initialise those to 0.
- 03:09 - 03:11
The next thing that we're going to do is we're going to check
- 03:11 - 03:13
the position of Target
- 03:13 - 03:16
against the current position of our transform
- 03:16 - 03:19
and figure our which direction to move in.
- 03:19 - 03:21
What we're going to do is we're going to check
- 03:21 - 03:25
if the difference between the X coordinate
- 03:25 - 03:27
of target's position
- 03:27 - 03:30
and the X coordinate of transform's position
- 03:31 - 03:35
is less than Epsilon, in this case which we're using to represent
- 03:35 - 03:36
a number close to 0.
- 03:36 - 03:38
So basically we're checking to see
- 03:39 - 03:42
are the X coordinates roughly the same,
- 03:42 - 03:45
meaning our enemy and our player
- 03:45 - 03:48
are in the same column.
- 03:48 - 03:50
If they are on the same column we're going to check
- 03:50 - 03:53
if the Y coordinate of our target's position
- 03:54 - 03:56
is greater than the Y coordinate
- 03:56 - 03:58
of our transform position.
- 03:58 - 04:00
If so we're going to move up,
- 04:00 - 04:02
meaning move towards the player
- 04:02 - 04:04
and if not we're going to move down,
- 04:04 - 04:06
to move towards the player.
- 04:06 - 04:08
So in this case if our condition
- 04:08 - 04:10
evaluates to true we're going to use
- 04:10 - 04:13
1, meaning we're going to move up
- 04:13 - 04:15
otherwise we're going to use -1,
- 04:15 - 04:17
meaning we're going to move down.
- 04:17 - 04:19
If our first conditional check to check
- 04:19 - 04:22
if we're in the same column evaluates to false
- 04:22 - 04:25
we're going to move along the horizontal axis.
- 04:26 - 04:29
To do this we're going to set xDir
- 04:29 - 04:33
based on if target's position.x
- 04:33 - 04:36
is greater than our transform position.x
- 04:37 - 04:39
we're going to move to the right
- 04:39 - 04:41
using 1, a positive value.
- 04:41 - 04:44
Otherwise we're going to move to the left using -1.
- 04:45 - 04:48
With that done we're going to call AttemptMove
- 04:48 - 04:51
parsing in Player as the generic parameter
- 04:51 - 04:55
and parsing in our xDir and our yDir to move in.
- 04:56 - 04:58
The last thing that we're going to do it we're going to
- 04:58 - 05:00
write our OnCantMove function.
- 05:00 - 05:02
OnCantMove is called if the enemy attempts
- 05:02 - 05:05
to move in to a space occupied by the player.
- 05:06 - 05:09
It overrides the OnCantMove function of MovingObject
- 05:09 - 05:12
which you'll remember we implemented as abstract.
- 05:13 - 05:15
It takes a generic parameter T
- 05:15 - 05:17
which we use to parse in the component we
- 05:17 - 05:20
expect to encounter, which in this case is a player.
- 05:21 - 05:24
OnCantMove takes a parameter of the type T
- 05:25 - 05:26
called component.
- 05:26 - 05:28
The first thing that we're going to do in OnCantMove
- 05:28 - 05:31
is declare a variable of the type Player
- 05:31 - 05:33
called hitPlayer,
- 05:33 - 05:35
and we're going to set that to equal the
- 05:35 - 05:37
component that we parsed in
- 05:37 - 05:39
which we're going to cast to a player.
- 05:39 - 05:43
Next we're going to call the LoseFood function from Player
- 05:44 - 05:47
parsing in playerDamage which is going to be the loss
- 05:47 - 05:51
parameter for LoseFood and specify how many food
- 05:51 - 05:54
points to subtract from the player's total
- 05:54 - 05:55
based on this enemy's attack.
- 05:56 - 05:58
Let's clean up our script a bit by deleting
- 05:58 - 06:00
the update function and the comment for start.
- 06:04 - 06:06
Now that we've got our Enemy script written
- 06:06 - 06:08
in the next video we're going to make some
- 06:08 - 06:10
additions to the Game Manager so that
- 06:10 - 06:13
it can manage the enemies, and we're also going to setup
- 06:13 - 06:16
our enemy animator controller.
Enemy
Code snippet
using UnityEngine; using System.Collections; //Enemy inherits from MovingObject, our base class for objects that can move, Player also inherits from this. public class Enemy : MovingObject { public int playerDamage; //The amount of food points to subtract from the player when attacking. private Animator animator; //Variable of type Animator to store a reference to the enemy's Animator component. private Transform target; //Transform to attempt to move toward each turn. private bool skipMove; //Boolean to determine whether or not enemy should skip a turn or move this turn. //Start overrides the virtual Start function of the base class. protected override void Start () { //Register this enemy with our instance of GameManager by adding it to a list of Enemy objects. //This allows the GameManager to issue movement commands. GameManager.instance.AddEnemyToList (this); //Get and store a reference to the attached Animator component. animator = GetComponent<Animator> (); //Find the Player GameObject using it's tag and store a reference to its transform component. target = GameObject.FindGameObjectWithTag ("Player").transform; //Call the start function of our base class MovingObject. base.Start (); } //Override the AttemptMove function of MovingObject to include functionality needed for Enemy to skip turns. //See comments in MovingObject for more on how base AttemptMove function works. protected override void AttemptMove <T> (int xDir, int yDir) { //Check if skipMove is true, if so set it to false and skip this turn. if(skipMove) { skipMove = false; return; } //Call the AttemptMove function from MovingObject. base.AttemptMove <T> (xDir, yDir); //Now that Enemy has moved, set skipMove to true to skip next move. skipMove = true; } //MoveEnemy is called by the GameManger each turn to tell each Enemy to try to move towards the player. public void MoveEnemy () { //Declare variables for X and Y axis move directions, these range from -1 to 1. //These values allow us to choose between the cardinal directions: up, down, left and right. int xDir = 0; int yDir = 0; //If the difference in positions is approximately zero (Epsilon) do the following: if(Mathf.Abs (target.position.x - transform.position.x) < float.Epsilon) //If the y coordinate of the target's (player) position is greater than the y coordinate of this enemy's position set y direction 1 (to move up). If not, set it to -1 (to move down). yDir = target.position.y > transform.position.y ? 1 : -1; //If the difference in positions is not approximately zero (Epsilon) do the following: else //Check if target x position is greater than enemy's x position, if so set x direction to 1 (move right), if not set to -1 (move left). xDir = target.position.x > transform.position.x ? 1 : -1; //Call the AttemptMove function and pass in the generic parameter Player, because Enemy is moving and expecting to potentially encounter a Player AttemptMove <Player> (xDir, yDir); } //OnCantMove is called if Enemy attempts to move into a space occupied by a Player, it overrides the OnCantMove function of MovingObject //and takes a generic parameter T which we use to pass in the component we expect to encounter, in this case Player protected override void OnCantMove <T> (T component) { //Declare hitPlayer and set it to equal the encountered component. Player hitPlayer = component as Player; //Call the LoseFood function of hitPlayer passing it playerDamage, the amount of foodpoints to be subtracted. hitPlayer.LoseFood (playerDamage); //Set the attack trigger of animator to trigger Enemy attack animation. animator.SetTrigger ("enemyAttack"); } }
Tutoriels apparentés
- Inheritance (Cours)
- Scripting Primer and Q&A (Cours) | https://unity3d.com/fr/learn/tutorials/projects/2d-roguelike-tutorial/writing-enemy-script?playlist=17150 | CC-MAIN-2019-35 | refinedweb | 2,252 | 55.47 |
@stevebaer and @Alain
I’m feeling tremendously stupid, because I can’t get EditPythonScript to work.
I did the following in the daily build of Trunk V6
Run EditPythonScript
Type this script:
import Rhino
d = Rhino.RhinoDoc.ActiveDoc
for object in d.Objects:
pass
I put a break point in the “pass” line.
Then I clicked the green Play button.
the EditPythonScript window disappeared
I brought it back up, and couldn’t tell what was going on. I couldn’t tell if the debugger was stopped on a breakpoint, or if it was done debugging. I couldn’t edit the text, so I assumed it was debugging.
I then clicked Stop. Nothing seemed to change.
Then I closed EditPythonScript by clicking the red X. Rhino asked if I wanted to stop debugging; I clicked Yes, and the window stayed open. I closed it again.
Opening EditPythonScript, I still can’t edit the script.
What’s going on? | https://discourse.mcneel.com/t/editpythonscript-broken/8630 | CC-MAIN-2020-45 | refinedweb | 157 | 78.45 |
Invisible and unselectable flow region in image
Bug Description
I created a PDF with XFig and imported it into Inkscape 0.46 (running on a Mac under OS X 10.5.6, Xquartz 2.1.5 - (xorg-server 1.3.0-apple22) (2.1.5)).
When I uploaded to Wikimedia commons, I noticed a black rectangle; see various versions on http://
I tried various proposed fixes I found on Google: selecting and converting to text; selecting and converting to path.
It took a helpful commons user to find out that the file contains an empty, invisible, unselectable flow region that caused the problem. He or she removed the region using a text editor.
Could be a duplicate - I was thrown off by the fact that in my case, I imported the image, whereas the other bug involved an original Inkscape drawing. But the apparently empty flowRoot regions look the same. Thanks!
The 'un-selectability' of empty 'Flowed Text' objects might have a common cause with bug #349602 “Textbox is unselectable after text is overflowed by empty lines.”
They can be created accidentally in Inkscape with the text tool: draw a rectangle (maybe thinking you're still using the select tool), don't enter any text, click somewhere else on the canvas and the textbox disappears but leaves a unvisible svg:FlowRoot element behind (watch it happening with the XML editor open) - see question "Black blocks appear on the image when I open an SVG file with Firefox." <https:/
OK, that could be it. I'm rather new to Inkscape, and could well have created empty text boxes in the way you describe. Thanks for the info!
Another workaround to find empty 'Flowed text' objects:
1) 'Edit > 'Flowed Text' object
5) continue with <TAB> until the first text object is selected again
Both issue as reported and workaround reproduced with Inkscape 0.46+devel r22575 on OS X 10.5.8.
Confirming this as bug because empty flowed text boxes should not be left behind invisible and barely selectable regardless of whether the flowed text object (svg:flowRoot containing svg:flowRegion and svg:flowPara) is part of the current SVG specification or is (not) recognized by other SVG viewers.
Thank you for the additional workaround!
Alternative steps to select all 'Flowed Text' objects (empty or not):
1) open 'Edit > Find…'
2) enter 'flowRoot' into the 'ID:' field
3) search
The resulting selection contains all 'Flowed text' objects which then can be deleted or converted to regular text (shift-click those you want to keep as 'Flowed Text' to remove them from the selection).
Duplicate of Bug #167335 (flowed text (flowRoot) must be moved to inkscape namespace )? | https://bugs.launchpad.net/inkscape/+bug/485269 | CC-MAIN-2014-15 | refinedweb | 445 | 58.52 |
Stephane Bortzmeyer wrote: > I'm trying to use Parsec for a language which have identifiers where > the '-' character is allowed only inside identifiers, not at the start > or the end. > > identifier = do > start <- letter > rest <- many (alphaNum <|> char '-') > end <- letter > return ([start] ++ rest ++ [end]) > <?> "characters authorized for identifiers" identifier = do start <- letter rest <- many (alphaNum <|> try inner_minus) return $ start : rest where inner_minus = do char '-' lookAhead alphaNum return '-' > because the parser created by "many" is greedy: it consumes > everything, including the final letter. Yes, it does. You could implement you own non-greedy many combinator, but you get the associated inefficiency. Or you could use ReadP, which doesn't have this problem (but replaces it with other surprises). Udo. -- Eagles may soar but weasels don't get sucked into jet engines. -- Steven Wright -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 189 bytes Desc: Digital signature Url : | http://www.haskell.org/pipermail/haskell-cafe/2006-September/017852.html | CC-MAIN-2014-15 | refinedweb | 154 | 54.93 |
On Sunday 20 June 2010 9:24:54 pm Alexander Solla This is not what recursive do does. For instance: do rec l <- (:l) <$> getChar return l will read one character, and return an infinite list with that character as the elements. By contrast: let l = (:) <$> getChar <*> l in l will, for one, never complete, and two, call getChar an infinite number of times. In general, it is based on the fixed point: mfix :: (MonadFix m) => (a -> m a) -> m a where the function given may not be separable into a pure function and return at all, which is what would be necessary to implement using let, via the identity: mfix (return . f) = return (fix f) The implementation of mfix is specific to the 'm' in question, not something you can write for all monads. -- Dan | http://www.haskell.org/pipermail/haskell-cafe/2010-June/079190.html | CC-MAIN-2014-15 | refinedweb | 136 | 61.19 |
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Movement of user causes AI to lag
john price
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Joined: Feb 24, 2011
Posts: 495
I like...
posted
Oct 12, 2011 00:36:26
0
I started writing a game 2 days ago. It is a simple platform game. There are 3 platforms total : a "floor" and 2 "floating ramps". On the ground, between the "floating ramps", there is a "coin". On the second floating ramp, there is another "coin". You can pick up the coins. On the first floating ramp, there is a "gun". If you pick up the "gun", you can "shoot" "bullets". Only one "bullet" by the user is allowed to be shot at one time. The user can physically control the object (cube, box, etc) with the arrow buttons. Up physically moves the object up a certain distance. Moving to the right causes the world to move left. Moving to the left causes the world to move right. You may destroy 2 "targets" with the "bullets" if you have picked up the "gun". If the "targets" are "destroyed", an AI "character" (box, cube, etc) comes running at a constant speed to the left. It spits out a stream of "bullets". If the user destroys the AI "character", the character disappears along with its bullets. The only issue is when the character moves while the AI character is still "alive" and shooting "bullets". The character's location algorithm is composed of this :
enemy1 = new Ellipse2D.Double(screenX + 1250 - walked, 360, 30, 30); //screenX = 0 - userInputToLeftAndRight //1250 = offset of character's advance //walked = amount of spaces walked already //360 = irrelevant (it's on the ground) //30 = irrelevant (it has 30 width) //30 = irrelevant (it has 30 height)
When a user pushes the left or right arrow on their keyboard, a timer starts :
moveLeft = new Timer(20, new ActionListener() { public void actionPerformed(ActionEvent e) { moving = true; screenX += 5; repaint(); } }); moveRight = new Timer(20, new ActionListener() { public void actionPerformed(ActionEvent e) { moving = true; screenX -= 5; repaint(); } });
These continue until the user stops holding down the key.
This is what happens when the AI "walks" (it walks if it is still "alive") :)); //Problem code } else { enemyBullets.remove(point); enemyBullets.put(new Point((int)point.getX() - 10, (int)point.getY()), howFarTraveled + 10); } } repaint(); } }); enemyShoot.setRepeats(false); enemyWalk = new Timer(20, new ActionListener() { public void actionPerformed(ActionEvent e) { walked += 3; enemyShoot.start(); repaint(); } });
I have marked what I believe to be the problem line above. I have tried changing the timer on the "enemyShoot" timer and it doesn't affect the problem. If a user is "running" full to the left, the "bullets" go out as far as they should. If a user is stopped, the "bullet's" path is shorter. If a user is "running" full to the right, the "bullets" start moving to the right at lower timer intervals (around 20 it is noticeably going to the left). I was wondering how to fix this problem. To me, it just seems like the lag of the repaint and the refreshing of the bullets. I would like the bullets to be consistently going to the right.
Here is the keyEvent info for left and right arrows :
case KeyEvent.VK_LEFT : if (!moving) { moveLeft.start(); repaint(); } break; case KeyEvent.VK_RIGHT : if (!moving) { moveRight.start(); repaint(); } break;
Here is the release key code :
public void keyReleased(KeyEvent x) { switch (x.getKeyCode()) { case KeyEvent.VK_RIGHT : moveRight.stop(); moving = false; break; case KeyEvent.VK_LEFT : moveLeft.stop(); moving = false; break; } } });
The AI's bullet display system is the same as the character's bullet display system :
for (Point point : bulletTracker.keySet()) { bullet = new Rectangle2D.Double(point.x, point.y + 10, 10, 5); //user's "bullet" g2.fill(bullet); if (bullet.intersects(rec1)) { //rec1 = user life --; } } for (Point point : enemyBullets.keySet()) { Rectangle2D enemyBullet = new Rectangle2D.Double(point.x, point.y, 10, 5); //AI's "bullet" g2.fill(enemyBullet); if (enemyBullet.intersects(rec1)) {// rec1 = user life --; } }
Thanks,
John Price
EDIT : So, to restate my question... I would like a solution or help to finding a solution to fix the problem of the movement of the user causing the AI's "bullets" to not be consistent.
EDIT(2) : Please note that the AI movement isn't lagging. It is the "bullets" that the AI shoots.
Oct 12, 2011 12:09:10
0
I found a solution. It was so simple. Instead of calculating it off of the previous point, which may be outdated, recalculate it based off of the AI character's position as you did in the first place, subtracting the amount of distance traveled :)); } else { enemyBullets.remove(point); //enemyBullets.put(new Point((int)point.getX() - 10, (int)point.getY()), howFarTraveled + 10); enemyBullets.put(new Point((int)enemy1.getBounds().x - howFarTraveled - 10, (int)enemy1.getBounds().y + 10), howFarTraveled + 10); } } repaint(); } });
Thanks,
John Price
EDIT : Although there is still some inconsistency when the user is running right or left (bullet stream is slower, but further when the user runs left and faster, but closer when the user runs right), it is much better than before. If anybody can give me a solution to how to make the algorithm better, that would be awesome.
Akhilesh Trivedi
Ranch Hand
Joined: Jun 22, 2005
Posts: 1526
posted
Oct 14, 2011 03:05:28
0
john price wrote:
...a solution to how to make the algorithm better, that would be awesome.
Will threading work?
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john price
Ranch Hand
Joined: Feb 24, 2011
Posts: 495
I like...
posted
Oct 14, 2011 16:49:30
0
Could you show me what you are talking about (IE an example)?
Thanks,
John Price
Randall Twede
Ranch Hand
Joined: Oct 21, 2000
Posts: 4340
2
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posted
Dec 22, 2011 11:13:12
0
using threads is certainly something you should think about. i will post an old homework assignment that will demonstrate for you.
/* * Horserace.java * Program to simulate a horserace * Created on February 24, 2004, 11:02 AM */ /** * * Randall Twede */ import java.awt.*; import java.awt.event.*; import javax.swing.*; public class Horserace extends JFrame implements ItemListener, ActionListener { private JPanel topControls = new JPanel(); private JPanel leftControls = new JPanel(); private Box santaAnita = Box.createVerticalBox(); private JTextArea results = new JTextArea(9, 40); private JButton start = new JButton("Start"); private JButton reset = new JButton("Reset"); private JRadioButton selected = new JRadioButton(); private JRadioButton optionsArray[] = new JRadioButton[8]; ButtonGroup optionsGroup = new ButtonGroup(); private Horse[] horses = new Horse[8]; private Thread[] threads = new Thread[8]; private String finished[] = new String[8]; private String chosenHorse = ""; private int place = 0; // Incremented time a horse calls postResults() /** Creates a new instance of Horserace */ public Horserace() { setTitle("Horserace"); Container c = getContentPane(); c.setLayout(new BorderLayout()); initComponents(); c.add(topControls, "North"); c.add(leftControls, "West"); c.add(santaAnita, "Center"); c.add(results, "South"); } // Improves readability of the constructor for this Class private void initComponents() { String labels[] = {"Seabiscuit", "Man O' War", "Native Dancer", "Secretariat", "Citation", "Seattle Slew", "Ruffian", "Cigar"}; // Initialize the top Jpanel start.addActionListener(this); reset.addActionListener(this); topControls.add(start); topControls.add(reset); // Initialize the left Jpanel leftControls.setLayout(new GridLayout(8, 1)); for(int i = 0; i < optionsArray.length; i++) { optionsArray[i] = new JRadioButton(labels[i]); leftControls.add(optionsArray[i]); optionsArray[i].addItemListener(this); optionsGroup.add(optionsArray[i]); } optionsArray[0].setSelected(true); selected = optionsArray[0]; // sets the default selection to Seabiscuit chosenHorse = selected.getLabel(); // Initialized the center JPanel for (int i = 0; i < horses.length; i++) { horses[i] = new Horse(labels[i], this); santaAnita.add(horses[i]); } } // Displays the results of the race public synchronized void postResults(String name) { finished[place] = name; // Add the horse's name to the array place++; // Increment the array index if(place == 8) // All the horses havea finished { String finish[] = {"first", "second", "third", "fourth", "fifth", "sixth", "seventh", "last"}; if(finished[0].equals(chosenHorse))//The chosen horse finished first { results.setText("Your horse won!\n"); } else { results.setText("Your horse did not win.\n"); } for(int i = 0; i < horses.length; i++) { results.setText(results.getText() + finished[i] + " finshed " + finish[i] + ".\n"); } place = 0; } } // A radio button was clicked public void itemStateChanged(ItemEvent e) { // Determine which horse was selected for(int i = 0; i < optionsArray.length; i++) { if(optionsArray[i].isSelected()) { selected = optionsArray[i]; chosenHorse = selected.getLabel(); } } } // A button was clicked public void actionPerformed(ActionEvent e) { // It was the Start button if(e.getSource() == start) { results.setText(""); // Clear the text area for (int i = 0; i < horses.length; i++) { threads[i] = new Thread(horses[i]); threads[i].start(); } System.gc(); // Garbage collect old threads. no guarantee } // It was the reset button else { for (int i = 0; i < horses.length; i++) { horses[i].newRace(); } } } public static void main(String args[]) { Horserace race = new Horserace(); race.setSize(600, 400); race.setLocation(100, 100); race.setVisible(true); race.setResizable(false); race.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } } [code=java] /* * Horse.java * Class to represent a Horse * Created on February 25, 2004, 3:21 PM */ /** * * Randall Twede */ import java.awt.*; import java.awt.event.*; import javax.swing.*; public class Horse extends JPanel implements Runnable { private int x = 0; private final static int Y = 7; private final static int WIDTH = 20; private final static int HEIGHT = 10; private Horserace parent; private String name; /** Creates a new instance of Horse */ public Horse(String n, Horserace hr) { name = n; parent = hr; setBackground(Color.GREEN); } // Move the horse accross the screen public void run() { while( (x + WIDTH + WIDTH / 2) < 400) { x += (Math.random() * 20); try{Thread.sleep(50);} catch(Exception e){} repaint(); } x = 400; repaint(); parent.postResults(name); // Tell the frame this horse finished } // Draw the horse public void paintComponent(Graphics g) { super.paintComponent(g); g.setColor( new Color(202, 101, 0)); g.fillOval(x, Y, WIDTH, HEIGHT); g.fillOval(x + WIDTH, Y, WIDTH / 2, HEIGHT); } // Move horse back to the starting line public void newRace() { x = 0; repaint(); } }
[/code]
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Phil Freihofner
Ranch Hand
Joined: Sep 01, 2010
Posts: 115
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posted
Jan 05, 2012 00:51:37
0
It's hard to know for sure, given the fragments of code that you show. But I am surprised to see an animated game with multiple Timers involved. Most of what I've seen is done via a single timed Game Loop (which might be triggered by a Timer, or might be managed via varying Sleep amounts, to keep the refresh rate constant).
You can learn a bit more about Game Loops at
if you are not already familiar with them.
I agree. Here's the link:
subject: Movement of user causes AI to lag
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Back in 2012 I posted an article on this blog called “Creating Packages with NuGet the MSBuild Way“. That post described an MSBuild-integrated method to create NuGet packages from your own source code. It has remained one of my most popular posts. Like many popular things on the internet, it has been out of date for sometime now. When I check on my blog and see that the most visited article of the day is “Creating Packages with NuGet the MSBuild Way“, I wonder if visitors know that its out of date. Do they dismiss me as a crank and leave the page immediately? Even worse: do they follow the outdated and complicated recipe described in the post?
In 2012, I needed to integrate packaging into MSBuild because I could not find a plug-in for CruiseControl.net that would create NuGet packages. There may be a plug-in now, I don’t know. After a couple years creating NuGet packages, many tools I use from day to day have changed including my source control and continuous integration options. Even though I now have the option to create CI builds on TFS, where NuGetter is available, I still use MSBuild to configure my projects to create packages every time I hit F6.
I have a new, simple process for setting this up and it usually takes me about five minutes to convert an existing project to produce a NuGet package as part of it’s build output. I start with some existing code, enable package restore, make one small edit to my project file, and build. That’s all it takes to get the first package in the first five minutes.
If I want to continue customizing after creating the first package, I pull the nuspec file out of the existing package, put the nuspec file next to my project file, and customize from there, that’s the second five minutes.
Finally, I make some small modifications to the nuget.targets file provided by package restore in order to automate some cleanup, that takes about five more minutes.
It takes me about fifteen minutes to get everything setup just how I like it, but if your needs are simple, you can be done in five minutes. Hopefully this simplified process will be much more useful to my future visitors and help you, dear reader, understand how easy it is to create NuGet packages for your open source (or private) packages. So read on for all the details!
Build
Start with Some Code
Any Class Library will do. The important thing is that its something you want to share. Either its your open source project, or a bit of private code which you’d like to share with your customers, other departments in your organization, or just your team.
For this example I’ve created a super-cool class called TemporaryFile. TemporaryFile provides a disposable wrapper around a FileInfo which deletes the file when the Dispose method executes. This allows the user to control the lifetime of the temporary file with a using statement, or trust the garbage collector to take care of it during finalization. I find myself creating and deleting temporary files for a certain class of unit tests, and a wrapper like this takes alot of the grunt work out of the task.
namespace TemporaryFile { using System; using System.IO; using ApprovalUtilities.Utilities; public class Temp : IDisposable { private readonly FileInfo backingFile; public Temp(string name) { this.backingFile = new FileInfo(PathUtilities.GetAdjacentFile(name)); this.backingFile.Create().Close(); } ~Temp() { this.Dispose(); } public FileInfo File { get { return this.backingFile; } } public void Dispose() { // File on the file system is not a managed resource if (this.backingFile.Exists) { this.backingFile.Delete(); } } } }
Notice that the class uses a method from PathUtilities in ApprovalUtilities (part of ApprovalTests). I added this method call solely to generate a dependency on another package, which in turn helps demonstrate how much metadata NuGet can infer for you without explicit configuration. Relying on inference is a big part of keeping this process fast an simple–as long as the inferred information meets your needs.
However, the way I used PathUtilities here turned out to be a bug. So don’t copy this code. It is useful to have a bug in the code when doing demos, so I left it in there. If you think the temporary file idea sounds super useful, then a bug free version is now available as part of ApprovalUtilities.
If you examine the NugetLikeAPro repository on GitHub, TemporaryFile is a plain old .net # class library. It has a test project but not much else is going on.
Enable Package Restore
The NuGet documentation is very good, and covers a lot of ground but if it covered everything then you wouldn’t need me! I think that “Using NuGet without committing packages to source control” contains a lot of good information about what happens when you click the “Enable Package Restore” menu item, but it does not emphasize something very important to us as package creators: the NuGet.Build package installed by package restore contains everything you need to convert a project to create packages.
When you enable package restore, two packages are added to your solution: NuGet.CommandLine and NuGet.Build. You could add these yourself, but that would be two steps instead of one. Package restore also performs a third, more tedious step for you: it updates your project files to reference a new MSBuild script and adds a $(SolutionDir) property so that the new script can do its work. The project files need to reference an MSBuild script (NuGet.targets) in order to run the package restore target before the build. The package restore article doesn’t mention that the script also defines a build package target, which can create a package for you after the build completes.
So, lets enable package restore on TemoraryFile and see what we get.
Just as promised by the documentation, the process added a solution folder and three files: NuGet.targets, NuGet.exe, and NuGet.Config. NuGet.Config is only needed by TFS users so you can probably delete it safely. It has no impact on what we are doing here. By observing red checkmarks in the Solution Explorer we can also see that the process modified TemporaryFile.csproj and TemporaryFile.Tests.csproj.
Lets see what changes package restore made to TemporaryFile.
diff --git a/NugetLikeAPro/TemporaryFile/TemporaryFile.csproj b/NugetLikeAPro/TemporaryFile/TemporaryFile.csproj index c1e5a2c..85e156b 100644 --- a/NugetLikeAPro/TemporaryFile/TemporaryFile.csproj +++ b/NugetLikeAPro/TemporaryFile/TemporaryFile.csproj @@ -11,6 +11,8 @@ <AssemblyName>TemporaryFile</AssemblyName> <TargetFrameworkVersion>v4.5</TargetFrameworkVersion> <FileAlignment>512</FileAlignment> + <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">..\</SolutionDir> + <RestorePackages>true</RestorePackages> </PropertyGroup> <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' "> <DebugSymbols>true</DebugSymbols> @@ -49,6 +51,13 @@ <None Include="packages.config" /> </ItemGroup> <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" /> + <Import Project="$(SolutionDir)\.nuget\NuGet.targets" Condition="Exists('$> <!-- To modify your build process, add your task inside one of the targets below and uncomment it. Other similar extension points exist, see Microsoft.Common.targets. <Target Name="BeforeBuild">
Lines 18-24 create the reference to the NuGet.targets file in the .nuget folder, and add some error handling if the script is missing during the build. On line 9 the $(SolutionDir) property is created, and its default value is the project’s parent directory. NuGet.targets uses this piece of configuration to find resources it needs, like NuGet.exe or the solution packages folder. Finally on line 10, package restore is enabled by adding the RestorePackages property and setting it’s value to true. (Side note: this is a bit misleading. It is getting harder and harder to opt-out of package restore. If you set this to false, Visual Studio will set it to true again during the build, unless you opt-out again using a separate Visual Studio option.)
Editing project files is a bit tedious because you have to unload them, open them again as XML files, make your changes and then reload them. Its not hard to learn but its at least four mouse clicks and then some typing in an obscure syntax without much intellisense (although R# helps here). It’s nice that the Enable Package Restore menu item did all that editing for you with one click. Remember that the process also added two NuGet packages for you, so you can add all that to your overall click-savings. Note that the documentation mentions a new feature available in NuGet 2.7 called “Automatic Package Restore“. This feature is enabled by default and solves some problems caused by package restore in certain scenarios. It’s already on by default, so we can imagine that someday a program manager at Microsoft is going to say, “Hey, lets get rid of that ‘Enable Package Restore’ menu item.”
If the Enable Package Restore “gesture” is ever removed then we can install the NuGet packages ourselves and make the necessary changes to the project files. This will get tedious and use way more than the five minutes I’ve allotted to the process, so I’m sure someone will think of a clever way to automate it again with yet another NuGet package. However, this is all just my own speculation. Today we live in the Golden Age of NuGet package creation, and package restore does 99% of the work for us.
One Small Edit
The NuGet.targets file provided by the NuGet.build package provides a “BuildPackage” target. Unlike the “RestorePackages” target, the build package target is not enabled by default. So, we have to edit our project file to turn it on. To edit the file in Visual Studio is a several step process. If I were to make the change from within the IDE, I would: right-click on the TemporaryFile node in Solution Explorer, select “Unload Project”, right click again, select “Edit Project”, edit the project file, save the project file, close the project file, right-click the project again, select “Reload Project”. It’s a hassle.
I find it’s easiest to use a regular text editor to make this change rather than Visual Studio. Anything should work, I often use Sublime Text or Notepad++. Plain old notepad or WordPad should work fine. I prefer Sublime because I keep a my “Projects” folder open in Sublime by default so that I can glance at code or edit these types of files quickly. However you choose to do it, you only need to add one property in order to turn on the BuildPackage target.
diff --git a/NugetLikeAPro/TemporaryFile/TemporaryFile.csproj b/NugetLikeAPro/TemporaryFile/TemporaryFile.csproj index 85e156b..e42d010 100644 --- a/NugetLikeAPro/TemporaryFile/TemporaryFile.csproj +++ b/NugetLikeAPro/TemporaryFile/TemporaryFile.csproj @@ -13,6 +13,7 @@ <FileAlignment>512</FileAlignment> <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">..\</SolutionDir> <RestorePackages>true</RestorePackages> + <BuildPackage>true</BuildPackage> </PropertyGroup> <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' "> <DebugSymbols>true</DebugSymbols>
I usually put it right below the RestorePackages property (line 9), but you can choose where it goes. For example, if you wanted to only create packages for debug builds, you could down a few lines to line 12, into the next PropertyGroup, which is only defined when Debug is selected. The same technique would work to restrict package creation to Release builds, if that’s what you would like to do. If you made the change out side Visual Studio, the IDE will notice and ask you if you want to reload the project. You do, so click “Reload” or “Reload All”.
Once the BuildPackage property is set to true, MSBuild will execute the corresponding target in NuGet.targets and create a package for you on every build. This package will get most of it’s configuration by inference, and appear in the bin directory next to your normal build outputs.
BuildPackage created two packages for me. One is an ordinary NuGet package, which contains the TemporaryFile assembly and one is a “Symbol” package, which includes the same assembly along with additional debugging resources.
We didn’t provide NuGet with any configuration information. NuGet configured these packages by convention, and used the project and assembly information to infer what the package configuration should be. By opening the standard package in NuGet Package Explorer we can see what NuGet came up with. The Id, Version, Title, and Copyright are all inferred by examining assembly attributes. These attributes are defined in AssemblyInfo.cs by default.
using System.Reflection; using System.Runtime.InteropServices; [assembly: AssemblyTitle("TemporaryFile")] [assembly: AssemblyDescription("")] [assembly: AssemblyConfiguration("")] [assembly: AssemblyCompany("")] [assembly: AssemblyProduct("TemporaryFile")] [assembly: AssemblyCopyright("Copyright © 2013")] [assembly: AssemblyTrademark("")] [assembly: AssemblyCulture("")] [assembly: ComVisible(false)] [assembly: Guid("4365a184-3046-4e59-ba28-0eeaaa41e795")] [assembly: AssemblyVersion("1.0.0.0")] [assembly: AssemblyFileVersion("1.0.0.0")]
Authors and Owners are both set to “James” which is my user name on the machine where I created the package. NuGet would prefer to use the value from “AssemblyCompany” for these fields, but I haven’t filled it out yet. Since AssemblyCompany was empty, NuGet moved on to the next convention and chose my user name instead. NuGet would also prefer to use “AssemblyDescription” to populate the Description value, but this was also blank. Since there is no other logical place (yet) for NuGet to find a description, the program simply gave up and used the word “Description” instead. NuGet uses the build log to warn me (lines 4, 5, 11, and 12 below) when this happens.
1> Attempting to build package.nupkg'. 1> 1> Attempting to build symbols package.symbols.nupkg'.
Notice on lines 3 and 10 that NuGet noticed that my project depends on another NuGet package. It infers this by detecting the ‘packages.config’ file where NuGet lists the project dependencies, reads that file, and automatically configures TemporaryFile to depend on ApprovalUtilities.
Overall NuGet did a pretty good job, and this package is actually usable. Before we move on to customizing this package lets take a look at it’s sibling, the symbol package.
The symbol package configuration is identical to the standard package. Version, Id, Authors, and the rest are all the same. However, there are more files in the symbol package. Along with the class library, the lib/net45 folder contains the debugging symbols. There is also a new folder called src. Under the src directory, we can find all the source code for TemporaryFile.dll. All together, this extra content gives Visual Studio enough information to provide a complete step-through debugging experience for this NuGet package. What to do with this package and how to configure Visual Studio to use it are topics better handled on their own, so I wont cover them further here. Stay tuned.
Customize
There are a few things I would like to change in this package before sharing it with the team/customers/world. I don’t like the default values for Author/Owner and Description. At a minimum the Author field should contain my last name, or perhaps my twitter handle or something I’d like the world to know me by. It is also appropriate to use your company name in this field. The description is important because this package will probably end up in a gallery and certainly be presented in the NuGet Package Manager inside Visual Studio. You need a good concise description so people have an idea what you are trying to share with them. The copyright isn’t claimed by anyone either, be careful here because some default Visual Studio installs automatically use “Microsoft” as the default copy right holder (this seems to have been fixed in 2013, now its just blank). Finally, I don’t like the default 3-dot version number, I prefer the 2-dot version, so I’d like to change that too. These are the low hanging fruit which can be customized using AssemblyInfo.cs.
diff --git a/NugetLikeAPro/TemporaryFile/Properties/AssemblyInfo.cs b/NugetLikeAPro/TemporaryFile/Properties/AssemblyInfo.cs index 7c3c830..bf494d8 100644 --- a/NugetLikeAPro/TemporaryFile/Properties/AssemblyInfo.cs +++ b/NugetLikeAPro/TemporaryFile/Properties/AssemblyInfo.cs @@ -2,14 +2,14 @@ using System.Runtime.InteropServices; [assembly: AssemblyTitle("TemporaryFile")] -[assembly: AssemblyDescription("")] +[assembly: AssemblyDescription("A file that deletes itself when disposed")] [assembly: AssemblyConfiguration("")] -[assembly: AssemblyCompany("")] +[assembly: AssemblyCompany("ACME Co.")] [assembly: AssemblyProduct("TemporaryFile")] -[assembly: AssemblyCopyright("Copyright © 2013")] +[assembly: AssemblyCopyright("Copyright © Jim Counts 2013")] [assembly: AssemblyTrademark("")] [assembly: AssemblyCulture("")] [assembly: ComVisible(false)] [assembly: Guid("4365a184-3046-4e59-ba28-0eeaaa41e795")] -[assembly: AssemblyVersion("1.0.0.0")] -[assembly: AssemblyFileVersion("1.0.0.0")] \ No newline at end of file +[assembly: AssemblyVersion("1.0.0")] +[assembly: AssemblyFileVersion("0.0.1")] \ No newline at end of file
I filled or edited out the attributes which NuGet checks when looking for configuration information: AssemblyDescription, AssemblyCompany. AssemblyCopyright and AssemblyVersion. I also changed AssemblyFileVersion, even though NuGet doesn’t use it, and I left AssemblyTitle alone because I was happy with the value already there. After building again, these changes should show up in the newly created package.
NuGet applied most of my changes automatically, and all the build warnings are gone. But I expected a 2-dot version number both in the package name and as part of the metadata. That 3-dot version is still hanging around. I can take greater control over the version number, as well as many other aspects of the package metadata by providing a “nuspec” metadata file. If this file has the same name as my project and is in the same directory as my project, then NuGet will prefer to use the data from the nuspec.
Pull the Nuspec File Out
You can generate nuspec files from assemblies or project files using NuGet.exe. In the past I’ve found this method for creating nuspec files to be tedious because it creates configuration I don’t always need or configuration with boilerplate text that I need to delete. My old solution was some fairly complex MSBuild scripts that transformed generated files, but today I just create the default package as described above, rip it’s metadata, then customize to my liking. If you have NuGet Package Explorer open, it’s pretty easy to use the “Save Metadata As…” menu item under “File” and save the nuspec file next to your project file (remove the version number from the filename if you do this).
Another way to retrieve the package nuspec file is with an unzip tool. NuGet packages are zip files, and tools like 7-zip recognize this, buy you can always change the extension from nupkg to zip, if 7-zip isn’t handy. Once the file has a zip extension, any zip utility can manipulate it, including the native support built into Windows.
You can extract all the files from the zip, or just the nuspec file. You will only need the nuspec file.
Put the Nuspec File Next to the Project
Once you have pulled the nuspec file out of the existing package, move it to the project directory. It should sit in the same folder where the csproj file is (or vbproj, or fsproj) and have the same base name as the csproj. There should be no version number in the nuspec file name, so remove it if there is.
You can also add the item to the project using Visual Studio for easy access from the IDE, but it is not required. I usually add it.
Make Changes
Now, let’s take a look at what is inside the nuspec file.
<?xml version="1.0"?> <package xmlns=""> <metadata> <id>TemporaryFile</id> <version>1.0.0.0</version> <title>TemporaryFile</title> <authors>ACME Co.</authors> <owners>ACME Co.</owners> <requireLicenseAcceptance>false</requireLicenseAcceptance> <description>A file that deletes itself when disposed</description> <copyright>Copyright © Jim Counts 2013</copyright> <dependencies> <dependency id="ApprovalUtilities" version="3.0.5" /> </dependencies> </metadata> </package>
We can see that most of the information in the nuspec file is the exact information displayed in the package explorer. I can now override the defaults by editing this file. Any XML or text editor will work, it’s very convenient to use Visual Studio if you add the nuspec file to the project, so that’s what I usually do.
diff --git a/NugetLikeAPro/TemporaryFile/TemporaryFile.nuspec b/NugetLikeAPro/TemporaryFile/TemporaryFile.nuspec index 5770b72..815c44e 100644 --- a/NugetLikeAPro/TemporaryFile/TemporaryFile.nuspec +++ b/NugetLikeAPro/TemporaryFile/TemporaryFile.nuspec @@ -2,15 +2,12 @@ <package xmlns=""> <metadata> <id>TemporaryFile</id> - <version>1.0.0.0</version> + <version>0.0.1</version> <title>TemporaryFile</title> - <authors>ACME Co.</authors> + <authors>@jamesrcounts</authors> <owners>ACME Co.</owners> <requireLicenseAcceptance>false</requireLicenseAcceptance> <description>A file that deletes itself when disposed</description> <copyright>Copyright © Jim Counts 2013</copyright> - <dependencies> - <dependency id="ApprovalUtilities" version="3.0.5" /> - </dependencies> </metadata> </package> \ No newline at end of file
I changed the version number to “0.0.1” and updated the the author to use my twitter handle. “ACME Co.” is still the owner, and I removed the dependency list. I prefer to allow NuGet to continue to infer this information on it’s own.
With these changes, the next package I build should reflect the new version number in the file name, and show updated metadata for Version and Authors. However, the dependency list should remain the same in the completed package.
Automate
You’ll need some way to share your package now that you’ve created one. If it’s an open source project you can definitely upload it to nuget.org if you like. For private code, that’s probably not a good idea. There are solutions out there, and I wrote about one of them in a previous article: Use ProGet to Host Your Private Packages. In the interest of making sure this article doesn’t get any longer than it already is, I won’t cover options for sharing private packages here.
However, there are a couple things you can do now which will make your life easier once you do start sharing your package. First, nuget.targets does not clean up after itself during clean and rebuild. This means that all your old package versions will hang around in the build folder until you delete them manually. Besides taking up space, those packages eventually slow you down when you get ready to share. If you are using the NuGet Package Explorer to share, you have to scroll past an increasingly longer list of old package versions to find the new version you want to upload, and if you use the command line utility, all those old versions increase the amount of typing and tabbing in order to complete the command. Finally, I find the quickest way to push packages is with a custom script which wraps the command line utility, and that script is much easier to write when the bin folder only contains the latest package.
Cleanup with nuget.targets
To integrate nuget.target with “Clean” and “Rebuild” you need to add a new target to the script, add a new item group which lists the files to clean, and finally ad a hook using the “CleanDependsOn” property that will actually execute the target.
Nuget.targets is already added to your solution in the .nuget folder, open it and add what you need.
diff --git a/NugetLikeAPro/.nuget/NuGet.targets b/NugetLikeAPro/.nuget/NuGet.targets index 8962872..a5cebf3 100644 --- a/NugetLikeAPro/.nuget/NuGet.targets +++ b/NugetLikeAPro/.nuget/NuGet.targets @@ -1,5 +1,8 @@ <?xml version="1.0" encoding="utf-8"?> <Project ToolsVersion="4.0" xmlns=""> + <ItemGroup> + <OutputPackages Include="$(TargetDir)*.nupkg" /> + </ItemGroup> <PropertyGroup> <SolutionDir Condition="$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*'">$(MSBuildProjectDirectory)\..\</SolutionDir> @@ -83,6 +86,11 @@ $(BuildDependsOn); BuildPackage; </BuildDependsOn> + + <CleanDependsOn Condition="$(BuildPackage) == 'true'"> + $(CleanDependsOn); + CleanPackages; + </CleanDependsOn> </PropertyGroup> <Target Name="CheckPrerequisites"> @@ -118,6 +126,10 @@ </Target> + <Target Name="CleanPackages"> + <Delete Files="@(OutputPackages)"></Delete> + </Target> + <UsingTask TaskName="DownloadNuGet" TaskFactory="CodeTaskFactory" AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.v4.0.dll"> <ParameterGroup> <OutputFilename ParameterType="System.String" Required="true" />
On lines 8-10 I define a collection of items called “OutputPackages” which uses a glob to find all the NuGet packages in the bin directory, referred to in the script as TargetDir.
Then I use this item collection with the new target defined on lines 30-32. The CleanPackages target is a very simple target that uses MSBuild’s built-in Delete task to remove the files in the OutptuPackages collection.
Finally, I instruct MSBuild to run this target during clean by hooking into the CleanDependsOn property using lines 19-22. CleanDependsOn is one of several hooks provided for modifying targets defined in Microsoft.Common.Targets. On line 20, I add back any existing dependencies and on line 21 I append the CleanPackages target to the end of the list. Now, MSBuild will clean up old packages whenever I Clean or Rebuild my project.
Write a push script
Pushing your packages to NuGet.org is pretty simple because it is the default for nuget.exe. Both NuGet.exe and the NuGet Package Explorer will allow you to specify a custom host to push your package to, but I’m paranoid that I will forget to specify the host and send packages to nuget.org that I don’t want to share publicly.
So, to speed things up, and to keep the risk of mistakes to a minimum, I use a simple shell script to push my packages. Here is an example that would push to a local ProGet server.
.nuget\NuGet.exe push .\TemporaryFile\bin\Debug\*.nupkg -apikey Admin:Admin -source
I specified ProGet’s default credentials as the API key, but if you plan to push to nuget.org I suggest you use the NuGet “setapikey” option to configure the API key on your machine, and that way you don’t have to commit the key to source control.
Recap
In this post I showed how to create basic packages with MSBuild, customize them, and gave a couple automation tips I find useful. Once you have converted a few of projects to produce packages this way, you can do the conversion in about 15 minutes for straightforward packages. NuGet packages can become complex and you may need to do a lot more in the customization stage. However, for most cases I find that these few steps are enough: enable package restore, add the BuildPackage property, rip the nuspec file from the first package, customize a few pieces of AssemblyInfo and nuspec metadata, and start sharing your package.
Once you have the package, you can quit, or you can make your life a little easier by adding a cleanup target and a push script. Either way, I hope you find this information useful, and bit more approachable than my previous post on this topic.
The GitHub repository to accompany this post is here: | https://ihadthisideaonce.com/tag/msbuild/ | CC-MAIN-2019-09 | refinedweb | 4,440 | 55.84 |
CodePlexProject Hosting for Open Source Software
I'm attemping to write a simple module that stores two strings in the database. My model has three properties, Id, String1, String2. when I run the following data migration:
Subsequent Create() actions fail because "Id is required," mainly I think because the primary key column Id isn't set to autoincrement.When I uncomment the Id column above and run the migration, the migration fails because Id is specified twice. I've tried several combinationsof
public int Create(){
SchemaBuilder.CreateTable("RegistrationRecord", table => table
.ContentPartRecord()
//.Column<int>("Id", column => column.PrimaryKey().Identity())
.Column<string>("String1")
.Column<string>("String2")
);
Subsequent Create() actions fail because "Id is required," mainly I think because the primary key column Id isn't set to autoincrement.
When I uncomment the Id column above and run the migration, the migration fails because Id is specified twice. I've tried several combinations of including one or the other with no luck. I've even compared mine to an existing module (the roles module
that comes with Orchard). Can someone tell me what I might be missing? How do I make a primary key column an identity column?
Your ContentPartRecord should be called "RegistrationPartRecord" and your ContentPart should be called "RegistrationPart". You shouldn't specify the Id column for a ContentPartRecord. It should just work if you follow that
convention.
Randompete, thanks for your response. You've answered a few of my questions now, and I appreciate it.
My ContentPartRecord and ContentPart are named as you suggested...it should be said that I'm not actually creating a content part, I'm just creating a simple database record that should be persisted...
Here's what I have with a little more code to clarify what I'm doing:
Migrations.cs
public int Create(){
SchemaBuilder.CreateTable("RegistrationRecord", table => table
.ContentPartRecord()
.Column<string>("String1")
.Column<string>("String2")
);
return 1;
}
RegistrationRecord.cs (model)
public class RegistrationRecord : ContentPartRecord
{
public virtual string String1{ get; set; }
public virtual string String2{ get; set; }
}
public class RegistrationPart : ContentPart<RegistrationRecord>
{
[Required]
public string String1 {
get { return Record.String1; }
set { Record.String1= value; }
}
[Required]
public string String2 {
get { return Record.String2; }
set { Record.String2 = value; }
}
}
When the migration is run, it creates a table with 3 columns, Id, String1, and String2. The problem occurs when I click the "create" button on my view (which basically just posts to another controller action decorated with HttpPost. In that action,
every time, there's a modelstate error stating "The Id field is required." Shouldn't this get filled in automatically, either via Orchard, or by having the column be an identity field?
No, you've named your record "RegistrationRecord" not "RegistrationPartRecord" - the difference is important :)
Ahh yes, you're correct, I remember removing that "Part" a long time ago...
Unfortunately, I just renamed it back and I'm still getting the "The Id field is required" modelstate error...
Also, I looked at Garside's contact us module, and their ContactUsSettingsRecord doesn't have "part" in the name. Even this page doesn't have part in it:
namespace Map.Models {
public class MapRecord : ContentPartRecord {
public virtual double Latitude { get; set; }
public virtual double Longitude { get; set; }
}
}
What is the "part" convention supposed to do?
Could this have something to do with the way I'm saving the record? I'm just injecting an IRespository<RegistrationPartRecord> into the constructor and then calling:
_respository.Create(registration);I know this should probably go through a service or some other abstraction, but I wanted to get it to work in raw form first...
If you need this to be a part, then it should be created as *part* of a content-item, i.e. through ContentManager. If you don't, then accessing the repository directly is fine but it will need an Id column.
Bertrand,
So, since I don't need this to be a part, here's what I think I'll need to do based on what you said:
1.) Get rid of the RegistrationPart wrapper
2.) Stop inheriting ContentPartRecord
3.) Add the id field to my record
4.) Remove "part" from the object name
So I'll have one class in my model:
public class RegistrationRecord
{
public virtual string Id { get; set; }
public virtual string String1{ get; set; }
public virtual string String2{ get; set; }
}
And my migration class will be:
public int Create(){
SchemaBuilder.CreateTable("RegistrationRecord", table => table
.Column<int>("Id", column => column.PrimaryKey().Identity()) .Column<string>("String1")
.Column<string>("String2") );
}I'll try this and see if it solves the problem.
public int Create(){
SchemaBuilder.CreateTable("RegistrationRecord", table => table
.Column<int>("Id", column => column.PrimaryKey().Identity()) .Column<string>("String1")
.Column<string>("String2") );
}I'll try this and see if it solves the problem.
Yes, that should work.
Now we're getting somewhere...
I'm getting:
"ids for this class must be manually assigned before calling save(): xxxx.xxxx.Models.RegistrationRecord"
Is there no way to make this field an autoincrement field?
I've done this plenty of times myself so it definitely works.
I notice in the code above you have a string for the Id field on RegistrationRecord. Could that be it?
Yeah, I trust that it does work. It's probably some minor thing I'm doing wrong...the string was a typo on my part...it is in fact set as an int, but it's still saying the Id field is required...
Are you starting from scratch or could this be a remnant of previous attempts?
It's getting to that point where I might need to start from scratch...I'll try that and post results...
I rebuilt the module from scratch, still telling me the Id field is required when trying to save. Not sure where else to go from here, but I'll keep digging. I know this has to be one simple thing I'm missing...
When you look at the table definition, what do you see for the Id column?
After doing some reading, it seems that I might want a "part" after all. I'm basically creating a registration module that allows an admin to create a new registration page for a given role and have the user automatically be assigned to that role when
they successfully register. Original I was just storing a rolename and a friendly name for the url (so if I wanted to register a monster, I'd go to mysite.org/monsters/register.
Instead of the two strings, perhaps I should be tying into the existing roles so I'd have an int, a roleid, and a friendly name. I think I need a part to accomplish this...that being said, I'd like to get it to work my denormalized way first just as
a proof that it works in case I ever need to do something like this again.
I see:
Id, int, don't allow nulls, Identity spec. = yes...it's creating it correctly in the database, so it seems. Furthermore, I know it's getting validated using the data annotation functionality because I'm able to change the error message that comes back
using DisplayName.
Does the property need to be a nullable int and not a non-nullable?
No, what you're doing seems to be perfectly identical to what's being done in countless other places throughout the Orchard code.
I got it to work using methods from this post:
So, if I include the following in my admin create, it works:
public ActionResult Create([Bind(Exclude = "Id")] RegistrationRecord registration)
Ah, I see, so the problem was actually in the controller?
Yeah, after you guys said several times that everything in my migration/models was correct, it felt like the problem had to be somewhere else. For some reason I needed to explicitly exclude the Id field from updating when the model was bound to the
form values being passed in. I'm able to successfully save records now.
Thanks for all your help, gentlemen. I'm sure I'll be back with a million more questions as I learn this stuff.
Are you sure you want to delete this post? You will not be able to recover it later.
Are you sure you want to delete this thread? You will not be able to recover it later. | http://orchard.codeplex.com/discussions/259778 | CC-MAIN-2017-43 | refinedweb | 1,382 | 66.13 |
I am currently working hard on writing this project i have for my java programming class. I have written almost all of the code but i am stuck while complieing it in its current form. I keep getting Java error: Cannot find symbol for the line of code i have underlined. well it says [U] next to the line. its not really underlined.
In this project i'm trying to get it to tell me if each character of a string is lower case, upper case or not a letter.
Please help me I have no idea how to correct this error. Thank you!
import java.util.Scanner; public class LetterCase { public static boolean isThisSpace(char sentence) { return sentence ==(' '); } public static boolean isThisUpperCase(char sentence) { return (sentence>= 'A' &&sentence <= 'Z'); } public static boolean isThisLowerCase(char sentence) { return (sentence>= 'a' && sentence <= 'z'); } public static void main(String[] args) { Scanner keyboard_input = new Scanner(System.in); System.out.print("Please enter a sentence : "); String sentence = keyboard_input.nextLine(); int length = sentence.length(); for(int i=0; i < length; i++) { char sentences = sentence.charAt(i); [U]if(sentence.isThisUpperCase(sentence))[/U] { System.out.println(sentence.charAt(i)+ ":" + "Upper Case"); } | http://www.javaprogrammingforums.com/whats-wrong-my-code/30130-i-keep-getting-symbol-not-found-error-when-i-already-defined-symbol-please-help.html | CC-MAIN-2015-32 | refinedweb | 194 | 57.47 |
Upgrading GAP in SAGE
Hello,
I'm attempting to upgrade the version of GAP that is used in SAGE. I installed the most recent version of GAP 4.8.8. When I open SAGE and run
gap.version() 4.8.3
I know I can point the GAP console in SAGE to the 4.8.8 version of GAP by running:
import sage.interfaces.gap GAP_PATH = "/home/captainhampton/gap4r8/bin/gap.sh" sage.interfaces.gap.gap_cmd = GAP_PATH
which is where I've installed the 4.8.8 version of GAP. Indeed, if I run
gap.console() ┌───────┐ GAP 4.8.8, 20-Aug-2017, build of 2017-10-12 22:05:03 (EDT) │ GAP │ └───────┘ Architecture: x86_64-pc-linux-gnu-gcc-default64 Libs used: gmp, readline Loading the library and packages ... Components: trans 1.0, prim 2.1, small* 1.0, id* 1.0 Packages: AClib 1.2, Alnuth 3.0.0, AtlasRep 1.5.1, AutPGrp 1.8, Browse 1.8.7, CRISP 1.4.4, Cryst 4.1.12, CrystCat 1.1.6, CTblLib 1.2.2, FactInt 1.5.4, FGA 1.3.1, GAPDoc 1.6, IO 4.4.6, IRREDSOL 1.4, LAGUNA 3.7.0, Polenta 1.3.7, Polycyclic 2.11, RadiRoot 2.7, ResClasses 4.6.0, Sophus 1.23, SpinSym 1.5, TomLib 1.2.6, Utils 0.46 Try '??help' for help. See also '?copyright', '?cite' and '?authors'
However, if in SAGE, this does not change gap.version(). It still gives 4.8.3. Is there a way I can point this gap to the 4.8.8 version? Thanks.
This would require you mucking with the code that gives the gap version in Sage, which may be hardcoded in the pkg. But clearly it is running correctly otherwise.
Right, but unfortunately I require the use of GAP 4.8.8 instead of 4.8.3 due to KBMAG package. So being able to update GAP in SAGE would be really really helpful to me. | https://ask.sagemath.org/question/39288/upgrading-gap-in-sage/ | CC-MAIN-2018-13 | refinedweb | 333 | 83.12 |
[ ]
Steve Hardy commented on AXISCPP-250:
-------------------------------------
The same thing happens when you have a
<xs:choice>
<xs:element
<xs:element
</xs:choice>
because you have minOccurs = 0 for all the fields.
Also, there is no way of creating the struct (class) in c++ to show that a simple type is
'missing'. ie you can't set 'a' to NULL because it is not a pointer.
The best option would be to have a union-like structure like
struct choice {
enum type { a,b };
union {
int a;
int b;
} value;
}
and have the serialiser / deserialiser only send/receive the one field that we want transmitting
/ receiving. I currently send a union struct with about 20 fields, of which only ever 1 is
used. This is currently transmitted as zero's in all the unused fields, which is rather wasteful.
> Errors in handling minOccurs="0" (optional) elemnts in SOAP message
> -------------------------------------------------------------------
>
> Key: AXISCPP-250
> URL:
> Project: Axis-C++
> Type: Bug
> Components: Serialization/Deserialization
> Versions: 1.3 Final
> Environment: All platforrms
> Reporter: Samisa Abeysinghe
> Priority: Critical
> Attachments: WS021A.wsdl
>
> The following is from the mailing list. See
for more information :
> > All elements in the response have minOccurs="0", so they can be
> omitted. Is this another issue?
> Good point Adrian! I missed that :(.
> This must be the reason that is causing the problem.
> To my knowledge, WSDL2Ws tool does not deal with this correctly (I came
> to this conclusion by
> looking at the generated code for the WSDL). It expects all the
> elements to be there, and throws
> an error, if at least a single element is missing.
> Also, the ordering of the element is very critical for the generated
> code to work.
> e.g.
> param->names = (xsd__string_Array&)pIWSDZ->getBasicArray(XSD_STRING,
> "names",0);
> param->addrs = (xsd__string_Array&)pIWSDZ->getBasicArray(XSD_STRING,
> "addrs",0);
> param->xdirInd = pIWSDZ->getElementAsString("xdirInd",0);
> param->noOfBillRecords = pIWSDZ->getElementAsInt("noOfBillRecords",0);
> (the '0' parameters in above code indicates that namespace is NULL - it
> must have used NULL
> instead of 0)
> If "xdirInd" is missing in the response, and "noOfBillRecords" is
> present,
> getElementAsString("xdirInd",0) call on the serializer will see that
> next element is
> "noOfBillRecords" and will error.
> If we are looking for an optional element, we are doing a serious
> mistake here (and thus this is a
> serious bug)
> The correct logic would be to
> 1. Test if the element is opetional
> if yes
> 1.1. Test if the current element is what we are looking for
> if yes
> 1.1.1 return Success
> if no
> 1.1.2 Back track to point to the start of the elemnt and
> return Success
> if no
> 1.2 return Failure
> I hope the above algorithm does not violate the pull model we have.
> Additionally, can we expect the SOAP message to have the elements in
> the same order defined by the
> WSDL? If yes (I think it is) we are OK. If not we have another bug :(
--
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If you want more information on JIRA, or have a bug to report see: | http://mail-archives.apache.org/mod_mbox/axis-c-dev/200412.mbox/%3C2084691298.1103548937689.JavaMail.apache@nagoya%3E | CC-MAIN-2018-30 | refinedweb | 517 | 54.32 |
Introduction
The Arduino Leonardo is a wonderful microcontroller. In addition to maintaining the same form factor as the venerable Uno, it also has the ability to serve as a USB keyboard. This means that you can program your Leonardo to press specific keys or print strings in response to various stimuli.
Pair it with a few capacitive touch pads and you can produce a device that essentially adds four fully-programmable keys to your workspace! Use each key to type commonly-used phrases, perform specific macros, press hard-to-use key combinations, and so much more! Let's get started.
Step 1: Assembly
This part is exceedingly simple. All you need to do is insert the included JST cables into the sockets and begin wiring. All the black wires should be connected to ground, the red wires to 5V, and the green wires to pins 2, 3, 4, and 5. The Leonardo only has a few power pins so it's helpful to connect the ground and VCC wires together using a breadboard. For simplicity's sake I recommend that you arrange the pads in numerical order, starting with the pad connected to pin 2 on the left and ending with pin 5 on the right.
I also used some double-sided tape to hold the pads in place. You could accomplish this with a whole number of different household products.
Step 2: Example Sketch
#include <Keyboard.h> void setup(){ pinMode(2, INPUT); pinMode(3, INPUT); pinMode(4, INPUT); pinMode(5, INPUT); Keyboard.begin(); } void loop(){ checkPress(2, 'd'); checkPress(3, 'f'); checkPress(4, 'g'); checkPress(5, 'h'); } void checkPress(int pin, char key) { if (digitalRead(pin)) { Keyboard.press(key); } else { Keyboard.release(key); } }
Try uploading the above software to your Leonardo. Click on an empty text box and try pressing the pads to ensure that each one outputs a character. Go to and you can use each of the keys to play chords!
Step 3: Creating Hotkeys
#include <Keyboard.h> const int delayValue = 100; const char cmdKey = KEY_LEFT_GUI; void setup(){ pinMode(2, INPUT); pinMode(3, INPUT); pinMode(4, INPUT); pinMode(5, INPUT); Keyboard.begin(); } void loop(){ if (digitalRead(2)) { Keyboard.press(cmdKey); Keyboard.press('c'); delay(delayValue); Keyboard.releaseAll(); while(digitalRead(2)); } if (digitalRead(3)) { Keyboard.press(cmdKey); Keyboard.press('v'); delay(delayValue); Keyboard.releaseAll(); while(digitalRead(3)); } if (digitalRead(4)) { Keyboard.press(cmdKey); Keyboard.press('n'); delay(delayValue); Keyboard.releaseAll(); while(digitalRead(4)); } if (digitalRead(5)) { Keyboard.press(cmdKey); Keyboard.press('z'); delay(delayValue); Keyboard.releaseAll(); while(digitalRead(5)); } }
The above sketch allows Mac users to use their pads for some common keyboard combinations. You can find the full list of all key definitions at.
Step 4: Going Further
Of course, simple key combinations and strings are not the only uses for such a system. Coupled with a program such as Keyboard Maestro, you could get your keys to perform extremely complex tasks. I set up some of my keys to lock my computer, turn sound on/off, and open specific programs! Consider it a fully-programmable computer interface that you can design for any purpose.
That's it! I'd love to hear what you used this project for, so post a comment below. If you want to see more of my work you can visit | https://www.hackster.io/AlexWulff/capacitive-touch-keyboard-extension-with-leonardo-13a387 | CC-MAIN-2019-30 | refinedweb | 549 | 58.69 |
CHI::Driver::SharedMem - Cache data in shared memory
Version 0.13
CHI driver which stores data in shared memory objects for persistently over processes. Size is an optional parameter containing the size of the shared memory area, in bytes. Shmkey is a mandatory parameter containing the IPC key for the shared memory area. See IPC::SharedMem for more information.
use CHI; my $cache = CHI->new( driver => 'SharedMem', size => 8 * 1024, shmkey => 12344321, # Choose something unique ); # ...
The shared memory area is stored thus:
# Number of bytes in the cache [ int ] 'cache' => { 'namespace1' => { 'key1' => 'value1', 'key2' => 'value2', # ... }, 'namespace2' => { 'key1' => 'value3', 'key3' => 'value2', # ... } # ... }
Stores an object in the cache
Retrieves an object from the cache
Remove an object from the cache
Removes all data from the current namespace
Gets a list of the keys in the current namespace
Gets a list of the namespaces in the cache
Constructor - validate arguments
If there is no data in the shared memory area, and no-one else is using it, it's safe to remove it and reclaim the memory.
Nigel Horne,
<njh at bandsman.co.uk>
Please report any bugs or feature requests to
bug-chi-driver-sharedmem at rt.cpan.org, or through the web interface at. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
CHI, IPC::SharedMem
You can find documentation for this module with the perldoc command.
perldoc CHI::Driver::SharedMem
You can also look for information at:
This program is released under the following licence: GPL | http://search.cpan.org/~nhorne/CHI-Driver-SharedMem-0.13/lib/CHI/Driver/SharedMem.pm | CC-MAIN-2014-23 | refinedweb | 257 | 63.8 |
RECOMMENDED: If you have Windows errors then we strongly recommend that you download and run this (Windows) Repair Tool.
A valid floating point number for atof using the "C" locale is formed by an optional sign character (+ or -), followed by one of: – A sequence of digits, optionally.
I am trying to convert a string to a double. The code is very simple. double first, second; first=atof(str_quan.c_str()); second.
The Lex & Yacc Page Yacc: Yet Another Compiler-Compiler Stephen C. Johnson AT&T Bell Laboratories Murray Hill, New Jersey.
Placing comment symbols /* */ around a code, also referred to as “commenting out”, is a way of isolating some codes that you think maybe causing errors in the program. This usually occurs while handling conditions wherein a series of.
How to detect if atof or _wtof failes to convert the string to double? But not by trying to check if the result is different form 0.0 because my input can be 0.0.
status argument passed to exit() is returned to O.S. to inform that whether or not program succeeded normally. Notice that this status argument is as same as status.
It returns NULL if there is an error (such. sum+=atof(argv[i]); printf("Average=%f n",sum/(float) num); } $./a.out 45 239 123 Average=135.666667 C Basic File Input/Output Manipulation C Programming – File Outline v File handling in C -.
This article covers a somewhat more advanced topic: features and techniques for putting better error-handling capabilities into your compiler. {DIGIT}+ { yylval.value = atof(yytext); return VALUE; } {DIGIT}+"."{DIGIT}* {.
Analysis of the Trans-Proteomic Pipeline (TPP) project – To be honest, I don’t know what the TPP project. errors look: void SAXSpectraHandler::pushPeaks(.) {. while(*pValue != ” && a < m_peaksCount) { while(*pValue != ” && isspace(*pValue)) pValue++; if(pValue == ”).
These functions provide more robust error handling than alternative solutions. Also. The atoi() , atol() , atoll() , and atof() functions convert the initial portion of a.
Feb 27, 2017. atof. strtod. No error indication, undefined behavior on error. atoi. strtol. for functions that have equivalent functions with better error handling.
Problem 1 calculate median(10 pts write a c program – Unformatted text preview: Problem 1 – Calculate Median (10 pts) Write a C++ program median. arguments are numeric values and use atof() Function to convert the argument into a double type variable. No error handling For malFormed.
Query failed: unknown local index 'forums_search_posts_main' in search request.
Mar 11, 2010. strtod() is similar to atof() except that it detects errors. char *a = "234.5"; double d; int r; r = sscanf(a, "%lf", &d); if (r <= 0) { // error handling. }
Error Lnk2019 Unresolved External Symbol C In this article, I’ll show you an example on how to integrate the PostgreSQL C++ library into your C++ project solution. The PostgreSQL version that i am using for. Linker Tools Error LNK2019 – msdn.microsoft.com – Linker Tools Error LNK2019. The latest version of this topic can be found at Linker Tools Error LNK2019. unresolved
#include <avr/eeprom.h> This header file declares the interface to some simple library routines suitable for handling the data EEPROM contained in the AVR.
Springer Science+Business Media – Error handling: if there is an error in a part program. According to the address has been read, the number may be translated as a float by atof() function or an integer value by atoi() function (Lan 2008). In the end stage, base on the.
atof – convert a string to a double-precision number. The call atof(str) shall be equivalent to: strtod(str,(char **)NULL), except that the handling of errors may differ. should be used because atof() is not required to perform any error checking.
Notes. strcpy_s is allowed to clobber the destination array from the last character written up to destsz in order to improve efficiency: it may copy in multibyte.
Installation Of Msi Package Failed 1603 Fatal Error
Sep 3, 2010. In particular, strtod takes two parameters instead of just one like atof. double d = 0; if ( std::cin >> d ) { // input is a double. handle that here. }.
If myfile.txt does not exist, a message is printed and abort is called. Data races Concurrently calling this function is safe, causing no data races.
RECOMMENDED: Click here to fix Windows errors and improve system performance | http://geotecx.com/atof-error-handling/ | CC-MAIN-2018-26 | refinedweb | 712 | 60.01 |
Visual Studio 2008 includes an Application Wizard that builds template programs and saves you a lot of the dirty work you'd have to do if you did everything from scratch.
Typically, starter programs don't actually do anything — at least, not anything useful. However, they do get you beyond that initial hurdle of getting started. Some starter programs are reasonably sophisticated. In fact, you'll be amazed at how much capability the App Wizard can build on its own, especially for graphical programs.
The following instructions are for Visual Studio. If you use anything other than Visual Studio, you have to refer to the documentation that came with your environment. Alternatively, you can just type the source code directly into your C# environment.
To start Visual Studio, choose Start --> All Programs --> Microsoft Visual Studio 2008 --> Microsoft Visual Studio 2008.
Complete these steps to create your C# console app:
1. Choose File --> New --> Project to create a new project.
Visual Studio presents you with lots of icons representing the different types of applications you can create.
2. From this New Project window, click the Console Application icon.
Make sure that you select Visual C# — and under it, Windows — in the Project Types pane; otherwise, Visual Studio may create something awful like a Visual Basic or Visual C++ application. Then click the Console Application icon in the Templates pane.
Visual Studio requires you to create a project before you can start to enter your C# program. A project is like a bucket in which you throw all the files that go into making your program. When you tell your compiler to build (compile) the program, it sorts through the project to find the files it needs in order to re-create the executable program.
The default name for your first application is ConsoleApplication1, but change it this time to Program1.
The default place to store this file is somewhere deep in your Documents directory. You can change this default program location by following these steps:
• a. Choose Tools --> Options --> Projects and Solutions --> General.
• b. Select the new location (for example, C:\C#Programs) in the Visual Studio Projects Location box and click OK.
Leave the other boxes in the project settings alone.
3. Click the OK button.
After a bit of disk whirring and chattering, Visual Studio generates a file called Program.cs. (If you look in the Solution Explorer window, you see some other files; ignore them for now. If Solution Explorer isn't visible, choose View --> Solution Explorer.) C# source files carry the extension .CS. The name Program is the default name assigned for the program file.
The contents of your first console app appear as follows:
using ...namespace Program1{ class Program { static void Main(string[] args) { } }}
Along the left edge of the code window, you see several small plus (+) and minus (-) signs in boxes. Click the + sign next to using.... This expands a code region, a handy Visual Studio feature that keeps down the clutter. Here are the directives when you expand the region in the default console app:
using System;using System.Collections.Generic;using System.Linq;using System.Text;
Regions help you focus on the code you're working on by hiding code that you aren't. Certain blocks of code — such as the namespace block, class block, methods, and other code items — get a +/- automatically without a #region directive. You can add your own collapsible regions, if you like, by typing #region above a code section and #endregion after it. It helps to supply a name for the region, such as Public methods. Here's what this code section looks like:
#region Public methods... your code#endregion Public methods
This name can include spaces. Also, you can nest one region inside another, but regions can't overlap.
For now, using System; is the only using directive you really need. You can delete the others; the compiler lets you know whether you're missing one. | http://www.dummies.com/WileyCDA/DummiesArticle/Creating-the-Source-Program-for-Your-First-C-Console-Application.id-5873.html | crawl-001 | refinedweb | 659 | 65.22 |
public class Task { public void setStartDate( Date d ) { _start_date = d; } ... private Date _start_date; } ... Date d = new Date( some-value ); Task task1; task1.setStartDate( d ); d.setDate( some-other-value );Therefore: an object that holds mutable objects as state must ReturnNewObjectsFromAccessorMethods. Additionally, it must make private copies of mutable objects that are passed to it and that it needs to store internally. For example:
public class Task { public void setStartDate( Date d ) { _start_date = (Date)d.clone(); } ... }-- NatPryce
public class Task { public void setStartDate( Date d ) { _start_date = new Date(d.getTime()); } ... }-- EricJablow
// Version 1 function foo(a) { a = modify(a); return process(a); } // Version 2 function foo(a) { var c = a; // make a local copy c = modify(c); return process(c); }Assume that "a" here is passed by value in this dummy language. Would you consider version 1 or version 2 to be the better coding practice? Version 1 is simpler code, but can be misleading if we need to use "a" for other purposes and forget that it's been modified earlier in the function. Whatever the others working on your project expect. Absent those, I tend to decide based on what semantics I've given the parameter. If it doesn't change the semantics, I tend to use 1. Otherwise, I tend to use 2. | http://c2.com/cgi-bin/wiki?CopyMutableParameters | CC-MAIN-2015-40 | refinedweb | 215 | 58.18 |
I'm finding it difficult to understand your question; it would help if you supplied a sample of (a) your input, (b) the output you want to get, (c) the output you are getting. Michael Kay > -----Original Message----- > From: owner-xsl-list@xxxxxxxxxxxxxxxxxxxxxx > [mailto:owner-xsl-list@xxxxxxxxxxxxxxxxxxxxxx] On Behalf Of > Eder de Oliveira > Sent: 05 January 2004 14:24 > To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx > Subject: [xsl] Fw: How can I do to clear a reference from > schema in xml > > > How can I do to clear a reference from schema in XML? > > Hi people! > > I am inserting an attribute with a namespace, but this > namespace is a reference to schema in XML, it's OK. but if > already exists a either reference Schema in XML, How can I do > to clear this reference? and insert a reference correct? this > I isn't work. This is my code: > > <xsl:template > <xsl:element xmlns: > <xsl:attribute xmlns: > ww.cnpq.br/200 > 2/XSD/lattes Document Schema.xsd</xsl:attribute> > <xsl:apply-templates/> </xsl:element> </xsl:template> > > My question is: > > Once, > How can I do to clear a reference from schema in XML? > > twice, > How can I do to insert a reference a new schema on same XML? > > thanks > Eder de Oliveira > > > > > XSL-List info and archive: > XSL-List info and archive: | http://www.oxygenxml.com/archives/xsl-list/200401/msg00059.html | CC-MAIN-2019-13 | refinedweb | 218 | 71.04 |
I mainly work with PHP, learning Go is something I do as a hobby. I really like teaching and showing others how things work, hopefully my guide here will do a decent job of explaining how to track the price of STEEM. When I explain things I will often compare it to how PHP works as that is what I am used to working with.
Let's get started. First thing is you will need to install go, you can do this on linux, mac or pc. Here is what I am using for this tutorial, everything except Go is optional.
- Go v1.8.3
- Gogland
- A macbook pro
- CryptoCompare API (You can probably follow along with any API with small adjustments)
So let's get started. I am using the CryptoCompare API which claims to be the best API around and lists several websites that use their API, all they ask is that you link to their site if you use their API. It allows for up to 4000 requests every hour but we should be ok with a request every minute for our own personal use, every 10 seconds to see that it's working.
I want to make use of their price method that takes 2 arguments, the currency you want to check and then a list of currencies you would like to see the price for the first currency in.
Lets navigate to our $GOPATH folder and create a new project. I created my project under /go/src/github.com/markustenghamn/golang-steem-cryptotracker and then added this folder as a new project in Gogland. I then created a file called price.go. The initial file looks like this:
package main func main() { }
So let's begin by declaring our variables. I want to know the value of 1 STEEM if I were to convert it to USD, thus a from and a to variable along with our url where I have added the variables. We will use this url to make our request and get our json data.
package main func main() { From := "STEEM" To := "USD" url := "" + From + "&tsyms=" + To }
Now, let's make our request.
package main import ( "net/http" "time" "log" } func main() { From := "STEEM" To := "USD" url := "" + From + "&tsyms=" + To // We create a http client with a timeout of 30 seconds, you can probably set this lower if you would like w := http.Client{ Timeout: time.Second * 30, } // We create a new request, I uses _ to ignore any error here req, _ := http.NewRequest(http.MethodGet, url, nil) // We execute the request res, getErr := w.Do(req) if getErr != nil { log.Println(getErr) } else { // We will put the rest of our code here. This runs if the request is successful } }
You may also have noticed that I added a few import statements. This is because we need http, log and time to setup the request, make the request and handle any errors. We will be adding a few more import statements before we are done. Right now we make the request but we also need to handle the data. I left a comment in the code where the next part will go. You can also find a link to the entire sample at the bottom of this article. So let's handle the data, we will parse the json, create a type to hold the data and then output the data. We could create a struct for the json data but this api is fairly simple so all we need is the type as a map (an array basically).
// We read the response body body, readErr := ioutil.ReadAll(res.Body) if readErr != nil { log.Println(readErr) } else { // If the response can be read we move on the parsing the json r := Result{} // We unmarshal the json using our result type jsonErr := json.Unmarshal(body, &r) if jsonErr != nil { log.Println(jsonErr) } else { // We loop through all of our results and echo them, should only be one result for _, p := range r { fmt.Println("1 "+From+" = "+To) } } }
I added a result type right below the import statement.
type Result map[string]float64
My import statement now looks like this:
import ( "net/http" "time" "io/ioutil" "encoding/json" "fmt" "log" )
Now if you run this you should get an output like this
1 STEEM = 1.270000 USD. Now, running the script every time we want to check the price is not optimal. Therefore we want to put all the code we just wrote into a function that we can call every 10 seconds for example so that we get the most recent price. My new function is called ´getPrice´ and takes a time parameter so we can output this in our console. My main function has been changed and looks like this:
func main() { doEvery(time.Second * 10, getPrice) }
My doEvery function looks like this:
func doEvery(d time.Duration, f func(time.Time)) { for x := range time.Tick(d) { f(x) } }
I also modified the output string so that it now looks like this:
fmt.Printf("%v: 1 "+From+" = "+strconv.FormatFloat(p, 'f', 6, 64)+" "+To+"\n", t)
That's it, now you should have a stream of data pouring in every 10 seconds. I plan to keep developing this app, make it a bit more useful. I would like to track my STEEM, Bitcoin and any other altcoin. It would be nice to see a statistics on when I earned or bought my coin and how the price has changed over time so that I know if I have lost or gained money. I think it might be a cool project to launch as a website if others find it interesting.
You can also build this as an application with 'go build' and the application will run on linux, mac or windows without the need to install golang.
I have uploaded the complete sample to GitHub if anyone wants to take a look at the code:
Wow!
Thanks for shedding some light on GO, please post more stuff like this.
I enjoy new twists and turns like you have displayed.
Followed, Upvoted and Resteemed
Thank you! Really appreciate the feedback, my plan is to keep making new posts in the future!
happy day | https://steemit.com/cryptocurrency/@tenghamn/how-to-make-a-simple-go-program-to-track-the-price-of-steem-via-an-api | CC-MAIN-2018-43 | refinedweb | 1,043 | 79.9 |
Enumerators Tutorial Part 2: Enumerator
October 2, 2010
Michael Snoyman
This content is now part of the Yesod book. It is recommended to read there, since the content is more up-to-date.
Note: code for this tutorial is available as a github gist.
Extracting a value
When we finished the last part of our tutorial, we had written a few iteratees, but we still didn't know how to extract values from them. To start, let's remember that Iteratee is just a newtype wrapper around Step:
newtype Iteratee a m b = Iteratee { runIteratee :: m (Step a m b) }
First we need to unwrap the Iteratee and deal with the Step value inside. Remember also that Step has three constructors: Continue, Yield and Error. We'll handle the Error constructor by returning our result in an Either. Yield already provides the data we're looking for.
The tricky case is Continue: here, we have an iteratee that is still expecting more data. This is where the EOF constructor comes in handy: it's our little way to tell the iteratee to finish what it's doing and get on with things. If you remember from the last part, I said a well-behaving iteratee will never return a Continue after receiving an EOF; now we'll see why:
extract :: Monad m => Iteratee a m b -> m (Either SomeException b) extract (Iteratee mstep) = do step <- mstep case step of Continue k -> do let Iteratee mstep' = k EOF step' <- mstep' case step' of Continue _ -> error "Misbehaving iteratee" Yield b _ -> return $ Right b Error e -> return $ Left e Yield b _ -> return $ Right b Error e -> return $ Left e
Fortunately, you don't need to redefine this yourself: enumerator includes both a run and run_ function. Let's go ahead and use it on our sum6 function:
main = run_ sum6 >>= print
If you run this, the result will be 0. This emphasizes an important point: an iteratee is not just how to process incoming data, it is the state of the processing. In this case, we haven't done anything to change the initial state of sum6, so we still have the initial value of 0.
To give an analogy: think of an iteratee as a machine. When you feed it data, you modify the internal state but you can't see any of those changes on the outside. When you are done feeding the data, you press a button and it spits out the result. If you don't feed in any data, your result is the initial state.
Adding data
Let's say that we actually want to sum some numbers. For example, the numbers 1 to 10. We need some way to feed that into our sum6 iteratee. In order to approach this, we'll once again need to unwrap our Iteratee and deal with the Step value directly.
In our case, we know with certainty that the Step constructor we used is Continue, so it's safe to write our function as:
sum7 :: Monad m => Iteratee Int m Int sum7 = Iteratee $ do Continue k <- runIteratee sum6 runIteratee $ k $ Chunks [1..10]
But in general, we won't know what constructor will be lying in wait for us. We need to properly deal with Continue, Yield and Error. We've seen what to do with Continue: feed it the data. With Yield and Error, the right action in general is to do nothing, since we've already arrived at our final result (either a successful Yield or an Error). So the "proper" way to write the above function is:
sum8 :: Monad m => Iteratee Int m Int sum8 = Iteratee $ do step <- runIteratee sum6 case step of Continue k -> runIteratee $ k $ Chunks [1..10] _ -> return step
Enumerator type synonym
What we've done with sum7 and sum8 is perform a transformation on the Iteratee. But we've done this in a very limited way: we've hard-coded in the original Iteratee function (sum6). We could just make this an argument to the function:
sum9 :: Monad m => Iteratee Int m Int -> Iteratee Int m Int sum9 orig = Iteratee $ do step <- runIteratee orig case step of Continue k -> runIteratee $ k $ Chunks [1..10] _ -> return step
But since we always just want to unwrap the Iteratee value anyway, it turns out that it's more natural to make the argument of type Step, ie:
sum10 :: Monad m => Step Int m Int -> Iteratee Int m Int sum10 (Continue k) = k $ Chunks [1..10] sum10 step = returnI step
This type signature (take a Step, return an Iteratee) turns out to be very common:
type Enumerator a m b = Step a m b -> Iteratee a m b
Meaning sum10's type signature could also be expressed as:
sum10 :: Monad m => Enumerator Int m Int
Of course, we need some helper function to connect an Enumerator and an Iteratee:
applyEnum :: Monad m => Enumerator a m b -> Iteratee a m b -> Iteratee a m b applyEnum enum iter = Iteratee $ do step <- runIteratee iter runIteratee $ enum step
Let me repeat the intuition here: the Enumerator is transforming the Iteratee from its initial state to a new state by feeding it more data. In order to use this function, we could write:
run_ (applyEnum sum10 sum6) >>= print
This results in 55, exactly as we'd expect. But now we can see one of the benefits of enumerators: we can use multiple data sources. Let's say we have another enumerator:
sum11 :: Monad m => Enumerator Int m Int sum11 (Continue k) = k $ Chunks [11..20] sum11 step = returnI step
Then we could simply apply both enumerators:
run_ (applyEnum sum11 $ applyEnum sum10 sum6) >>= print
And we would get the result 210. (Yes, (1 + 20) * 10 = 210.) But don't worry, you don't need to write this applyEnum function yourself: enumerator provides a $$ operator which does the same thing. Its type signature is a bit scarier, since it's a generalization of applyEnum, but it works the same, and even makes code more readable:
run_ (sum11 $$ sum10 $$ sum6) >>= print
$$ is a synonym for ==<<, which is simply
flip >>==. I find
$$ the most readable, but YMMV.
Some built-in enumerators
Of course, writing a whole function just to pass some numbers to our sum function seems a bit tedious. We could easily make the list an argument to the function:
sum12 :: Monad m => [Int] -> Enumerator Int m Int sum12 nums (Continue k) = k $ Chunks nums sum12 _ step = returnI step
But now there's not even anything Int-specific in our function. We could easily generalize this to:
genericSum12 :: Monad m => [a] -> Enumerator a m b genericSum12 nums (Continue k) = k $ Chunks nums genericSum12 _ step = returnI step
And in fact, enumerator comes built in with the enumList function which does this. enumList also takes an Integer argument to indicate the maximum number of elements to stick in a chunk. For example, we could write:
run_ (enumList 5 [1..30] $$ sum6) >>= print
(That produces 465 if you're counting.) The first argument to enumList should never affect the result, though it may have some performance impact.
Data.Enumerator includes two other enumerators: enumEOF simply passes an EOF to the iteratee. concatEnums is slightly more interesting; it combines multiple enumerators together. For example:
run_ (concatEnums [ enumList 1 [1..10] , enumList 1 [11..20] , enumList 1 [21..30] ] $$ sum6) >>= print
This also produces 465.
Some non-pure input
Enumerators are much more interesting when they aren't simply dealing with pure values. In the first part of this tutorial, we gave the example of the user entering numbers on the command line:
getNumber :: IO (Maybe Int) getNumber = do x <- getLine if x == "q" then return Nothing else return $ Just $ read x sum2 :: IO Int sum2 = do maybeNum <- getNumber case maybeNum of Nothing -> return 0 Just num -> do rest <- sum2 return $ num + rest
We referred to this as the pull-model: sum2 pulled each value from getNumber. Let's see if we can rewrite getNumber to be a pusher instead of a pullee.
getNumberEnum :: MonadIO m => Enumerator Int m b getNumberEnum (Continue k) = do x <- liftIO getLine if x == "q" then continue k else k (Chunks [read x]) >>== getNumberEnum getNumberEnum step = returnI step
First, notice that we check which constructor was passed, and only perform any actions if it was Continue. If it was Continue, we get the line of input from the user. If the line is "q" (our indication to stop feeding in values), we do nothing. You might have thought that we should pass an EOF. But if we did that, we'd be preventing other data from being sent to this iteratee. Instead, we simply return the original Step value.
If the line was not "q", we convert it to an Int via read, create a Stream value with the Chunks datatype, and pass it to k. (If we wanted to do things properly, we'd check if x is really an Int and use the Error constructor; I leave that as an exercise to the reader.) At this point, let's look at type signatures:
k (Chunks [read x]) :: Iteratee Int m b
If we simply left off the rest of the line, our program would typecheck. However, it would only ever read one value from the command line; the
>>== getNumberEnum causes our enumerator to loop.
One last thing to note about our function: notice the b in our type signature.
getNumberEnum :: MonadIO m => Enumerator Int m b
This is saying that our Enumerator can feed
Ints to any Iteratee accepting
Ints, and it doesn't matter what the final output type will be. This is in general the way enumerators work. This allows us to create drastically different iteratees that work with the same enumerators:
intsToStrings :: (Show a, Monad m) => Iteratee a m String intsToStrings = (unlines . map show) `fmap` consume
And then both of these lines work:
run_ (getNumberEnum $$ sum6) >>= print run_ (getNumberEnum $$ intsToStrings) >>= print
Exercises
Write an enumerator that reads lines from stdin (as Strings). Make sure it works with this iteratee:
printStrings :: Iteratee String IO () printStrings = do mstring <-return () Just string -> do liftIO $ putStrLn string printStrings
Write an enumerator that does the same as above with words (ie, delimit on any whitespace). It should work with the same Iteratee as above.
Do proper error handling in the getNumberEnum function above when the string is not a proper integer.
Modify getNumberEnum to pull its input from a file instead of stdin.
Use your modified getNumberEnum to sum up the values in two different files.
Summary
An enumerator is a step transformer: it feeds data into an iteratee to produce a new iteratee with an updated state.
Multiple enumerators can be fed into a single iteratee, and we finally use the run and run_ functions to extract results.
We can use the $$, >>== and ==<< operators to apply an enumerator to an iteratee.
When writing an enumerator, we only feed data to an iteratee in the Continue state; Yield and Error already represent final values. | http://www.yesodweb.com/blog/2010/10/enumerators-tutorial-part-2 | CC-MAIN-2016-40 | refinedweb | 1,836 | 57.61 |
LoPy to LoPy communication issue with button
Hi,
I am new to the Pycom platform and I am trying to get a LoPy to communicate over LoRa with another LoPy when a button is pressed.
I have tried the LoPy to LoPy example code and have this working fine:
I now have a breadboard set up with a momentary pushbutton connected to digital pin 9 through the Expansion 3 board.
The issue I am having is that when I push the button, I believe the LoPy is sending a LoRa signal as I am printing to the console after the packet is sent but the receiving LoPy is not receiving the signal.
In its simplest form, the code below is how I am trying to send and receive the LoRa signal:
from network import LoRa from machine import Pin import pycom import socket import time lora = LoRa(mode=LoRa.LORA, region=LoRa.EU868) s = socket.socket(socket.AF_LORA, socket.SOCK_RAW) s.setblocking(False) pycom.heartbeat(False) activateButton = Pin('P9', mode=Pin.IN) print('Starting to send....') while True: if (activateButton() == 1): s.send('Hi') print('Signal sent') time.sleep(1)
from network import LoRa import pycom import socket import time lora = LoRa(mode=LoRa.LORA, region=LoRa.EU868) s = socket.socket(socket.AF_LORA, socket.SOCK_RAW) s.setblocking(False) pycom.heartbeat(False) print('Starting') while True: if s.recv(64) == b'Hi': print('Signal received') time.sleep(1)
I have tried various other ways of coding the same thing. I have also tried to just modify the LoPy to LoPy example, which works, but instead of just sending a signal automatically I send it when I push the button. Once again this does not have the desired outcome on the receiving side.
I have been at this for days now and have searched through community postings but cannot find anything that can point me in the right direction.
From what I can gather, what I am doing is very simple and should work.
I am also having an issue where by after sending 8-14 LoRa packets I get an EAGAIN error.
Please let me know where I am going wrong.
Thank you
Hi Guys,
I seemed to have solved this by moving the time.sleep(1) of code into the if statement.
This also solved the EAGAIN error that I was receiving.
Thank you for the time you all took to reply.
- Gijs Global Moderator last edited by
I am also having an issue where by after sending 8-14 LoRa packets I get an EAGAIN error.
I would really like to learn more about this error. I custom compiled a firmware for someone earlier this week to determine the cause of this as I cannot reproduce it, would you like to send it to you as well (here). You can use the firmware updater tool to flash from local file, it will provide some additional debug information in that area.
Other than that, I have no issues running the example from the documentation (as you mention as well) and am quite puzzled why yours does not work, as the code does work on my device. Please try the suggestion by @jcaron and maybe add some indication, like changing the color on the RGB LED when a LoRa packet is sent
@Alex-Ray One problem I always have with the simple Raw mode LoRa sensing from one device to the other using LoPy4 devices, that it will not work unless I push hard reset at the button on both devices after power on, and then run the code.
Note that lora.reset() still causes a core dump, and besides that is an No-operation on LoPy4.
@Alex-Ray try logging the return value of the
s.recv(64)call, to see if anything has been received, and if so, what.
You may also want to explicitly set frequency, bandwidth, spreading factor, etc. I suppose the defaults should be the same in both sides, but it’s always better to know what they are. | https://forum.pycom.io/topic/6763/lopy-to-lopy-communication-issue-with-button | CC-MAIN-2021-10 | refinedweb | 673 | 62.48 |
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Preview
[MUSIC] 0:00
Now that we've been introduced to REST APIs and the WEB API framework, 0:04
we're ready to work on our API. 0:09
Let's get started. 0:11
There are two options for getting started with the WEB API framework. 0:13
Creating a new project with the necessary dependencies and configuration. 0:17
We're adding those things to an existing project. 0:21
When creating a new ASP.NET project, you actually have two options. 0:28
The first option, is to use the empty project template and 0:33
select to add the Web API folders and core references to your project. 0:37
Your project won't contain any API controllers, but 0:44
it'll have everything that you need to get started with adding your first controller. 0:47
The second option, is to select the Web API project template. 0:51
This will give you a project that not only contains the Web API folders and 0:56
core references, but also a single example controller. 0:59
The project will also contain an example of how to combine Web API and 1:03
MVC, to provide help pages for your API. 1:08
For more information on how to provide help pages for 1:11
your API, see the teacher's notes. 1:14
Since we're starting with an existing project, 1:17
we need to add the necessary dependencies and configuration to our project. 1:19
To do that, we can use the NuGet package manager. 1:23
If we browse for packages and scroll down in the list of it, 1:29
We should see the Microsoft.AspNet.WebApi package. 1:38
If you don't see it in this list, try typing WebApi in the search box. 1:43
At the time of this recording, the latest stable version is 5.2.3, 1:48
which is actually WebApi 2.2. 1:53
Once you've found the correct package, go ahead and install it. 1:56
Web API itself is dependent on a number of other packages. 2:02
Newtonsoft.Json, AspNet.WebAPI.Client, 2:07
AspNet.WebAPI.Core, and AspNet.WebAPI.WebHost. 2:12
Go ahead and click OK, and accept the end user agreement. 2:21
Now that we've installed Web API, 2:34
we need to define a static method to configure Web API. 2:36
First, add a folder named App_Start, Add, New Folder. 2:40
Then add a new C# class named Web API Config to the App_Start folder. 2:51
Go ahead and remove App_Start from the end of the namespace. 3:04
Typically, the convention is for 3:10
the last segment of the namespace to match the folder name. 3:12
But for classes located in the ASP.NET App_Start folder, 3:15
the convention is to use the project's route namespace. 3:18
Doing this will make it slightly easier to reference our static method 3:22
from the Global.asax CS file. 3:26
The WebApiConfig class will only contain a single static method. 3:30
So let's make the class itself static 3:34
by adding the static keyword right before the class keyword. 3:36
Doing this will prevent the class from ever been instantiated. 3:41
Now, add the static method named registered, 3:45
public static void Register, 3:51
And a parameter of type HttpConfiguration. 3:57
Add a using statement for the System Web.Http namespace. 4:06
And name the parameter, config. 4:12
In later videos, we'll add code to this method to configure our API. 4:15
Now that we have our API configuration method, 4:20
we need to ensure that it'll get called when an application is starting up. 4:22
We can do that by updating the Global.asax CS file located in the root 4:27
of our project. 4:31
The Global.asax CS file defines a class containing a method named, 4:36
Application_Start, which is called every time that the web app is started. 4:41
To ensure that our configuration method will get called at the right time 4:47
when the Web API framework is being initialized, we call the global 4:51
configuration, Configure method, and pass a reference to our configuration method. 4:55
Remember, WebApiConfig is the name of the static class. 5:23
And Register is the name of our static configuration method. 5:28
By not including a set of parentheses here, 5:32
we're passing a reference to the method instead of calling it. 5:34
Our project isn't using the MVC web framework. 5:38
But if we were adding WebApi to an existing MVC project, 5:41
we'd need to make sure to call the global configuration, Configure method, 5:44
before calling the method that configures the routes for MVC. 5:49
The easiest way to ensure that happens is to always place this method call at 5:53
the top of the Application_Start method. 5:57
Okay, we've got our Configuration method stubbed out, but 6:04
it's not doing anything yet. 6:07
Let's fix that next. 6:09 | https://teamtreehouse.com/library/adding-web-api-to-our-project?t=56 | CC-MAIN-2021-21 | refinedweb | 914 | 73.68 |
How I Built Emojitracker
Adventures in Unicode, Real-time Streaming, and Media Culture
Em.
Emojitracker wasn’t my first megaproject, but it is definitely the most complex architecturally.
While the source code for emojitracker has been open-source since day one, the technical concepts are complex and varied, and the parts of the code that are interesting are not necessarily obvious from browsing the code. Thus, rather than a tutorial, in this post I intend to write about the process of building emojitracker: the problems I encountered, and how I got around them.
This is a bit of a brain dump, but my hope is it will be useful to others attempting to do work in these topic areas. I have benefited greatly from the collective wisdom of others in the open-source community, and thus always want to try to do my best to contribute back domain knowledge into the commons.
This post is long, and is primarily intended for a technical audience. It details the origin story and ideas for emojitracker, the backend architecture in detail, frontend client issues with displaying emoji and high-frequency display updates, and the techniques and tools used to monitor and scale a multiplexed real-time data streaming service across dozens of servers with tens of millions of streams per day (on a hobby project when you don’t have any advance warning!).
Prologue: Why Emoji?
I’ve also always had a soft spot for emoji. My friends and colleagues know that emoji makes an appearance in many aspects of my life, including my wifi network, LinkedIn recommendations, and domain names. I even once signed a part-time employment contract stipulating emoji was my native language and all official notices be provided to me that way (which I don’t necessarily endorse). Oh, and then there’s the emoji nail art (which I do endorse).
I’d been playing around with the idea of realtime streaming from the Twitter API on a number of previous projects (such as goodvsevil, which was the spiritual predecessor to emojitracker), and I was curious about seeing how far I could push it in terms of number of terms monitored. At 842 terms to track, emoji seemed like a prime candidate.
Emoji are also a great way to get insight to the cultural zeitgeist of Twitter: the creative ways in which people appropriate and use emoji symbols is fascinating, and I hoped to be able to build a lens that would enable one to peer into that world with more detail.
And finally, (and quite foolishly) emoji seemed simple at the time. Normally I try to pick hacks that I can implement pretty quickly and get out into the world within a day or two. Boy, was I wrong in this case. Little did I know how complex emoji can be… This post is a testament to the software development journey emoji brought me on, and the things I learned along the way.
Background Understanding: Emoji and Unicode
The history of Emoji has been written about in many places, so I’m going to keep it brief here and concentrate more on the technical aspects.
TLDR: Emoji emerged on feature phones in Japan, there were a number of carrier specific implementations (Softbank/KDDI/Docomo), each with its own incompatible encoding scheme. Apple’s inclusion of Emoji on the iPhone (originally region-locked to Asia but easily unlocked with third-party apps) led to an explosion in global popularity, and now Emoji represents the cultural force of a million voices suddenly crying out in brightly-colored pixelated terror.
But for the modern software developer, there are a few main things you’ll need to know to work with Emoji. Things got a lot better in late 2010 with the release of Unicode 6.0… mostly. The emoji glyphs were mostly standardized to a set of Unicode codepoints.
Now, you may be thinking: “Wait, standards are good, right? And why do you say ‘mostly’ standardized, that sounds suspicious…”
Of course, you’d be correct in your suspicions. Standardization is almost never that simple. For example, take flags. When time came to standardize Emoji codepoints, everyone wanted their country’s flag added to the original 10 in the Softbank/DoCoMo emoji. This had the potential to get messy fast, so instead what we ended up with were 26 diplomatically-safe “Regional indicator symbols” set aside in the Unicode standard. This avoided polluting the standard with potentially hundreds of codepoints that could become quickly outdated with the evolving geopolitical climate, while preserving Canada’s need to assert their flag’s importance to the Emoji standardization process:
These characters can be used in pairs to represent regional codes. In some emoji implementations, certain pairs may be recognized and displayed by alternate means; for instance, an implementation might recognize F + R and display this combination with a symbol representing the flag of France.
Note the standards-body favorite phrases “CAN BE” and “MAY BE” here. This isn’t a “MUST BE,” so in practice, none of the major device manufacturers have actually added new emoji art flags, infuriating iPhone-owning Canadians every July 1st:
For a detailed and amusing exploration of this and other complex issues surrounding the rough edges of Unicode, I highly recommend Matt Mayer’s “Love Hotels and Unicode” talk, which was invaluable in helping my understanding when parsing through these issues.
For these double-byte emoji glyphs, the popular convention is to be represent them in ID string notation with a dash in between the codepoint identifiers, such as 1F1EB-1F1F7.
This of course makes the life of someone writing Emoji-handling code more difficult, as pretty much all the boilerplate you’ll find out there assumes a single Unicode code point per character glyph (since after all, this was the problem that Unicode was supposed to solve to begin with).
For example, say you want to parse and decode an emoji character from a UTF-8 string to identify its unified codepoint identifier. Conventional wisdom would be that this a simple operation, and you’ll find lots of sample code that looks like this:
# return unified codepoint for a character, in hexadecimal
def char_to_unified(c)
c.unpack("U*").first.to_s(16)
end
If you have a sharp eye, you’ll probably notice the danger-zone of using first() to convert an array into a string: assuming we’re always going to get one value back from the unpack() since we only sent one character in. And in most cases, it will of course work fine. But for our strange double-byte emoji friends, this won’t work, since that unpack() operation is actually going to return two values, the second of which we’ll be ignoring. Thus, if we pass in the American Flag emoji character, we’ll get back 1f1fa—which represents the rather boring on its own REGIONAL INDICATOR SYMBOL U:
So instead, we have to do some string manipulation hijinks like this:
# return unified codepoint for a character, in hexadecimal.
# — account for multibyte characters, represent with dash.
# — pad values to uniform length.
def char_to_unified(c)
c.codepoints.to_a.map {|i| i.to_s(16).rjust(4,'0')}.join('-')
end
Now, char_to_unified() on a UTF-8 string containing the American Flag emoji will return the properly patriotic value 1f1fa-1f1f8.
Surprisingly, there wasn’t a good Ruby library in existence to handle all this (most existing libraries concentrating on encoding/decoding emoji strictly in the :shorthand: format).
Thus, I carved that portion of the work in emojitracker out into a general purpose library now released as its own open source project: emoji_data.rb. It handles searching the emoji space by multiple values, enumeration, convenience methods, etc. in a very Ruby-like way.
For example, you can do the following to find the short-name of all those pesky double-byte Emoji glyphs we mentioned:
>> EmojiData.all.select(&:doublebyte?).map(&:short_name)
=> [“hash”, “zero”, “one”, “two”, “three”, “four”, “five”, “six”, “seven”, “eight”, “nine”, “cn”, “de”, “es”, “fr”, “gb”, “it”, “jp”, “kr”, “ru”, “us”]
For more examples, check out its README. This library is consistently used across almost all of the different software projects that make up Emojitracker, and hopefully will be useful for anyone else doing general purpose Emoji/Unicode operations!
Emojitracker Backend Architecture
Here’s the overall architecture for Emojitracker in a nutshell: A feeder server receives data from the Twitter Streaming API, which it then processes and collates. It sends that data into Redis, but also publishes a realtime stream of activity into Redis via pubsub streams. A number of web streamer servers then subscribe to those Redis pubsub streams, handle client connections, and multiplex subsets of that data out to clients via SSE streaming.
We’ll talk about all of these components in detail in this section.
Feeding the Machine: Riding the Twitter Streaming API
If you’re doing anything even remotely high volume with Twitter, you need to be using the Streaming APIs instead of polling. The Streaming APIs allow you to create a set of criteria to monitor, and then Twitter handles the work of pushing updates to you whenever they occur over a single long-life socket connection.
In the case of Emojitracker, we use our EmojiData library to easily construct an array of the Unicode chars for every single Emoji character, which we then send to the Streaming API as track variables for status/filter. The results are easy to consume with a Ruby script utilizing the TweetStream gem, which abstracts away a lot of the pain of dealing with the Twitter Streaming API (reconnects, etc) in EventMachine.
From this point it’s simple to have an EventMachine callback that gets triggered by TweetStream every time Twitter sends us a matching tweet. It’s important to note that the Streaming API doesn’t tell you which track term was matched, so you have to do that work yourself by matching on the content of the tweet.
Also, keep in mind that it’s entirely possible (and in our case, quite common!) for a tweet to match multiple track terms—when this happens, the Twitter Streaming API is still only going to send it to you once, so it’s up to you to handle that in the appropriate fashion for your app.
Then, we simply increment the count for each emoji glyph contained in the tweet (but only once per glyph) and also push out the tweet itself to named Redis pubsub streams (more details on the structure for this in the next section).
The JSON blob that the Twitter API sends for each tweet is pretty massive, and at a high rate this will get bandwidth intensive. The feeder process for Emojitracker is typically receiving a full 1MB/second of JSON data from Twitter’s servers.
Since in our cases we’re going to be re-broadcasting this out at an extremely high rate to all the streaming servers, we want to trim this down to conserve bandwidth. Thus we create a new JSON blob from a hash containing just the bare minimum to construct a tweet: tweet ID, text, and author info (permalink URLs are predictable and can be recreated with this info). This reduces the size by 10-20x.
As long as you drop-in a performant JSON parsing engine (I use and highly recommend Oj), you can do all this parsing and recombining with relatively low server impact. Swap in hiredis for an optimized Redis driver and things can be really fast and efficient: the feeder component for Emojitracker is acting upon ~400-500 tweets-per-second at peak, but still only operates at ~10-12% CPU utilization on the server it runs on, in MRI Ruby 1.9.3. In reality, network bandwidth will be the biggest constraint once your code is optimized.
Data Storage: Redis sorted sets, FIFO, and Pubsub streams
Redis is an obvious data-storage layer for rapidly-changing and streaming data. It’s super fast, has a number of data structures that are ideally suited for this sort of application, and additionally its built-in support for pubsub streaming enables some really impressive ways of shuffling data around.
For emojitracker, the primary piece of data storage we have is a set of emoji codepoint IDs and their respective counts. This maps very well to the Redis built-in data structure Sorted Set, which conveniently maps strings to scores, and has the added benefit of making it extremely fast to query that list sorted by the score. From the Redis documentation:.
This makes keeping track of scores and rank trivially easy. We can simply fire off ZINCRBY increment commands to the set for the equivalent emoji codepoint ID every time we see a match—and then call ZRANK on an ID to find out it’s current position, or use ZRANGE WITHSCORES to get the entire list back in the right order with the equivalent numbers for display.
This gives us an easy way to track the current score and ranking, but we want to stream updates in realtime to clients, so what we really need in addition is way to send those update notifications out. Thankfully, Redis PUBLISH and SUBSCRIBE is essentially perfect for that.
With Redis Pubsub streams, the feeder can simply publish any updates to a named stream, which an client can subscribe to to receive all messages. In Emojitracker, we publish two types of streams:
- General score updates. Anytime we increment a score for an Emoji symbol, we also send an activity notification of that update out to stream.score_updates.
- Tweet streams. 842 different active streams for these (one for each emoji symbol). This sounds more complex than it is—in Redis, streams are lightweight and you don’t have to do any work to set them up, just publish to a unique name. For any matching Tweet, we just publish our “small-ified” JSON blob to the equivalent ID stream. For example, a tweet matching both the dolphin and pistol emoji symbols would get published to the stream.score_updates.1f42c and stream.score_updates.1f52b streams.
Clients can then subscribe to whichever streams they are interested in, or use wildcard matching (PSUBSCRIBE stream.score_updates.*) to get the aggregate of all tweet updates.
While this live stream of tweets in Emojitracker is mostly powered by the aforementioned Pubsub streams, there are cases where they won’t work. For example, when a new web client connects to a detail stream it’s necessary to “backfill” the most recent 10 items for display so that the client starts with some data to show the user (especially on the less frequently used emoji symbols).
Redis doesn’t have a built-in concept of a fixed-size FIFO queue (possibly more accurately described as a fixed-size evicting queue?), but this is easy to emulate by using LPUSH and LTRIM. Push to one side of a list, and then immediately trim from the other to maintain the fixed length. Like most things in Redis, it doesn’t matter if these commands come out of order, it will balance out and the overall size of the list will remain relatively constant. Easy-peasy.
Putting it all together, here’s the relevant section of source code from the Ruby program that feeds Redis from the Twitter streaming API (I included the usage of the aforementioned EmojiData library to do the character conversion):
matches = EmojiData.chars.select { |c| status.text.include? c }
matches.each do |matched_emoji_char|
# get the unified codepoint ID for the matched emoji char
cp = EmojiData.char_to_unified(matched_emoji_char)
REDIS.pipelined do
# increment the score in a sorted set
REDIS.ZINCRBY 'emojitrack_score', 1, cp
# stream the fact that the score was updated
REDIS.PUBLISH 'stream.score_updates', cp
# for each emoji char, store most recent 10 tweets in a list
REDIS.LPUSH "emojitrack_tweets_#{cp}", status_json
REDIS.LTRIM "emojitrack_tweets_#{cp}",0,9
# also stream all tweet updates to named streams by char
REDIS.PUBLISH "stream.tweet_updates.#{cp}", status_json
end
end
It’s common knowledge worth repeating that Redis is highly performant. The current instance powering Emojitracker routinely peaks at 2000-4000 operations/second, and only is using ~3.98MB of RAM.
Pushing to Web Clients: Utilizing SSE Streams
When thinking about streaming data on the web, most people’s thoughts will immediately turn to WebSockets. It turns out, if you don’t need bidirectional communication, there is a much simpler and well suited technology that accomplishes this over normal HTTP connections: Server-Sent Events (SSE).
I won’t go into detail about the SSE protocol (the above link is a great resource for learning more about it), instead I’ll just say it’s trivially easy to handle SSE in Javascript, for example the full logic for subscribing to an event source and passing events to a callback handler can be accomplished in a barely more than a single line of code. The protocol will automatically handle reconnections, etc. The more interesting aspect for us is how we handle this on the server side.
Each web streamer server maintains two connection pools:
- The raw score stream — anything connected here is going to get everything rebroadcast from the score update stream, and everyone gets the same thing. Pretty simple.
- The tweet detail updates queue is more complex. We use a connection wrapper that maintains some state information for each client connected to the stream. All web clients receiving tweet detail updates from the streaming server are actually in the same connection pool, but when they connect they pass along as a parameter the ID of the emoji character they want updates on, which gets added to their wrapper object as tagged metadata. We later use this to determine which updates they will receive.
There are typical Sinatra routes that handle incoming stream connections, and essentially all they do is use stream(:keep_open) to hold the connection open, and then add the connecting client’s information to to the connection pool. When the client disconnects, Sinatra removes it from that pool.
In order to populate the SSE streams on the server side, we need to get the data out of Redis to pass along. Each web streamer server spawns two independent event-propagation threads, each of which issues a SUBSCRIBE to a Redis stream. Not surprisingly, these are the two types of streams we mentioned in the previous section: 1.) The overall score updates stream, and 2.) a wildcard PSUBSCRIBE representing the aggregate of all individual tweet streams.
Each thread then processes incoming events from the Redis streams, iterating over every client in the connection pool and writing data out to it. For the raw score updates, this is just a simple iteration, for the tweet details, each wrapped connection in the pool has it’s tag compared to the event ID of the current event, and is only written to in the case of a match.
The end result is a relatively efficient way to stream updates out to many clients simultaneously, even though they may be requesting/receiving different data.
Performance Optimizations for High Frequency SSE Streams
SSE is great, but when you start to approach hundreds of events per second, raw bandwidth is going to become a concern. For Emojitracker, we needed to turn to a number of performance enhancements were necessary to reduce the bandwidth of the stream updates so that people without super-fat pipes could play along.
Note: both of these optimizations are probably overkill unless you are handling at least tens if not hundreds of events per second, but in extremely high-frequency applications they are the only way to make things possible.
Trim the actual SSE stream format as much as possible.
Every character counts here. SSE streams can’t be gzipped, so you need to be economical with your formatting. For example, the whitespace after the colon in DATA: is optional. One character multiplied by potentially hundreds of times per second ends up being quite a bit over time.
Consider creating a cached “rollup” version of the stream that aggregates events.
You’re never going to need to update your client frontend more than 60 times per second, as that’s above what humans can perceive. That seems pretty fast, but in Emojitracker’s case, we actually are high frequency enough that we typically have many score updates occur in every 1/60th of a second ticket.
Thus, instead of rebroadcasting each of these events out immediately upon receiving them from the Redis pubsub stream, each web stream holds them in an in-memory queue which we expunge in bulk 60 times per second, rolling up the number of events that occurred for each ID in that timeframe.
Therefore, where normally in one 1/60th of a second tick we would send this:
data: 2665 \n\n
data: 1F44C \n\n
data: 1F44F \n\n
data: 1F602 \n\n
data: 2665 \n\n
data: 1F60B \n\n
data: 1F602 \n\n
We can instead send this:
data:{"2665":2,"1F44C":1,"1F44F":1,"1F602":2,"1F60B":1}\n\n
The size savings from eliminating the redundant data headers and repeat event IDs is nontrivial at scale (remember, no gzipping here!). You can compare and see the difference in action yourself by curl-ing a connection to emojitracker.com at /subscribe/raw and /subscribe/eps.
Even though in emojitracker’s case we go with 60eps for maximum disco pyrotechnics, in many cases you can likely get away with far more aggressive rollups, and broadcast at 30eps or even 5-10fps while still maintaining the user experience of full-realtime updates.
Gotcha: Many “cloud” environments don’t properly support this (and a workaround)
The crux: after building all this in development environment, I realized it wasn’t quite working correctly in production when doing load testing. The stream queue was filling up, getting bigger and bigger, never reducing in size. After much spelunking, it turned out that the routing layer used by many cloud server providers prevents the web server from properly seeing a stream disconnection on their end. In an environment where we are manually handling a connection pool, this is obviously no good.
My solution was to hack in a REST endpoint where clients could send an asynchronous “I just disconnected” post— the stream server would then manually expunge the client record from the pool.
I wasn’t 100% satisfied with this solution— I figured some portions of clients would disconnect without successfully transmitting the cleanup message (flakey net connections for example). Thus, the stream server also sweeps for and manually disconnects all stream connections after they hit a certain stream age. Clients that were actually active will then automatically reestablish their connection. Again, it’s ugly, but it works. I maintained the appearance of a continuous stream without stutter by reducing the EventSource reconnect delay significantly.
These were, of course, temporary hacks that were far less efficient in terms of extra HTTP requests (albeit ones that managed to carry emojitracker through it’s peak traffic). Thankfully, they are no longer needed. Very recently, Heroku finally rolled out labs support for Websockets which also fixes the underlying routing issues affecting SSE, thus removing the need for the workaround. (Thankfully, I made my workaround hacks enabled via a config variable, so once I added websockets support to my dynos I was able to quickly disable all those hacks and see everything worked fine.)
(You may be thinking that with all these workaround hacks it wasn’t worth hosting at Heroku at the time, and I should have just used my own conventional dedicated server. However, you’ll see later why this would have been a bad idea.)
With all these changes, one might wonder how I monitored the streaming connection pool to see how things were working. The answer: a custom admin interface.
Not crossing the streams: The admin interface
When attempting to debug things, I quickly realized that tailing a traditional log format is a really terrible way to attempt to understand what’s going on with long-lived streams. I hacked up a quick web interface showing me the essential information for the connection pools on a given web server: how many open connections and to whom, what information they were streaming, and how long those connections had been open:
The stream admin interface is actually open to the public, so you can mess around with it yourself.
Having an admin interface like this was absolutely essential to being able to visualize debug the status of streaming pools. From just watching the logs, there’s no way I would have noticed the connection pool problem in the previous section.
Frontend Architecture
For the most part, there is nothing that surprising here. Consuming a SSE stream is a fairly simple endeavor in Javascript, with widespread browser support. However, there were a number of “gotchas” with secondary functionality that ended up being somewhat complex.
Rendering Emoji Glyphs
Spoiler alert: sadly, most web browsers don’t support emoji display natively (Google, get on this! Forget Google+, we want emoji in Chrome!). Thankfully, you can utilize Cal Henderson’s js-emoji project to sniff the browser and either serve native emoji unicode or substitute in images via JS for the other browsers.
For that though, you still need to host a few thousand images for all the different emoji symbols. If you’re going to want to display in more than one resolution, multiply that by 5x. Too add to the problems, most of the existing emoji graphic sets out there (such as a the popular gemoji), have unoptimized PNGs and are missing many common display resolutions.
I wanted to solve this problem once and for all, so I created emojistatic.
Emojistatic is a hosted version of the popular gemoji graphic set, but adds lots of optimizations. It has multiple common sizes, all losslessly compressed and optimized, hosted on GitHub’s fast infrastructure for easy access.
It does more too, out of necessity. There are unfortunately many other problems inherent in display emoji beyond just swapping in appropriate images. I’ll discuss some of them here, and try to show what the emojistatic library does to help address them.
Image combination to reduce HTTP requests
Swapping in images is great in some instances, but what if you are displaying a lot of emoji? For example, in emojitracker’s case, we are displaying all 862 emoji glyphs on the first page load, and making 862 separate HTTP requests to get the images would be crazy.
Therefore, I built-in automatic CSS spritesheet generation to emojistatic. I used the embedded data-URI CSS sheet technique instead of a spritesheet, because shuffling around literally thousands of copies of a 1MB image in memory could have grave performance implications. In order to facilitate this, I ended up spinning off another open-source tool, cssquirt, a Ruby gem to embed images (or directories of images) directly into CSS via the Data URI scheme.
In order to get this to work with js-emoji, I had to fork it to add support to it for using the data-URI technique instead of loading individual images. The changes are in a pull-request, but until the maintainer accepts it (nudge nudge), you’ll unfortunately have to use my fork.
Native emoji display: the cake is a lie
What a pain. At least it must be easier on those web clients that support Emoji fonts natively, right? Right?!?! If we just stick to Safari on a fancy new OSX 10.9 install, surely Apple’s love for technicolor cuteness will save us? …Unfortunately, no. (Insert loud sigh) Can’t anything ever be simple?
What doesn’t work properly? Well, if you have a string with mixed content (for example, most tweets containing both words and emoji characters), and you specify a display font in CSS, characters that have non-Emoji equivalents in their font-face will default to their ugly, normal boring versions. So you get a ☁︎ symbol instead of the lovely, fluffy emoji cloud the person used in their original tweet.
If you try to get around this on a Mac by forcing the font to AppleColorEmoji in CSS, you will have similarly ugly results, as the font actually contains normal alphanumeric characters, albeit with weird monospace formatting.
To get around this problem, I stumbled along the technique of creating a Unicode-range restricted font-family in CSS, which will let us instruct the browser to only use the AppleColorEmoji font for those particular 842 emoji characters.
Listing out all 842 codepoints would work, but would result in a bulky and inefficient CSS file. Unfortunately, a simple unicode-range won’t work either, as Emoji symbols are strewn haphazardly across multiple locations in the Unicode spec. Thus, to generate the appropriate ranges in an efficient manner for emojistatic, we turn again to our EmojiData library, using it to find all sequential blocks of Emoji characters greater than 3 in size and compressing them to a range. Go here to examine the relevant code (it’s a bit large to paste into Medium), or just check out the results:
>> @emoji_unicode_range = Emojistatic.generate_css_map
=> "U+00A9,U+00AE,U+203C,U+2049,U+2122,U+2139,U+2194-2199,U+21A9-21AA,U+231A-231B,U+23E9-23EC,U+23F0,U+23F3,U+24C2,U+25AA-25AB,U+25B6,U+25C0,U+25FB-25FE,U+2600-2601,U+260E,U+2611,U+2614-2615,U+261D,U+263A,U+2648-2653,U+2660,U+2663,U+2665-2666,U+2668,U+267B,U+267F,U+2693,U+26A0-26A1,U+26AA-26AB,U+26BD-26BE,U+26C4-26C5,U+26CE,U+26D4,U+26EA,U+26F2-26F3,U+26F5,U+26FA,U+26FD,U+2702,U+2705,U+2708-270C,U+270F,U+2712,U+2714,U+2716,U+2728,U+2733-2734,U+2744,U+2747,U+274C,U+274E,U+2753-2755,U+2757,U+2764,U+2795-2797,U+27A1,U+27B0,U+27BF,U+2934-2935,U+2B05-2B07,U+2B1B-2B1C,U+2B50,U+2B55,U+3030,U+303D,U+3297,U+3299,U+1F004,U+1F0CF,U+1F170-1F171,U+1F17E-1F17F,U+1F18E,U+1F191-1F19A,U+1F201-1F202,U+1F21A,U+1F22F,U+1F232-1F23A,U+1F250-1F251,U+1F300-1F31F,U+1F330-1F335,U+1F337-1F37C,U+1F380-1F393,U+1F3A0-1F3C4,U+1F3C6-1F3CA,U+1F3E0-1F3F0,U+1F400-1F43E,U+1F440,U+1F442-1F4F7,U+1F4F9-1F4FC,U+1F500-1F507,U+1F509-1F53D,U+1F550-1F567,U+1F5FB-1F640,U+1F645-1F64F,U+1F680-1F68A,U+1F68C-1F6C5"
This is then dropped into an appropriately simple ERB template for the CSS file:
@font-face {
font-family: 'AppleColorEmojiRestricted';
src: local('AppleColorEmoji');
unicode-range: <%= @emoji_unicode_range %>;
}
.emojifont-restricted {
font-family: AppleColorEmojiRestricted, Helvetica;
}
When we then use the resulting .emojifont-restricted class on our webpage, we can see the improved results:
Yay! But unfortunately, this technique isn’t perfect. Remember those double-byte Unicode characters we talked about earlier? You may have noticed we rejected them in the beginning of our unicode-range generation algorithm. Well, turns out that they are obscure enough that there is no way to represent them in standard CSS unicode-range format. So by doing this, we do lose support for those few characters represented in a mixed string, and we can actually only display 821 of the emoji glyphs.Win some, lose some, eh? I’ve looked long and hard without being able to find a solution, but if anyone has a secret workaround for this, please let me know! For now though, this seems to be the best case scenario.
Keeping it all up to date: chained Rake file tasks
Keeping all these assets up to date in emojistatic could be a pain in the rear when something changes. For example,add one emoji glyph image, you’ll not just need new optimized versions of it, but also to generate new versions of the rollup spritesheets, minify and gzipped versions of those, etcetera. Rake file are incredibly powerful, because they allow you to specify the dependency chain, and then are smart enough to rebuild just the necessary tasks for any change. A full run of emojistatic can take 30-40 minutes from a fresh state (there’s a ton of image processing that happens), but subsequent changes occur in seconds. Once you get it working, it feels like magic.
Going into the detail of complex Rake file tasks is beyond the scope of what I want to cover in this blog post, but if you do anything at all like this, I highly recommend watching Jim Weirich’s Power Rake talk, which was immensely helpful for me in grokking proper usage for this technique.
Frontend Performance
It took lots of attempts to figure out how to get so many transitions to occur on the screen without slowdown. My goal was to have emojitracker work on my iPad, but early versions of the site were bringing my 16GB RAM quad-core Core i7 iMac to its knees begging for mercy.
Crazy, since it’s just a webpage, right? The DOM really wasn’t meant for handling this many operations at this speed. Every single manipulation had to be optimized, and using jQuery for DOM manipulation was out of the question — everything in the core update event loop needed to be written in pure Javascript to shave precious milliseconds.
Beyond that though, I looked at a number of different techniques to try to optimize the DOM updates and visual transitions (my good pal and Javascript dark wizard Jeff Tierney was extremely helpful with this). Some of the comparisons and optimizations we examined were:
- Utilizing explicit CSS animations vs. specifying CSS transitions. (using Javascript based animation was entirely out of the question as we needed native rendering to get GPU acceleration.)
- Different methods of force triggering the transition animation to display:replacing an entire element vs. forcing a reflow vs. using a zero length timeout.
- Maintaining an in-memory cache of DOM elements as a hash, avoiding repeated selection.
And of course, all of the various combinations and permutations of these things together (as well as the 60eps capped event stream mentioned in the backend section versus the full raw stream). Some might work better with others, and vice versa. The end user’s computer setup and internet connection also would play a factor in overall performance. So what combination would get us the absolute best average frames-per-second display in most environments?
To test this, all methods are controlled via some variables at the beginning of our main Javascript file, and the logic for each remains behind branching logic statements in the code. As a result, we can switch between any combination of methods at runtime.
A special benchmark page can be loaded that has test metrics visible with a benchmark button. The additional JS logic on that page basically handles stopping and restarting the stream for a distinct period of time using every possible combination of methods, while using FPSMeter.js to log the average client performance.
Upon completion, it creates a JSON blob of all the results for viewing, with a button that will send the results back to our server for collation.
This gave me an easy way to ask various people to easily yet exhaustively test how it performed on their machines in a real world way, while getting the results back in a statistically relevant fashion.
If you’re interested, you can check out the the full test suite logic in the source.
(Oh, and by the way, the overall winner in this case ended up being using the capped stream, cached elements and zero-length timeouts. This is probably not what I would have ended up choosing based on testing on my own machine and gut intuition. Lessons learned: test your assumptions, and sometimes the ugly hacks work best.)
In the future, I’m almost certain I could achieve better performance by using Canvas and WebGL and just drawing everything from scratch (ignoring the DOM entirely), but that will remain an exercise for another day—or for an intrepid open source contributor who wants to send a pull request!
Deploying and Scaling
The first “soft launch” for Emojitracker was on the Fourth of July, 2013. I had been working on emojitracker for months, getting it to work had consumed far more effort than I had ever anticipated, and I just wanted to be done with it. So I bailed on a party in Red Hook, cabbed it back up to North Brooklyn, and removed the authentication layer keeping it hidden from the public pretty much exactly as the fireworks displays began.
Perhaps this stealth approach was a bit too stealth, because the attention it received was minimal. A couple of friends told me it was cool. I pretty much forgot about it the next day and left it running, figuring it’d be like many of my projects that just toil away for years on their own, chugging along for anyone who happens to stumble across them. But then…
One crazy day
Fast forward about a month. I had just finished up getting a fairly large forearm tattoo the previous night, and I was trying to avoid using my wrist much to aide in the healing (e.g. ideally, avoiding the computer).
Over morning espresso I noticed the source had picked up a few stars on GitHub, which I found interesting, since it had gone fairly unnoticed until that point. Wondering if perhaps someone had mentioned it, I decided to do a quick Twitter search…
Oh shit.
It was certainly out there. Just to be safe I spun up a second web dyno. Within an hour, emojitracker was on the front page of Buzzfeed, Gizmodo, The Verge, HuffPo, Digg… when it happens, it really happens fast, and all at once. Massive amounts of traffic was pouring in.
Here’s where Heroku’s architecture really saved me. Although I had never put much initial thought into multiple servers, their platform encourages developing in a service-oriented way that you can naturally scale horizontally. Adding a new web server was as simple as a single command, and it would be up and serving traffic in under a minute, with requests load balanced across all your available instances. Press-drive traffic spikes go away almost as quickly as they arrive, so you’re going to be scaling down as often as you scale up.
Even better, you pay per-minute for web dyno use, which is really helpful for someone on a small budget. I was able to have a massive workforce of 16 web servers during the absolute peaks of launch craziness, but drop it down when demand was lower, saving $$$.
By carefully monitoring and adjusting the amount of web dynos to meet demand, I was able to serve tens of millions of realtime streams in under 24hrs while spending less money than I do on coffee in an average week.
Riding the Wave: Monitoring and Scaling
I primarily used two tools to monitor and scale emojitracker during the initial wave of crazy.
Log2viz is a Heroku experiment in which is essentially a simple web visualization that updates with the status of your web dynos based the last 60 seconds of app logs.
I was also periodically piping event data into Graphite for logging purposes.
In order to see total size of pools we want each web streaming server to report independently and have Graphite roll those numbers up. This can be a bit tricky on Heroku because you aren’t going to have useful hostnames but it turns out you can get the short form dyno name by accessing the undocumented $DYNO environment variable, which is automatically set to reflect the current position of the dyno, e.g. web.1, web.2, etc. Thus you can wrap Graphite logging in a simple method:
# configure logging to graphite in production
def graphite_log(metric, count)
if is_production?
sock = UDPSocket.new
sock.send @hostedgraphite_apikey + ".#{metric} #{count}\n", 0, "carbon.hostedgraphite.com", 2003
end
end
# same as above but include heroku dyno hostname
def graphite_dyno_log(metric,count)
dyno = ENV['DYNO'] || 'unknown-host'
metric_name = "#{dyno}.#{metric}"
graphite_log metric_name, count
end
Then you can use the graphite_dyno_log() method to log, and then query in graphite for web.*.stat_name to get an aggregate number back.
Between these two things.
I did this manually. That first evening I needed a break from intense computer usage all day, so I actually spent the evening in a bar across the street from my apartment with some friends, having a drink while passively monitoring these charts on some iPhones sitting on the table. Whenever it looked like something was spiking, I used the Nezumi Heroku client to scale up instances from my phone directly. I didn’t even have to put down my drink!
If you have the extra cash, you certainly don’t need to micromanage the instances so closely, just set above what you need and keep an eye on it. But it’s nice to have the option if you’re riding out a spike on a budget.
People have experimented with dyno auto-scaling, but in order to implement it for something like this, you’ll need to have a really good idea of your performance characteristics, so you can set appropriate metrics and rules to control things. Thus, it’s better if you are operating a stable service with historical performance data — it’s not really a realistic option for the pattern of totally obscure -> massively huge suddenly and without any warning.
Things I’d still like to do
There are a few obvious things I’d still love to add to Emojitracker.
Historical Data
This should be relatively simple, I just need to figure out what the storage implications would be and the best way to structure it would be. Showing trend-lines over time could be interesting to see!
Trending Data
Right now the only way to see when things are trending are to eyeball them, but this is a natural thing for Emojitracker to highlight explicitly. This may actually be a prime application for bitly’s ForgetTable project, so hitting up my alma-mater may be the next step.
Alternate Visualizations
Emojitracker does have a JSON API, and the SSE streams don’t require authentication. I’d love to see what more creative folks than myself can come up with for ways to show the data in interesting ways. I’d be happy to work with anyone directly who has a cool idea that requires additional access.
Remember, emojitracker is open source, so if any of the above projects sound interesting to you, I would love collaborators!
Reception and conclusions
So was it worth it?
For me creating emojitracker was primarily a learning experience, an opportunity for this non-engineer to explore new technologies and push the boundaries of what I could create in terms of architectural complexity.
Still, it was incredibly gratifying to see all the positive tweets, the funny mentions, and the inexplicable drive of people to try to drive up the standing for poor LEFT LUGGAGE or rally for their latent scatalogical obsessions.
(Since I’ve been told I’m supposed to keep track of press mentions, I’ll post the press list here, mostly so I can ask you all to send me anything that I may have missed!)
The best part has been the people I’ve met through Emojitracker I may not have otherwise. At XOXO one guy came up to me to introduce himself and tell me that he was a big fan of Emojitracker. Suddenly, I realized it was Darius Kazemi (aka @tinysubversions), an amazingly prolific creator of “weird internet stuff” whose work I’d admired for quite some time.
I’ve had the opportunity to work professionally on some amazing things (with amazing people!) in the past. But it was at that point, for the first time, that I felt like that what I had used to consider my “side projects” were now what should define my career moving forward, rather the companies I’d worked at.
I know, and have always known, that Emojitracker is a silly project, one with dubious utility and requiring a bit of lunacy to have spent so much time and effort building. Still, for all the people who saw it and smiled, and may have had a slightly better day than they would have otherwise — it was worth it.
For that reason, I hope that this braindump of how I built Emojitracker will help others to create things that are worth it to them.
ENJOYED THIS ARTICLE?: You might also enjoy the followup post enumerating all the changes involved in scaling over the next 1.5 years here: “How I Kept Building Emojitracker”
Epilogue: Emoji Art Show!
I’m thrilled to announce that Emojitracker is going to be featured in the upcoming Emoji Art and Design Show at Eyebeam Art & Technology Center, December 12-14th 2013.
I’m working on an installation version of it now, and there may be a few surprises. Hope to see you there if you are in the New York area!
xoxo,
-mroth
P.S. I’m publishing this using Medium as an experiment. If you want to keep up to date with my future projects, the best way is to follow me on Twitter at @mroth. | https://medium.com/@mroth/how-i-built-emojitracker-179cfd8238ac | CC-MAIN-2017-26 | refinedweb | 7,596 | 57.91 |
:
This version adds a few more features:
My most recent C# column has gone live on MSDN. In it, I talk about what I learned
in trying to build a remote control application that runs on the PocketPC using the
compact framework.
If you have comments on the column, please enter them, and I'll be sure to respond.
I have a fair amount of windows forms code that uses multiple threads. Because of
the way that Windows handles its user interface, you should only be updating the user
interface from the main thread. If you try to do it on other threads, bad things happen,
and they can be pretty hard to track down.
Windows forms includes some code to detect when that is happening, but it can't do
it in all cases. Well, it could, but if it did, the perf would be pretty atrocious.
When you get in this situation, you need to call Invoke() on the form, and pass it
a delegate to the function that you want to be called on the main thread. In my case,
I need to do an update to my form text when I get an event from the other thread.
My code looks something like this:
// setup code
object.RemoteUpdate += new UpdateHandler(RemoteUpdateFunc);
public void RemoteUpdateFunc2(object sender, RemoteUpdateEventArgs args)
{
// use the values here.
}
public void RemoteUpdateFunc(object sender, RemoteUpdateEventArgs args)
{
this.Invoke(new UpdateHandler(RemoteUpdateFunc2), new object[]
{sender, args});
}
I have to create a separate function just to do the forwarding, and I have to do that
for every event that I want to hook to. That's a lot of boilerplate code that I don't
want to write.
So, I set out to try to create a class that could wrap the object. Here's the class
that I wrote:
public class Invoker
{
Delegate d;
Form form;
public Invoker(Form form, Delegate d)
{
this.d = d;
this.form = form;
}
public Delegate Handler
{
get
{
return Delegate.CreateDelegate(d.GetType(), this, "Dispatcher");
}
}
public void Dispatcher(object sender, EventArgs args)
{
form.Invoke(d, new object[] { sender, args });
}
}
The goal would be to write code like this:
Invoker invoker = new Invoker(this, new UpdateHandler(RemoteUpdateFunc));
object.RemoteUpdate += (UpdateHandler) invoker.Handler;
Unfortunately, delegates can only point to methods that are *identical* to the delegate
definition. You can't, for example use a delegate that's defined as:
public delegate void EventHandler(object sender, EventArgs args);
to point to:
public delegate void UpdateHandler(object sender, RemoteEventArgs args);
even though RemoteEventArgs is derived from EventArgs. So, that means that you can
only use this approach to point to delegates that have EventArgs as their second parameter,
which doesn't make it very interesting.
So, I had to abandon this approach. The alternative is to modify the class that I'm
using so that it can make the call. I didn't want that class to have to have a reference
to the Form class, so I created a delegate like:
public delegate void InvokeHandler(Delegate d, object[] args);
and passed that to my the class that has the events. It can then use the delegate
to make the Invoke happen. Not as clean as I had hoped, but it does help a bit.
I.
Today, Scoble gave me a field
promotion.
After I publicly gave him a hard time for it, I got thinking about what a strange
thing it is to be a program manager, and that some people might be interested in what
we really do. I'm therefore going to talk about what I do from time to time.
The last few days, I've been trying to create a summary of an SDR the C# team held
recently. An SDR (Strategic Design Review, Software Design Review) is when we bring
in a group of customers, NDA them, and then show them what our plans are for the next
release. They then tell us what they think, and we go back and revise our plans based
on that feedback.
To create the summary, I go through the official notes we have, the MP3 recordings
we made, and the summaries that other people wrote, and try to pull out the salient
points for each session that we want to use to get the right things happening. Whenever
possible, I use customer quotes, because if a customer says, "It would be better for
customers if you killed <x> and forced your customers to buy <y> instead",
it's not *my* opinion, it's the customer's opinion.
An SDR is always a humbling experience, as our attendees a very good at telling us
what we're doing wrong (and believe me, we're doing a lot wrong).
The summary will be created as a powerpoint presentation (being good at powerpoint
is an important PM skill), which will be forwarded throughout the developer division.
Our trip to Maui involved lots of camera issues. We're a Canon family, with a G1 for
me, an A20 (the aforementioned waterlogged A20) for my wife, and a low-end Canon for
my 9-year-old daughter (bought after she shot 15 rolls of APS film in Europe last
year).
My G1 has been a great camera. It's not quite as flexible as an SLR - you don't get
interchangable lenses, and it doesn't zoom enough to do kid's sports, but overall
I take a lot more pictures. My plan was to take the G1 to Maui with me, but 3 hours
before the flight I realized that I had left it at our ski cabin, so it was time for
an unscheduled upgrade. I chose the 4
megapixel G3.
The G1 is a "prosumer" model. It has 2048x1500 resolution, decent glass, a 3x zoom,
aperture and shutter priority, manual focus, a really-nice flip and tilt-LCD, and
a bunch of other features I've probably forgotten. The two features that had the most
effect on my shooting are the tilt-LCD (take high and low angles easily), and the
multiple-exposure panorama (aka stitching) support. Both let you get shots that you
just couldn't get before.
It's amazing how much better the G3 is than the G1.
The faster processor is great, as is the high spead multiple exposure. When I take
candid pictures (of kids or adults), I like to take 5 or 6 exposures in every situation,
and this gets them muh faster. The better zoom is great. There are two features especially
worthy of mention.
The first is the intervalometer. I used this to take sunset pictures one night, and
just set it up to take pictures while we barbecued and drank Mai-Tais. Every 55 seconds
or so, the camera would turn on, take a picture, and turn off. Neat
The second big new feature is the neutral density filter. It reduces the light by
3 stops. So, why would you want to do that?
The two big variables in photography are aperture (how much the lens is open), and
shutter speed (how long it's open). To get the right exposure, these two variables
have an inverse relationship - the more the lens is open, the shorter the exposure
needs to be. The aperture also controls the depth of field, so if you want everything
in focus you need a small aperture (big number), or if you want the foreground and
background out of focus, you need a large aperture (small number). Similarly, if you
want to stop action, you need a short exposure time, and if you want to blur action,
you need a long exposure time.
If.
I had an interesting discussion a day or so ago on when you should implement IDisposable
on a class. Like many things, it's more complicated when you dig a little. There are
three scenarios that are interesting:
1) A class that wraps an unmanaged resource
2) A class that has fields that implement IDisposable
3) A class where no fields implement IDisposable
The first one is the easy one. Since you are directly responsible for that unmanaged
object, you will need to implement a finalizer (written using destructor syntax in
C#) to do the cleanup. You will also *probably* want to implement IDisposable, so
the user can call Dispose() to clean things up. There's a standard idiom in the docs
for doing this.
In the second case, there is no direct cleanup you need to do, so you shouldn't write
a finalizer (what would it do?). If your users will want to clean up early, you may
want to implement IDisposable and call Dispose() on your fields from your Dispose()
function.
In the third case, you should do either. If you do implement a finalizer, you will
just slow things down.
Another related question is whether setting fields to null will result in quicker
recovery of memory. This was important to do in the VB6 world, but in the .NET world,
it rarely does anything. The only time it would help is if there was a variable that
held a live reference, but wouldn't drop off the stack for a long time. I think I
could construct a loop like that, but I think it's pretty rare.
Spent the last 10 days in Maui (Pictures),
with no internet connection. This a a computer-free post.
6/25 Blue Water Rafting
This morning, we went on a charter boat operated by Blue Water Rafting. This was a
trip in a small, 7-person Zodiac-like craft. The boat left from Kihei Boat Ramp (definitely
an advantage if you're staying in Kihei), and we journeyed south to the most recent
lava flows (circa 1790). We spent a lot of time very close to the lava or inside some
caves at the side.
The trip included 5 stops for snorkling, including 4 sites on the west shore and the
obligatory trip to Molokini. Molokini is the
top of a cinder cone with a reef on the inside, and part of the cinder cone under
water. It is the #1 snorkling destination on Maui. This mostly because it's fairly
big and can support a lot of boats, but there are better places to journey to. It
does have the advantage of being fairly sheltered, and the reef is pretty.
Advantages:
1) You rent the boat, you choose where it goes.
2) Spend time where you want.
3) Nobody else goes close to the lava flow.
4) Snorkel with Dolphins (if you're lucky), or off the backside of Molokini.
5) Captains know where the fish and the turtles are.
Disadvantages
1) Ride is very rough (the rafting moniker is deserved)
2) Breakfast and lunch are limited (muffins/fruit, sandwiches)
3) Expen$ive. For the 6 person boat for 5 1/2 hours, you will pay $800. That's helicopter
tour territory.
6/25 Canon
Waterproof Camera Housing
I got my wife a waterproof housing housing for her Canon A20 camera (about $150).
You put the camera in it, seal it up, and it has controls on the outside. The display
might as well be off, and it's hard to look through the viewfinder, so I had my best
luck pointing and shooting. It helps immensely if you can surface dive, as the fish
are often 15 or 20 feet down. A nice option, especially since waterproof housings
for my G3 cost around $800.
6/26 Snorkling at the Fishbowl. Or, perhaps the aquarium. We're not sure.
On the advice of our captain, Kim and I and my sister and brother in law decide to
snorkel at the "fishbowl". It's near Ahihi
marine preserve (also a great place to snorkel), but to get there you have to
a) find the trailhead and b) hike for 30 minutes across the lava field. Not as bad
as it sounds.
Once we get there, we find out that this is now a destination for sea kayak tours.
3 boats when we get in there, which isn't bad, but another 20 arrive when we're snorkling,
which means avoiding them and the 40 people who don't really know how to snorkel.
The four of us go outside the bay, and Kim and I see a turtle, but that's about it.
We come back in, dry off, and hike back another 30 minutes to the car. Not really
better than Ahahi.
6/26 Canon Waterproof Camera Housing (redux)
Used the waterproof housing again today. My wife and I conspired together, which is
never a good thing. If I had prepared the camera, it would have been fine, and if
she had done it the way she wanted, it would have been fine, but unfortunately, she
did what I had said, and left the carry strap on, but didn't get it tucked in sufficiently.
The housing worked fine for about 10 minutes, but then I got it down about 3 feet,
and it quickly filled with water. I did all the the right things (kept it wet,
soaked in in fresh water for a long time to get all the salt out), but the camera
is DOA right now. I may try cleaning it more once I get home, but it's probably a
goner. Sigh. Off to EBay...
6/26 Kinston Technology 128MB Compact Flash Card
Despite the warning on the back that says, "do not bend this card or expose it to
strong physical or electrical shocks, water, solvents", the compact flash card from
the camera survived immersion in salt water fine, and I was able to pull 12 pictures
off of it. It's a bit like looking at the images of the Challenger before it exploded
and knowing that something bad is going to happen, as you can see a bit of fog on
some pictures, and then the last picture has droplets inside the lens.
6/29 Maui Thoughts
Maui is certainly a wonderful place. The weather in Kihei (and presumably, also in
Kanapali) is perfect - not too hot, not too cool.
Unfortunately, it appears that everybody in the Western Hemisphere feels the same
way. Despite the lack of Japanese money for the past few years, prices in Maui make
San Francisco prices look cheap. We're in a 900 sq. ft. one bedroom condo a block
from the beach, with what is technically known in real estate circles as a water view
(ie the water can be seen if you lean out over the railing). A similar unit in this
building with no view is going for $200K. The place where we stayed last time (Hale
Hui Kai), a condo on the water, one of the units is selling for $750K. Or, you can
buy a large house 3 blocks from the beach for $800K. Oh, and if you have a condo,
you also have a maintenance fee of $300 a month..
(review.
Yester?
Body.
The Online Slang Dictionary is
a reference everybody needs sometime, especially those of us who find it increasingly
hard to appear cool to our 9-year-old daughters.
Le Tour de France 2003 started
last weekend. The tour, if you don't know, is a 2000ish-mile, three-week race
up and down the mountains in France. It's widely regarded as one of the toughest physical
challenges around.
The best coverage in the US is on OLN.
Back in March, I wrote a column entitled "Unit
Testing and Test-First Development".
I've been playing around with unit testing a bit more since then, and have a few tentative
conclusions.
I'e also been playing with Test-driven development. I'm not sure about it yet, though
it is true that if you write the tests up front, you're much more likely to write
them.
Yesterday's stage was the best one I've watched in a long time. Lance Armstrong gets
attacked, and doesn't blow away the field. Tyler Hamilton rides with Lance despite
having a broken collarbone. Jan Ulrich loses 90 seconds to Lance. Iban Mayo does blow
away the field.
All of this in front of thousands of rabid fans.
Lance ends up in the yellow jersey, but not by much. This is going to be much more
interesting than last year.
Best moment in the coverage was when they showed 3 cows in a pasture, wearing jerseys
yellow, green, and spotted.
This came
to me from one of the members of the VB team.
Yesterday.
I.
The.
Little known fact of the day...
Noted Physicist Stephen Hawking also has a career as a dope
MC
Every week the Visual C# PM team spends a few minutes watching Red
vs. Blue, a serial told using the characters in Halo on the XBox. Funny even if
you don't play Halo, very funny if you do.
If you like this, pony up the $10 or $20 to help defray the costs, and get the hi-res
versions. | http://blogs.msdn.com/b/ericgu/archive/2003/07.aspx?PostSortBy=MostViewed&PageIndex=1 | CC-MAIN-2014-23 | refinedweb | 2,840 | 70.84 |
Taking Screenshots with LinuxFollow @ggarron
Find here how to take Screen Shots with Linux, could help you specially if you like to write Linux tutorials
If you like to write tutorial, or need a screen shot for any homework or job, the Linux Operating System gives you some very good resources to have this task done.
The Gimp
With Gimp you have to go to:
File->Acquire->Screeshot
and you will get a dialog box like this
As you see you have three options:
- Take Screenshot of a singe window: This will make your cursor be a thick cross, and you can select the window to take the screenshot of
- Take a Screenshot of the entire screen: This will take a screenshot of the entire screen
- Select a region to grab: This will make the cursor into a cross and you can grab a region of the screen to take a screenshot of it
Gnome
If you use Gnome you can just press PrtSC (Print Screen) key, this will take a screen shot of the whole screen, you can only choose where to save the screenshot, the size will be the size of you screen, I mean the same resolution.
Imagemagick
First install the software:
Fedora / Centos
yum install imagemagick
Debian / Ubuntu
sudo apt-get install imagemagick
Then you can use one of its tools, which is import
Take a screenshot of the full screen
import -window root screenshot.jpg
If you need some time to arrange the screen for your screenshot.
Updated, thanks to a friend of the blog
import -pause 3 -window root screenshot.jpg
This will give you 3 seconds before the screen shot is taken.
Take a screenshot of just a region of the screen
import screenshot.jpg
This will make your cursor looks like a cross and you can select the region of the screen to take the screenshot, here you can also use the sleep command.
Vmware
If you are using VMware you can select
vm->capture screen
And you will see a dialog box like this:
And you will take a screenshot of the whole screen of the vmware screen.
Two more tips
I will show you now two more very useful when managing screenshots.
Crop images with gimp
Select the circled tool, and use it to select the region of the image you want to crop.
Changing the size of the image, and creating thumbnails
If you need to resize your images, or create thumbnails for them you can use imagemagick once again:
convert -resize 150x imputfile.jpg outputfile.jpg
This will resize your image to 640 to anything the imputfile.jpg and save it as outputfile.jpg, it is always better to only specify one of the sizes to maintain the proportion of the image.
If you want to convert a lot of images at the same time, you can use a trick I learned from my friend of bashcurescancer
find . -type f -name '*.png' -exec convert -resize 640x {} {} \;
This way you will find files ending in .png and resize them to 640x size, the output files will be named the same as the input ones, take care with this if you do not want to loose the original files. | http://go2linux.garron.me/taking-screenshots-with-linux | CC-MAIN-2013-20 | refinedweb | 539 | 68.64 |
CSS is what makes the web look and feel the way it does: the beautiful layouts, fluidity of responsive designs, colors that stimulate our senses, fonts that help us read text expressed in creative ways, images, UI elements, and other content displayed in a myriad of shapes and sizes. It’s responsible for the intuitive visual cues that communicate application state such as a network outage, a task completion, an invalid credit card number entry, or a game character disappearing into white smoke after dying.
The web would be either completely broken or utterly boring without CSS.
Given the need to build web-enabled apps that match or outdo their native counterparts in behavior and performance (thanks to SPAs and PWAs), we are now shipping more functionality and more code through the web to app users.
Considering the ubiquity of the web, its very low friction (navigate through links, no installation), and its low barrier to entry (internet access on very cheap phones), we will continue to see more people come online for the first time and join millions of other existing users engage on the web apps we are building today.
The less code we ship through the web, the less friction we create for our applications and our users. More code could mean more complexity, poor performance, and low maintainability.
Thus, there has been a lot of focus on reducing JavaScript payload sizes, including how to split them into reasonable chunks and minify them. Only recently did the web begin to pay attention to issues emanating from poorly optimized CSS.
CSS minification is an optimization best practice that can deliver a significant performance boost — even if it turns out to be mostly perceived — to web app users. Let’s see how!
What is CSS minification?
Minification helps to cut out unnecessary portions of our code and reduce its file size. Ultimately, code is meant to be executed by computers, but this is after or alongside its consumption by humans, who need to co-author, review, maintain, document, test, debug, and deploy it.
Like other forms of code, CSS is primarily formatted for human consumption. As such, we add spacing, indentation, comments, naming conventions, and instrumentation hacks to boost our productivity and the maintainability of the CSS code — none of which the browser or target platform needs to actually run it.
CSS minification allows us to strip out these extras and apply a number of optimizations so that we are shipping just what the computer needs to execute on the target device.
Why minify CSS?
Across the board, source code minification reduces file size and can speed up how long it takes for the browser to download and execute such code. However, what is critically important about minifying CSS is that CSS is a render blocking resource on the web.
This means the user will potentially be unable to see any content on a webpage until the browser has built the CSSOM (the DOM but with CSS information), which only happens after it has downloaded and parsed all style sheets referenced by the document.
Later in this article, we will explore the concept of critical CSS and best practices around it, but the point to establish here is that until CSS is ready, the user sees nothing. Unnecessarily large CSS files, due to shipping unminified or unused CSS, helps to deliver this undesirable experience to users.
Minify vs. compress — any difference?
Code minification and compression are often used interchangeably, maybe because they both address performance optimizations that lead to size reductions. But they are different things, and I’d like to clarify how:
- Minification alters the content of code. It reduces code file size by stripping out unwanted spaces, characters, and formatting, resulting in fewer characters in the code. It may further optimize the code by safely renaming variables to use even fewer characters.
- Compression does not necessarily alter the content of code — well, unless we consider binary files like images, which we are not covering in this exploration. It reduces file size by compacting the file before serving it to the browser when it is requested.
These two techniques are not mutually exclusive, so they can be used together to deliver optimized code to the user.
With the required background information out of the way, let’s go over how you can minify the CSS for your web project. We will be exploring three ways this can be achieved and doing so for a sample website I made, which has the following CSS in a single external
main.css file:
html, body { height: 100%; } body { padding: 0; margin: 0; } body .pull-right { float: right !important; } body .pull-left { float: left !important; } body header, body [data-view] { display: none; opacity: 0; transition: opacity 0.7s ease-in; } body [data-view].active { display: block; opacity: 1; } body[data-nav='playground'] header { display: block; opacity: 1; } /* Home */ ; }
Standalone online tools
If you are totally unfamiliar with minifying CSS and would like to approach things slowly, you can start here and only proceed to the next steps when you are more comfortable. While this approach works, it is cumbersome and unsuitable for real projects of any size, especially one with several team members.
A number of free and simple online tools exist that can quickly minify CSS. They include:
All three tools provide a simple user interface consisting of one or more input fields and require that you copy and paste your CSS into the input field and click a button to minify the code. The output is also presented on the UI for you to copy and paste back into your project.
From the above screenshot of CSS Minifier, we can see the that the Minified Output section on the right has CSS code that has been stripped of spaces, comments, and formatting.
Minify does something similar, but can also display the file size savings due to the minification process.
In either of these cases, our minified CSS looks like the below:
body,html{height:100%}body{padding:0;margin:0}body .pull-right{float:right!important}body .pull-left{float:left!important}body [data-view],body header{display:none;opacity:0;transition:opacity .7s ease-in}body [data-view].active{display:block;opacity:1}body[data-nav=playground] header{display:block;opacity:1}}
Minifying CSS in this way expects you to be online and assumes the availability of the above websites. Not so good!
Command line tools
A number of command line tools can achieve the exact same thing as the above websites but can also work without internet, e.g., during a long flight.
Assuming you have npm or yarn installed locally on your machine, and your project is set up as an npm package (you can just do
npm init -y), go ahead and install cssnano as a dev dependency using
npm install cssnano --save-dev or with
yarn add install cssnano -D.
Since cssnano is part of the ecosystem of tools powered by PostCSS, you should also install the postcss-cli as a dev dependency (run the above commands again, but replace
cssnano with
postcss-cli).
Next, create a
postcss.config.js file with the following content, telling PostCSS to use cssnano as a plugin:
module.exports = { plugins: [ require('cssnano')({ preset: 'default', }), ], };
You can then edit your
package.json file and add a script entry to minify CSS with the
postcss command, like so:
... "scripts": { "minify-css": "postcss src/css/main.css > src/css/main.min.css" } ... "devDependencies": { "cssnano": "^4.1.10", "postcss-cli": "^6.1.2" } ...
main.min.css will be the minified version of
main.css.
With the above setup, you can navigate to your project on the command line and run the following command to minify CSS:
npm run minify-css (or, if you’re using yarn,
yarn minify-css).
Loading up and serving both CSS files from the HTML document locally (just to compare their sizes in Chrome DevTools — you can run a local server from the root of your project with http-server) shows that the minified version is about half the size of the original file.
While the above examples work as a proof of concept or for very simple projects, it will quickly become cumbersome or outright unproductive to manually minify CSS like this for any project with beyond-basic complexity since it will have several CSS files, including those from UI libraries like Bootstrap, Materialize, Material Design, etc.
In fact, this process requires you to save the minified version and update all style sheet references to the minified file version — manually. Chances are, you are already using a build tool like webpack, Rollup, or Parcel. These come with built-in support for code minification and bundling and might require very little or no configuration to take advantage of their workflow infrastructure.
Bring your own bundler (BYOB)
Given that Parcel has the least configuration of them all, let’s explore how it works. Install the Parcel bundler by running
yarn add parcel-bundler -D or
npm install parcel-bundler --save-dev.
Next, add the following script entries to your
package.json file:
"dev": "parcel src/index.html", "build": "parcel build src/index.html"
Your
package.json file should look like this:
{ ... "scripts": { "dev": "parcel src/index.html", "build": "parcel build src/index.html" }, ... "devDependencies": { "parcel-bundler": "^1.12.3" } ... }
The
dev script allows us to run the
parcel-bunder against the
index.html file (our app’s entry point) in development mode, allowing us to freely make changes to all files linked to the HTML file. We’ll see changes directly in the browser without refreshing it.
By default, it does this by adding a
dist folder to the project, compiling our files on the fly into that folder, and serving them to the browser from there. All of this happens by running the dev script with
yarn dev or
npm run dev and then going to the provided URL on a browser.
Like the
dev script we just saw, the
build script runs the Parcel bundler in production mode. This process does code transpilation (e.g., ES6 to ES5) and minification, including minifying our CSS files referenced in the target
index.html file. It then automatically updates the resource links in the HTML file to the output code (transpiled, minified, and versioned copies). How sweet!
This production version is put in the
dist folder by default, but you can change that in the script entry within the
package.json file.
While the above process is specific to Parcel.js, there are similar approaches or plugins to achieve the same outcome using other bundlers like webpack and Rollup. Do take a look at the following as a starting point:
- webpack
- Rollup
Code coverage and unused code
Minifyng CSS in itself is not the goal; it is only the means to an end, which is to ship just the right amount of code the user needs for the experiences they care about.
Stripping out unnecessary spaces, characters, and formatting from CSS is a step in the right direction, but like unnecessary spaces, we need to figure out what portions of the CSS code itself is not totally necessary in the application.
The end goal is not really achieved if the app user has to download CSS (albeit minified CSS) containing styles for all the components of the Bootstrap library used in building the app when only a tiny subset of the Bootstrap components (and CSS) is actually used.
Code coverage tools can help you identify dead code — code that is not used by the current page or the application. Such code should be stripped out during the minification process as well, and
Chrome DevTools has an inbuilt inspector for detecting unused code.
With DevTools open, click on the “more” menu option (three dots at extreme top right), then click on More tools, and then Coverage.
Once there, click on the option to reload and start capturing coverage. Feel free to navigate through the app and do a few things to establish usage if need be.
After using the app to your heart’s content — and under the watchful eyes of the Coverage tool — click on the stop instrumenting coverage and show results red button.
You will be presented with a list of loaded resources and coverage metrics for that page or usage session. You can instantly see what percentage of the resource entries are used vs unused, and clicking each entry will also show what portions of the code is used (marked green) vs. unused (marked red).
In our case, Chrome DevTools has detected that nowhere in my HTML was I using the
.pull-right and
.pull-left CSS classes, so it marked them as unused code. It also reports that 84 percent of the CSS is unused. This is not an absolute truth, as you will soon see, but it gives a clear indication for where to begin investigating areas to clean up the CSS during a minification process.
Determining and removing unused CSS
I must begin by saying removing unused CSS code should be carefully done and tested, or else you could end up removing CSS that was needed for a transient state of the app — for instance, CSS used to display an error message that only comes into play in the UI when such an error occurs. How about CSS for a logged-in user vs. one who isn’t logged in, or CSS that displays an overlay message that your order has shipped, which only occurs if you successfully placed an order?
You can apply the following techniques to begin more safely approaching unused CSS removal to drive more savings for your eventual minified CSS code.
Add just the CSS you need — no more!
This technique emphasizes the leverage of code splitting and bundling. Just like we can key into code splitting by modularizing JavaScript and importing just the modules, files, or functions within a file we need for a route or component, we should be doing the same for CSS.
This means instead of loading the entire CSS for the Material Design UI library (e.g., via CDN), you should
import just the CSS for the
BUTTON and
DIALOG components needed for a particular page or view. If you are building components and adopting the CSS-in-JS approach, I guess you’d already have modularized CSS that is delivered by your bundler in chunks.
Inline CSS meant for critical render — preload the rest!
Following the same philosophy of eliminating unnecessary code — especially for CSS, since it has a huge impact on when the user is able to see content — one can argue that CSS meant for the orders page and the shopping cart page qualifies as unused CSS for a user who is just on the homepage and is yet to log in.
We can even push this notion further to say CSS for portions below the fold of the homepage (portions of the homepage the user has to scroll down to see) can qualify as unnecessary CSS for such a user. This extra CSS could be the reason a user on 2G (most emerging markets) or one on slow 3G (the rest of the world most of the time) has to wait one or two more seconds to see anything on your web app even though you shipped minified code!.
– Addy Osmani on Critical
Once you have extracted and inlined the critical CSS, you can preload the remaining CSS (e.g., for the other routes of the app) with link-preload. Critical (by Addy Osmani) is a tool you can experiment with to extract and inline critical CSS.
You can also just place such critical-path CSS in a specific file and inline it into the app’s entry point HTML — that is, if you don’t fancy directly authoring the CSS within STYLE tags in the HTML document.
Remove unused CSS
Like cssnano, which plugs into PostCSS to minify CSS code, Purgecss can be used to remove dead CSS code. You can run it as a standalone npm module or add it as a plugin to your bundler. To try it out in our sample project, we will install it with:
npm install @fullhuman/postcss-purgecss --save-dev
If using yarn, we will do :
yarn add @fullhuman/postcss-purgecss -D
Just like we did for cssnano, add a plugin entry for Purgecss after the one for cssnano in our earlier
postcss.config.js file, such that the config file looks like the following:
module.exports = { plugins: [ require('cssnano')({ preset: 'default', }), require('@fullhuman/postcss-purgecss')({ content: ['./**/*.html'] }), ], };
Building our project for production and inspecting its CSS coverage with Chrome DevTools reveals that our purged and minified CSS is now 352B (over 55 percent less CSS code) from the earlier version that was only minified.
Inspecting the new output file, we can see that the
.pull-left and
.pull-right styles were removed since nowhere in the HTML are we using them as class names at build time.
Again, you want to tread carefully with deleting CSS that these tools flag as unused. Only do so after further investigation shows that they are truly unnecessary.
Design CSS selectors carefully
In our sample project, we might have intended to use the
.pull-right and
pull-left classes to style a transient state in our app — to display a conditional error message to the extreme left or right hand side of the screen.
As we just saw, Purgecss helped our CSS minifier remove these styles since it detected they were unused. Perhaps there could be a way to deliberately design our selectors to survive preemptive CSS dead code removal and preserve styling for when they’d be needed in a future transient app state.
It turns out that you can do so with CSS attribute selectors. CSS rules for an error message element that is hidden by default and then visible at some point can be created like this:
body [msg-type] { width: 350px; height: 250px; padding: 1em; position: absolute; left: -999px; top: -999px; opacity: 0; transition: opacity .5s ease-in } body [msg-type=error] { top: calc(50% - 125px); left: calc(50% - 150px); opacity: 1 }
While we don’t currently have any DOM elements matching these selectors, and knowing they will be created on demand by the app in the future, the minify process still preserves these CSS rules even though they are marked as unused — which is not entirely true.
CSS attribute selectors help us wave a magic wand to signal the preservation of rules for styling our error message elements that are not available in the DOM at build time.
This design construct might not work for all CSS minifiers, so experiment and see if this works in your build process setup.
Recap and conclusion
We are building more complex web apps today, and this often means shipping more code to our end users. Code minification helps us lighten the size of code delivered to app users.
Just like we’ve done for JavaScript, we need to treat CSS as a first-class citizen with the right to participate in code optimizations for the benefit of the user. Minifying CSS is the least we can do. We can take it further, too, by eliminating dead CSS from our projects.
Realizing that CSS has a huge impact on when the user sees any content of our app helps us prioritize optimizing its delivery.
Finally, adopting a build process or making sure your existing build process is optimizing CSS code is as trivial as setting up cssnano with Parcel or using a few plugins and configuration for webpack or Rollup.. | http://blog.logrocket.com/the-complete-best-practices-for-minifying-css/ | CC-MAIN-2019-39 | refinedweb | 3,283 | 58.82 |
Code. Collaborate. Organize.
No Limits. Try it Today.
public class Naerling : Lazy<Person>{
public void DoWork(){ throw new NotImplementedException(); }
}
Dalek Dave wrote:I would put £50 on the Dalai Lama if I was a Tibetan man.
The report of my death was an exaggeration - Mark Twain
Simply Elegant Designs JimmyRopes DesignsThink inside the box! ProActive Secure Systems
I'm on-line therefore I am.
JimmyRopes
delete this;
thewazz wrote:anyone following bb?
thewazz wrote:any good/interesting news in sight?
General News Suggestion Question Bug Answer Joke Rant Admin
Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages. | http://www.codeproject.com/Lounge.aspx?msg=4390248 | CC-MAIN-2014-23 | refinedweb | 109 | 57.67 |
The <ios> header declares the classes, types, and manipulator functions that form the foundation of the C++ I/O library (which is often called I/O streams). The class ios_base is the base class for all I/O stream classes. The class template basic_ios derives from ios_base and declares the behavior that is common to all I/O streams (e.g., establishing a stream buffer and defining the I/O state).
Refer to Chapter 9 for more information about input and output, including the use of manipulators, formatting flags, streams, and stream buffers.
The <ios> header #includes <iosfwd>.
The basic_ios class template is the root of all I/O stream class templates. It provides a common functionality for all derived stream classes; in particular, it manages a stream buffer. In the following descriptions, the name buf refers to a private data member that points to the stream buffer. An implementation can use any name.
The following are the member functions of basic_ios:
The default constructor leaves the data members uninitialized. In a derived class, the default constructor must call init to initialize the members.
The copy constructor is declared private and is not defined, which prevents the copying of any I/O stream objects.
Calls init(sb) to initialize the members.
If fail( ) returns true, the void* operator returns a null pointer; otherwise, it returns a non-null pointer to indicate success. operator void* is most often used as an implicit conversion in a conditional (e.g., while (cin) cin >> data[i++]).
Returns fail( ). operator ! is most often used in a conditional (e.g., if (!cout) cerr << "output error\n").
The assignment operator, like the copy constructor, is private, so it cannot be used and is not defined. Assigning or copying an I/O stream would corrupt the stream buffer.
Returns true if badbit is set in rdstate( ), or false otherwise.
Sets the I/O state to state. If rdbuf( ) is a null pointer, badbit is also set (to state | ios_base::badbit). After setting the state, if any state bit is an exception bit ((rdstate( ) & exceptions( )) != 0), basic_ios::failure is thrown.
The second form is deprecated. See ios_base::iostate later in this section for details.
Copies formatting information from rhs. In particular, the format flags, fill character, locale, and the contents of the iword( ) and pword( ) arrays are copied. The I/O state and stream buffer are not copied. Before copying any callback functions, each one is called with erase_event. The callbacks are then replaced with those copied from rhs, and each one is called with copyfmt_event. (See ios_base for information about callbacks.) The exceptions( ) mask is copied last. The return value is *this.
Returns true if eofbit is set in rdstate( ), or false otherwise.
Returns or sets the exception mask. (See the clear function for how and when an exception is thrown.) The third form is deprecated. See ios_base::iostate later in this section for details.
Returns true if badbit is set or if failbit is set in rdstate( ), or false if neither bit is set.
Returns or changes the fill character (also called the pad character). When setting the fill character, the old fill character is returned.
Returns true if the I/O state is cleanthat is, it returns rdstate( ) == 0.
Calls ios_base::imbue(loc) and rdbuf( )->pubimbue(loc) (if rdbuf( ) is not null). The return value is the previous value of ios_base::imbue( ).
Initializes the basic_ios object. Table 13-12 lists the observable effects of initialization. Also, the arrays for iword( ) and pword( ) are initially null pointers.
Narrows the character c by returning the following:
std::use_facet<ctype<char_type> >(getloc( )).narrow(c, deflt)
Returns or changes the stream buffer, buf. After changing the stream buffer, the rdbuf function calls clear( ). The function returns the previous value of rdbuf( ).
Returns the current I/O state bitmask. See the bad, eof, fail, and good functions for convenient ways to test different bits in the state mask.
Sets the specified bits in the I/O state bitmaskthat is, it calls clear(rdstate( ) | state). The second form is deprecated. See ios_base::iostate later in this section for details.
Ties a stream (typically an input stream) to an output stream, tiestr. Any input operation on this stream is prefaced by flushing tiestr. Tying streams can be used to ensure that prompts appear at the proper time. With no arguments, the tie function returns the currently tied stream, or 0 if no stream is tied.
Widens the character c by returning the following:
std::use_facet<ctype<char_type> >(getloc( )).widen(c)
ios_base class, ctype in <locale>, basic_streambuf in <streambuf>
The boolalpha function is a manipulator that sets the boolalpha flag, which tells the stream to read or write a bool value as text, according to the stream's locale. Specifically, the function calls stream.setf(ios_base::boolalpha) and returns stream.
ios_base::fmtflags type, noboolalpha function, num_get in <locale>, num_put in <locale>
The dec function is a manipulator that sets the conversion radix to base 10. The function calls stream.setf(ios_base::dec, ios_base::basefield) and returns stream.
hex function, ios_base::fmtflags type, noshowbase function, oct function, showbase function, num_get in <locale>, num_put in <locale>
The fixed function is a manipulator that sets the floating-point output style to fixed-point. The function calls stream.setf(ios_base::fixed, ios_base::floatfield) and returns stream.
ios_base::fmtflags type, noshowpoint function, scientific function, showpoint function, num_get in <locale>, num_put in <locale>
The fpos class template represents a position in a stream. The stateT template parameter is a multibyte shift state, such as mbstate_t. Objects of type fpos can be compared for equality or inequality, they can be subtracted to yield a stream offset, or a stream offset can be added to an fpos position to produce a new fpos. Also, stream offsets can be converted to and from fpos values. Although the declaration in this section shows these functions as member functions, they might be global functions or be provided in some other fashion.
streamoff type, mbstate_t in <cwchar>
The hex function is a manipulator that sets the conversion radix to base 16. The function calls stream.setf(ios_base::hex, ios_base::basefield) and returns stream.
dec function, ios_base::fmtflags type, noshowbase function, oct function, showbase function, num_get in <locale>, num_put in <locale>
The internal function is a manipulator that sets the stream's alignment to internal. The function calls stream.setf(ios_base::internal, ios_base::adjustfield) and returns stream. Internal padding works as follows:
If the formatted number begins with a sign, insert the padding after the sign.
If the formatted number begins with 0x or 0X, insert the padding after the x or X.
Otherwise, insert the padding before the number (like ios_base::right).
ios_base::fmtflags type, left function, right function
The ios_base class is the root class for all the I/O stream classes. It declares fundamental types that are used throughout the I/O library. It also has members to keep track of formatting for input and output, storing arbitrary information for derived classes, and registering functions to be called when something interesting happens to the stream object.
The io_state, open_mode, seek_dir, streamoff, and streampos types are deprecated and might not be included in a future revision of the C++ standard. The first three are integer types that are equivalent to iostate, openmode, and seekdir. (See their respective subsections later in this section for details.) The streamoff and streampos types have equivalent types at namespace scope. See streamoff later in this section and streampos in <iosfwd> for details.
The following are the member functions of ios_base:
The default constructor is protected so you cannot accidentally declare an object of type ios_base. It does not initialize its members. That is left to the basic_ios::init function.
The copy constructor is private and not defined so you cannot copy objects of type ios_base or its derived classes.
Calls every registered callback with the erase_event if the ios_base object has been properly initialized. See basic_ios::init.
The assignment operator is private and not defined to prevent the assignment of ios_base objects or its derivatives.
Returns the current format flags or sets the flags. When setting the flags, the previous flags are returned.
Returns the stream's currently imbued locale.
Saves loc as the new locale and calls all registered callbacks with imbue_event. The new locale is stored before calling any callbacks, so if a callback function calls getloc, it gets the new locale.
Returns a reference to a long integer that is stored in a private array, at index index. If iword has been called before with the same index, a reference to the array element is returned. Otherwise, the array is extended as needed so that index is a valid index, and the new entry is initialized to 0. iword with a different index
After calling basic_ios::copyfmt for this object
When the object is destroyed
If iword fails (perhaps because the internal array cannot grow), it returns a reference to a valid long& with a value that is initially 0. If the member function is called for an object whose class derives from basic_ios<>, badbit is set (which might throw ios_base::failure).
See the xalloc member function to learn how to obtain a suitable index.
Returns or sets the precision (places after the decimal point) used to format floating-point numbers for output. When setting a new precision, the previous precision is returned.
Returns a reference to a void* that is stored in a private array, at index index. If pword has been called before with the same index, a reference to the array element is returned. Otherwise, the array is extended as needed so that index is a valid index, and the new entry is initialized to a null pointer. pword with a different index
After calling basic_ios::copyfmt for this object
When the object is destroyed
If pword fails (perhaps because the internal array cannot grow), it returns a reference to a valid void*& with a value that is initially 0. If the object derives from basic_ios<>, badbit is set (which might throw ios_base::failure).
See the xalloc member function to learn how to obtain a suitable index.
Registers a function fn to be called when one of three events occurs for the ios_base object:
The object is destroyed (erase_event)
copyfmt is called (erase_event followed by copyfmt_event)
imbue is called (imbue_event)
Each callback function is registered with an integer index. The index is passed to the callback function. Functions are called in the opposite order of registration. The callback function must not throw exceptions.
For example, suppose a program stores some debugging information with each stream. It allocates a struct and stores a pointer to the struct in the stream's pword array. When copyfmt is called, the debugging information should also be copied. Example 13-14 shows how to use callbacks to make sure the memory is managed properly.
void manage_info(std::ios_base::event event, std::ios_base& stream, int index) { infostruct* ip; switch(event) { case std::ios_base::erase_event: ip = static_cast<infostruct*>(stream.pword(index)); stream.pword(index) = 0; delete ip; break; case std::ios_base::copyfmt_event: stream.pword(index) = new infostruct; break; default: break; // imbue_event does not affect storage. } } void openread(std::ifstream& f, const char* name) { f.open(name); int index = f.xalloc( ); f.pword(index) = new infostruct; f.register_callback(manage_info, index); }
Sets the addflags bits of the formatting flags. It is equivalent to calling flags(flags( ) | addflags).
Clears the mask bits from the formatting flags and then sets the newflags & mask bits. It is equivalent to calling flags((flags( ) & ~mask) | (newflags & mask)). The two-argument version of setf is most often used with multiple-choice flags (e.g., setf(ios_base::dec, ios_base::basefield)).
Determines whether the standard C++ I/O objects are synchronized with the C I/O functions. Initially, they are synchronized.
If you call sync_with_stdio(false) after any I/O has been performed, the behavior is implementation-defined.
Clears the mask bits from the formatting flags. It is equivalent to calling flags(flags( ) & ~mask).
Returns or sets the minimum field width. When setting the width, the previous width is returned.
Returns a unique integer, suitable for use as an index to the iword or pword functions. You can think of ios_base as having a static integer data member, xalloc_index, and xalloc is implemented so it returns xalloc_index++.
basic_ios class template
The ios_base::event type denotes an interesting event in the lifetime of an I/O stream object. See the register_callback function in the ios_base class, earlier in this section, to learn how to register a function that is called when one of these events occurs.
ios_base class, ios_base::event_callback type
The ios_base::event_callback type denotes a callback function. See the register_callback function in the ios_base class, earlier in this section, to learn how to register a callback function, which a stream object calls when an interesting event occurs.
ios_base class, ios_base::event type
The ios_base::failure class is the base class for I/O-related exceptions. Its use of the constructor's msg parameter and what( ) member function are consistent with the conventions of the exception class.
basic_ios::clear function, exception in <exception>
The fmtflags type is an integer, enum, or bitmask type (the exact type is implementation-defined) that represents formatting flags for input and output. In the ios_base class, several static constants are also defined, which can be implemented as enumerated literals or as explicit constants. Table 13-13 lists the flag literals.
Some formatting items are Boolean: a flag is set or cleared. For example, the uppercase flag can be set to perform output in uppercase (that is, the 0X hexadecimal prefix or E in scientific notation), or the flag can be cleared for lowercase output. Other flags are set in fields. You can set a field to one of a number of values. Table 13-14 lists the field names, definitions, and the default behavior if the field value is 0. Each field name is used as a mask for the two-argument form of the ios_base::setf function.
ios_base class, ctype in <locale>, num_get in <locale>, num_put in <locale>
The Init class is used to ensure that the construction of the standard I/O stream objects occurs. The first time an ios_base::Init object is constructed, it constructs and initializes cin, cout, cerr, clog, wcin, wcout, wcerr, and wclog. A static counter keeps track of the number of times ios_base::Init is constructed and destroyed. When the last instance is destroyed, flush( ) is called for cout, cerr, clog, wcout, wcerr, and wclog.
For example, suppose a program constructs a static object, and the constructor prints a warning to cerr if certain conditions hold. To ensure that cerr is properly initialized and ready to receive output, declare an ios_base::Init object before your static object, as shown in Example 13-15.
class myclass { public: myclass( ) { if (! okay( )) std::cerr << "Oops: not okay!\n"; } }; static std::ios_base::Init init; static myclass myobject;
<iostream>
The ios_base::iostate type is an integer, enum, or bitset type (the exact type is implementation-defined) that represents the status of an I/O stream. The io_state type is an integral type that represents the same information. Some functions that take an iostate parameter have an overloaded version that accepts an io_state parameter and has the same functionality as its iostate counterpart. The io_state type and related functions are deprecated, so you should use the iostate versions.
Table 13-15 lists the iostate literals and their meanings. The basic_ios class template has several member functions for setting, testing, and clearing iostate bits.
basic_ios class template, <bitset> | http://etutorials.org/Programming/Programming+Cpp/Chapter+13.+Library+Reference/13.27+ltios/ | CC-MAIN-2016-44 | refinedweb | 2,602 | 65.93 |
A guest post by Timothy Pratley, who currently works for Tideworks Technology as a Development Manager building Traffic Control software for logistics clients including SSA Marine, CSX, and BNSF.
Have you ever coded away on a great idea, and reached the point where you needed to store some data? It can be a buzzkill when you consider how the choices you are making in storage will affect your code, and how the storage target might change in the future. Should I design a database schema? Do I want to use a database? If my storage strategy changes, will I have to refactor? In this post I share with you why I default to event sourcing, and how simple it is to do in Clojure.
The Event Sourcing pattern is designed to save every change that is made to your domain model. You can reconstruct the domain model by replaying all of the events. To do this effectively requires discipline. Every change to your domain model must be done with commands that raise events. Commands validate that the caller is producing a valid update, and produce an event that represents the update. The event is sent to a pipeline that stores, publishes, and applies the update to the domain model.
Commands and events
A command validates whether an update can be done, and if so, it gathers up all of the information required to perform the update, and raises this information as an event. In Clojure we represent data in hashmaps in preference to defining structures or objects, so my events will be hashmaps that have the data required to perform the desired transform (Note that the source code for this post is available at):
Commands look so straightforward that you might be tempted to forget about them and just call
raise where you need it. I prefer to keep all of the event processing and commands in pairs together in the same namespace for easy comparison, since the event processing method will be expecting matching fields in the event.
Defining the update itself is the important part. For every event type we define a transformation function of the current domain state into a new domain state. Instead of having the command call the event processor directly, we hand the event off to a pipeline. The pipeline needs to know how to dispatch the function to call by event type.
In Clojure, a polymorphic dispatch can be done with multimethods. We define a signature for accepting a world and an event. Implementations of
accept will perform a data transform, returning a new world. Raising events will call
accept, which will dispatch to the appropriate implementation. When defining the signature of a multimethod, we provide a function that returns the
:event property from an event hashmap (which will be the event type):
Implementing event handlers is a matter of conforming to the signature and providing the event type that it is appropriate for:
When an event is raised it goes through a pipeline that will call
accept. That pipeline is where we may make implementation decisions about how and where we want to store data. If we only consider the command/event/transform pattern, there is very little code overhead to conform to this pattern in Clojure.
The trade off is conforming to a command/event/transform pattern in exchange for durability, debugging, logging, history, storage flexibility, arbitrary denormalization, and read separation. In my experience, the catch is that implementing the pattern in C# is tricky. Assuming you get that part right or use a good library you are still stuck with type fatigue.
Clojure alters many implementation pain points:
- passing around an immutable world is safe and convenient
- multimethod dispatch is expressive
- data format matches memory model (edn)
- philosophical alignment (transform functions, deep nesting, hashmaps and vectors)
The event pipeline
Raising an event is primarily storing it and calling
accept to apply the changes to the domain model:
I like to mix in some metadata with the event: when it happened and a sequence number. The
event-type is mandatory for dispatch. Clojure does allow you to specify metadata separately, so you can do that if you prefer.
I choose to use an atom to store the domain model in. The semantic I want is one synchronous writer of state. An agent is almost perfect for this except that quite often you want to return a result to the caller indicating success or failure, whereas agents are send and forget. To ensure all events are raised synchronously I use plain old locking on a private object. Your domain semantics might require commands to be processed synchronously for validating against the domain.
We have many options available for storage, but for now we will use the straightforward file based approach:
I append to an events file and write the event data structure using Clojure’s data format. The file has the same base name as the current snapshot.
Storing history is powerful. If you want to mine your data by reprocessing events and calculating some new views, you have all the data to do so. You are not limited to the domain state.
What is publish all about? Right now publish is just a way to define additional functions to be called on each event. One obvious use is to send out notifications to clients of relevant events. Another use is when you want to maintain separate models. For example, your domain logic may not care about statistics, but you might want to build up a view of statistics by processing events as they happen in a separate model. If you have a high traffic website, you might want to have several read servers. You can feed these read servers the events and they can perform denormalization of those events into their local read model (this pattern is called Command Query Responsibility Segregation).
Rebuilding the domain
Rehydrating the domain model is a matter of replaying all of the events that were stored. We specify which state file to load as the initial model, and optionally an
event-id for a particular point in time:
This is convenient for testing and debugging. You can set up state files to test a scenario, or load up the domain model just prior to an error occurring to recreate an issue.
If you need to handle a very large number of events, it is convenient to take periodic snapshots of the domain model state. That way when you want to rehydrate a state, you only need to process the subsequent events from the latest snapshot. Clojure data structures are immutable so we can write the snapshot asynchronously without fear of the world changing under our feet.
A new thread is spawned by
future, which may take some time to complete storage if the domain model is very large. Subsequent events are written to the new label and may be written even before the snapshot completes. If a snapshot fails to write, we still have all of the data and can rehydrate by going back to the previous snapshot and processing all of those events and then the events with the new label.
Conclusion
Not much effort was required to get durability, as shown in this post. Our storage solution can be changed without changing the logic of our application, and we get some additional benefits in logging, debugging, and history.
Clojure’s multimethods, immutable data structures, readable data syntax, and data transform functions align closely with the command/event/transform pattern. To implement the pattern, define accept methods for every state transition, and commands to create valid events. Working on disk is usually convenient for experimenting. You can migrate to another infrastructure later without touching your logic. Event sourcing is a good default choice during application development when you reach the point where storage is required.
Be sure to look at the Clojure resources that you can find in Safari Books Online.
Jan Kronquist
I have also been exploring event sourcing in Clojure! I like the way you store the data on file and add metadata. However, I really think you should consider avoiding locks and mutable state.
The way I solve this is simply by returning the events instead of raising/publishing/whatever. This way the business logic in the command handler becomes really well structured: First check the preconditions, then create the events and no mutable state. Both command handles and event handlers become pure functions. Have a look and let me know what you think:
I have also recently implemented storage using EventStore. This is currently only available as a branch in my github repo, but I’m going to write a blog post describing how it works.
niquola
I like the idea of event sourcing, but i have a question:
What if the structure of domain model and event logs was changed, should we change/migrate all historical events or make switch by event’s versions in code applying events?
Timothy Pratley
@Jan: Good observations. Semantically a Command returns a value that indicates success or failure. Imagine a web service that places an order. The consumer of the service needs to get confirmation that the order was successfully processed. The command contains conditionals governing when the event should be accepted, but even if they pass, an exception might still occur in the application of the event. So a command as I define it requires validation, event creation, and a success/fail result of event application. You can certainly structure code such that all web services pass through a generic “command” handler which does the event raising, splitting out the event production into separate functions to enable more concise pairing and testing of the validate/event/accept code.
Thank you for pointing out your approach. To explain my design choices:
1) Events are any data. EDN is a system for the conveyance of values. It is not a type system, and has no schemas.
2) Accept is a multimethod, as the minimalist way to dispatch to state transformation functions.
3) Snapshots let me see the data and more easily set up for debugging/experimentation.
I present an event stream solution for saving and restoring state, based upon storing change causing events. Managing state mutation is the mechanism. The path is to move from an in memory only model:
(dosync (alter world update-in [:things id :attr] inc))
;; (f state arguments) => new state ;; managed by STM ;;
to and in memory + durable model:
domain + event => saved event, new domain
;; (f state event) => new state ;;
(defmethod accept :event-type [world event] (update-in world [:things (event :id) :attr] inc))
Recognizing that the function that creates a new state is *mostly* the same in both cases. The motivation for this post is that the important choice to make is establishing those transformation functions.
@niquola: Absolutely, that is one of the great things about having a precise history. In principle no matter how the events or behavior change, so long as you know when those changes occur you can reprocess the entire event stream. The reason to reprocess old version events is to calculate some new information over old history. I have run into version issues when calculating a metric over old events. It has been more practical to handle the differences based on the data of the event (not a version number). For a change to event processing I snapshot the domain when switching to the new logic to avoid reprocessing old version events. For a completely new domain I calculate it into a snapshot, then hydrate it and begin from there. Versioning is mental overhead for a problem you might solve differently in the future. Yes version management can be very strong and general in an event stream if you do really need it to be.
Thank you both for your comments | https://www.safaribooksonline.com/blog/2013/09/04/event-sourcing-in-clojure/ | CC-MAIN-2017-09 | refinedweb | 1,976 | 60.65 |
A general game setting or variable (like fraglimit). More...
#include <serverstructs.h>
A general game setting or variable (like fraglimit).
This object is safe to copy.
Definition at line 144 of file serverstructs.h.
Command-line argument that sets this GameCVar.
When launching a game, this command() is passed as one of the command line arguments and the value() is what follows directly after.
Definition at line 156 of file serverstructs.cpp.
Is any value assigned to this GameCVar.
Definition at line 161 of file serverstructs.cpp.
'Null' objects are invalid.
Definition at line 166 of file serverstructs.cpp.
Nice name to display to user in Create Game dialog and in other widgets.
Definition at line 171 of file serverstructs.cpp.
Assign value() to this GameCVar.
Definition at line 176 of file serverstructs.cpp.
Passed as the second argument, following command().
Definition at line 181 of file serverstructs.cpp. | https://doomseeker.drdteam.org/docs/doomseeker_1.0/classGameCVar.php | CC-MAIN-2021-25 | refinedweb | 149 | 63.15 |
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which book learn of java language | http://www.roseindia.net/tutorialhelp/comment/99848 | CC-MAIN-2014-10 | refinedweb | 1,322 | 53.41 |
Frequently asked: Blockchain Interview Questions and Answers
Q1..
Q2. What are block records?
A block records some or all of the most recent transactions not yet validated by the network. Once the data are validated, the block is closed. Then, a new block is created for new transactions to be entered into and validated.
Q3. What is a Genesis Block?
In 2009, a developer named Santoshi Nakamoto created the genesis block. The genesis block is the first block in the blockchain and is also referred to as block 0. Some features of this block are as follows:
• It is the only block that does not refer to any previous block.
• It defines parameters of blockchain such as level of difficulty, consensus mechanism, etc. to mine the blocks.
The genesis block forms the foundation of the Bitcoin trading system, and it is the prototype for all other blocks in the blockchain.
Q4. Is it possible to modify the data written in the block?
No, it is not possible to modify the data in one particular block. If the need arises, the organization has to erase data from all the other blocks. Due to this reason, it is very important to deal with data with utmost care in the blockchain.
Q5. What is the difference between public and private keys?
Public Keys:
• It is used for identification.
• The sender can send a message in the blockchain network using the public key of the receiver.
• It is free to use and publicly available.
Private Keys:
• It is used for encryption and authentication purposes.
• The receiver can decrypt the message the received message in the blockchain network using the private key.
• It is kept secret and is not available publicly.
Q6. What is a 51% Attack?
A miner or a group of miners attempting to control more than 50% of a network’s hashing capacity, processing power, or hash rate is known as a 51 percent attack on a blockchain network. The attacker may prevent new transactions from taking place or being verified in this attack. They can also reverse transactions that have already been verified while in charge of the network, resulting in a double-spending problem.
Q7. What is Merkel Tree?
Merkel Tree is a data structure that is used for verifying a block. It is in the form of a binary tree containing cryptographic hashes of each block. A Merkle tree is structured similarly.
Q8. What are smart contracts on blockchain?
Smart contracts are simply programs stored on a blockchain that run when predetermined conditions are met. They typically are used to automate the execution of an agreement so that all participants can be immediately certain of the outcome, without any intermediary’s involvement or time loss.
Q9. What are ADA smart contracts?
A smart contract is an automated digital agreement, written in code, that tracks, verifies, and executes the binding transactions of a contract between various parties. The transactions of the contract are automatically executed by the smart contract code when predetermined conditions are met.
Q10. What is solidity in blockchain?
Solidity is an object-oriented programming language for writing smart contracts. It is used for implementing smart contracts on various blockchain platforms, most notably, Ethereum.
Q11. Can anyone remove blocks from a Blockchain?
The manner in which blocks are removed from a blockchain is entirely dependent on how they are treated. Manually removing a block is not possible. If it is destroyed, however, the blockchain may attempt to restore the database using other peers. They can be removed after they’ve been checked to reduce the blockchain’s size since they don’t need someone to perform regular operations. It can be re-downloaded if necessary. This process is called pruning.
Q12. List and explain the parts of EVM Memory.
The EVM memory can be divided into three parts:
• Storage: It is extremely expensive and the storage values are stored permanently on the blockchain network.
• Memory: It is temporary modifiable storage that can be accessed only during the contract execution. Once the contract execution is finished, all the data is lost.
- Stack: It is temporary non-modifiable storage and the content is lost once the execution completes.
Q13. What is a Dapp and how is it different from a normal application?
Dapp:
• A Dapp is a decentralized application that is deployed using a smart contract
• A Dapp has its back-end code (smart contract) which runs on a decentralized peer-to-peer network
• Process: Front-end, Smart contract (backend code), and Blockchain (P2P contract)
Normal application:
• Normal application has a back-end code that runs on a centralized server
• It’s a computer software application that is hosted on a central server
• Process: Front-end, API, and Database
Q14. What is MetaMask?
MetaMask is a type of Ethereum wallet that bridges the gap between the user interfaces for Ethereum (For Example, Mist browsers, DApps, etc.) and the regular web (For Example, Google Chrome, Mozilla Firefox, Websites, etc.). Its function is to inject a JavaScript library called web3.js into the namespace of each page the browser loads. It is mainly used as a plugin in the regular web (For Example, Google Chrome, Mozilla Firefox, etc.)
Q15. How can you stop double-spending?
Double spending is prevented using the consensus algorithm. The consensus algorithm ensures that the requested transaction is genuine and records it in the block. It is thus verified by the multiple nodes thus making double-spending not possible.
To read more Blockchain Interview Questions and answer check out our Android App from play store:
Our app contains 1600+ Interview Questions and answers with clear code examples from trending technologies. | https://vigowebs.medium.com/frequently-asked-blockchain-interview-questions-and-answers-c68e0204e670?source=user_profile---------2---------------------------- | CC-MAIN-2022-21 | refinedweb | 942 | 65.52 |
History
Note: MikeSmith created this page. The following people have added or edited content on it: HenriSivonen, ...
This page records a particular 10-year chunk of the history of milestones in the development of the HTML language (in the two forms of the language understood by most current browsers); the 10-year chunk recorded here is from the publication of the HTML4 recommendation on through to the publication of the first W3C Working Draft of the HTML5 specification. It also records a variety of related milestones of significance, including events in the evolution of Web applications and the underlying browser technologies that support them, as well as events related to important uses of those technologies, such as in blogs and social networking services.
See also A feature history of the modern Web Platform
1997-12
- HTML 4.0 Recommendation published and announced. Developed under the code name Cougar, its first public working draft had been released only five months earlier; after the publication of HTML4 as a Recommendation, the first W3C HTML Working Group closes.
- W3C HTML Validation service publicly launched at. Originally developed by Gerald Oskoboiny, it followed an earlier validation service developed in 1994 by Dan Connolly and Mark Gaither. It will go on to be titled the W3C Markup Validation Service, with Olivier Thereaux, and (later) Ville Skyttä, doing much of the work of managing its continued refinement, with involvement of a number of important contributors.
- The term weblog first coined by Jorn Barger to describe the list of links on his site Robot Wisdom.
1998-02, 1998-03
- XML 1.0 Recommendation published; it will among other things bring to the Web the notion of draconian error handling -- though key members of the group working on the XML spec (including the group's Technical Lead, James Clark) opposed adopting draconian error handling in XML. The XML language will also be used as the basis for the RSS and Atom syndicated-feed formats.
- Mozilla code open-sourced by Netscape and Mozilla.org is launched
1998-05
- Shaping the Future of HTML workshop with the conclusion/outcome:.
- CSS 2 Recommendation published.
1998-06
- PHP 3.0 released. PHP will become one of the most widely used server-side languages for creating "dynamic web content" and Web applications.
1998-07
- Second W3C HTML Working Group (effectively the first XHTML working group) chartered with the goal of redefining HTML as a modular application of XML and statement that maintenance of HTML 4.0 [will now be] limited to tracking messages and keeping errata; the group later successfully delivers XHTML 1.0, though its work does not produce any major updates to the core HTML language supported by browsers.
- Todd Fahrner posts a message to the mozilla-layout mailing list proposing use of a doctype switching mechanism in Mozilla:
Please consider taking a modal approach: ship a browser with 2 independent rendering systems. Use the legacy system for legacy content. Use NGLayout when rendering documents authored in either HTML 4.0 Strict or XML (this will include HTML 5.0). Pay attention to the DOCTYPE.It will be two more than a year before the idea is realized in any browser -- first in version 5.0 of Internet Explorer for Mac, then shortly after that, in Mozilla.
1998-09
- Google Inc. opens its doors. During the last part of 1998, the Google search engine quickly gains attention and a rapidly growing user base; in a December 1998 Salon article titled Yes, there is a better search engine, Scott Rosenberg writes: idea of the "collective wisdom of the Web" (stated, among other ways, as "the wisdom of crowds") will go on to become one of the hallmarks of "Web 2.0" discussions (when such discussions start in 2004 and 2005) and Google will go on to launch a variety of Web applications that are notable in making innovative use of asynchronous scripting (Ajax) and client-side/browser techologies.
- eBay initial public offering (IPO); online since 1995, eBay is often cited as a high-profile example of a sophisticated Web application (though unlike Google, eBay never really breaks any new ground in its use of browser technologies).
1998-10
- Mozilla project moves to Gecko as its layout engine; Gecko (called NGLayout at the time) is a significant improvement over the engine used in previous Netscape releases, and provides the foundation for Mozilla as we now know it (and eventually for Firefox).
- Open Diary. Though not exactly a household name now, Open Diary is cited as the first community for blogs (or for what will later become known as blogs), also as the place where blog comments were first introduced (shortly after its launch, a feature was added to enable users to post notes on each others' diary pages), and as an early example of a social networking service.
1999-03
- XMLHttpRequest (XHR) support first released, in Microsoft Internet Explorer version 5; as XHR support is later added to other browsers, it will go on to become a cornerstone that enables cross-platform Web applications that make use of asynchronous scripting (Ajz) to provide behavior similar to that of desktop applications.
- RSS created by Ramanathan V. Guha (who was employed at Netscape at the time, and who will go on to join Google in 2005). It becomes the most widely used format for syndicating feeds (from news sites, blogs, and so on).
- LiveJournal launched by Brad Fitzpatrick. It pioneers use of certain social networking features eventually common to sites such as Facebook and becomes one of the most prominent blogging sites. Fitzpatrick will go on to sell LiveJournal to SixApart in January 2005 and later move on to work at Google.
1999-06
1999-08
- Lars Knoll rewrites KHTML to use the standard W3C DOM as its internal document representation, enabling integration with Harri Porten's KJS to add Javascript support shortly afterward. In the closing months of 1999 and first few months of 2000, Knoll does further work with Antti Koivisto and Dirk Mueller to add CSS support and to refine and stabilize the KHTML architecture -- thereby building a Web engine that will, in addition to its use in KDE, later be picked up by Apple for their Safari browser (forming the basis of what will eventually become Webkit).
- Blogger.com launched; one of the earliest dedicated blog-publishing tools, it is credited for helping popularize the format (quote from Wikipedia entry); it will be acquired by Google in February 2003.
- First non-confidential draft of XHTML™ Extended Forms Requirements published saying After careful consideration, the HTML Working Group has decided that the goals for the next generation of forms are incompatible with preserving backwards compatibility with browsers designed for earlier versions of HTML..
1999-11
- HTML Working Group Roadmap first public version published; its "Working Group Goals" section includes a statement that W3C has no intention to extend HTML 4 as such. Instead, further work is focusing on a reformulation of HTML in XML.
1999-12, 2000-01
- ECMAScript 3rd Edition published
- HTML 4.01 Recommendation published (final version of HTML4); described in the HTML Working Group Roadmap as an updated recommendation for HTML 4.0 that incorporates editorial corrections and bug fixes for problems detected since HTML 4.0.
- XHTML 1.0 Recommendation published, with one of its inherent principles being draconian error handling -- something previously foreign to HTML and seen by many as fundamentally not Web-friendly -- since it was at the time (and continues to be) at odds with how existing browser actually process existing HTML content.
2000-03
- Internet Explorer 5 for the Macintosh released; along with being the first browser to fully support CSS1, it's the first released browser to implement doctype switching.
- Mozilla developers adds support for doctype switching to the Mozilla codebase. A subsequent Transitional DOCTYPE with URI should trigger strict layout mode bug report leads to further refinements of the switching code (in part to more closely match the behavior in IE5 for Mac).
2000-05
2000-06
- Third W3C HTML Working Group (effectively the second XHTML working group) chartered, with a statement that the scope of this charter is to see through to completion the transition to XML; the group later successfully delivers XHTML 1.1 and begins developing XHTML 2.0, though its work does not produce any major updates to the core HTML language supported by browsers.
- XForms Working Group chartered. Even though the WG was chartered to produce Proposed Recommendation in the XForms area, DOM APIs were included only on the level of investigation: An investigation into the requirements for an XForms DOM. The plan is to obsolete the current HTML DOM, and the issue to be considered is whether the XML DOM is sufficient or whether an XForms DOM is warranted..
2000-07, 2000-09
- XMLHttpRequest support enabled by default in Mozilla codebase
- What is an XHTML document? thread related to handling of XHTML served as text/html, initiated by David Baron on the www-html list: The XHTML spec [...] says that XHTML Documents may be sent as "text/html" [...] there have been a number of bugs filed against Mozilla arguing that our XHTML support is broken because XHTML documents are parsed loosely when sent as "text/html" [...] If these conformance requirements do not apply to XHTML documents served as "text/html", then the XHTML spec should say that.
- Sniffing XHTML sent as text/html thread in response to David Baron's request to the HTML Working Group for guidance on the question of "how should Mozilla detect whether a text/html document is XHTML or not?"; Steven Pemberton responds: The HTML WG has discussed this [...] documents served as text/html should be treated as HTML and not as XHTML. There should be no sniffing of text/html documents to see if they are really XHTML.
2001-01
- Wikipedia is launched.
2001-05
- XHTML 1.1 Recommendation published; after its publication, the third W3C HTML Working group will focus an increasing amount of its energies toward developing XHTML 2.0.
2001-08
- Microsoft Internet Explorer version 6 released with improved CSS and W3C DOM support, but no XHTML support. It is the first version of IE for Windows that implements doctype switching.
- CSS 2.1 First Public Working Draft published.
2001-09
- SVG 1.0 Recommendation published. Native support for SVG will go on to be implemented in all major desktop browsers, including (beginning in 2010) Microsoft Internet Explorer, as well as being supported across a range of mobile devices.
2002-06
- Mozilla 1.0 released; incorporates the first compatible native implementation of XMLHttpRequest
- Mozilla developers add an "almost standards" doctype-switching mode to the Mozilla codebase.
2002-07
- David Hyatt moves to Apple from Mozilla to work on what will become Safari
2002-08
- Fourth W3C HTML Working Group (effectively the third XHTML working group) chartered, with a statement that the main scope of this charter is to complete the transition from HTML to XHTML... this includes finishing work on XHTML 2.0 [which] will include new features such as XForms and XML Events as replacements for legacy HTML/XHTML features.
- XHTML 2.0 First Public Working Draft published, with a statement that while the ancestry of XHTML 2 comes from HTML 4, XHTML 1.0, and XHTML 1.1, it is not intended to be backward compatible with its earlier versions.
- How liberal is too liberal? blog posting by Mark Pilgrim: Look at it this way: imagine you made a browser that only rendered sites authored in valid HTML or XHTML. How much of the web would your users be able to see? 1%? 0.1%? Less?
2002-09
- HLink draft published by the W3C HTML Working Group, signaling a rift that is significant in the history of HTML in that it was a key indicator that some W3C recommendations for XML-based technologies might be out of sync with Web realities and that is foreshadowed a similar rift that would take place later with regard to XForms; for more details, see the HLink page.
2002-12
- XHTML 2 second public Working Draft published, with some continuing to hail it as a much-needed and long-overdue refactoring of the language but with some Web notables (including Daniel Glazman, Mark Pilgrim and Jeffrey Zeldman) greeting it with objections; Glazman writes:
XHTML 2.0 seems to me the live proof that something is going wrong at W3C... I strongly suggest dropping all "XHTML 2.0" efforts in favor of a new "xHTML 5.0" language. Clearly a successor to HTML 4, feature-oriented, made for the _web_.
2003-01
- Safari first beta released by Apple, based on the KHTML rendering engine and KJS Javascript interpreter.
- SVG 1.1 Recommendation published. SVG 1.1 is essentially a modularized version of SVG 1.0, with few other differences.
2003-03
- Wordpress.org domain registered. The PHP-based Wordpress blogging engine will go on to become perhaps the most widely used open-source blogging engine -- as an alternative to blogging services such as Blogger.com and other blogging engines such as Movable Type (particularly in the months after May 2004, when licensing fees for Movable Type were changed in way that made it more attractive for users to consider alternatives).
2003-07
- Anatomy of a Well Formed Log Entry posting by Sam Ruby, announcing creation of a a new Wiki the purpose of which is describing a conceptual data model of what constitutes a well formed log entry. That Wiki will go on to become "the Atom Wiki" and the intial basis for collaborative work on developing the specification for the Atom syndicated-feed format.
- atom-syntax mailing list created; it becomes the central forum for discussion of Atom.
2003-08, 2003-09
- XForms Proposed Recommendation published; includes dependencies on XPath, XML Schema, and XML Events.
- Apple and Opera submit review comments on the XForms Proposed Recommendation, and in a follow-up posting, Håkon Wium Lie states:
Opera Software has been working on an XHTML module which would add some functionality from XForms (e.g. basic data typing and XML submission) without introducing large numbers of extra dependencies. We hope to continue this work in cooperation with W3C and its members.
2003-10, 2003-12
- XForms 1.0 Recommendation published
- Web Forms 2.0 first public draft published under the title "XForms Basic"; as described earlier by Håkon Wium Lie, it is intended to "add some functionality from XForms... without introducing large numbers of extra dependencies"; see also the announcement and discussion on the www-forms list.
- Atom 0.3 released. It is quickly adopted across a range of applications and sites, including Blogger, Google News, and Gmail.
2004-01
- Void filling: Web Applications Language blog posting from Ian Hickson: The W3C had so far failed to address a need in the Web community: There is no language for Web applications... I intend to do something about this (hopefully within a W3C context, although that will depend on the politics of the situation).
- Draconian error handling with respect to syndicated feeds becomes the subject of a flurry of blog postings and mailing-list postings, with (among others) Mark Pilgrim and Ian Hickson advocating the position that draconian error handling is a counterproductive way of dealing with problem: Authors will write invalid content regardless... Specifications [...] should state what the authors must not do, and then tell implementors what they must do when an author does it anyway.
2004-02
- Safari 1.2 released; first version of Safari with XMLHttpRequest support
- Web Forms 2.0 draft published under "Web Forms 2.0" title for first time.
- Flickr launched; making innovative use of asynchronous scripting/Ajax mechanisms in its user interface, it will go on to become the Web application most often cited in "Web 2.0" discussions.
- CSS 2.1 Candidate Recommendation published; however, after this initial CR publication, the CSS 2.1 spec will then go back to Working Draft status before returning again to CR status in July 2007.
2004-03
- whatwg.org domain registered
- Ramblings from the North blog posting from Ian Hickson: I've been taking the opportunity to work on a proposal for a Web Applications specification... something along the same lines as Web Forms 2, but specifically for client-side application development.
2004-04
- Gmail launched in invitation-only beta.
- Web Applications 1.0; first public draft of what will eventually become HTML5
2004-05
- Fragmentation of document formats on the Web essay posted by David Baron: If the W3C does not act, the problem will have to be solved either by some other standardization body or by the market... it is worth remembering that the rules for error-handling in traditional HTML were solved by the market, and the end result was bad for competition and bad for small devices.
- Backwards Compatibility blog posting from Ian Hickson: Authors still want to write Web applications, and the currently deployed standards are inadequate. Since completely new standards won't cut it [...] this leaves us with the solution we (Opera and Mozilla) have been advocating: updating HTML and the DOM.
2004-06
- W3C Workshop on Web Applications and Compound Documents held at Adobe offices in San Jose; Opera and Mozilla jointly submit and present a position paper with a set of proposed Design Principles for Web Application Technologies; but some subsequent blog postings from Brendan Eich, David Baron, and Ian Hickson make it clear that they have come away from the workshop with a realization that their goals with respect to Web applications are not in sync with others in attendance. Brendan Eich:
The dream of a new web, based on XHTML+SVG+SMIL+XForms, is just that -- a dream. It won't come true no matter how many toy implementations there are... The best way to help the Web is to incrementally improve the existing web standards, with compatibility shims provided for IE, so that web content authors can actually deploy new formats interoperably... Mozilla is joining with Opera and others to explore the sort of incremental improvements to HTML proposed by us at the workshop.
- WHATWG launched: The group aims to develop specifications based on HTML and related technologies to ease the deployment of interoperable Web Applications [...] for implementation in mass-market Web browsers, in particular Safari, Mozilla, and Opera; [the group] intends to ensure that all its specifications address backwards compatibility concerns [...] and specify error handling behavior to ensure interoperability even in the face of documents that do not comply to the letter of the specifications.
- Atom Publishing Format and Protocol Working Group (atompub) chartered within the IETF Applications Area to 'use experience gained with RSS [...] as the basis for a standards-track document specifying the [Atom] model, syntax, and feed format. The feed format and HTTP will be used as the basis of work on a standards-track document specifying the editing protocol' and noting that the group will take steps to ensure interoperability, by unambiguously identifying required elements in formats, clearly nominating conformance levels for different types of software, and providing clear extensibility mechanisms and constraints upon them.
2004-07
- XML on the Web Has Failed article by Mark Pilgrim, with this comment on draconian error handling:.
2004-08
- First public release of an Opera build with with some degree of XMLHttpRequest support (v7.60 Technical Preview for Windows)
2004-10
- Google Suggest launched in beta
- Web 2.0 Conference first takes place in San Francisco, eventually causing the term Web 2.0 to be brought into general use.
- Compound Document Formats Activity and Working Group launched, with deliverables described as: Specifications for combining W3C technologies, such as SMIL, SVG and XML Events, with XHTML by reference and Specifications for combining W3C technologies, such as XHTML, XML Events, CSS, SVG, SMIL and XForms, into a single document by inclusion.
2005-02
- Google Maps launched in beta with support across all major browsers (Internet Explorer, Mozilla, Opera, and Safari).
- Ajax: A New Approach to Web Applications by Jesse James Garrett (coining the term Ajax)
2005-04
- Opera 8 released; first release version of Opera with (limited) XMLHttpRequest support
- Web Forms 2.0 published as a W3C Member Submission
- Validation Service for RELAX NG first launched by Henri Sivonen. It will later become the basis for the validator.nu HTML5 conformance checking service.
2005-09
- What Is Web 2.0 article by Tim O'Reilly. Subsequent discussions of the term Web 2.0 often cite this article; excerpt: It's clear that standards and solutions [...] will enable the next generation of applications. [...] AJAX is also a key component of Web 2.0 applications such as Flickr [...] We're entering an unprecedented period of user interface innovation, as web developers are finally able to build web applications as rich as local PC-based applications.
2005-11
- Web API and Web Application Formats Working Groups chartered at the launch of the W3C Rich Web Client Activity
2005-12 and 2006-01
- RFC 4287 (The Atom Syndication Format) published by the IETF.
- The future of HTML, Part 1: WHATWG and The future of HTML, Part 2: XHTML 2.0 articles by Edd Dumbill as that IBM developerWorks site:... The grassroots-organised WHATWG aims for a gently incremental enhancement of HTML 4 and XHTML 1.0, whereas the consortium-sponsored XHTML 2.0 is a comprehensive refactoring of the HTML language.
- Web Authoring Statistics report published at Google Code site: ...we did an analysis of a sample of slightly over a billion documents, extracting information about popular class names, elements, attributes, and related metadata".
2006-01
2006-08
- Web Forms 2.0 First Public Working Draft published by W3C Web Application Formats Working Group; see also the subsequent public discussion initiated by John Boyer and cross-posted to several mailing lists (following an earlier discussion thread on the member-only list for W3C chairs): IBM strongly advocates for the renewed charter of the XForms and HTML working groups to include unification of the Web Forms 2.0 work with emphases on the ease-of-use benefits from WF2 and the XML basis from XForms.
- SVG Tiny 1.2 Candidate Recommendation published.
- jQuery 1.0 released.
2006-10
- Microsoft Internet Explorer version 7 released with CSS and W3C DOM improvements, but still no XHTML support
- Reinventing HTML posting by Tim Berners-Lee: Some things are clearer with hindsight of several years. It is necessary to evolve HTML incrementally. The attempt to get the world to switch to XML, including quotes around attribute values and slashes in empty tags and namespaces all at once didn't work... The plan is to charter a completely new HTML group. Unlike the previous one, this one will be chartered to do incremental improvements to HTML, as also in parallel xHTML.
2006-11
- Proposed charter for HTML Working group posted by Ian Hickson (following the earlier posting of shorter proposed charter, specific feedback and some public discussion about charter review); among some language of the proposed charter that don't make it into the final charter is the phrase APIs for the manipulation of sound, 2D bitmap and vector graphics, 3D graphics, video, which gets reduced instead to the phrase APIs for the manipulation of linked media.
2007-03
- Fifth W3C HTML Working Group chartered (second W3C HTML working group to focus on the core HTML language), with a mission to continue the evolution of HTML (including classic HTML and XML syntaxes) and with a statement that this group will maintain and produce incremental revisions to the HTML specification [to produce] a language evolved from HTML4 for describing the semantics of documents and applications on the World Wide Web.
2007-05
- Google Gears released.
2007-06
2008-01 | https://www.w3.org/html/wg/wiki/History | CC-MAIN-2017-09 | refinedweb | 3,953 | 51.07 |
C++ - New Standard Concurrency Features in Visual C++ 11
By Diego Dagum | March 2012
The latest C++ iteration, known as C++11 and approved by the International Organization for Standardization (ISO) in the past year, formalizes a new set of libraries and a few reserved words to deal with concurrency. Many developers have used concurrency in C++ before, but always through a third-party library—often directly exposing OS APIs.
Herb Sutter announced in December 2004 that the “free performance lunch” was over in the sense that CPU manufacturers were prevented from shipping faster CPUs by physical power consumption and increasing heat reasons. This led to the current, mainstream multicore era, a new reality to which C++—the standard one—has just made an important leap to adapt.
The rest of this article is organized in two main sections and smaller subsections. The first main section, starting with Parallel Execution, covers technologies that allow applications to run independent or semi-independent activities in parallel. The second main section, starting with Syncing up Concurrent Execution, explores mechanisms for synchronizing the way these activities handle data, thus avoiding race conditions.
This article is based on features included in the upcoming version of Visual C++ (for now, called Visual C++ 11). A few of them are already available in the current version, Visual C++ 2010. Although not a guide to model parallel algorithms, nor an exhaustive documentation about all the available options, this article is a solid introduction to new C++11 concurrency features.
Parallel Execution
When you model processes and design algorithms over data, there’s a natural tendency to specify them in a sequence of steps. As long as performance is within acceptable bounds, this is the most recommendable schema because it’s typically easier to understand—a requirement for maintainable code bases.
When performance becomes a worrisome factor, a classic initial attempt to overcome the situation is to optimize the sequential algorithm in order to reduce the consumed CPU cycles. This can be done until you come to a point where no further optimizations are available—or they’re hard to achieve. Then the time to split the sequential series of steps into activities of simultaneous occurrence has come.
In the first section you’ll learn about the following:
- Asynchronous tasks: those smaller portions of the original algorithm only linked by the data they produce or consume.
- Threads: units of execution administrated by the runtime environment. They relate to tasks in the sense that tasks are run on threads.
- Thread internals: thread-bound variables, exceptions propagated from threads and so on.
Asynchronous Tasks
In the companion code to this article, you’ll find a project called Sequential Case, as shown in Figure 1.
The main function asks the user for some data and then submits that data to three functions: calculateA, calculateB and calculateC. The results are later combined to produce some output information for the user.
The calculating functions in the companion material are coded in a way such that a random delay between one and three seconds is introduced in each. Considering that these steps are executed sequentially, this leads to an overall execution time—once the input data is entered—of nine seconds in the worst-case scenario. You can try this code out by pressing F5 and running the sample.
So I need to revise the execution sequence and find steps to be performed concurrently. As these functions are independent, I can execute them in parallel by using the async function:
int main(int argc, char *argv[])
{
getUserData();
future<int> f1 = async(calculateB), f2 = async(calculateC);
c = (calculateA() + f1.get()) * f2.get();
showResult();
}
I’ve introduced two concepts here: async and future, both defined in the <future> header and the std namespace. The first one receives a function, a lambda or a function object (functor) and returns a future. You can understand the concept of a future as the placeholder for an eventual result. Which result? The one returned by the function called asynchronously.
At some point, I’ll need the results of these parallel-running functions. Calling the get method on each future blocks the execution until the value is available.
You can test and compare the revised code with the sequential case by running the AsyncTasks project in the companion sample. The worst-case delay of this modification is about three seconds versus nine seconds for the sequential version.
This is a lightweight programming model that releases the developer from the duty of creating threads. However, you can specify threading policies, but I won’t cover those here.
Threads
The asynchronous task model presented in the previous section might suffice in some given scenarios, but if you need a deeper handling and control of the execution of threads, C++11 comes with the thread class, declared in the <thread> header and located in the std namespace.
Despite being a more complex programming model, threads offer better methods for synchronization and coordination, allowing them to yield execution to another thread and wait for a determined amount of time or until another thread is finished before continuing.
In the following example (available in the Threads project of the companion code), I have a lambda function, which, given an integer argument, prints its multiples of less than 100,000 to the console:
auto multiple_finder = [](int n) {
for (int i = 0; i < 100000; i++)
if (i%n==0)
cout << i << " is a multiple of " << n << endl;
};
int main(int argc, char *argv[])
{
thread th(multiple_finder, 23456);
multiple_finder(34567);
th.join();
}
As you’ll see in later examples, the fact that I passed a lambda to the thread is circumstantial; a function or functor would’ve sufficed as well.
In the main function I run this function in two threads with different parameters. Take a look at my result (which could vary between different runs due to timings):
I might implement the example about asynchronous tasks in the previous section with threads. For this, I need to introduce the concept of a promise. A promise can be understood as a sink through which a result will be dropped when available. Where will that result come out once dropped? Each promise has an associated future.
The code shown in Figure 2, available in the Promises project of the sample code, associates three threads (instead of tasks) with promises and makes each thread call a calculate function. Compare these details with the lighter AsyncTasks version.
typedef int (*calculate)(void); void func2promise(calculate f, promise<int> &p) { p.set_value(f()); } int main(int argc, char *argv[]) { getUserData(); promise<int> p1, p2; future<int> f1 = p1.get_future(), f2 = p2.get_future(); thread t1(&func2promise, calculateB, std::ref(p1)), t2(&func2promise, calculateC, std::ref(p2)); c = (calculateA() + f1.get()) * f2.get(); t1.join(); t2.join(); showResult(); }
Thread-Bound Variables and Exceptions
In C++ you can define global variables whose scope is bound to the entire application, including threads. But relative to threads, now there’s a way to define these global variables such that every thread keeps its own copy. This concept is known as thread local storage and it’s declared as follows:
If the declaration is done in the scope of a function, the visibility of the variable will be narrowed to that function but each thread will keep maintaining its own static copy. That is to say, values of the variable per thread are being kept between function invocations.
Although thread_local isn’t available in Visual C++ 11, it can be simulated with a non-standard Microsoft extension:
What would happen if an exception were thrown inside a thread? There will be cases in which the exception can be caught and handled in the call stack inside the thread. But if the thread doesn’t deal with the exception, you need a way to transport the exception to the initiator thread. C++11 introduces such mechanisms.
In Figure 3, available in the companion code in the project ThreadInternals, there’s a function sum_until_element_with_threshold, which traverses a vector until it finds a specific element, summing all the elements along the way. If the sum exceeds a threshold, an exception is thrown.
thread_local unsigned sum_total = 0; void sum_until_element_with_threshold(unsigned element, unsigned threshold, exception_ptr& pExc) { try{ find_if_not(begin(v), end(v), [=](const unsigned i) -> bool { bool ret = (i!=element); sum_total+= i; if (sum_total>threshold) throw runtime_error("Sum exceeded threshold."); return ret; }); cout << "(Thread #" << this_thread::get_id() << ") " << "Sum of elements until " << element << " is found: " << sum_total << endl; } catch (...) { pExc = current_exception(); } }
If that happens, the exception is captured via current_exception into an exception_ptr.
The main function triggers a thread on sum_until_element_with_threshold, while calling that same function with a different parameter. When both invocations have finished (the one in the main thread and the one in the thread triggered from it), their respective exception_ptrs will be analyzed:
const unsigned THRESHOLD = 100000; vector<unsigned> v; int main(int argc, char *argv[]) { exception_ptr pExc1, pExc2; scramble_vector(1000); thread th(sum_until_element_with_threshold, 0, THRESHOLD, ref(pExc1)); sum_until_element_with_threshold(100, THRESHOLD, ref(pExc2)); th.join(); dealWithExceptionIfAny(pExc1); dealWithExceptionIfAny(pExc2); }
If any of these exception_ptrs come initialized—a sign that some exception happened—their exceptions are triggered back with rethrow_exception:
This is the result of our execution, as the sum in the second thread exceeded its threshold:
Syncing up Concurrent Execution
It would be desirable if all applications could be split into a 100 percent-independent set of asynchronous tasks. In practice this is almost never possible, as there are at least dependencies on the data that all parties concurrently handle. This section introduces new C++11 technologies to avoid race conditions.
You’ll learn about:
- Atomic types: similar to primitive data types, but enabling thread-safe modification.
- Mutexes and locks: elements that enable us to define thread-safe critical regions.
- Condition variables: a way to freeze threads from execution until some criteria is satisfied.
Atomic Types
The <atomic> header introduces a series of primitive types—atomic_char, atomic_int and so on—implemented in terms of interlocking operations. Thus, these types are equivalent to their homonyms without the atomic_ prefix but with the difference that all their assignment operators (==, ++, --, +=, *= and so on) are protected from race conditions. So it won’t happen that in the midst of an assignment to these data types, another thread irrupts and changes values before we’re done.
In the following example there are two parallel threads (one being the main) looking for different elements within the same vector:
When each element is found, a message from within the thread is printed, telling the position in the vector (or iteration) where the element was found:
void find_element(unsigned element) { unsigned iterations = 0; find_if(begin(v), end(v), [=, &iterations](const unsigned i) -> bool { ++iterations; return (i==element); }); total_iterations+= iterations; cout << "Thread #" << this_thread::get_id() << ": found after " << iterations << " iterations." << endl; }
There’s also a common variable, total_iterations, which is updated with the compounded number of iterations applied by both threads. Thus, total_iterations must be atomic to prevent both threads from updating it at the same time. In the preceding example, even if you didn’t need to print the partial number of iterations in find_element, you’d still accumulate iterations in that local variable instead of total_iterations, to avoid contention over the atomic variable.
You’ll find the preceding sample in the Atomics project in the companion code download. I ran it, getting the following:
Mut(ual) Ex(clusion) and Locks
The previous section depicted a particular case of mutual exclusion for writing access on primitive types. The <mutex> header defines a series of lockable classes to define critical regions. That way, you can define a mutex to establish a critical region throughout a series of functions or methods, in the sense that only one thread at a time will be able to access any member in this series by successfully locking its mutex.
A thread attempting to lock a mutex can either stay blocked until the mutex is available or just fail in the attempt. In the middle of these two extremes, the alternative timed_mutex class can stay blocked for a small interval of time before failing. Allowing lock attempts to desist helps prevent deadlocks.
A locked mutex must be explicitly unlocked for others to lock it. Failing to do so could lead to an undetermined application behavior—which could be error-prone, similar to forgetting to release dynamic memory. Forgetting to release a lock is actually much worse, because it might mean that the application can’t function properly anymore if other code keeps waiting on that lock. Fortunately, C++11 also comes with locking classes. A lock acts on a mutex, but its destructor makes sure to release it if locked.
The following code (available in the Mutex project in the code download) defines a critical region around a mutex mx:
This mutex is used to guarantee that two functions, funcA and funcB, can run in parallel without coming together in the critical region.
The function funcA will wait, if necessary, in order to come to the critical region. In order to make it do so, you just need the simplest locking mechanism—lock_guard:
The way it’s defined, funcA should access the critical region three times. The function funcB, instead, will attempt to lock, but if the mutex is by then already locked, funcB will just wait for a second before again attempting to get access to the critical region. The mechanism it uses is unique_lock with the policy try_to_lock_t, as shown in Figure 4.
void funcB() { int successful_attempts = 0; for (int i = 0; i<5; ++i) { unique_lock<mutex> ul(mx, try_to_lock_t()); if (ul) { ++successful_attempts; cout << this_thread::get_id() << ": lock attempt successful." << endl; ... // Do something in the critical region cout << this_thread::get_id() << ": releasing lock." << endl; } else { cout << this_thread::get_id() << ": lock attempt unsuccessful. Hibernating..." << endl; this_thread::sleep_for(chrono::seconds(1)); } } cout << this_thread::get_id() << ": " << successful_attempts << " successful attempts." << endl; }
The way it’s defined, funcB will try up to five times to enter the critical region. Figure 5 shows the result of the execution. Out of the five attempts, funcB could only come to the critical region twice.
funcB: lock attempt successful. funcA: locking with wait ... funcB: releasing lock. funcA: lock secured ... funcB: lock attempt unsuccessful. Hibernating ... funcA: releasing lock. funcB: lock attempt successful. funcA: locking with wait ... funcB: releasing lock. funcA: lock secured ... funcB: lock attempt unsuccessful. Hibernating ... funcB: lock attempt unsuccessful. Hibernating ... funcA: releasing lock. funcB: 2 successful attempts. funcA: locking with wait ... funcA: lock secured ... funcA: releasing lock.
Condition Variables
The header <condition_variable> comes with the last facility covered in this article, fundamental for those cases when coordination between threads is tied to events.
In the following example, available in project CondVar in the code download, a producer function pushes elements in a queue:
The standard queue isn’t thread-safe, so you must make sure that nobody else is using it (that is, the consumer isn’t popping any element) when queuing.
The consumer function attempts to fetch elements from the queue when available, or it just waits for a while on the condition variable before attempting again; after two consecutive failed attempts, the consumer ends (see Figure 6).
void consumer() { unique_lock<mutex> l(m); int failed_attempts = 0; while (true) { mq.lock(); if (q.size()) { int elem = q.front(); q.pop(); mq.unlock(); failed_attempts = 0; cout << "Consumer: fetching " << elem << " from queue." << endl; ... // Consume elem } else { mq.unlock(); if (++failed_attempts>1) { cout << "Consumer: too many failed attempts -> Exiting." << endl; break; } else { cout << "Consumer: queue not ready -> going to sleep." << endl; cv.wait_for(l, chrono::seconds(5)); } } } }
The consumer is to be awoken via notify_all by the producer every time a new element is available. That way, the producer avoids having the consumer sleep for the entire interval if elements are ready.
Figure 7shows the result of my run.
Consumer: queue not ready -> going to sleep. Producer: element 0 queued. Consumer: fetching 0 from queue. Consumer: queue not ready -> going to sleep. Producer: element 1 queued. Consumer: fetching 1 from queue. Consumer: queue not ready -> going to sleep. Producer: element 2 queued. Producer: element 3 queued. Consumer: fetching 2 from queue. Producer: element 4 queued. Consumer: fetching 3 from queue. Consumer: fetching 4 from queue. Consumer: queue not ready -> going to sleep. Consumer: two consecutive failed attempts -> Exiting.
A Holistic View
To recap, this article has shown a conceptual panorama of mechanisms introduced in C++11 to allow parallel execution in an era where multicore environments are mainstream.
Asynchronous tasks enable a lightweight programming model to parallelize execution. The outcomes of each task can be retrieved through an associated future.
Threads offer more granularity than tasks—although they’re heavier—together with mechanisms for keeping separated copies of static variables and transporting exceptions between threads.
As parallel threads act on common data, C++11 provides resources to avoid race conditions. Atomic types enable a trusted way to ensure that data is modified by one thread at a time.
Mutexes help us define critical regions throughout the code—regions to which threads are prevented access simultaneously. Locks wrap mutexes, tying the unlocking of the latter to the lifecycle of the former.
Finally, condition variables grant more efficiency to thread synchronization, as some threads can wait for events notified by other threads.
This article hasn’t covered all the many ways to configure and use each of these features, but the reader now has a holistic vision of them and is ready to dig deeper.
Diego Dagum is a software developer with more than 20 years of experience. He’s currently a Visual C++ community program manager with Microsoft.
Thanks to the following technical experts for reviewing this article: David Cravey, Alon Fliess, Fabio Galuppo and Marc Gregoire
MSDN Magazine Blog
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Receive the MSDN Flash e-mail newsletter every other week, with news and information personalized to your interests and areas of focus. | https://msdn.microsoft.com/en-gb/magazine/hh852594.aspx | CC-MAIN-2016-07 | refinedweb | 2,972 | 54.02 |
This set of pure C# classes implements the cryptographic Tiger hash algorithm. It inherits from .NET's HashAlgorithm class and so is usable as drop-in in any place where .NET's built-in hash functions are already used. Although not as fast as native machine code generated by C++ or ASM, it's still about 30% faster than the other C# implementations I found (2010).
HashAlgorithm
The program has been tested with a number of different binaries, and most of the test vectors supplied by the creators of Tiger.
A cryptographic hash maps an arbitrary-length data block (e.g., password, file) to a fixed-length hash value as one-way function (= irreversible).
Tiger was designed in 1995, so it had enough time to be well-analyzed, and no successful attacks on full 24-round Tiger are known to date. It is always a good idea to consult Wikipedia or The Hash Function Lounge to check if new vulnerabilities have been found since this article was written.
Its level of security is comparable to RIPEMD-160 or SHA-256. It works on whole 512-bit input data blocks, and produces 192 bits of hash value output. Input data that doesn't align to 512-bit boundaries (as usually is the case) is padded accordingly.
Tiger itself is a 64-bit-optimized algorithm, but still runs well on narrower buses. This implementation does some optimizations that do not drag down the 64-bit performance noticeably but help the 32-bit systems very much.
The underlying cryptographic design is basically described on Wikipedia and in more detail on the inventors´ webpage. The data for the S-Boxes has been taken from the reference implementation.
Some of the functionality (e.g., FileStream processing) is provided by the .NET Framework through the abstract HashAlgorithm base class.
FileStream
The class is being created/instantiated directly, but used/called through the abstract HashAlgorithm class:
using System.Security.Cryptography;
using softwareunion;
HashAlgorithm myhash;
switch(AlgorithmToUse)
{ case "MD5": myhash=new MD5CryptoServiceProvider();
case "TIGER": myhash=new Tiger(); // <<-- create the object
// [...]
default: throw new NotImplementedException();
}
// vv-- then ask framework's HashAlgorithm class to
// coordinate and call our own class methods
myhash.ComputeHash( File.OpenRead("myfile.bin") );
byte[] the_hash_result=myhash.HashValue;
There is a version 2 of Tiger that only differs in the padding value of 0x01 being upgraded to 0x80 (there's already a comment for it in the ProcessFinalBlock function).
ProcessFinalBlock
Array.Copy(...)
(byte)
&0xFF
int
BitTools.RotLeft
Array
TypeBlindCopy(...)
byte
ulong. | http://www.codeproject.com/Articles/149061/A-Tiger-Hash-Implementation-for-C?fid=1606316&df=90&mpp=10&sort=Position&spc=Relaxed&tid=4186030 | CC-MAIN-2016-44 | refinedweb | 414 | 57.37 |
Created on 2014-08-29 11:00 by eddygeek, last changed 2016-04-19 13:41 by berker.peksag. This issue is now closed.
_make_iterencode in python2.7/json/encoder.py encodes custom enum types incorrectly (the label will be printed without '"') because of these lines (line 320 in 2.7.6):
elif isinstance(value, (int, long)):
yield buf + str(value)
in constract, _make_iterencode in python 3 explicitly supports the enum types:
elif isinstance(value, int):
# Subclasses of int/float may override __str__, but we still
# want to encode them as integers/floats in JSON. One example
# within the standard library is IntEnum.
yield buf + str(int(value))
The enum types was added to the stdlib in 3.4. There are no the enum types in Python 2.7. There is no a bug, support for the enum types is new feature.
Edward, is this a regression? If yes, we should probably fix it.
This is not a regression. json only deals with standard types (int, str, etc.), and Enum is not a standard type.
Enum was introduced in 3.4, so corresponding changes were made to json to support int and float subclasses, of which IntEnum is one.
In other words, this was a bug that no one noticed for many many releases, and I'm not sure we should fix it in 2.7 now.
Arguments for fixing?
One argument against fixing: If we do fix in 2.7.9 then any program targeting it will be unable to target 3.0-3.3, as those versions do not have the fix from 3.4.
On Aug 30, 2014, at 07:34 PM, Ethan Furman wrote:
>In other words, this was a bug that no one noticed for many many releases,
>and I'm not sure we should fix it in 2.7 now.
>
>Arguments for fixing?
-1 on fixing it, but we *can* document workarounds. Here's what I use in
Mailman 3.
class ExtendedEncoder(json.JSONEncoder):
"""An extended JSON encoder which knows about other data types."""
def default(self, obj):
if isinstance(obj, datetime):
return obj.isoformat()
elif isinstance(obj, timedelta):
# as_timedelta() does not recognize microseconds, so convert these
# to floating seconds, but only if there are any seconds.
if obj.seconds > 0 or obj.microseconds > 0:
seconds = obj.seconds + obj.microseconds / 1000000.0
return '{0}d{1}s'.format(obj.days, seconds)
return '{0}d'.format(obj.days)
elif isinstance(obj, Enum):
# It's up to the decoding validator to associate this name with
# the right Enum class.
return obj.name
return json.JSONEncoder.default(self, obj)
(Frankly, I wish it was easier to extend the encoder, e.g. by registering
callbacks for non-standard types.)
I don't automatically decode enums because on PUTs, POSTs, and PATCHs, I know
which attributes should be enums, so I can convert them explicitly when I
validate input forms.
The arguments for fixing:
* int subclasses overriding str is a very common usecase for enums (so much so that it was added to stdlib in 3.4).
* json supporting a standard type of a subsequent python version, though not mandatory, would be beneficial to Py2/Py3 compatibility.
* fixing this cannot break existing code
* the fix could theoretically be done to 3.0-3.3 if Ethan's argument is deemed important.
-1 from me, too. | http://bugs.python.org/issue22297 | CC-MAIN-2016-40 | refinedweb | 556 | 68.26 |
# Done by Reinhard Max # at the Texas Tcl Shoot-Out 2000 # in Austin, Texas, # with subsequent updates proc do {script arg2 {arg3 {}}} { # Implements a "do <script> until <expression>" loop # The "until" keyword ist optional # # It is as fast as builtin "while" command for loops with # more than just a few iterations. if {$arg3 eq {}} { # copy the expression to arg3 if only # two arguments are supplied set arg3 $arg2 } else { if {$arg2 ne {until}} return -code 1 {Error: do script ?until? expression} } } set ret [catch {uplevel $script} result copts] switch $ret { 0 - 4 {} 3 return default { return -options [dict replace $copts -level 2] $result } } set ret [catch {uplevel [list while !($arg3) $script]} result copts] return -options $copts $result }You can alter this from do-until to do-while by removing the !() from the uplevel'ed while .I'll leave the analysis up to the reader, because this is an excellent example of control construct creation.DGP: An update of this proc for Tcl 8.5 (TIP 90
RS: If you change the proc line to
proc do {script {arg2 {}} {arg3 {}}} { if {![string length $arg2$arg3]} {set arg2 0}you win the added functionality of calling do $body which works like the not too unfrequent while 1 $body. Switching between while and until can of course also be built in...
if {$arg3 ne {}} { switch -- $arg2 { until {set bool !} while {set bool {}} default {return -code 1 {usage: do script ??until|while? expr?}} } } # ... set ret [catch {uplevel [list while ${bool}($arg3) $script]} result]
rmax: This "do while|until" loop is now a part of tcllib's control package.
PYK 2014-06-19Here is another do ... until that uses tailcall, the primary advantage of which is that do gets out of the business of handling all the possible return and error conditions, making it more straight-forward to implement new control structures.
proc do {script until args} { if {[llength $args]} { if {$until ne {until}} { set errorcode [ list {until missing} { with 3 arguments, argument 2 should be {until}}] return -code error -errorcode $errorcode $errorcode } set until [lindex $args 0] } set script [string map [ list @[email protected] [list $script] @[email protected] [list !($until)]] { while 1 { switch [catch @[email protected] ::errorCode ::errorInfo] { 4 {} default { return -options $::errorInfo $::errorCode } } while @[email protected] @[email protected] break } }] tailcall if 1 $script }To avoid polluting the caller's namespace, $::errorInfo and $::errorCode are used to capture the necessary catch information. It's a little hacky, but so far it's the best strategy I've found.
DKF: Another version, this time that uses try. That allows for much simpler handling of errors to get a higher-quality implementation:
proc do {script while expression} { if {$while ne "while"} { return -code error {error: do script ?while? expression} } append body [list try $script on continue {} {} on error {a b} { return -options [dict replace $b -inside $b] $a }] ";" [list if "!\[[list expr $expression]\]" break] try {return [uplevel 1 [list while true $body]]} on error {a b} { catch {set b [dict get $b -inside]} dict incr b -level dict set b -errorinfo [ regsub {\("try"( body line \d+)\)$} [dict get $b -errorinfo] \ {("do"\1)}] return -options $b $a } }What marks this as high quality? The error handling. Consider this code:
do { puts [incr y [incr x]],$x seek foo bar } while {[incr i]<5}OK, that's going to get an error from the seek, and indeed it does, while concealing how the do works internally…
can not find channel named "foo" while executing "seek foo bar" ("do" body line 3) invoked from within "do { puts [incr y [incr x]],$x seek foo bar } while {[incr i]<5}" (file "/tmp/do_example.tcl" line 18)Not as good as a nice bit of bytecoding (which would also be much faster), but a lot easier to write!(Exercise for the reader; handle errors in the expression nicely.) | http://wiki.tcl.tk/917 | CC-MAIN-2018-05 | refinedweb | 637 | 64.75 |
Creating Channel Providers for effbot.exe/effnews
January 8, 2003 | Fredrik Lundh
Release 0.9 of the effnews RSS reader adds support for pluggable channel providers. Providers are simply Python scripts that process data from an external source, and present it to the application as if it were an RSS file.
Using a Channel Provider
The provider mechanism is used to control how data is read from a given URL. Each provider is associated with one or more URLs. For example, the Daily Python-URL provider is associated with the URL.
To use an installed provider, just drag the source URI to the EffNews window as usual. EffNews will now use the provider to fetch data, instead of the standard RSS reader.
Writing Simple Channel Providers
Providers should be installed in the c:/effbot.exe/effnews directory, and must use the .provider extension. The actual filename doesn’t matter; the application loads all provider scripts, and uses data in the script to figure out what provider to use for a given URL.
The current version only supports the simpleprovider protocol. This protocol uses the standard HTTP transport to read data from the source, and passes the data to a parser function which turns it into an RSS-style channel header and a list of RSS-style items. To implement a channel provider, create a Python module which defines two names:
- urls
This variable should contain a list of URLs associated with this provider.
- simpleprovider
This function is used to parse the data. It is called with two arguments: a context object, and the text to parse. The context object has a single public method, called push. This method is used to add RSS-style channel and item elements to the internal database.
Example:
import re urls = [ "" ] pattern = r"..." def simpleprovider(context, text): context.push("channel", title="my channel", link=urls[0]) for title, body in re.findall(pattern, text): context.push("item", title=title, description=body)
The push method takes an RSS element name (“channel” or “item”), and one or more keyword arguments which provide RSS subelements.
The channel element can have title, link, and description subelements. All subelements are optional.
The item element can have title, link, and description subelements. You must specify at least one of the title or description elements. The link element is always optional.
Element values should be either ASCII strings, or Unicode strings. Do not use encoded 8-bit strings. Embedded HTML is allowed, but should be avoided.
If the provider cannot parse the input data, it should raise an appropriate Python exception. | http://effbot.org/zone/effnews-provider.htm | crawl-002 | refinedweb | 429 | 67.45 |
Overview
Atlassian Sourcetree is a free Git and Mercurial client for Windows.
Atlassian Sourcetree is a free Git and Mercurial client for Mac.
pydot - Python interface to Graphviz's Dot language Ero Carrera (c) 2004-2007 ero@dkbza.org
This code is distributed under the MIT license.
Requirements:
- pyparsing: pydot requires the pyparsing module in order to be
- able to load DOT files.
- GraphViz: is needed in order to render the graphs into any of
- the plethora of output formats supported.
Installation:
Should suffice with doing:
python setup.py install
Needless to say, no installation is needed just to use the module. A mere:
import pydot
should do it, provided that the directory containing the modules is on Python module search path. | https://bitbucket.org/prologic/pydot | CC-MAIN-2018-26 | refinedweb | 122 | 58.28 |
Squaring the first several odd numbers reveals the following pattern: 3 squared = 8 + 1 5 squared = 24 + 1 7 squared = 48 + 1
8, 24, and 48 are all multiples of 8. Does this pattern hold for all squares of odd numbers? Prove it!
Let n be an odd integer, and assume as a base case that n^2 is one more than a multiple of 8. The next higher odd integer is given by n+2, since we're skipping the even integer in between. Expanding (n+2)^2 gives n^2 + 4n + 4. We assumed that n^2 is one greater than a multiple of 8, so we need to show that 4n + 4 is always a multiple of 8 to prove the pattern. Factoring out a 4 gives 4(n+1). Since n is an odd number, n+1 must be even and therefore divisible by 2. So 4n+4 is divisible by 4 and by 2 and therefore is also divisible by 8. So we've added a multiple of 8 to our n^2 term preserving congruence in mod 8. Assuming that n^2 is one more than a multiple 8, (n+2)^2 must also be one more than a multiple of 8! Use one of the examples given in the problem as a base case and the inductive proof is complete.
PROOF: Let p be any odd no. (2p+1)^2-1 =4p^2 + 4p +1-1 =4p^2 + 4p =4(p^2 + p) ----(1) clearly when p is an odd no. then p^2 is also an odd no. thus p^2+p is an even no.(as sum of two odd no. is an even no.) let say, p^2 + p =2 x; then eqn (1) becomes: (2p+1)^2-1 = 4(p^2 + p) =42x = 8x proved...
excellent
There sure are a lot of smart people here with a lot of really clever answers. However, you all forgot one thing: 1^2=1 1+1=2
And 2 is not a multiple of 8.
There sure are a lot of smart people here with a lot of really clever answers. However, you all forgot one thing: 1^2=1 1+1=2
And 2 is not a multiple of 8.
awsome.....watch this also
Very interesting proof. Are there any other patterns like this that exist among square (or nth powers in general)?.
Whoa, the triangular number sounds surprising..could you explain it with another example? If we have 2 and 3: 2^3 = 8, 3^3 = 27.
In this case, what's our "triangular number ending in k"?.
So interesting...I'll check wikipedia out for some proofs..
Ah too bad - you publish any of these, by chance?
I'm not a mathematician, I just loooooove math. I also don't know any mathematicians (minus random people on the internet who I don't really know).
Fair enough - I'm an engineer...I know just enough math to be dangerously wrong sometimes. You might enjoy this one if you haven't seen it already.
Sorry I write a lot (and talk a lot).
No worries - solid explanation!
Butts.
Odd number squares can be written as : (2n-1)^2 , n>1 (2N-1)^2 = 4nn - 4n +1 =4n(n-1) + 1 For any n>1 , n(n-1) will always be even => 4n(n-1) + 1 => 8*x +1 where x=n(n-1)/2
hence Odd no square can always be written as 8x+1
I kind of ended up with something similar, but I didn't quite use a formal proof. I noticed right away that 8 was multiplied by a triangular increasing number, or that it was the sum + x, or n(n+1)/2. You can multiply this by 8 and get 4n(n+1) + 1 = x^2. With a little work you can then notice the pattern in x, is that it is 2n+1, or the progression of odd numbers. In summary, 4n(n+1) + 1 = (2n+1)^2
Yeah I think I might have done something closer to that the first time I did it, and this time through I went ahead and did it inductively. Very nice!
any odd integer can be written as 2k+1, k is an integer >=1 for this problem => (2k+1)^2 = 4k^2 +4k+1 = 4k(k+1) + 1 k, k+1 are consective integers, hence one is even =>k(k+1) = 2n =>4k(k+1) + 1 = 8n +1 and we are done
Or 2k-1 if you want to include 1. Well phrased solution, thanks.
Agreed, great solution!
A little Python code to illustrate the proof:
Import Pylab:
from pylab import *
m=0 c=0 k = [1,3,5,7,9,11,13,15,] for x in k: m=m+c c=c+1 n=m8+1 print (x,'^2 = 8 ',m,'+ 1','=',n) print ('The multiple of 8 increases by the sequence 0,1,3,6,10, etc...') print ('In other words: 1, then 2, then 3, etc... is added to the multiple at each iteration.')
Execute:
1 ^2 = 8 * 0 + 1 = 1 3 ^2 = 8 * 1 + 1 = 9 5 ^2 = 8 * 3 + 1 = 25 7 ^2 = 8 * 6 + 1 = 49 9 ^2 = 8 * 10 + 1 = 81 11 ^2 = 8 * 15 + 1 = 121 13 ^2 = 8 * 21 + 1 = 169 15 ^2 = 8 * 28 + 1 = 225 The multiple of 8 increases by the sequence 0,1,3,6,10, etc... In other words: 1, then 2, then 3, etc... is added to the multiple at each iteration.
}
Yes. (2n + 1)^2 = 4 n(n + 1) + 1 = [as n or n+1 is even => n(n+1) is even => n( n + 1) = 2m ] = 4 * 2m + 1 = 8m + 1
The product of n consecutive integers is always divisible by n! [i.e. n factorial, where 0! = 1, 1! = 1, 2!= 2x1, 3!=3x2x1, 4!=4x3x2x1, and so on for positive integer n.] Now let us take the odd number under test as (2n+1) for all n>=1. .............. (Theorem)
So, if p = (2n+1)^2 ......................(1) then, p = 4n^2 + 4n + 1 .....................(2) => p = 4n(n+1) + 1 ............................(3)
Now, as n is a positive integer greater than or equal to 1, n(n+1) is the product of two consecutive integers, which by above stated theorem, will always be divisible by 2! = 2. Thus for some positive integer k , n(n+1) = 2k ........................(4)
Substituting (4) in (3), we get,
p = 4n(n+1) + 1 = 4(2k) + 1 = 8k + 1 for some positive integer k.
Thus, p = 8k+1 ..............................(5)
Hence Proved. Q.E.D.
A variation is the difference of squares of any two odd numbers is always a multiple of 8.
(2r-1)^2 = 4r^2 -2r +1 (2(r+n) -1)^2 = 4r^2 +8nr =4n^2 -4r -4n +1
The difference = 4n^2 +8nr - 4n
8nr has 8 as a factor. The remaining terms 4n^2-4n = 4n(n-1) Since n or n-1 has to be even, 4n(n-1) has to to be a multiple of 8 also hence as required!
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*
»
Swing / AWT / SWT
Author
creating a record index?
darren malt
Greenhorn
Joined: Aug 17, 2002
Posts: 23
posted
Oct 26, 2002 04:03:00
0
hi ya guys, hope you can give me some help here.
I am trying to create a searchable index, with a textfield at the top where you enter the record name, and a scrollable panel below that shows an alphabetical list of the record names.
no problem.
However, I want the record list to automaticaly set focus to the appropriate record name as you enter the name you are searching for,(like you have in a help topic index, for example).
So if I type the letter 'd' in the textField, the first record that begins with a d in the index is highlighted. then if I type an 'a', if there is a record name starting with "da", then this will be highlighted.
If you have any ideas on how I can go about the automatic highlight, I'd love to hear them as I don't have a clue at the moment.
Thanks.
"Know where I can get a compiler with a sense of humour?"
San Su
Ranch Hand
Joined: Jul 06, 2001
Posts: 313
posted
Oct 26, 2002 20:16:00
0
One solution I can think of is, store all the names in an array and whenever user types the word, search the particial word in the array. Get the index if you find one and select the corresponding record in the table. I did something similar for our project couple of years ago (autocomplete in ComboBox). I used binarysearch to search the text in the array. I dont have the code rightnow, but if you need it, let me know. I will search for it.
darren malt
Greenhorn
Joined: Aug 17, 2002
Posts: 23
posted
Oct 27, 2002 12:51:00
0
Sankar, if you wouldn't mind sending me that code I would appreciate it. I'm currently using the same kind of system as you said in your reply, and I THINK (hope) I'm getting there although it's always nice to see how someone else done it. I'm sure I will learn from it as I am quite new to AWT/swing.
thanks for the reply.
Daz...
San Su
Ranch Hand
Joined: Jul 06, 2001
Posts: 313
posted
Oct 28, 2002 08:49:00
0
darren,
The file is too big, so I am posting the code piece of codes related to this functionality..
BinarySearch. It takes the partical
string
as key and search the key in the array.
public int binarySearch(Object[] array, Object key) { if( (array != null) && (key != null) ){ int low = 0; int high = array.length-1; int nLength = (key.toString()).length(); int nLocation = -1; while (( low < high ) || ( (low == high ) && (low > 0) )){ int mid =(low + high)/2; String midVal = array[mid].toString().toLowerCase(); int cmp =-1; String subString = new String(); if( midVal.length() >= nLength ){ if( bEnter && bAllowAnyChars ){ subString = midVal; }else{ subString = midVal.substring( 0 , nLength ).toLowerCase(); } cmp = subString.compareTo(key.toString().toLowerCase()); }else{ cmp = midVal.compareTo(key.toString().toLowerCase()); } if( ( midVal.length() == nLength ) && ( cmp == 0 ) && ( bEnter )){ bEnter = false; nLocation = mid; break; } if (cmp < 0){ low = mid + 1; } else if (cmp > 0){ high = mid - 1; } else{ if( (midVal.equals( subString )) && (nLocation >= 0 )){ break; }else{ if( nLocation == mid ){ nLocation = mid; break; } nLocation = high = mid; // key found } } } return nLocation; } return -1; }
This code is there in editor's setDocument method. It looks for unselected text value in the textfield and adds the newly typed key and search it in the array.
String strString = editor.getText().substring( 0 , nCaretPos ) + key; if( ( strString.length() > 0 ) &&( nCaretPos <= strString.length())){ String subString = strString; int nLocation = binarySearch( tComboValues , subString); if( nLocation >= 0 ){ tSelectedObject = tComboValues[ nLocation ]; selectListItem( nLocation ); model.setSelectedObject( tSelectedObject ); comboBox.getEditor().setItem( tSelectedObject ); String setString = new String(tSelectedObject.toString()); editor.select( nCaretPos+1 , setString.length() ); editor.setCaretPosition( nCaretPos+1 ); bReturnValue = false; }else{
Please let me know if you need more information.
[ October 28, 2002: Message edited by: Sankar Subbiah ]
Sri Rangan
Ranch Hand
Joined: Dec 08, 2001
Posts: 160
posted
Oct 30, 2002 22:03:00
0
Here is another example code:
import java.io.PrintStream; import javax.swing.*; import javax.swing.plaf.basic.BasicComboBoxEditor; public class CustomComboEditorForGrid extends BasicComboBoxEditor { int rowCount; DefaultComboBoxModel model; JComboBox cb; public CustomComboEditorForGrid(DefaultComboBoxModel defaultcomboboxmodel, int i, JTable jtable, JComboBox jcombobox) { model = defaultcomboboxmodel; rowCount = i; cb = jcombobox; editor.addKeyListener(new Object() /* anonymous class not found */ class _anm1 {} ); editor.addActionListener(new Object() /* anonymous class not found */ class _anm2 {} ); editor.addFocusListener(new Object(jtable) /* anonymous class not found */ class _anm3 {} ); } void processEvent() { String s = editor.getText(); try { boolean flag = true; boolean flag1 = false; for(int j = 0; j < rowCount; j++) { if(!model.getElementAt(j).toString().toUpperCase().startsWith(s.toUpperCase())) { continue; } editor.selectAll(); editor.setText(model.getElementAt(j).toString()); editor.setSelectionStart(s.length()); flag = false; int i = j; break; } if(flag) { editor.setText("-None-"); } } catch(Exception exception) { System.out.println(getClass() + " : Exception Occured: " + exception.getMessage()); exception.printStackTrace(); } } }
I agree. Here's the link:
subject: creating a record index?
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, Aug 28, 2007 at 01:02:29PM -0400, luis cota wrote:
> Can I create a condition that forces the ts/id_str combination within each
> row to be unique?
Create a unique index in the database.
Oleg.
--
Oleg Broytmann phd@...
Programmers don't die, they just GOSUB without RETURN.
Is it possible to set conditions on a table entry? For example, if you have
a data set with these cols:
ts = DateTimeCol () // time stamp
id_str = StringCol // string identifier
Can I create a condition that forces the ts/id_str combination within each
row to be unique?
Thanks!
- Luis
Oleg and readers:
I'm glad you're interested in this idea, even if you're finding potential
problems. It has a lot of potential!
>> PREPARED STATEMENTS EXECTUTE SIGNIFICANTLY FASTER than parsed ones
> Yes, prepared statements by itself should be faster, but you are
> going to change SQLObject._init() which is used in all creation
> and retrieval operations. And the change is rather big...
Yes, agreed.
I'm also increasingly thinking this approach won't work (the multiply-nested
try/except one). This seems to be because the moment I hit the first
error, the dbconnection says 'current transaction is aborted, commands
ignored until end of transaction block'. So, if I try and fail, I've
toasted my transaction. Yuck. I could be wrong about this behavior, but it
looks as if that's what is happening.
I could change the code to only call the prepared statements I know exist,
then I'll always succeed, and I failover to the old way. I'm working on
figuring out how to find out from Postgres if a prepared statement exists.
It's not clearly documented, and the #postgres chat is not in this case
all-knowing. Alas.
BACK TO THE PROBLEM:
We are doing a LOT of selects on ID's, which is really stressing our db.
I want to reiterate that I have a very limited goal: Increase speed of
get-by-id select statements by using prepare.
IDEA #2 FOR PREPARE:
I've just been playing with sqlbuilder.py, changing the return value of
__sqlrepr__ to be 'execute prepStatementForThisTable(idval)' if there's only
one table (no joins). This would seeminly work in the very simple case.
But, then it would require creating and running one prepare statement per
table. I'm thinking the best time for that would be every time our
AppServer starts up, that is, as a method call I could make:
class dumbTable(SQLObject):
class sqlmeta:
idName = 'dumbTableID'
table = 'dumbTable'
firstField = NumericCol(dbName='amount')
def __init__(self):
self.createPreppedGetByIDStatement()
#... Make a call to Sqlobject's __init__()??
def createPreppedGetByIDStatement(self):
return '''prepare SQLObject_dumbTable_getByID (int)
as select firstField from dumbTable where dumbTableID = $1'''
def executePreppedGetByIDStatement(self, id):
return '''execute SQLObject_dumbTable_getByID (id)'''
Ideally, this could be done automatically in SQLObject's __init__() and I
wouldn't have to define the methods in my class. I could just set a sqlmeta
'getByIDprepname', then call something like 'd = dumbTable;
d.createPreppedIDStatement()' at the module level so when the .py file is
parsed it loads it.
>From then on, any call that iterates over the table getting a row at a time
by id (as all the joins do) could use this execute.
> cursor.execute("SELECT * FROM atable WHERE id=?", id)
This might be a wonderful idea, I just don't know.
Is this close to done? What are the performance impacts?
> ... to speed up joins try SQL*Joins classes ...
Yes. Hmmm. We've tried this. Consider:
...Presume standard sql*join setup...
for recA in tableA.select():
.. Do stuff with recA
for brec in recA.btablerecs:
.. do stuff with brec.field1
.. Do other stuff with recA
This generates something like 12 bazillion selects:
Select record_id_list from tableA
Select * from tableA where record id = 1
Select record_id_list from tableB where tableb.tableaid = 1
Select * from tableB where record id = 1
Select * from tableB where record id = 2
... (until done)
Select * from tableA where record id = 2
... (until done)
Select * from tableA where record id = 3
...
SQLObject is not fixing this kind of thing, it's just the way it works.
So, I'm living with that. I'd just like to speed up the get by ids.
I've checked, and SQLite, MySQL, and Postgres all support prepare, with
seemingly the same syntax (unless there's something subtle I'm missing).
So, the cross platform issue isn't, which is a good thing.
-- Kevin
___________________________________
Kevin J. Rice
Senior Software Engineer, Textura LLC
51-K Sherwood Terrace, Lake Bluff IL
(847) 235-8437 (spells VISAFLUIDS)
(847) 845-7423 (845-RICE, cellphone)
___________________________________
-----Original Message-----
From: sqlobject-discuss-bounces@...
[mailto:sqlobject-discuss-bounces@...] On Behalf Of Oleg
Broytmann
Sent: Monday, August 27, 2007 11:22 AM
To: sqlobject-discuss@...
Subject: Re: [SQLObject] Attempt at Implementing Bound Params in
SQLObjectfor get-by-id calls
Ok, I am back, let's continue...
On Fri, Aug 24, 2007 at 04:12:03PM -0500, Kevin J. Rice wrote:
> Important point #1: PREPARED STATEMENTS EXECTUTE SIGNIFICANTLY FASTER
> than parsed ones
Yes, prepared statements by itself should be faster, but you are going to
change SQLObject._init() which is used in all creation and retrieval
operations. And the change is rather big:
> Pseudocode:
> - come up with the prep'd statement's name,
> - try to execute it;
> - if that doesn't work:
> - destroy anything by that name,
> - try to recreate it,
> - try to run it again, and
> - if that doesn't work:
> - failover to the old way.
Are you sure SQLObject in general will not suffer significant performance
decrease?
> Oleg, I'm confused by your mentioning converting different types in
> different databases.
With the code in my private branch I have tried to solve much more
generic problem - to make all SELECT/INSERT/UPDATE/DELETE statements to use
DB API bound parameters:
cursor.execute("SELECT * FROM atable WHERE id=?", id)
That's a different goal from using PREPARE/EXECUTE.
> The issue I'm concerned with on different databases is the fact that
> some might have a "prepare" syntax that's different from others. But,
> I'll worry about other databases once there is a working prototype.
That difference have to be processed in concrete connection classes like
PostgresConnection; see how LIMIT/OFFSET and other backend-specific issues
are encapsulated in the connection classes.
And final note - if your aim is only to speed up joins try SQL*Joins
classes (SQLMultipleJoin, SQLRelatedJoin) - instead of iterating over
"SELECT id FROM join" they construct a proper SelectResults which is faster
(one query for a join) and more correct (orderBy is implemented in SQL
instead of Python).
Oleg.
--
Oleg Broytmann phd@...
Programmers don't die, they just GOSUB without RETURN.
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BARKS from the Guild Issue 32 / September 2018 BARKSfromtheGuild.com
CANINE Educating Clients in Communication
TRAINING Car Anxiety and Sickness
AVIAN Behavior Change for Self-Mutilation TRAINING Bunny Behavior Best Practices
CONSULTING The Value of Mentorship TRAINING Targeting for Tortoises
BUSINESS Insurance Essentials
Cool for Cats:
Appropriate socialization, training, physical and mental enrichment, and meeting basic needs to reduce behavior issues TM
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A
from the editor
ccording to the American Pet Products Association’s 2017-2018 National Pet Owners’ Survey, 68 percent of Americans (or 85 million families) currently share their homes with one or more pets. Cats are the number one pet, because there is often more than one cat living in any one home, but overall, more people have dogs. The actual figures state that there are 60 million dog-owning families with 90 million dogs at home and 47 million cat-owning families with 94 million cats at home. That’s a lot of pets in a lot of homes and, as a result, professional canine trainers, behavior consultants, and dog-related service providers in general often tend to find themselves being asked about cat-related issues, even when they have primarily been retained to assist with the family dog. Our Cover Story this month delves a little deeper into feline behavior, and will be something both cat and dog behavior specialists will find helpful. It discusses not only some of the similarities between cats and dogs, including some that are not always widely acknowledged (e.g. you can clicker train cats too), but also how pet professionals can ensure kittens and cats in the family home or shelter environment receive the appropriate socialization, training, physical and mental enrichment, as well as have their basic needs met to reduce the likelihood of behavior issues developing further down the line. Some of the most common reasons cats are relinquished or abandoned are litter box issues, not getting along with other pets, scratching in areas owners don’t want them to, and human-directed aggression. With the right knowledge and understanding, these issues can all be addressed, thus ensuring that cats and their owners stay happy and that fewer cats are relinquished. In addition to cats, our issue this month is something of a multispecies issue, with a whole variety of articles that feature dogs, horses, birds, rabbits and tortoises. Many of those who attended PPG’s Training and Behavior Workshop at Best Friends Animal Society in Kanab, Utah in April remarked upon how inspiring they had found the opportunity to work with species they would not usually encounter in their daily professional life (as well as cats and dogs, species featured in the workshops included chickens, rabbits, pigs, parrots and tortoises), and how helpful it had been for them in terms of honing their mechanical training skills. If you are wondering what tortoises find reinforcing, or why rabbits do not like being picked up, then look no further. We have all the answers here in our expanded Training section, as well as features on a behavior change program for a self-mutilating umbrella cockatoo and the presence (or, indeed absence) of hierarchies in equine social structure. Coming back to dogs, communication is a big theme, as always, and we look into the need for better client education to help people better understand and communicate with their dogs and thus help prevent behavior problems – including when dogs are deaf, blind, or both deaf and blind. We also feature a protocol to combat canine car sickness and anxiety, a commonly encountered issue, based on the power of associative learning. The issue of standards, or sometimes a lack thereof, is an ever present issue for all who live and/or work with animals and we again look into the lack of industry regulation and the need for better education in the first of a four-part series. We also have an extended Business and Consulting section this month, featuring the all-important topics of mentorship, workers’ compensation insurance, and how to ensure your individual training sessions with clients are as effective as possible. I would like to take this opportunity to thank our incredible contributors who generously share their knowledge and expertise to make BARKS the publication that it is. If you would like to join them, please do get in touch: barkseditor@petprofessionalguild.com.
BARKS from the Guild/September 2018
n Susan Nilso
3
contents 6 10 18 22 26 29 32 36 39 42 44 48 52 56 58 60 62
4
N EWS
An update of all the latest developments at PPG, plus upcoming podcasts, webinars and workshops
C OOL
C ATS
FOR
Tabitha Kucera discusses how pet professionals can ensure kittens and cats receive appropriate socialization, training, physical and mental enrichment and have their basic needs met in order to reduce behavior issues
A S HIFT
M INDSET
IN
Anna Bradley discusses the importance of educating clients in body language, canine communication and enrichment as part of preventing behavior problems
C ANINE C AR ANXIETY
10
T HE A RT
18
Lori Nanan discusses the issue of dogs with car sickness and anxiety and sets out a training plan to help improve matters OF
C OMMUNICATION
Debbie Bauer talks double merles, and how to help clients with deaf, blind, or deaf and blind dogs connect with and train their pet
T RAINING
THE
WILD F RIENDS
AT
26
B EST FRIENDS
Vicki Ronchette talks tortoises and the importance of working with different species to improve mechanical skills
G ETTING
ON
T HEIR L EVEL
Emily Cassell explains why rabbits don’t like being picked up and how to help them feel more comfortable with being handled
A L ONG -T ERM S OLUTION
Lara Joseph details her behavior modification plans for an umbrella cockatoo who was screaming and selfmutilating as a result of inappropriate enrichment
32
E QUINE S OCIAL S TRUCTURE
Kathie Gregory examines the two groups of social organization found in Equidae and debates the presence of dominance and submission
C ORE
AND
N ON -C ORE VACCINATIONS
Lauri Bowen-Vaccare highlights specific vaccinations usually required so dogs stay healthy at day care or boarding
B EHIND
THE
S CENES
Frania Shelley-Grielen addresses the lack of regulation in the pet care and services industry, and wonders how standards can be improved
C RITICAL
TO
29
S UCCESS
Niki Tudge describes how she breaks down client visits into lessons within sessions to ensure maximum efficacy
A H ELPING H AND
Sheelah Gullion discusses the value of mentorship in the pet industry and invites trainers to weigh in
A SK
THE
E XPERTS : O PTIMIZING YOUR WEBSITE
Veronica Boutelle of dog*biz responds to your business and marketing questions
C LAIMING
36
FOR I NJURIES
David Pearsall of Business Insurers of the Carolinas discusses the important issue of workers’ compensation insurance for pet professionals
P ROFILE : H ELPING P EOPLE C ONNECT
Featuring Tracey Prall of Canine Connections Dog Training and Dog Hotel in Walterstone, Hereford, England
B OOK R EVIEW : F ROM
AN
E THOLOGIST ’ S P ERSPECTIVE
Breanna Norris reviews How Dogs Work by Raymond Coppinger and Mark Feinstein
BARKS from the Guild/September 2018
42
39 58
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Shock-Free Coalition Opens First Regional Chapters
T
he Shock-Free Coalition (shockfree.org), PPG’s international advocacy campaign, has announced its first regional coordinators, so if you
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PPG Announces 2018 Scholarship Winners
P
PG has announced the names of this year's candidates to be awarded under its Education Scholarship Program. Launched in January 2017, the program provides a limited number of scholarships for PPG members to further their education in force-free training, behavior consulting and/or pet care offered by organizations that support PPG's Guiding Principles and goals, and are approved educational providers to PPG. This year's recipients, Mary Thompson and Emily Tronetti, have been notified. "Our inaugural year of distributing awards through our Education Scholarship Program began in great style with some outstanding candidates, and we are thrilled to have been able to maintain that same high standard again this year," said PPG president Niki Tudge. "Again, like last year, it was not an easy task to make the final selections from the extremely high caliber of candidates that applied, and it took a great deal
W
Your Insurance Questions Needed! hether you are a trainer, groomer, behavior consultant, day care attendant, or work anywhere else in the pet industry, professional insurance is an essential component of your business plan. BARKS will be featuring an interview with David Pearsall of PPG corporate partner Business Insurers of the Carolinas (business-insurers.com/pet-insurance) and is looking for your questions on all things insurance. All questions welcomed! Please email your questions to BARKS editor Susan Nilson (barkseditor@petprofessionalguild.com) with “Insurance” in the subject line. 6
BARKS from the Guild/September 2018
of deliberation on the part of our scholarship committee, chaired by PPG steering committee and board member Debra Millikan, to objectively review each applicant. "Because the pet industry is currently unregulated, it remains a core part of PPG's mission that our members are able to provide high standard, force-free, science-based behavior consulting, training and pet care services to the pet owning public via their knowledge and skill set. Education is an essential part of this mission and by helping our scholarship recipients achieve their educational goals at such quality institutions as Peaceable Paws and The Academy for Dog Trainers, we can ensure they remain up-to-date with current research in the fields of animal behavior and training, and thus serve as an invaluable resource to clients and their pets. At the same time, PPG members all over the world continue to work as ambassadors and practitioners of the forcefree message as we collectively work towards a world free of unnecessary, outdated, aversive training methods or equipment and a better, kinder world for pets." More information about PPG's Education Scholarship Program and details of how to apply: petprofessionalguild.com/Scholarship-Program.
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PPG Names June Project Trade Ambassador
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news
ongratulations to Erika Gonzalez of From Dusk Till Dog, LLC (fromdusktilldog.com) in New Jersey, USA for collecting six choke collars, four prong collars and one shock collar and is Project Trade Ambassador for June 2018. Congratulations too to Daniel Antolec of Happy Buddha Dog Training (happybuddhadogtraining.com) in Wisconsin, USA who collected two prong collars and one shock collar, Breanna Norris of Canine Insights (canineinsightsllc.com) in Maine, USA who collected four choke collars and two prong collars, and to Anastasia Tsoulia of Hug4Pets & Hug4Dogs (hug4pets.com) in Thessaloniki, Greece for collecting six prong collars.
(Top row, left to right): Aversive gear collected by Erika Gonzalez, Breanna Norris and Daniel Antolec and (center and bottom rows) Anastasia Tsoulia
BARKS BARKS from the Guild blog
Project Trade (projecttrade.org) is an opt-in program for PPG members that has been designed to create incentives for pet owners to seek professionals who will exchange aversive training and pet care equipment for alternative, more appropriate tools, training, and educational support.
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New Links for BARKS Podcasts, BARKS Blog and Blog Subscriptions ARKS is slowly rolling out its new, all-encompassing media platform (barksfromtheguild.com) and the BARKS Blog and BARKS Podcasts (both upcoming and past podcasts) are already available on the new site. Please take a moment to renew your subscription for the Blog (barksfromtheguild.com/subscribe) to make sure you don’t miss any new posts!
BARKS from the Guild/September 2018
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news
Canine Aggression and Bite Prevention Seminar, Portland, Oregon 2019
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PG and co-host Doggone Safe (doggonesafe.com) are taking registrations for their Canine Aggression Safety and Education Seminar (petprofessionalguild.com/2019-Portland) taking place at the Crowne Plaza hotel in Portland, Oregon on April 26-28, 2019. Attendees will have access to all-day general sessions supported by an afternoon feline specialty track. Presentation sessions include: • The neuroscience of aggression. • Functionally analyzing aggression. • Behavior modification standard operating procedures. • Resource guarding. • Help and insights on managing clients through canine aggression. • Learn about dog bite safety. • Liability concerns and issues. • Bite facts and fiction. • How to implement and market effective dog bite safety pro-
grams. • Speciality feline track featuring multiple topics related to the various types of feline aggression. Presenters include Dr. Lisa Radosta, Dr. Nathan Hall, Dr. Ilana Reisner, Dr. Lynn Honeckman, Chirag Patel, Judy Luther, Pat Miller, David Pearsall, Niki Tudge, Paula Garber, Francine Miller, Tabitha Kucera, and Beth Adelman. Key points to note: • General sessions all day every day. • Feline specialty track every afternoon. • April 25 - Chat, Chuckle & Learn private dinner hosted by Niki Tudge with guest speaker Dr. Lisa Radosta. • April 27 - Gala Dinner with a presentation by Dr. Ilana Reisner Special payment packages are available that include your entrance fee, accommodation, meals and evening events. (For more details, see ad on back cover).
Force-Free Apparel Is Back!
PPG Hosts Inaugural Australia Summit in Sydney
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how your support for the Shock-Free Coalition (shockfree.org) by wearing one of these cool Shock-Free Pledge T-shirts! Visit the PPG Apparel Store (teespring.com/take-the-pledge-tshirt?t#pid=2&cid=2122 &sid=front) and make your order now! You can also help advocate for force-free training and pet care by wearing one of these cool force-free T-shirts, sweatshirts or hoodies while you are out! Place your order here: ow.ly/Kl0G30l1Be7.
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BARKS BARKS from from thethe Guild/September Guild/January 2018
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PG marked another milestone at the end of July by hosting its first ever Australian summit at the Bankstown Sports Center in Sydney. PPG Australia president Barbara Hodel delivered the opening address and welcomed both attendees and a number of key international speakers, including globally recognized canine behavior expert and PPGBI special counsel member Chirag Patel, guide dog trainer Michele Pouliot, and applied animal behaviorist Kathy Sdao, who are based in the United Kingdom (Patel) and United States (Sdao and Pouliot). They were joined by a select group of Australian pet behavior, pet care and training specialists, including Dr. Kat Gregory, Louise Ginman, Louise Newman, Alexis Davison, Laura Ryder, in what was a mix of lectures and applied behavior analysis workshops. We’ll have a full report in our November issue but here’s a sneak preview with pictures (below, left) showing Hodel (right) kicking off proceedings by introducing the first general session presenter, Sdao; and (below, right) presenters (left to right) Patel, Sdao and Pouliot at registration.
BARKS Podcasts: Schedule
news Recent Podcasts:
June 20, 2018 Guests: Sam Redmond, and Pam and Miranda Mahar. Topics: Sam Redmond on the rise of the wolfdog: what we are likely to see in our professional practices and what we can expect from these dogs; Pam and Miranda Mahar of PPG Corporate Partners 4 Legs 4 Pets (see ad on p.63) showcase the company’s USA-made indoor and outdoor cots for pets: bit.ly/2LWNUVh.
Tuesday, October 2, 2018 - 3 p.m. EST Guest: Jane Bowers. Topic: Assessing and Interpreting Dog Behaviour, a course for law enforcement personnel and others who meet unfamiliar dogs in the course of their duties. Register to listen live: attendee.gotowebinar.com/register/1140693125320611075
July 10, 2018 Guest: Dr. Lynn Bahr. Topics: The issue of pain, how well cats can hide it, and the impact chronic pain can have on behavior. She also talked about the long-term physical and behavioral effects of declawing cats, a procedure that is banned in over 20 countries but is still widely practiced in the United States: vimeo.com/279343417
July 19, 2018: “Let's Opinionate!” Veronica Boutelle and Gina Phairas of PPG corporate partner dog*biz (see ad on p.2) give expert tips on how to successfully grow your business: bit.ly/2uTU8yq. Note: schedule is correct at time of going to press but is subject to change
Earn Your CEUs via PPG’s Webinars, Workshops and Educational Summits! Webinars
Understanding Animal Welfare: The Five Freedoms to the Five Domains and Beyond with Frania Shelley-Grielen Thursday, September 20, 2018 - 1:30 p.m. (EDT) petprofessionalguild.com/event-2940490
Sugar, Serotonin and Schmackos: Raw Food and Canine Behaviour with Dr. Nick Thompson Wednesday, September 26, 2018 - 1 p.m. (EDT) petprofessionalguild.com/event-2991296
Service Dog Owner Training -- Is this the path for you? With Sharon Wachsler Monday, October 29, 2018 - 1 p.m. (EDT) petprofessionalguild.com/event-2983619 Is Loose Lead Walking a Self-Control Behavior? - Presented by Sian Ryan Tuesday, November 13, 2018 - 1 p.m. (EST) petprofessionalguild.com/event-2892968
Educational Summits
PPG Canine Aggression and Safety Education Seminar 2019 (Portland, Oregon) (see also ad on back cover) Friday, April 26, 2019 - Time TBC Sunday, April 28, 2019 - Time TBC petprofessionalguild.com/2019-Portland
Residential Workshops
PPG Florida Members - A Full Day of Networking, Sessions and Competitions with Niki Tudge, Angelica Steinker and Dr. Lynn Honeckman (Tampa, Florida) Sunday, September 16, 2018 - 9 a.m. (EDT) petprofessionalguild.com/event-2858895 Let's Coach Scent Work! with Robert Hewings (Tampa, Florida) (see also ad on p. 21) Saturday, October 20, 2018 - 9 a.m. (EDT) Sunday, October 21, 2018 - 4 p.m. (EDT) petprofessionalguild.com/event-2822576
The Walk This Way Instructor Certification Workshop with Louise Stapleton-Frappell and Niki Tudge (Tampa, Florida) (see also ad on p. 24) Monday, October 22, 2018 - 9 a.m. (EDT) Tuesday, October 23, 2018 - 4 p.m. (EDT) petprofessionalguild.com/event-2822678
Successfully Train and Compete in The Show Ring - Learn The Knowledge and Skills You Need to Compete or Teach a Professional Curriculum with Vicki Ronchette, supported by Niki Tudge (Tampa, Florida) (see also ad on p.46) Saturday, September 21, 2019 - 9 a.m. (EDT) Sunday, September 22, 2019 - 4 p.m. (EDT) petprofessionalguild.com/event-2688824
Note: All dates and times are correct at time of going to press but are subject to change. Please check website for an updated list of all live webinars, as well as discounted and on-demand webinars: petprofessionalguild.com/educational-resources BARKS from the Guild/September 2018
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Cool for Cats
Tabitha Kucera discusses some of the similarities between cats and dogs, and how pet
professionals can ensure that kittens and cats receive the appropriate socialization,
training, physical and mental enrichment as well as have their basic needs met
to reduce the likelihood of behavior issues developing
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Photo © Tabitha Kucera
Cats search for treats in a ball pen; according to Dr. Lisa Radosta, in terms of behavior, virtually “every disorder in cats will respond to some degree to environmental enrichment.”
t may seem like I am stating the obvious if I start this article by stating that a cat is not a dog! Having said that, however, in many ways cats have similar needs to dogs, and are able to be as affectionate and engaged as our canine companions. Just like dogs, too, they have specific needs related to socialization, enrichment, and training and it is important for these needs to be met so they can thrive in our homes. In actual fact, keeping cats happy in their homes and with new experiences can be just as simple and rewarding as working with dogs. In this article, then, I want to share with you some the cat “basics,” so you can help your clients with their cats as well as their dogs. 10
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We are all familiar with puppy socialization, but do not hear about kitten socialization anywhere near as often. In fact, however, it is as important for kittens to be properly socialized and trained as it is for puppies. The effects of poor socialization can result in cats who hide from visitors, fear other pets, adapt slowly to new environments, and they can also be fearful and aggressive with handling at veterinary visits. These cats are more likely to become stressed and/or fearful and start urinating out of the litter box, which can result in the human-animal bond being damaged and owners then relinquishing their cats. However, well-socialized kittens who have received positive experi-
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ences. Kitten kindergarten is a concept created by Dr. Kersti Seksel, an Australian veterinary behaviorist, to help socialize cats and educate owners about normal feline behavior. Since first creating and sharing kitten kindergarten over 10 years ago, her idea has spread and is now being held at numerous veterinary clinics and humane societies. The classes are “ideally three one-hour sessions over three weeks with a maximum of six kittens and the kittens should be 8-12 weeks of age and no older than 14 weeks at the end of the class.” (Burns, 2017). The key socialization period for kittens is 2-7 weeks of age but can extend up to 14 weeks. This is the period during which they are most receptive and open to learning new things and bonding with other kitties and humans. During this period, they may startle but recover very quickly. In these classes, kittens learn essential developmental and social skills needed to thrive in their environment. Cat owners are taught how to understand their cat’s behavior by learning cat body language, appropriate scratching surfaces, appropriate litter box setup, how to shape behavior using a clicker, and how to raise a confident cat. Kittens learn important behaviors such as targeting, how to happily go into a carrier and how to accept medications and nail trims. Kittens also play and socialize with other kittens and will have opportunities to have positive interactions with dogs, children, and various adults. Ultimately, kitten kindergarten can help save lives..
Cat Training
There is a common misconception that cats cannot be trained, and even if it is possible, it is a lot more difficult than training dogs. Both of those statements are inaccurate and can be detrimental if a cat owner believes them.. They can learn anything, including foundation behaviors (targeting, attention), positive husbandry behaviors (nail trims, brushing, and handling), and fun tricks (roll over, high five). Training can also be very effective in stopping and replacing unwanted behaviors.
Reinforcers: Cats, like any species, have their own motivations and priorities and this should be taken into consideration prior to starting any train-
...well-socialized kittens who have received positive experiences.
Photo © Tabitha Kucera
Cat-friendly shelving is an ideal way to vary the environment for cats
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cover. ing. Reinforcers must have value to the learner to be reinforcing, and in many cases, cat owners feel that their cats do not like treats and are unaware of what is high value to their cats, so a great first step is to provide the owner with a list of common reinforcers so that they can find out what is reinforcing to their individual cat(s). I provide my clients with a list of reinforcers that includes food reinforcers from the fridge, pantry, and pet stores along with play and praise reinforcers (e.g. whipped cream, squeezy cheese, freeze-dried treats, and crunchy cat treats).
Using a Clicker: Just like with dogs, the clicker is a great tool to help
communicate with and teach cats new behaviors. A click is a distinct sound that the cat learns and means only one thing, a reward is coming. A click, unlike our voices, sounds the same every time which means the whole family can be involved in the training process, from the children to parents. This is crucial in successful outcomes. In clicker training, the click works as an event marker to indicate the moment in time the desired behavior happens. Once the behavior is learned, the clicker is no longer needed to maintain the behavior. (For further details, see Clicker Training for Cats, BARKS from the Guild, November 2017, pp. 16-23).
Reinforcement: As always, it is important to deliver the reinforcer
(treat) right after the click. Rewards should be given immediately, within three seconds, so that you don't inadvertently reward other behavior that may happen after the desired one. Rewards can be used to train a cat to do a desired behavior or to teach him which behavior is wanted. It is important that rewards are not unintentionally given for undesirable behavior. Ignoring and then redirecting negative behavior is the best way to eliminate that behavior. For example, if a cat is meowing for food and you ignore the cat while meowing, he will likely stop meowing to be fed (Overall, et al., 2005).
Focus on the good: As a
clicker trainer, I focus on the positive behaviors and build upon
those instead of telling an animal and client what not to do. This helps to not only keep training fun for both the teacher and the learner but also creates enthusiastic learners and encourages creativity. When using punishment-based methods (i.e. spraying with water, shocking, yelling, hitting), animals learn to do the minimum possible to stay out of trouble and are afraid to offer new behaviors because they are concerned that will be punished. Positive training methods also accelerate learning since animals can better understand what we are asking of them instead of repeatedly telling them “no.” Imagine if you were trying to teach someone a new skill, how to jump rope for example, and instead of reinforcing behaviors that lead up to jumping rope (walking to the rope, picking it up, jumping with two feet, swinging the arms), you said “no” or poked a person every time they did not perform the full goal behavior of jumping rope. That person is going to become frustrated very quickly and give up – versus the person who receives encouragement and is given direction. Another concern with using punishment-based teaching methods is that they do not teach the correct behavior and tend to stop working in the absence of punishment. This is unlike clicker training, which helps to teach animals behaviors, and once they learn the behavior, it is on cue. There is no need to click, because the animal actually understands the behavior. Often, cats will associate a punishment with the punisher, which will create fear, stress, and uncertainty in the learner and can lead to a damaged human-animal bond. As force-free trainers and behavior professionals, we already know that focusing on the positive and using clicker training works with any animal. It is versatile and can be used for solving behavioral problems, teaching basic manners and very advanced service tasks, is free of any behavioral side effects that punishment-based training creates (aggression, fear, stress), strengthens the human animal bond, and is fun for both the trainer and learner.
Greeting
Cats are companion animals that benefit from consistent, friendly and predictable social interactions with humans. It is important to note that how a person greets his or her cat or a new cat can affect the cat’s perception and reaction to a person. Every cat is an individual, and based on this, individual preferences do play a part in what greetings they prefer. However, there are greeting specifics that a majority of cats perceive to be safe and friendly. Appropriate introduction to a cat (again, many of these can be applied to dogs or other animals): • Avoid staring, standing or bending over, chasing, reaching out, or forcing contact with a cat as these are all perceived to be threatening to them. • Avoid negative body language, yelling, or speaking loudly. • Speak in calm, quiet tones. • Let the cat
Kittens who have received positive experiences around many different people, unfamiliar kittens, environments, and handling procedures are more likely to be outgoing, social, and have better coping skills as adults
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© Can Stock Photo/andreykuzmin
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initiate, choose, and control the type of human contact (does the cat enjoy being held, picked up, sitting in laps, pet down their back, etc.?). • Sit or kneel down and turn to the side rather than directly facing the cat to make yourself appear smaller and less threatening. • At a distance (a few feet, increase distance if you do not know the cat, or the cat is showing signs of stress) extend your pointer finger or soft hand (this is the human to cat equivalent to touching noses to simulate a cat hello). Some common signs of stress that would indicate you need to give the cat some space would be ears out to the side or down, tense body, furrowed brow, tail twitching or the tail close to the body, whiskers back, pupils dilated, body crouched or leaning away, and the cat staring at you. • If the cat chooses to approach you, he will smell your hand, and if he rubs on your hand or leans his head into it, then he is communicating that he would like you to pet him. If he sniffs your hand and then moves back, that is him kindly asking to not be petted. • When petting, many cats prefer short strokes on the temples, cheeks, and under the chin. • If the cat ends the interaction, do not pursue or force contact..
Photo © Tabitha Kucera
About About Litter Litter Boxes Boxes
As far as litter boxes are concerned, one size does not fit all, but many As far as litter boxes are concerned, one size does not fit all, but many cats will have their preferences. Below are four basic things to consider cats will have their preferences. Below are four basic things to consider when setting up litter boxes to help prevent accidents and create posiwhen setting up litter boxes to help prevent accidents and create positive associations between cats and their boxes. tive associations between cats and their boxes.
Litter are meticulously clean animals and, justifiLitter box box hygiene: hygiene: Cats Cats are meticulously clean animals and, justifi-
ably, will avoid using a dirty litter box in favor of a cleaner place, even if ably, will avoid using a dirty litter box in favor of a cleaner place, even if that place is a carpet. To prevent this from happening, it is recomthat place is a carpet. To prevent this from happening, it is recommended that the boxes get scooped once to twice daily and cleaned mended that the boxes get scooped once to twice daily and cleaned every one-four weeks with a mild soap and hot water. Avoid strong every one to four weeks with a mild soap and hot water. Avoid strong chemicals like bleach or any ammonia-based products because cats may chemicals like bleach or any ammonia-based products because cats may find the smell aversive, which can cause an aversion to their box. find the smell aversive, which can cause an aversion to their box. Litter box type and size: Size does matter when it comes to litter boxes in that bigger is always better: “Most cats show a definite preference for Litter box type and size: Size does matter when it comes to litter a larger litter box than is typically available to them in homes and that boxes in that bigger is always better: “Most cats show a definite preferother factors such as box cleanliness and location may have a comence for a larger litter box than is typically available to them in homes pounding influence on this choice.” (Guy, Hopson & Vanderstiche, and that other factors such as box cleanliness and location may have a 2014). compounding influence on this choice.” (Guy, Hopson & Vanderstiche, When choosing a box, your cat should be able to comfortably turn 2014). When choosing a box, your cat should be able to1 comfortably the around in the box – ideally the box should be at least 1 ⁄2 times turn around in the box – ideally the box should be at least 11⁄2 times the length of the cat from the nose to the base of the tail. Under the bed length of the cat from the nose to the base of the tail. Under the bed storage containers, 30-gallon storage containers, and cement mixing storage containers, 30-gallon storage containers, and cement mixing tubs are a few appropriate sized alternatives to their small commercial tubs are a few appropriate sized alternatives to their small commercial counterparts. When choosing boxes for small kittens or senior cats, I counterparts. When choosing boxes for small kittens or senior cats, I recommend using low sided boxes or purchasing a storage container recommend using low sided boxes or purchasing a storage container and cutting a low entry so the senior cats cat easily walk in and avoid and cutting a low entry so the senior cats cat easily walk in and avoid lifting their legs high or jumping in, which can be painful. lifting their legs high or jumping in, which can be painful. Many cats are not fond of covered boxes for a variety of reasons. Many cats are not fond of covered boxes for a variety of reasons. The boxes are often too small, and they trap odors and dust inside, The boxes are often too small, and they trap odors and dust inside, which can be very unpleasant for the cats. Also, cats are both predator which can be very unpleasant for the cats. Also, cats are both predator and prey animals. In terms of the latter, asking them to go in a covered and prey animals. In terms of the latter, asking them to go in a covered
Photo © Tabitha Kucera
Photo © Tabitha Kucera
(Top to bottom): A window perch to keep cats occupied; a scratch post doubling as a resting place; vertical space and puzzle toys are all good ways of providing environmental enrichment
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Size does matter when it comes to litter boxes in that bigger is always better. When choosing a box, your cat should be able to comfortably turn around in the box – ideally the box should be at least 11⁄2 times the length of the cat from the nose to the base of the tail. Under the bed storage containers, 30-gallon storage containers, and cement mixing tubs are a few appropriate sized alternatives to their small commercial counterparts. box where, from their perspective, they cannot see possible predators and are made to feel vulnerable or exposed to threats, is not ideal. In such cases, a clear litter box can be helpful to make cats feel safer.
Litter box substrate: While litter preferences vary between individual
cats, “in studies, most cats prefer unscented and finely particulate litter material as is typical of the clumping type litters compared with other litter options.” (Neilson, 2004, citing Borchelt, 1991). Indeed, with their sensitive noses, “scented cat litter can be unpleasant for cats.” (Johnson-Bennett, 2018). Cats have “twice as many receptors in the olfactory epithelium (i.e. smell-sensitive cells in their noses) as people do, meaning that cats have a more acute sense of smell than humans. ” (Purves, et al., 2001). This is also a good reason to avoid using litter deodorizers or air fresheners near the litter box. Odor should not be a problem if you are keeping the box clean. Cats also have a natural instinct to bury their waste in order to avoid attracting predators and will look for a soft, loose substrate that is easy to dig into. I recommend sticking with whatever they prefer, and if your cats prefer a specific litter, try not to change it.
Litter box location and number: The golden rule for number of litter
boxes in a house is one box per cat plus one extra. Bear in mind that three boxes right next to each other are considered as one box from a cat’s perspective. The location of litter boxes is key in preventing aversions and accidents. Do not place boxes in the same area as your cat’s food and water. You would not want to eat where you eliminate and neither does your cat. Cats prefer to use their boxes in quiet and private places.. I recommend that cat owners avoid placing boxes in busy areas or where a cat could feel trapped by another cat, a dog, or other people in the house.
Enrichment
Providing for your cat’s mental wellbeing is just as important as providing for their physical wellbeing. Cats have natural behaviors and needs, and they must have opportunities to express those behaviors. An enriched environment should provide various types of scratching surfaces, outlets for predatory and prey behavior, safe places, and should respect all five of your cat’s senses which provides an environment in which an animal has variety, choice, and control over their daily activities. According to Radosta (2018): “Virtually every disorder in cats will respond to some degree to environmental enrichment. That’s right: the kitty who doesn’t want to leave your lap, or the one that bites you when you stop petting, and even (a favorite) the cat that howls through the night, can at least partly improve with proper enrichment.” Here are some examples:
Photo © Tabitha Kucera
Photo © Tabitha Kucera
Photo © Tabitha Kucera
Photo © Tabitha Kucera
An enriched environment should provide various types of scratching surfaces, outlets for predatory and prey behavior, safe places, and should respect all five of a cat’s senses to provide a habitat in which he has variety, choice, and control over his daily activities
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Photo © Liz Waynick
Target training: Contrary to popular belief, cats are responsive to training, and it is an ideal way to provide mental stimulation
Food-based enrichment: Food puzzles can help to slow down eating, prevent boredom and obesity, and allow cats to eat more instinctively by allowing them to forage and “hunt” for their food. There are various food dispensing toys for cats that you can purchase, and you can even make your own. I recommend starting with an easier, beginner puzzle and work up based on your individual cat’s preference. A great starter puzzle toy would be an ice cube tray or coffee mug where the cat can use foraging behaviors to easily obtain the food. Along the same lines, one of my favorites is a lunch paper bag. Place a few treats inside the bag, twist the top, cut one to two small to large holes in the bottom of the bag and allow the cats to open and tear apart the bag. Sensory enrichment: Scent signals are an important part of cat com-
munication and exploration. Cats exposed to new odors are more active and exploratory. Catnip, silvervine, cat grasses, safe houseplants (Note: many plants are toxic to cats – see the American Society for the Prevention of Cruelty to Animals’ Toxic and Non-Toxic Plant List – Cats for more details), toys with owner's scent, and pheromones such as Feliway can all help encourage exploration and play. Placing a small amount of a scent in paper ball toys, boxes, bags, etc. can also provide sensory enrichment. Switching available scents and presenting them randomly can add surprise and delight to the cat's daily exploration. One example of sensory enrichment is placing fleece blankets (touch) on a perch near a window so that your cat can climb up and observe (sight, hearing, smell) birds and squirrels at a strategically placed feeder (The Ohio State University, n.d.).
Playtimes: Exercising his prey drive with interactive play is a crucial
part of a cat’s development and contributes greatly to his quality of life. I recommend using a wand toy such as a feather wand or a mouse on a string and move the toy like the prey it is supposed to represent. Just like us, not all cats love the same things, so try a few wand toys to see what the cat enjoys. Also, providing your cat with toys he can play with on his own is recommended. This can include everything from ping pong balls, motorized toys, and catnip kicker toys, which are great for cats to attack, bunny kick, and snuggle with. Toy rotation is a simple idea that will keep your cat more interested in playing and prevent boredom.
Photo © Tabitha Kucera
Many cats enjoy the scent of catnip, but many plants are toxic for cats so owners should take care to check first if they are safe
(For more about play, see Keeping It Fresh, BARKS from the Guild, July 2015, pp. 44-45).
Environmental enrichment: Provide a variety of vertical spaces and
hiding spaces. More hiding spots and perches will allow your cats to space themselves out as they prefer. Cats enjoy exploring vertical spaces as well as having a high vantage point from which to view the outside world. Window perches, cat trees and cat-friendly shelving are ideal ways to vary your cat’s environment. Incorporate safe hiding areas (e.g. boxes and tunnels) too. I recommend using these throughout the home, but especially in the areas where you tend to spend the most time, since cats like to spend time with their people. Cat shelves are great additions to a cat’s environment, but when placing them be sure to have an entrance and exit ramp. Cats need to scratch, so providing various types of scratching surfaces based on your cat’s preferences is recommended. Your cats may prefer vertical, horizontal, or angled surfaces made of sisal, carpet, wood or cardboard. When purchasing cat scratching posts, they should be steady and should be a minimum of 3 feet high to allow cats to fully extend their body and stretch when scratching. (For more information on scratching, see Scratch Here, Not There, BARKS from the Guild, July 2016, pp.25-26).. BARKS from the Guild/September 2018
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Positive training: Another form of enrichment can be clicker training your cat, which I discussed earlier on. Cats are curious and intelligent and clicker training is an ideal way to mentally stimulate your cat and teach him new tricks! Once all these various components are slotted into place, owners
will be setting up the home environment so they meet their cats’ individual physical and mental needs as best they possibly can, thereby enhancing the pet-owner bond and helping to prevent behavior issues arising, while ensuring the optimum welfare and wellbeing for their pets. n
References
Borchelt, P. (1991, March).Cat elimination behavior problems. The Veterinary Clinics of North America: Small Animal Practice 21 257–264. Available at: bit.ly/2NWXau1 Burns, K. (2017, November 29). Feline development, from kitten kindergarten onward. Journal of the American Veterinary Medical Association News. Available at: bit.ly/2L3pkFM Guy, N.C., Hopson, M., & Vanderstiche, R. (2014, March). Litterbox size preference in domestic cats (Felis catus). Journal of Veterinary Behavior: Clinical Applications and Research (9) 2 78-82. Available at: bit.ly/2mwDhxr Johnson-Bennett, P. (2018). Litter Basics. Available at: catbehaviorassociates.com/litter-basics Neilson, J. (2004, November). Feline house soiling: Elimination and marking behaviors. Companion Animal Medicine (19) 4 216–224. Available at: bit.ly/2L8h7Al Overall, K.L, Rodan, I., Beaver, B.V., Carney, H., Crowell-Davis, S., Hird, N, … Wexler-Mitchel, E. (2005). Feline Behavior Guidelines from the American Association of Feline Practitioners. Journal of the American Veterinary Medical Association (227) 1 70-84. Available at: scribd.com/document/8745122/Feline-Behavior-Guidelines Purves, D., Augustine, G.J., Fitzpatrick, D., Hall, W. C., LaMantia, A-S., & White, L. E. (2001). Neuroscience (2nd ed.). Sunderland, MA: Sinauer Associates Radosta, L. (2018, January 1). Your Cat Is Bored! Psychology Today. Available at: bit.ly/2JyeK3T The Ohio State University. (n.d.). Basic Indoor Cat Needs. The Indoor Pet Initiative. Available at: bit.ly/2LsqXc8
Resources
American Society for the Prevention of Cruelty to Animals. (2018). Toxic and Non-Toxic Plant List – Cats. Available at: bit.ly/2O0bUs3 Bahr, L. (2018, February 19). Why Every Cat Needs a Place to Hide. BARKS Blog. Available at: bit.ly/2NUePT3 Ehrlich, J. (2015, July). Keeping It Fresh. BARKS from the Guild (13) 4445. Available at: bit.ly/2uMzmzY Fisher, P. (2016, July). Scratch Here, Not There. BARKS from the Guild (19) 25-26. Available at: bit.ly/2ysmmRe Garber, P. & Miller, F. (2017, November). Clicker Training for Cats. BARKS from the Guild (27) 16-23). Available at: bit.ly/2moXtRD Krieger, M. (2017, May 5). Thinking Outside the (Litter) Box. BARKS Blog. Available at: bit.ly/2zZjJeH Mauger, J. (2018, June 6). How Big Should a Cat’s Litter Box Be? BARKS Blog. Available at: bit.ly/2zLw2uK Todd, Z. (2016, April 20). Enrichment Tips for Cats (That Many People Miss). Companion Animal Psychology. Available at: bit.ly/2Ns4aOa Todd, Z. (2017, December 13). How to Make the World Better for Cats. Companion Animal Psychology. Available at: bit.ly/2Nnvtcu
Photo © Tabitha Kucera
Exercising a cat’s prey drive with interactive play is a crucial part of his development and contributes greatly to his quality of life too
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Tabitha Kucera is the owner of Chirrups and Chatter cat behavior consulting and training (chirrupsandchatter.com) based in Cleveland, Ohio. She is a certified cat behavior consultant, a registered veterinary technician and is low stress handling and fear free certified. She currently serves as the co-chair of Pet Professional Guild’s Cat Committee, president elect of the Society of Veterinary Behavior technicians, and on the board of The Together Initiative for Ohio’s Community Cats. She also lectures on making veterinary visits less stressful for both clients and patients and feline and canine behavior, and is the behavior advocate for her veterinary hospital, leading the initiative of implementing fear free, performing happy, successful visits, and assisting the veterinarians with behavior cases.
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BARKS from the Guild/September 2018
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canine
A Shift in Mindset
Anna Bradley discusses the importance of educating clients in body language, canine
A
communication and enrichment as an integral part of preventing behavior problems s pet professionals, we often spend a long time – and I most definitely include myself here – working to fix, or at least improve, behavior issues. But shouldn’t we also be thinking about actually preventing them in the first place? Of course, in many instances we don’t have that luxury because dogs that are newly adopted or rehomed may already be well-practiced in certain inappropriate behaviors. Even in these situations, though, we can still take measures to reduce the chances of issues getting worse, or the risk of the dog struggling further. What actually is a so called “problem behavior?” Firstly, if a dog displays any behavior which is suddenly out of character, then it should be investigated by a veterinary professional in order to rule out (or in) clinical factors. That done, we should consider that what a client may consider a behavior issue may simply be “normal” behavior which has become “abnormal” because it is out of context and, therefore, deemed inappropriate. Take, for instance, a border collie snapping at a child’s heels. A client might also class behavior as a “problem” because communication with their dog has broken down and they are having trouble reading their pet. Aggression is a very good example here. There are many reasons that behavioral issues arise, and the interesting thing is that, if we look truly objectively, human intervention (or sometimes the lack of it) can be at the root of the problem in some cases.
In the Genes
The nature vs. nurture issue with respect to specific behavior issues is a contentious one and beyond the scope of this article. Behavioral genetics is a rapidly expanding field and it is clear that traits such as fearfulness and particular repetitive behaviors in specific breeds are heritable. When purchasing or adopting a puppy, it is crucial that you obtain your new family member from a trusted and reliable source. If you are obtaining your pup from a breeder, ensure you view the puppies with the mother in a home environment and assess the temperament of all. Ideally, they should not be unduly shy or nervous. If you are adopting a puppy or adult dog, ensure you choose a reputable rehoming center which can give you assistance when choosing your dog and follow-up care. Human intervention with regards to artificial selection has had a pretty deep influence on specific breed traits. Selective breeding is often thought of in terms of accentuating desirable features. However it can have serious consequences upon the dog’s behavioral development. Houpt (1991), cited in Rooney and Sargan (2009), notes the example of the Hungarian puli, selectively bred for profuse hair covering the eyes, and suggests the possibility of fear aggression resulting from the dog becoming startled due to vision impairment.
...if dogs are punished for displays of growling or biting, they may learn to suppress earlier gestures (which are actually “red flag” and positive signs), and leap straight to snapping next time that uncomfortable situation or event presents itself. 18
BARKS from the Guild/September 2018
© Can Stock Photo/plysiukvv
Owners may be unaware of the signals their dogs project when fearful or uncomfortable in a given situation, or misinterpret them as “dominance” and punish the dog
Leaver and Reimchen (2008), cited in Rooney and Sargan (2009), also suggest that brachycephalic dogs (pugs, boxers, etc.) are less able to use facial expressions, adding that dogs with docked, curled tails or those with droopy or permanently erect ears, raised hackles or dense fur are unable to signal their intentions to other dogs and so have difficulty in social encounters. A tendency toward selection of juvenile characteristics such as dependency, play, leadership etc. has also been seen. This has led to problems such as separation anxiety as dogs become dependent upon humans and unable to cope with social isolation. While we may enjoy our perfectly bred companion, then, there are issues when he/she and our lifestyle conflict. We may be striving for what we perceive to be perfection in our lives, but for the sake of their behavioral welfare, that should not extend to our dogs.
Out and About
I think most owners are aware that inappropriate socialization with a dog’s own and co-habitant species (humans, other dogs, cats, horses, small furries etc.) has a detrimental effect on their behavioral development. Of most consequence in a puppy’s development is the sensitive period (3-14 weeks), a time when puppies begin to exhibit adult behavior and form strong social bonds with humans. To assist my clients, I prepare a positive socialization tick list. This contains a “hit list” of lots of places to visit and people to meet and greet of all different appearances. There are lots of similar resources online (see PPG’s Puppy Training Resources). The whole idea is that puppy is exposed to wide and). varying environmental stimuli so that they become of little consequence in adulthood. Braastad and Bakken (2002) explain that families who continue broad socialization experiences will have a dog who can cope with wide ranging experiences in adulthood. They suggest the consequences of inappropriate socialization being the exhibition of behavioral symptoms of fear and fear aggression towards humans. Certainly inadequate or poor socialization experiences are a common factor in the majority of behavioral cases I see.
Preparation
Can we prepare more? This is something we just don’t do enough of, in my opinion. Sometimes people become so caught up in the excitement of adopting a new dog or the collection date of a new puppy. When the new family member comes home, it is important to allow him space, quiet and time to transition to his new home. In the case of adopted dogs there is often a “honeymoon” period of calm followed by the development of some teething issues. Allow your new dog time to settle, establish a clear routine and start as you mean to go on. Keep the household quiet and calm and expect that you may have issues (such as toileting mishaps). In the case of puppies, allow them to sleep. I cannot stress this enough! Don’t feel pressure to constantly occupy them. If you have children, remind them of the need to allow puppy quiet time as well as play time. My tip for new puppy owners is to think now about their expectations for their dog as an adult and set their boundaries today, i.e. don’t allow mouthing your fingers, jumping up, etc. “just because it’s cute” at 13 weeks and then abruptly stop it at 7 months when your dog has a full mouth of teeth and is approaching full size.
canine
ceed with punishment. The Ladder of Aggression (Shepherd, 2009) incorporates a good depiction of gestures, from subtle nose licking and blinking to progressive escalation to crouching with tail tucked, growling and eventually biting. Dogs may display such gestures in response to a perceived stressor or threat, in an attempt to repel both. The problem is that owners, having missed (or been unaware of) the earlier, more subtle signs, may only react when they witness top rung of the ladder signals – growling, snarling, snapping, etc. and the dog may then be punished for these displays. Owners may also (mistakenly) believe their dog is behaving in a “dominant” manner when actually he is probably fearful. What is needed, then, is better communication skills and understanding of the more subtle canine gestures amongst both owners and those who work with dogs.). Similarly, if dogs are punished for displays of growling or biting, they may learn to suppress earlier gestures (which are actually “red flag” and positive signs), and leap straight to snapping next time that uncomfortable situation or event presents itself.
Giving Dogs More to Do
Thankfully, I think owners are increasingly aware of a dog’s need for enrichment. If dogs don’t have things to do, problems can happen: a lack
Matchmaking
For me personally, one of the most significant causes of problems between dog and owner is the wrong dog-wrong person combination or simply the wrong environment. It is incredibly important to both research the breed prior to purchase/adoption, and if you are adopting, to ask lots of questions about that individual dog. It seems so obvious and simple that a border collie would not be suited to a life in a high rise apartment and never being walked more than 10 minutes a day, yet instances like this still occur. Always consider the breed traits prior to homing, as well as the size of the dog, his energy requirement, drive, motivation etc. We really should not be surprised if we place a dog in an inappropriate situation and then he expresses normal behavior for his breed, especially if we provide no other outlet. And yet, so often, the dog gets the blame.
Communication
Communication is #1 for me. This is all about education. If we could provide our clients with more information regarding canine communication, I believe we could make a dent in the behavioral caseload, particularly aggression cases. It is concerning that, frequently in my experience, owners may be unaware of the signals their dogs project when fearful or uncomfortable in a given situation and even more concerning how many misinterpret those signals as “dominance” and proBARKS from the Guild/September 2018
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of enrichment certainly plays a significant role in the development or maintenance of behavioral issues, e.g. abnormal repetitive behavior. Think of enrichment as social and mental. Social enrichment involves making enhancements to a dog’s environment, perhaps adding variation to her surroundings and lifestyle and incorporating novelty (new walks, digging areas, sandpits, water pools, new activities, dog TV, new games, etc.) Mental enrichment refers to the addition of problem solving tasks which become mental challenges for the dog (activity toys, puzzle games, hiding treats, scatter feeding, etc. Busy dogs in general equal happier dogs, but do watch for overarousal. In my opinion, a shift in the common mindset is needed, from cure to prevention. We need to think more about our dogs’ behavioral wellbeing as well as their physical health, and although we are progressing in this respect, I don’t think we’re quite there yet. The onus, in my experience, is too much on “wait and see” and then treat the dog or put up with the issue, rather than ensure it never occurs in the first place. I think it is also a case of prioritizing and realizing that our dogs’ behavioral health is actually as important as their physical wellbeing. This is another area which I, personally, don’t feel is as well developed – yet. If we can strike the balance, our dogs will be better for it. n
Resources
Pet Professional Guild. (2017). Puppy Training Resources. Available at: petprofessionalguild.com/PuppyTrainingResources Shepherd, K. (2009). Ladder of Aggression. BSAVA Manual of Canine and Feline Behaviour, 2nd edn. (Eds. D.F. Horwitz & D. S. Mills), pp.13–16
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BARKS from the Guild/September 2018
References
Braastad, B.O. & Bakken, M. (2002) Behaviour of Dogs and Cats. In: P. Jensen (Ed). Ethology of Domestic Animals, pp 173-190. Wallingford, UK: CABI Houpt, K.A. (1991),) Leaver, S.D.A. & Reimchen, T.E. (2008),) Shepherd, K. (2009). BSAVA Manual of Canine and Feline Behaviour, 2nd edn. (Eds. D.F. Horwitz & D. S. Mills), pp.13 – 16 Anna Francesca Bradley MSc BSc (Hons) is a United Kingdomebased provisional clinical, certified IAABC animal behavior consultant and ABTC accredited behavior consultant. She owns Perfect Pawz! Training and Behavior Practice (perfectpawz.co.uk) in Hexham, Northumberland), where the aim is always to create and restore happy relationships between dog and owner in a relaxed way, using methods based on sound scientific principles, which are both force-free and fun.
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training
Canine Car Anxiety
M
Lori Nanan discusses the issue of dogs with car sickness and anxiety and sets out a training
plan to improve the situation for all based on the power of associative learning
any people are left ious in the car for the rest of scratching their her life. Thankfully, once we heads when it had adopted her and comes to car sickness and switched to our own vet, we anxiety. It often feels much were able to get pharmaceulike a chicken or egg question: tical relief for her in the form which came first? Why is my of the anti-nausea medicadog getting sick in the car? Is tion, Cerenia. This was a cruit because he’s anxious about cial start to being able to being in the car and this break the cycle. But, it was makes him feel sick? Or is my only that: the start. Addressdog suffering from motion ing the nausea allowed me to sickness and has become anxget to the work of addressing ious in the car because of the anxiety. It was at this this? Often, people will start point I was extremely glad I experimenting to see if they was a dog trainer, because I can work it out: over the knew that I could use the counter medications, principles of desensitization pheromones, crates and conand counterconditioning finement and so on. It makes (DS/CC) to help my dog. sense to explore the two comTo help me get a better ponents separately, but doing perspective on how veterinarso effectively can be a bit ians handle these issues, I tricky. asked my colleague, Dr. I will use my own dog, Rachel Szumel of Blue Lake Hazel, as an example. After Animal Care Center in South Photo © Lori Nanan bringing her home, we noLake Tahoe, California, to fill Author Lori Nanan’s dog Hazel would get sick in the car when she was about ticed that she seemed to get me in on some of the decithree-quarters of the way into the journey, regardless of how far or long it was sick in the car when we were sion-making vets engage in, about three-quarters of the based on owner reports. way to where we were going, no matter how far or long the trip. We First, I asked her if, when an owner reports car sickness, she pretried over the counter anti-nausea meds, Benadryl (an antihistamine) scribes medication right away. She answered affirmatively, stating that and pheromone sprays with little to no success. We tried short trips she may suggest an over the counter motion sickness medication (like only, with little to no success. We tried confinement, with zero success. Dramamine) first, but that she sees less success with those. Her preAnd through it all, her anxiety seemed to worsen. She would drool, look scription go-to (and the medication that changed Hazel’s life) is Cerenia. around frantically and seemed afraid to move even a single muscle. The The primary usage for Cerenia is exactly this: to prevent nausea due to unfortunate part was that, throughout much of this period of trial and motion sickness. Speaking from my own experience, it is incredibly eferror, she was in foster care with us, and we had to drive her to the shel- fective and depending on the dog, simply ends the nausea and vomitter, which was an hour away, for testing and medications for her mange. ing, or reduces the nausea and vomiting to allow enough comfort for the training process to begin. And for many dogs, the training process is So she had many trips on which to a) feel sick, and b) feel anxious. Looking back, it was the perfect set-up for creating a dog who would be anxnecessary, because the cycle of nausea --> vomiting --> anxiety or anxiety --> nausea --> vomiting has been going on for a while, the associaWhile we are dabbling in alternative remedies, tions have been made and will not be broken without some behavioral our dogs are suffering. I learned this the hard help. Even if the dog is no longer getting sick, then, the underlying anxiway: while I was trying Benadryl, pheromones ety remains and needs to be worked on. The power of associative learnon bandanas and Dramamine, my dog was still ing has been doing its work in the background, even if we are not aware getting sick in the car and the association was of it. This is a good example – and reason – to discuss anti-anxiety medications with your veterinarian. getting stronger – contributing to the anxiety According to Dr. Szumel, for puppies, addressing the motion sickfactor. So, she was not feeling well and she was ness component often solves the problem, but not always. Multiple unscared. And I was wasting money, letting my car pleasant experiences can cause the development of a negative get ruined, and feeling helpless. conditioned emotional response (-CER) and anxiety that needs to be worked on, just as in adult dogs. Thankfully, in these cases, we can use 22
BARKS from the Guild/September 2018
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DS/CC in the exact same way. I had the opportunity to work with one such puppy a few years after working through it with Hazel, and using the same principles, was able to help little Bailey and her parents resume their trips to New England from Pennsylvania, which had temporarily been put on hold due to Bailey’s extreme motion sickness and anxiety. In little Bailey’s case, she would start backing away from the car as soon as she was about 20 feet away. This made the DS/CC a bit trickier and “splittier” than Hazel’s, but I was confident using a training plan, we would get there, and we did.
Training Plan
Here is an example of how a trainer or dog owner might set out to write a plan:
Step 1: If there’s a car sickness component: See your vet.
I am a firm believer that “can’t hurt, could help” might actually hurt. Here’s why: While we are dabbling in alternative remedies, our dogs are suffering. I learned this the hard way: while I was trying Benadryl, pheromones on bandanas and Dramamine, my dog was still getting sick in the car and the association was getting stronger – contributing to the anxiety factor. So, she was not feeling well and she was scared. And I was wasting money, letting my car get ruined, and feeling helpless.
Step 2: Re-build a positive conditioned emotional response to the car.
In Hazel’s case, I was able to do this in the car as her anxiety didn’t kick in until the car was in motion. In little Bailey’s case, this involved starting way back from the car. When she saw the car, a steady flow of chicken began. We gradually and carefully closed the gap, always dropping back if she showed any signs of fear (in her case, this looked like backing away), moving closer (pushing) at clear signs of comfort, and sticking when she appeared neutral.
Step 3: Proceed based on the Push, Drop, Stick rules for fear and anxiety.. Some may drool and whine, some may freeze and some may tremble, etc. It is critically important that we only push to a harder step on a clear +CER (the dog looks “happy” or is anticipating something, like when your dog looks as you open the treat bag), we drop on fear (the dog is clearly still uncomfortable or avoidant) and we stick on neutral (no clear signs of a +CER, but also not looking uncomfortable).
Step 4: Break the scary components down.
If the history is strong, many people can identify exactly at what point the anxiety starts. It might be when the door is opened, when the key goes into the ignition, when the gears shift, etc. This is important because if we don’t begin addressing the anxiety at that point, but later in the chain, we risk sensitizing the dog (making the anxiety worse) and have it start earlier in the chain.
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© Can Stock Photo/Boarding1Now
When working through the individual training plan to address car sickness and anxiety, only move through the components that are scary for the dog if the dog is clearly comfortable, while being aware that this may look different in each individual dog
Step 5: Begin taking short trips and gradually build to driving to places with positive outcomes.
Start simply with driving down the driveway, and then around the block, to a nearby park, and so on. Many dogs only go for car rides when they are going to the veterinarian, and because that in itself can be scary, it is no wonder that they develop anxiety (projects like The Academy for Dog Trainers’ Husbandry Project and initiatives such as Fear Free Pets aim to change all of that!). As we proceed on resolving the anxiety, we want to provide some padding and opportunities for car rides that result in something the dog likes. For Hazel, that meant to a park around the corner for walkies, and for little Bailey it meant a quick drive to the tennis court, where she would meet and play with her housemate, Benny.
Step 6: Gradually increase the length of the car rides, interspersing short ones with longer ones.
We don’t want to undermine all our progress by taking radical jumps in duration. Hazel’s current vet is about a half an hour away, so we built up to that and included trips to a park that was about the same distance. We also concurrently worked on building +CERs to all things related to veterinary care, which I believe to be something very worthwhile for those dogs who have made a negative association there, as well.
Keep in Mind
1. For dogs who have a mild fear of getting into the car, training an alternative behavior in the form of a differential reinforcement of an incompatible behavior (DRI), such as hand targeting, can work very well. See video, Car Phobia (Your Pit Bull and You, 2015) for a short example of this, as well as a brief overview of my work with Hazel.
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BARKS from the Guild/September 2018
23
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2. The longer the negative association, or -CER, has been able to build, the more likely you are to have to break down more of the components. Pay careful attention each step of the way and always remember the Push, Drop, Stick rules when writing your training plan, as you may have to insert some splits, or extra steps, along the way. 3. According to Dr. Szumel, starting anti-nausea meds can be very important with puppies right away as the longer they are getting sick, the more likely they are to develop anxiety. Her advice is to get started before the -CER really has a chance to set in as this can often make the process easier. To that end, my work with little Bailey did proceed much more quickly and with fewer splits and setbacks than my work with Hazel, as the anxiety had less time to dig in and puppies tend to be more resilient. 4. Avoid getting lured into “can’t hurt, could help” solutions. The internet is rife with information that can actually delay success and cause a worsening of symptoms in the meantime. Always speak to a veterinarian first, and consider medications where appropriate. Using medications only as a last resort may actually not only delay improvement, but cause a worsening of symptoms. 5. Use situational medications as per a veterinarian’s advice when car rides are unavoidable, as this can help protect your training and allow you to continue moving forward and avoid setbacks. Dr. Szumel concurs on the use of situational (anti-anxiety) meds for car anxiety and replied that the use of Alprazolam (Xanax), Trazodone, or a combination would be appropriate for people who needed to have their dogs travel while working through a training protocol. This can help protect the training as you go. n
training...It is critically important that we only push to a harder step on a clear +CER. Resources
Yaletown Dog Training. (2017). Push Drop Stick Rules – a way make your training more efficient. Available at: bit.ly/2JxNKRX Your Pit Bull and You [Video File]. (2015, May 25). Car Phobia. Available at: youtu.be/bkzT6em0Q18 Lori Nanan is the owner of LoriNanan.com (lorinanan.com), which provides online courses for dog owners and dog professionals, as well as support services for positive dog trainers. She is also a staff member at The Academy for Dog Trainers and is the founder of the nonprofit Your Pit Bull and You (yourpitbullandyou.org). She lives in New Hope, Pennsylvania with her husband and their dog Hazel, who is her best friend and greatest teacher. BARKS from the Guild/September 2018
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training
The Art of Communication
Debbie Bauer explains everything you need to know about double merles, and how to help
clients with deaf, hearing-impaired and/or blind dogs connect with and train their pet
Y
Photo © Debbie Bauer
Photo © Debbie Bauer
Treasure works on a puzzle toy: for dogs who are both blind and deaf, owners can teach all the usual cues as tactile signals, i.e. signals the dog can feel
Blind and deaf double merles: Sheltie, Treasure (left) and collie, Vinny enjoy the same activities that other dogs enjoy
ou may have heard the terms double merle, lethal white, double dapple, or double dilute. These are all commonly used terms to describe a dog that has been born with two copies of the merle color pattern gene. The technical term is homozygous merle. It means that a particular puppy received a copy of merle from each of its parents. Merle is a pattern in a dog’s coat that creates a mottled coloring. There are many breeds that can carry merle. Some of the most common are Australian shepherds, Great Danes, collies, Shelties, Chihuahuas, Dachshunds (called dapple), and there are many more. With the rise in purposely breeding mixed breed dogs, the merle pattern is being seen now in breeds that it was not seen in before, and in many mixes of these breeds. It is difficult to tell just by looking if a dog is a double merle, although there are some signs that could point in that direction. Many are mostly white and may have splotches of color. But not all white or mostly white dogs are double merles. Double merles often have visual and/or hearing impairments, although not all white dogs with impairments will be double merles. If both of the dog’s parents are merle, and the puppy is mostly white with impairments, chances are it is a double merle. But the only true, foolproof way to tell is to have the dog genetically tested. There are more and more double merles showing up in rescues, shelters, and homes. You may be seeing them online, at the dog park, or in training classes. With the exploding popularity of merle in various breeds and mixes of dogs, many people are breeding without carefully considering genetics and the responsibility of their decisions. The visual and/or hearing impairments found in double merles can range from slight to being completely affected. Double merles are also totally preventable. Yes, we, as a dog-loving public, can prevent puppies from being born this way. The key is education. Merle is a beautiful coat pattern that many people find highly desirable. A merle colored puppy only needs one
merle gene. So, a solid patterned dog bred to a merle patterned dog can produce merle puppies with no chance of double merles being born. It is only when two merle dogs are bred together that the dice are rolled and double merle puppies can be produced. In my experience, most people living with merle dogs do not know this. Neither do people living with breeds of dog in which merle is common.
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BARKS from the Guild/September 2018
Communication
With the popularity of adopting dogs, many people are coming across double merles needing homes and are quick to jump in and adopt. This is especially true when there are heart-grabbing stories about puppies that are visually and/or hearing impaired. It sure pulls at the heart strings. Many adopters are not prepared for how to communicate in a different way with dogs that are visually and/or hearing impaired. As the newness wears off, reality will set in. Can you imagine living with a dog and having no way to communicate with him? Most of us communicate with our dogs all day long in one way or another. Imagine if you didn’t even know where to begin. How difficult would that be?.
Deaf Dogs
training
Deaf dogs learn hand and body signal cues very
easily. Training programs utilizing luring in early There are many degrees of deafness. A dog can be completely deaf in one or both ears. He may be partially deaf in one or both ears as well, or stages of teaching can very easily fade the lure he may have any degree of hearing loss in any combination. If there is and continue to use an adapted version of the some hearing, it is important to realize that the dog may notice a sound, hand motion as the new signal cue. This is an but not be able to pinpoint where it was coming from or what caused it. easy way for adopters to teach new behaviors. If the dog has usable hearing, use that to its fullest in communication. It may require some experimenting to find out what the dog can hear well enough to use for training. For example, a dog may be able to Clickers or verbal markers work very well. Sometimes adopters may be recognize a loud clicker, but not differentiate verbal cues. reluctant to talk to their dogs a lot in a new public class setting. An alterDeaf dogs learn hand and body signal cues very easily. Training pronative is for them to wear a small bell around their wrist or ankle to grams utilizing luring in early stages of teaching can very easily fade the help their dog keep track of them with all the commotion and noise lure and continue to use an adapted version of the hand motion as the going on in the room. new signal cue. This is an easy way for adopters to teach new behaviors. When teaching a blind dog to come when called, it is important to I do teach deaf dogs a marker signal – many people use a thumbs up continue calling or clapping until the dog gets all the way to its person. as a marker. A hand flash (closed fist opening quickly to a wide-open This provides an auditory signal the dog can orient to and follow. Otherhand with fingers spread) is also popuwise the dog may start out in the right lar. Some people advise using the flash direction, but then lose track of a perof a penlight. There is some controson who has gone quiet. versy as to whether this encourages Teach verbal cues that will help the unwanted behaviors of light and dog in everyday life – step up, step shadow focus/chasing. I prefer to use a down, wait, slow, go around, careful. hand signal marker, personally. These will go a long way toward buildIt is important to show adopters ing the dog’s confidence and helping how to teach and reinforce a deaf dog the adopter to learn to communicate for checking in with them automatiabout obstacles in the dog’s environcally. Each and every time the dog ment. Utilizing obstacle courses in class looks at them or comes to them, there is an excellent way to teach and pracshould be lots of reinforcement in the tice these cues. beginning to really instill in a dog that When feeding treats, it is helpful to he needs to keep his eye on his person. always feed in the same place around This is important for communication. A the dog. I always present treats in front deaf dog that checks in often will be of the dog’s nose. This way the dog aleasier to give a cue sign to. Obviously, a ways knows where the treat will appear deaf dog must be looking in order to after a click or verbal marker. This will see a sign. help cut down on the amount of time In a class situation, it can be helpful the dog spends sniffing and searching to place deaf dogs in areas of the room all over the air or floor, and it will also where their backs are not to a doorway decrease any snapping at the treat. or the other students so they can Teach the person to hold the treat still gather information about their surand present it in the same place in roundings with their eyes. Trying to get front of the dog each time. them to face away from the activity is hard for beginner dogs and people. AlPhoto © Debbie Bauer Blind and Deaf Dogs lowing them to see is important for Vinny the blind and deaf collie poses with one of his many trick dog With dogs that are both blind and deaf, their comfort levels. If the dog is overtitles I use a combination of the above tips. I stimulated by what he sees, utilizing do teach an automatic check in although screens can be helpful, gradually opening them as the dog is more comthis looks a bit different than a deaf dog looking back at me for informafortable and able to focus on his person. tion. A blind/deaf dog will actually come over to me and often touch me Blind Dogs as a check in. I always reinforce this. The side effect is that I have dogs that may seem underfoot or that poke me often. This can sometimes be Just as with deaf dogs, blind dogs can have a huge range of visual abilifrustrating to new adopters as they teach this exercise. Be prepared to ties. Some may have no eyes at all. Some may have only tissue showing coach them and remind them that this is how their dog gathers informabut may be able to sense the difference between light and dark. Others tion. may see shapes and movement. Some may be able to see certain conFeeding treats in front of the dog in the same position is important trasts or at certain distances. Others may appear to see fine in most sithere too. You can teach all the same cues as tactile signals. Use signals uations but can be unable to see in bright sun or to distinguish depths the dog can feel. For example, my tactile cue for step down (as in a flight properly. of stairs or a curb) is a quick double tap at the bottom of the front of my Surfaces are very important to blind dogs. Some surfaces may be dog’s chest. He will immediately search low to find the drop off and will new and scary, such as tile floors, or scent-laden rubber training mats. then step down. My marker signal is tactile also. Floors that have highly contrasting colors or patterns or hard shadows Depending on how the class is set up, it is important to realize that can be confusing for a dog that can see a little bit but not well. blind and blind/deaf dogs are not always good at recognizing and reIf the dog can hear, use that in all ways when training a blind dog. BARKS from the Guild/September 2018
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training
sponding to the body language of other dogs. If the exercises in the class involve greeting or interacting with other dogs, proceed cautiously. Blind/deaf dogs can and do greatly enjoy dog-dog interaction. Just like any dogs, however, they can be overwhelmed, or can show bullying type behaviors. The difference is that they don’t always recognize the other dogs’ signals, so cannot adjust their interactions accordingly. It is unfortunate that double merles are usually born with visual and/or hearing differences. Hopefully, one day soon, education about this issue will be more widespread and there will be no more double merles being born. There are many people working hard to get this message out and helping to teach adopters, rescues, and pet professionals how to help these special dogs. Having said that, it is important to know that blind, deaf and blind/deaf dogs are not helpless. Far from it. They enjoy exactly the same activities that other dogs enjoy, especially when we teach their people how to communicate with them effectively. n Debbie Bauer HTACP is the owner of Your Inner Dog (yourinnerdog.com) in Effingham, Illinois and has over 25 years of experience teaching and consulting with dogs and their people. She is known worldwide for her expertise in working with dogs that are blind and/or deaf. She is also the author of several books and keeps an informative and fun blog, The White Dog Blog (your-innerdog.blogspot.com) about life with her blind and deaf dogs. She has also trained dogs in a variety of fields, including therapy work, flyball, herding, obedience, agility, musical freestyle, conformation, lure coursing, tricks and scent work.
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BARKS from the Guild/September 2018
When teaching a blind dog to come when called, it is important to continue calling or clapping until the dog gets all the way to its person. This provides an auditory signal the dog can orient to and follow. best of Bringing the stry to the pet indu nd share a a ch t, chuckle BARKS Podcasts is the international e-radio web-casting arm of PPG, showcasing global news and views on force-free pet care. Join hosts Niki Tudge and Louise Stapleton and their special guests every month!
barksfromtheguild.com/podcasts
training
Training the Wild Friends at Best Friends
Vicki Ronchette talks training tortoises to target and station, thinking outside the box to find
high value reinforcers, and the importance of working with different species to improve
mechanical skills
W
Photo © Vicki Ronchette
Via clicker training, the workshop tortoises were quick to learn to target and trainers were quickly able to add duration to the behavior
hen I received the phone call last year asking me if I would teach three workshops for PPG’s inaugural Training and Behavior Workshop at Best Friends Animal Society in Kanab, Utah, I immediately said yes. How could I not? Visiting Best Friends is on the bucket list for many people and I had been interested in seeing this amazing place for a long time. I also felt a little bit of pressure as the quality of instructors I would be teaching alongside was more than impressive. Nevertheless, I still had to say yes. My assigned area was Wild Friends at Best Friends Animal Sanctuary. Wild Friends is the area that cares for animals that don’t obviously fit into one of the other areas, such as Dogtown or Parrot Garden. As in all the areas, animals come and go. They are accepted into the program and many are adopted out, if they are adoptable. What makes Wild Friends different is that you never know what species will be there. I was told they had raptors, chickens and reptiles at the time, but that it could change any time. Teaching at a big workshop or conference can be
Photo © Vicki Ronchette
Learning to effectively deliver reinforcers like greens and grape pieces while working with a completely new species can be tricky, but is an excellent skill for trainers to have
stressful enough, but to not know what animals I would be working with was a whole other ball game. In order to keep it simple and workable, then, I created a workshop that would work with just about any species. When I arrived in Kanab, Chirag Patel, who was also hosting workshops in the Wild Friends area, and I were taken on a tour of Best Friends including the Wild Friends area, so we could see which animals might be options for us to work with. There were a lot of wonderful animals and it was hard not to want to work with all of them. There was a gorgeous red-tailed hawk, one of my favorite species and a bird I love working with. However, using a non-releasable wild bird of prey in a workshop to work with 10 people is not a great idea. We would have spent the entire time just working on the bird being comfortable with us standing around. There was also a beautiful Peking duck that had an issue with chasing people in his enclosure. I really wanted to work with him and immediately had ideas of incompatible behaviors we could train to help with this behavior. But again, with one duck and 10 people
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training
Photo © Vicki Ronchette
Photo © Vicki Ronchette
Photo © Vicki Ronchette
For the tortoises, reinforcers come in the form of dandelion greens and chopped-up greens, and, very occasionally, fruit if something of higher value is needed (see photo, center, with Thar, who was initially not so interested in the food)
I was concerned about how that would flow in a workshop setting. As we continued through the tour, I saw pigeons and doves that I thought could be a possibility. We also met the chickens and Chirag decided to work with them in his workshop. Then, as we reached the end of the tour, we met the tortoises. There were 10 tortoises in a habitat that was perfect for a workshop. People could easily have access to the tortoises, and there was no need for protected contact so we could be inside the separate areas. I knew immediately I wanted to work with these animals. I think the caretakers thought I was a little crazy when I said this, but I have worked with tortoises in the past and knew I could make this work.
First Approach
My workshop was titled Approaching, Training and Bonding with Rescue Birds (oops, not birds after all!). I was only a little concerned that people would be upset when they found out we would not be working with birds because I knew that they would be excited once they met the tortoises. My plan for the workshops was for people to think about how they initially approach and meet the animals they will be working with, so rather than going straight in and trying to start training immediately, I encourage people to use that time to build a relationship by approaching thoughtfully and watching the animal’s body language. Once we assess that the animals are relaxed, then we can consider beginning our training. From there, we need to talk about reinforcers. For tortoises, these come in the form of dandelion greens and chopped-up greens. Then, we would work on training two behaviors, targeting and stationing. I also asked the Best Friends animal caretakers if there was anything we could work on that would be helpful to them or beneficial to the animals and they told us about one overweight tortoise who they thought could benefit from recall training for exercise. During the first workshop, we worked with whichever tortoises the
It is very possible to pressure and overwhelm an animal even when you are trying to offer food and train using positive reinforcement, so it is important to wait until the animal is ready. 30
BARKS from the Guild/September 2018
caretakers felt were the most food motivated. Attendees were divided up into three groups and each group worked with one tortoise. These animals are comfortable with people and have a lot of space in their enclosures, so it was easy to approach and work with them. With every tortoise we worked with it took a little time to get them to take food, but this was fine as it is all part of the process. It is very possible to pressure and overwhelm an animal even when you are trying to offer food and train using positive reinforcement, so it is important to wait until the animal is ready. All the tortoises were taking the food quickly, so we introduced the clicker and started working on our targeting and stationing behavior. I was beyond impressed with how the animals did and how quickly the attendees took to working with tortoises. I was also happy – but not surprised – at how much they enjoyed working with them, even though they may have been an animal they wouldn’t previously have thought could be very exciting. For the second workshop the following day, I wanted to try and work with new animals. I asked the group what they thought about this, and if they would be willing to work with tortoises that had been labeled “not food motivated.” To my delight, everyone wanted to give it a try. I asked the caretakers if we could use fruit as it may be a higher value reinforcer. At Best Friends, they do not feed fruit often because of the sugar content, but agreed to let us use it as long as it was not every day with the same animals, which worked out perfectly. One tortoise, Thar, was still not very interested in the food, so I asked if his group wanted to try working with another tortoise. Two people in the group decided to move on, but one person, who has turtles at home, asked to continue working with Thar. And indeed, she got Thar eating and successfully had him targeting and stationing. Another!
I feel strongly that our training and mechanical skills can be greatly improved by working with different species...Some people question whether tortoises can be trained, but all animals can learn and these little dinosaurs are no different. One thing that I really enjoyed seeing was the animals we had worked with on the first day come rushing out to greet us as soon as they saw us the next time. They were asking to be trained again! During the last workshop on the final day, we trained both sets of animals that we had used the previous two days. Again, we had a day of successes and were able to add some duration to the stationing behavior as well as duration to following the targeting. Two people worked on the recall with the one tortoise who needed more exercise and I was thrilled to be able to leave her and her caretakers with that skill. For me personally, teaching these workshops and working with the tortoises and their caretakers was an amazing experience. I feel strongly that our training and mechanical skills can be greatly improved by working with different species. To see people discover this with the tortoises was incredible. Watching the tortoises go from being still and suspicious to being so quick that attendees had to rush to deliver reinforcement in a timely manner was a great learning opportunity for all of us. Also, being required to work out the challenge of delivering reinforcers like greens and grape pieces while working with a completely new species can be tricky, but a great skill to have. However, the best part of all was seeing people fall in love with tortoises. Some people question whether tortoises can be trained, but all animals can learn and these little dinosaurs are no different. I am thrilled to have been able to introduce this group of talented trainers to these sometimes unappreciated animals. n
training
Photo © Vicki Ronchette
On the final day of the workshop, trainers were able to add some duration to the tortoises’ stationing behavior as well as duration to following the target
Vicki Ronchette began training dogs in the late 80s and has competed in various dog sports with her own dogs obtaining several titles. She has attained multiple animal training certifications including CPDT, CAP2, CNWI and is the owner of Braveheart Dog Training (braveheartdogtraining.com) in San Leandro, California, which offers conformation classes, workshops and webinars, as well as bird training and behavior consulting. She is also author of Positive Training for Show Dogs – Building a Relationship for Success, From Shy to Showy - Help for Your Shy Show Dog, Ready? Set. SHOW! – A Handbook for Dog Shows and has written numerous dog training articles. In addition, she has been a raptor handler with California-based Native Bird Connections, and has worked with a variety of animals, including dogs, cats, parrots, chickens, raptors, goats, corvids, doves and tortoises.
training
Getting on Their Level
Emily Cassell explains why rabbits don’t like being picked up, and how to implement
“
a desensitization/counterconditioning protocol to help them feel more comfortable
with being handled
So, who’s cranky?” It’s the first question I ask when I begin a volunteer shift at my local shelter. I like to give the “pocket pet” staff a break from their “problem children,” and offer to clean the cages of the rabbits (it’s always the rabbits) who give them a hard time. After they point out their scary bunnies, I follow up by asking for a description of exactly what’s going on with each individual. Typically, I expect issues with “cage aggression,” a label used to describe rabbits who thump, growl, lunge, bite, box, and/or scratch at the human hands that invade their home. Typically exhibited by does (female rabbits), cage aggression is completely normal behavior. A female’s natural instincts to defend her nesting chamber from intruders often transfers to the cage, pen, or run where the rabbit lives. Naturally, it’s quite difficult (and surprisingly scary) to clean a cage while a seemingly adorable rabbit attacks your hand with lightning-fast strikes of chiseled teeth. However, it is not always cage aggression that staff are referring to when they describe a rabbit as problematic. “He’s fine, he just struggles and thumps when we try to pick him up,” they might say. Over time, I am pretty sure my response has turned into a bit of a spiel, as my approach to this “problem” is very different from my approach to other undesirable behavior. In the case of cage aggression, for example, the rabbits are likely to intensify their aggression as the aversive situation (i.e. cage cleaning) happens day after day. Threat displays are likely to escalate to bites as the animal’s warnings are ignored, and animals that bite in a shelter could potentially be in a life-threatening situation. Obviously, those behaviors need to be addressed. If a rabbit doesn’t want to be picked up, though, I view the issue quite differently. My goal has nothing to do with the rabbit’s behavior and everything to do with education. If a potential adopter comes in and is disheartened by not being able to hold a rabbit, then a rabbit is likely not the pet for them. But wait! Aren’t rabbits the poster children for cute and cuddly? Don’t people hold them all the time? Sure. People do a lot of things with their pets all the time. It doesn’t necessarily mean the animals are enjoying it. To understand why, we need to go through a little natural history lesson first.
Prey Animal
Rabbits are the “fast food” of the animal world. They exist on every continent except Antarctica, and just about everything preys on them, from large animals like wolves and lynx all the way down to birds of prey, snakes, and foxes. Although it is not the most glamorous position in the food chain, it is undeniable that rabbits play a critical role in the natural world. This does not mean, however, that they haven’t developed some
Typically exhibited by does (female rabbits), cage aggression is completely normal behavior. A female’s natural instincts to defend her nesting chamber from intruders often transfers to the cage, pen, or run where the rabbit lives. 32
BARKS from the Guild/September 2018
Photo © Emily Cassell
Cage aggression is a normal leporine behavior and likely to intensify, often escalating to bites when warnings are ignored, as an aversive situation such as cage cleaning continues happening day after day
pretty amazing adaptations to protect them in that role. Rabbits are well known for their ability to, well, multiply like rabbits. They are not however, well known for maternal care. Indeed, every spring wildlife rehabbers are plagued with baby bunnies that were “abandoned” and then “rescued” by well-intentioned animal-lovers.. Yes, that’s my little PSA: leave baby bunnies in their nest! This behavior transfers to domesticated life as well. When litters are born in the shelter, mom often chooses to rest as far away from her kits as she can. This “paws-off” approach to motherhood also means that?
Domestication
Another factor to consider in all of this is the domestication of rabbits. With the exception of dogs, cats, and horses, domesticated animals were bred for some sort of product rather than companionship, including rabbits. Rabbits were originally bred for their meat and pelt. Later, breeding became more focused on laboratory use, and, most recently,
rabbit showing. While dog breed standards often include a few notes on temperament, rabbit breed standards focus entirely on physical traits. Breeding for companionship is really only a recent development in the history of rabbit domestication. Many pet rabbit breeders will handle the kits from birth to help them feel more comfortable when being picked up, but the vast majority of the pet rabbit population did not get this early advantage. With all of that being said, there are plenty of rabbits who enjoy being held and loved on by their humans, and don’t mind being picked up. However, I would say these are the exceptions. The majority of bunnies will struggle and kick out on the way up, which is dangerous as their back feet are so powerful that they can kick hard enough to break their own backs. If a bunny manages to get away in the struggle, the human typically receives a disapproving “foot flick” towards the face as he runs off. For a prey animal, negative reinforcement, or escape, is an incredibly powerful motivator. It is literally how a bunny learns how to survive, so escape is the ultimate reinforcer. If a bunny is being picked up, struggles, and gets away, the rabbit may view his escape maneuvers as lifesaving. Considering the danger in the struggle itself, this is a big problem for a bunny guardian to have. When I work with rabbit owners who complain that their rabbit doesn’t like to be picked up, my first question is, “Why does he/she need to be picked up?” and we typically work on the rabbit voluntarily participating in whatever it is that the human is trying to achieve. However, a rabbit will inevitably need to be lifted at times throughout his life, so it is important to put in the work and ensure bunny is comfortable with it.
Desensitization/Counterconditioning
Like most fears, the best way to approach this is with desensitization and counterconditioning (DS/CC). Like all DS/CC programs, the process for picking up bunny is slow and tedious. If bunny doesn’t even like to be touched, the process is that much longer. For the purposes of brevity, I will overview my experiences with my current rabbit. I will preface by saying that these guidelines are by no means comprehensive, and, of course, each animal is an individual and will require an individualized approach. I adopted Tula about a year ago. She was a stray who had been successfully avoiding escape for about three months before being rescued
Photo © Emily Cassell
When kept as pets, rabbits may struggle when being picked up; their back feet are so powerful they can kick hard enough to break their own backs with escape becoming the ultimate reinforcer
training. from the vegetable garden she was raiding. Basically, then, Tula was a wild bunny for at least three months before I got her, and I’m not sure where she was before that. I feel pretty confident that she was somebody’s pet, though, because after day six of being in my home, she decided we were friends and solicited petting from me. I had not touched her up to that point. From that moment on, she was an incessant attention seeker who really loved being touched. So, that was our starting point. When rabbits groom each other, it is mostly on the face, right between the eyes. A rabbit is typically the most comfortable with touch between the eyes and on the top of the back. For the purposes of picking up, desensitization needs to happen on the sides, belly, rump, and bottom. When beginning training, I always advise rabbit owners to stop picking up their rabbit completely unless there is an emergency…but make sure there isn’t one! When petting Tula, I began to slowly let my hand expand from her back down to her side. I started with a stroke where I let my fingers gently drape down about level with her shoulder, then over her ribs, and gradually lower and lower. Once she was comfortable with me touching her side where her belly met the floor, I would slide one finger just slightly under her middle. Eventually, I used my whole hand, and moved it under her belly while she laid on it. At this point, the purposes of my desensitization were about being able to check her incision post-spay. Once she had the surgery, I waited a week (to allow healing to begin) then began checking the incision daily. That work had been really successful, so we went to the next step. Other variables I began to work into Tula’s desensitization work were two hands on her body instead of one, touching her rump, and my hands not moving on her back. Finally, I gradually began to do little lifts
Photo © Emily Cassell
Whether born in the wild or in a shelter or home environment, mother rabbits often choose to rest as far away from their kits to avoid drawing attention to the nest
BARKS from the Guild/September 2018
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training
Photo © Emily Cassell
Desensitization and Counterconditioning
Photo © Emily Cassell
Mother rabbits do not pick up and carry their kits. This means that the only time a wild rabbit is picked up is when a predator is doing it. As such, many pet rabbits are not comfortable with being picked up, but will inevitably need to be lifted at times throughout their life, so it is important to put in the work to make sure they are comfortable with it. As with any desensitization and counterconditioning process, this can be slow and tedious, and will vary between individuals. As rabbits are typically the most comfortable with touch between the eyes and on the top of the back (top left), author Emily Cassell started the process by slowly letting her hand expand from rabbit Tula’s back down to her side (top right). Other variables she worked on were two hands on Tula’s body instead of one, touching her rump, and her hands not moving on Tula’s back (bottom left). Finally, she gradually began to do little lifts with Tula’s front end (bottom right). She is now able to lift and move Tula short distances without stress.
Photo © Emily Cassell
with her front end. I first applied a little pressure as if I was going to lift, and before long, I could support her front end with one hand and pet her with the other while she was totally relaxed. Continuing on that work, I am able to lift and move her short distances without stress.
Solid Ground
Being carried and being held are two separate behaviors that have to be worked independently, but, in my case, I choose to not work them at all. Rather than carry Tula, I have taught her to crate herself or to “shift” from one place to the other by hopping there. As far as being held, I will teach a rabbit to hop into my lap, but they often don’t enjoy balancing on the unevenness of a person’s lap. I usually just get down on my bunny’s level and spend time with them on solid ground, where they are comfortable. When it comes to being held for other purposes, I teach whatever behavior is needed. Tula and I are currently working on a voluntary nail trim, and she has learned to take medications voluntarily. In an emergency situation, it may be necessary to hold bunny when he is not comfortable with it, but there are still ways to reduce his stress. The most important thing to avoid is chasing the rabbit. Chasing 34
BARKS from the Guild/September 2018
Photo © Emily Cassell
a prey animal really amps up their stress level, and if they are successful avoiding capture, they view it as such. The best way to avoid a chase is to stroke the bunny before picking him up. Often, they don’t run off, making it easy to quickly press them to your chest to prevent them from injuring themselves if they struggle. If bunny needs to be held for longer periods, like for taking medications or syringe-feeding, securely wrapping his body in a towel is a safe, effective alternative. If bunnies don’t enjoy being held and snuggled, then, what do you
Rabbits are the “fast food” of the animal world..?
training
do with them? Get on their level! Sitting and hanging out with bunny is a great way to begin an interaction. Rabbits are curious and highly social, and bond closely with their families. While learning to be comfortable when being picked up is an essential husbandry skill, it isn’t necessary for bonding with a rabbit. It isn’t necessary to pick up many of the animals we train, yet we are able to still build strong relationships with them. Relationships of any kind require understanding of and by those involved, so learning the likes and dislikes of an individual are the best ways to build a strong foundation. I feel the work involved in earning the trust of an animal who, at the bottom of the food chain, has no reason to trust anyone, makes the relationship all the more special. You can totally snuggle your bunny…once you’ve earned it! n
Emily Cassell is a zookeeper and professional pet trainer based in Tampa, Florida. She began her career in 2010 with dogs before expanding to fish, guinea pigs, cats, rabbits, and other pets while operating her own training business, Phins with Fur Animal Training (sites.google.com/site/phinswithfurtraining/home). While pursuing a degree in Animal Science at the University of Florida, she worked with Class Act for Dogs in Gainesville before returning to Tampa to work at Courteous Canine, Inc. After completing internships with Tampa’s Lowry Park Zoo and Clearwater Marine Aquarium working with manatees, dolphins, otters, and birds, she landed a job as a full-time keeper and trainer at one of world’s most respected zoological institutions, located in Tampa. Her primary responsibilities now include orangutans, tigers, gibbons, bats and various other species. Despite her career with much larger animals, she has always maintained an interest in small pets. She has presented multiple webinars and written various articles on small pet care and behavior. In addition, she operates Small Animal Resources (facebook.com/smallanimalresources), a service providing free help for those needing assistance with small mammal care as well as private behavior consultation for small pets.
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BARKS from the Guild/September 2018
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avian
A Long-Term Solution
Lara Joseph details her behavior modification plans for an umbrella cockatoo who was
screaming and self-mutilating due to inappropriate enrichment, and the importance
of consulting with a behavior professional with knowledge of the species – rather
I
than taking advice for free
n this article, I am going to share details of a behavior modification plan that epitomizes the importance of consulting with a professional who has specific knowledge and understanding of the relevant species in any individual behavior case. Let me introduce you to Abbey, the male umbrella cockatoo. (Just to explain, the gender of most parrots is determined via a blood draw, but in this instance, Abbey's blood draw took place after he was named.) At one of the zoos I consult with, I noticed one day the arrival of an older, rehomed, umbrella cockatoo. I inquired about his history, and learned that he came from a family who no longer had the time for him. I was curious, so asked for details about how the zoo cared for him currently. They told me there was one keeper who was consistently getting Abbey out of his cage on a daily basis. News of this social interaction was joy to my ears as I know what social parrots cockatoos are. Nevertheless, I warned the keeper how important it was to keep a balance in Abbey’s daily life so he had time with other people as well as time on his own to forage and interact with different forms of environmental enrichment. I also made sure she was aware that cockatoos can bond to one person very quickly. The keeper told me that Abbey sat on her shoulder while she worked. Well, I have my own opinion about parrots on shoulders, especially if you haven't taken the time to understand them:. The next time I consulted at the zoo, I decided to stop and visit with Abbey again. He was in his cage chewing on a large box at the bottom of the cage. I sighed. I had suggested enrichment and they had given it to him, but this particular form was reinforcing a behavior sure to bring about behavior issues. As parrots sexually mature, they may want to engage in the natural behavior of breeding and rearing their young. Trying to prevent or redirect a natural behavior of an undomesticated, complex, social animal can keep you on your toes where you are consistently having to redirect behavior. Boxes, dark corners, closets, covers,. 36
BARKS from the Guild/September 2018
Photo Š Lara Joseph
Umbrella cockatoo Abbey started self-mutilating after his keepers followed advice from an inexperienced trainer who told them to reduce his food and isolate him because of his screaming
and drawers are all areas likely to draw the attention of a sexually mature parrot. They are all potential nesting sites, but are usually not areas and behaviors the average companion parrot caretaker is aware of. Providing boxes as enrichment can lead to undesirable behaviors such as lunging at people, biting, flying, and biting people walking by, in addition to medical concerns. Also, providing or allowing time in nesting sites often causes a parrot to become protective of the area. This is a natural behavior. I informed the zoo about my concerns and suggested foraging toys and other enrichment that hung from the cage top instead of boxes on the cage floor.
Nesting
The next time I stopped in at the zoo, there was another box in the bottom of the cage. I approached the keeper again, and she told me she was not there every day, so was not sure who put it in his cage. She did
tell me it was keeping Abbey busy and that was their plan. I mentioned to her there is a familiar pattern of a parrot losing his or her home. It goes like this: The new parrot is exciting. The parrot gets out of the cage the majority of the day and gets used to being with people. Then real life starts again, and the parrot starts spending more time back in his cage. He isn't used to this and begins screaming for attention. People unknowingly reinforce the screaming with attention and inadequate enrichment. The parrot is then likely to start searching for other enrichment such as pulling up papers on the cage bottom and creating nesting material. Whenever the bird does get out, nesting behaviors have now been reinforced, and anyone who comes into close contact with the preferred person will get bitten, or even the favored person may get bitten. That person then becomes afraid of the bird and, from then on, he is in his cage where he will spend the majority of his time from then on. A few months later I was called in to the zoo due to a serious concern with Abbey. I could see immediately that he had begun mutilating his chest. Unfortunately, this is more common with cockatoos, African Greys, and parrots, but not limited to these species. After making some inquiries, I found out they had taken the advice of an inexperienced trainer – because it was free. The information they were given was to reduce Abbey’s food and to isolate Abbey due to his screaming. Sadly, I informed them this was the worst thing they could have done. I immediately put two behavior modification plans into place, one for the screaming and one for the mutilating. I worked with all of the keepers explaining the screaming modification plan, and it took effect within the first five minutes. Abbey was screaming for attention, so we picked any other, acceptable vocalizations and reinforced them with a continuous schedule of reinforcement that included attention, talking back to him from a distance, and proximity to him. The behavior modification plan I suggested for the mutilating behavior was not going to be as easy. I suggested moving Abbey back to the area he had been in before the mutilating began. This was also a place where he would have more access to people to help create distractions to keep him busy, rather than be preoccupied with his chest. Unfortunately, they said they couldn't do this, so I had to work with what I had. To start with, I suggested stopping the delivery of the majority of the treats the keepers handed to him as they walked by and, instead, putting those treats into foraging toys so he could only get them by working for them. This needed to be consistent and done numerous times throughout the day. I informed the keepers that this was extremely important and should be of highest priority.
Emotionally Involved
I called the zoo two days later, and was informed the mutilating behavior was getting worse. The keepers admitted they couldn't give their attention to creating the foraging toys I had advised, and told me Abbey was now taking his food and placing it into the hole he had created in his chest. I understood the keepers’ in-
avian
...the mutilating behavior was getting worse. The keepers admitted they couldn't give their attention to creating the foraging toys I had advised, and told me Abbey was now taking his food and placing it into the hole he had created in his chest.
ability to dedicate the time to the toys. Unfortunately, I also noticed a decrease in the ability to divert Abbey from his chest. The behavior had increased dramatically. I got him out of his cage, and even when standing on my arm, he was more focused on his chest than on the attention I was giving him. This increase in attention he was giving to his chest was the behavior I was most concerned with preventing. In this video, Baseline behavior of Abbey, the mutilating cockatoo, you will see Abbey’s tongue clicking, which occurs in correlation with nesting behaviors. You will also see him trying to maneuver my hand to sexually selfstimulate. When not allowed to do either, he quickly reverts back to his chest. All the keepers were emotionally involved at this stage, as was I. I told the zoo I strongly recommended Abbey move to an environment where he could get individualized attention, and that this could not happen fast enough. The next day they agreed, so I started making arrangements for Abbey to come to my training center. When she found out about this, a client of mine, Shellie, offered to take Abbey on the condition that she could consult with me on a daily basis. Not bringing Abbey into my direct care and allowing him to go to someone else was a very emotional decision for me to make, but I knew if I brought him under my direct supervision, the quality of care I could give to my other animals would suffer. I didn't want to do that to them, so I agreed for Shellie to take Abbey. The next day, off he went. I cannot emphasize enough how significant this quick move was in this case. When Shellie got Abbey home, one of the first things she did was put a soft collar on him. Was the collar an aversive? A positive punisher? Yes, it was both of these, but the alternative of not using it was worse. We were all afraid of losing Abbey to infection. Even though we had medical advice from an avian veterinarian and a behavior modification in place, we were on pins and needles for the next several days. Each day I was receiving texts with photos and videos from Shellie along with her training notes. I would advise where needed. We introduced foraging opportunities immediately and tried to identify a variety of food reinforcers, which can be tricky with rehomed parrots. Active training was implemented within a few days as the list of food reinforcers grew and Shellie began Photo © Lara Joseph target training Abbey to touch a tarAbbey interacts with foraging toy, his replacement behavior for get stick with his beak. Then, she self-mutilating, while in his soft collar (worn as a temporary measure to allow the hole he had created in his chest to heal) started training tricks with the target BARKS from the Guild/September 2018
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avian Abbey, four months after intervention, no longer needs to wear his soft collar now his chest is healed and he has received a clean bill of health from the vet; replacement behaviors for the self-mutilation are firmly in place
Photo © Lara Joseph
stick. Next, she introduced him to the aviary which was full of visual, audible, and tactile enrichment. I watched the videos daily and felt very confident with her progress and dedication. Here we are, only four months later and the combination of quick action and a very detailed behavior modification plan has resulted in Abbey being on the mend. At the time of writing, Shellie had just been able to take off the soft collar. Over the past four months, she and Abbey have worked on creating many replacement behaviors and, more importantly, Abbey is with Shellie to stay. This video, Abbey's lack of mutilation after four months of behavior modification implementation, shows his progression with Shellie and the help she received via distance consulting. In the short run, it may be more expensive to consult with a professional. In the long run though, it is quite the opposite, as Abbey’s case demonstrates so resoundingly. When we know better, we do better, and there is a lot more room to do better in the quality of care we give to these incredible, loyal, intelligent, and social creatures. n
References
The Animal Behavior Center [Video File]. (2018, July 1). Baseline behavior of Abbey, the mutilating cockatoo. Available at: youtu.be/Pm9wAkkCV40 The Animal Behavior Center [Video File]. (2018, July 1). Abbey's lack of mutilation after four months of behavior modification implementation. Available at: youtu.be/C6CF3w0D2qY Lara Joseph is the owner of Sylvania, Ohio-based The Animal Behavior Center LLC (theanimalbehaviorcenter.com), an international educational center that focuses on teaching people how to work with animals using positive reinforcement and approaches in applied behavior analysis. She travels internationally giving workshops, lectures, and provides online, live-streaming memberships on animal behavior, training and enrichment. She also sits on the advisory board for All Species Consulting, The Indonesian Parrot Project, and is director of animal training for Nature’s Nursery, a wildlife rehabilitation center in Whitehouse, Ohio. She is a published author, writes regularly for several periodicals, and will also be a guest lecturer in the upcoming college course Zoo Biology, Animal Nutrition, Behavior and Diagnostics taught by Dr. Jason Crean at St. Xavier University, Chicago, Illinois.
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BARKS from the Guild/September 2018
Equine Social Structure
equine
Kathie Gregory examines the two groups of social organization found in Equidae, including
E
group structure, dynamics and relationships, and debates whether hierarchies within
groups actually exist
quidae have evolved into two groups of social organization over time. One group consists of Grevy's zebra (E Grevyi) and wild asses (E africanus, E hemionus); the other consists of the horse (Equus ferus), plains zebra (Equus quagga), and mountain zebra (Equus zebra). In terms of relationships, Grevy's zebra and wild asses tend to live alone amongst each other. Personal bonds between animals generally do not exist, other than between a mare and her foal. These species may or may not be in groups. Groups consist of different sizes and are made up of different ages and sex. They are variable and changes to the group may happen every few hours. Male stallions can have extremely large territories. Territorial boundaries are marked by dung piles to identify the territory, rather than to warn intruders. A stallion’s territory is a mating territory, so stallions are generally tolerant of other stallions in their territory. Disputes and fights are over females in estrus, typically when the female is near to boundary lines, and the fighting is between neighboring stallions. Once she has made a decision to walk into a territory the stallions stop fighting, with the resident of the territory following the mare, and the other stallion remaining at the boundary line. These species split up for part of the year, coming together for the mating season. The horse, plains zebra and mountain zebra, meanwhile, form permanent family groups, with less permanent stallion, bachelor, and peer groups. Young leave family groups at defined ages. There are no established territories, and movement is seasonal with the group relocating together. These species do not live in changeable temporary groups, neither are there solitary territorial males (Berger, 1977). Observations of feral and free range horses consistently show they belong to the group of social organization that form permanent groups. There are many preconceptions and myths around how horses naturally live, dating back to equine studies from the 1960s. Observations were accurate. However, there were, and still are, even in modern studies, incorrect interpretations of information. Firstly, in the 1960s, the human perception of animals was narrower and distinct in that their behavior was considered to be either dominant or submissive. This resulted in observational studies being written from that perspective rather than as a purely factual account. It is human nature to explain why things happen, and thus the popular viewpoint of dominance and submission was applied to what was observed. This led to the general public's perceived understanding of equine behavior. Some still believe dominance theory today, and studies, blogs, books etc., will be written from that perspective. Scientists have long tried to establish clear hierarchies when observing groups of horses and other animals. Thus, any interaction between two horses may be interpreted as one being dominant, the other submissive, and dominance hierarchies emerge as
Š Can Stock Photo/haak78
Scientists have long tried to establish clear hierarchies when observing groups of horses and other animals, yet studies often report that disagreements between horses in a social group are low key, with individuals being tolerant of each other
a theory. However, this simple, tidy explanation for what is a very complex social structure is incorrect. Any group needs cohesion and give and take in order to function effectively, and the lack of understanding of what was being observed led to this incorrect interpretation. As far back as the 1970s, there were those who found problems with this theory (Kiley-Worthington, 1977; Syme & Syme, 1979), but they were largely ignored, and the neat, easily measured dominance hierarchies informed the majority of observational reports. A further issue is that the definition of the terms, dominance and submission, is not clear or definitive. Rather, it is open to the individual interpretation of the researcher. Some define dominant as having greater reproductive success, a higher ranking, or priority access to food and water. There is no evidence to support these types of dominance and many studies have shown that these perceived goals horses are claimed to vie for simply do not exist. Time and time again, researchers report that there is no clear correlation between these supposed issues and dominance.
Environment and Habitat
Data is also dependent on what is being studied. Ethology is the study of species in their natural environment, but some studies have not adhered to this standard. Many studied equine groups that were not natural. Human intervention meant that the sex, age, and numbers within the groups were not what would be seen BARKS from the Guild/September 2018
39
equine
Studies by Rees (2017) show that there is no one mare who leads the group, and that any horse, including the youngsters, may initiate a change in movement or direction. The overriding factor for who initiates a change is driven by whoever is the most motivated. in the wild. Restricted and non-natural habitats are also an issue. These influence the social structure of the group, and subsequently any findings cannot be an accurate account of how equines live. Further, as is in the case of the first horse behavior study on New Forest Ponies (Tyler, 1972), the situation was manipulated to specifically cause altercations, e.g.: “Hay was supplied to the ponies in winter to provide competition, so that large numbers of threats could be recorded in a short time - far more than would be observed during 'normal grazing’.” In studies that have not been subject to manipulation, I have yet to find reports of dominance hierarchy. Disagreements are low key, with horses being tolerant of each other. This is true even in studies where food and drink restriction is part of the study parameters. The exception is studies that have starved horses before conducting experiments to determine ranking and dominance, resulting in strong agonistic responses between the horses in competition for food. These studies are inherently flawed because they manipulate and distort natural behavior. They also show a human flaw in that setting up a situation for a desired response is not a scientific study. It is impossible to draw any conclusions on how group social structure naturally functions from this type of study. However, this is exactly what has informed our perception of the social structure and interactions of the horse. Generally speaking, feral groups of horses are those that do not have human intervention, except where fences are put up to exclude the population from richer grazing land reserved for cattle. However, there are exceptions. Feral horses that live in areas that can only support so many, and without predators, can result in over population, necessitating human intervention. Free ranging horses, such as Exmoor Ponies, tend to have more human input and management, for example. Studies that observe feral populations without human intervention gather the most accurate data on social structure and interactions. The data then needs impartial interpretation, without attributing the observer’s beliefs to it, in order to understand how equines live. What has been determined from these studies is that equines form lasting social relationships within long-term family groups. Changes are due to few situations: • Youngsters leave their family group of their own accord, between the ages of two and four. • Those that do not leave by choice are eventually chased away, usually by their father. • Death of a group member. • A group is taken over by a competing stallion, the existing stallion is expelled.
Family Group Structure
The first incarnation of a group leader stated it was always the dominant stallion who leads the group. Some studies, however, found this not to be the case, stating that a dominant mare leads the group, deferring to the stallion when the group is threatened. Other labels are “alpha” and “boss.” A possible reason for some studies observing a specific individual who initiates movement 40
BARKS from the Guild/September 2018
Photo © Susan Nilson
Studies have shown that perceived goals horses are claimed to vie for, such as greater reproductive success, a higher ranking, or priority access to food and water, simply do not exist
could be due to those populations not being feral or not being a natural group composition. When there are very small groups, it is likely that an older, experienced horse initiates more movement than younger ones. These factors make it look like horses have one specific leader, but this is unnatural equine behavior due to the influence of external conditions and incorrect to apply these findings to all horse populations. Studies by Rees (2017) show that there is no one mare who leads the group, and that. Bourjade, Thierry, Maumy and Petit (2009) have reported the same in Przewalski's horses, as have Krueger, Flauger, Farmer and Hemelrijkc, (2013) in feral horses.
Family Groups
There is usually one stallion in a family group, along with a small number of mares (from one to five, the average being three), and their young (Feist & McCullough, 1976). A number of following studies observed the same groupings. However, Pusey and Packer (1997) observed groups of two to 20 or more horses. A study of the Kaimanawa wild horse groups in New Zealand from 1994 to 1997 observed stable groups of between two and twelve breeding adults, observing one to 11 mares. Changes to the groups were small: 83 percent of mares remained in the same group over a three year study period. Stallion numbers within groups ranged from one to four: 88 percent remained in their group for the duration of the study period. The average number of breeding adults in a group was between two and 8.4. (Linklater, Cameron, Stafford & Veltman, 2000). Mares usually stay a group, regardless of the size of the group. They spend more of their time with their friends than away from them, and engage in a number of reciprocal activities (Feh, 1987). Notable observations include: • Agonistic interactions increase when there is social stress. • There is also no evidence to support territorial dominance. • Horses defend their group, and mares in estrus, not their habitat. All in all, there is a wide range of variability between horse group sizes, composition, and the age when adolescents leave the family group. To some extent, group size is determined by population density. A more dense population of horses leads to smaller groups. Environment also influences the size of the group. A United States Geological Survey study (Ransom & Cade, 2009) reported that larger groups were found in more open, larger ranges, and smaller groups were observed where the habitat has dense vegetation or trees, and that predators may exert a third influence on group size, with highly predated areas giving rise to larger family groups of horses to increase safety. n Kathie Gregory is a qualified animal behavior consultant, presenter and author who specializes in advanced cognition and emotional intelligence. Passionate about raising standards and awareness in how we teach and work with animals, she has developed Freewill TeachingTM (freewillteaching.com), a concept that provides the framework for animals to enjoy life without compromising their own free will. Her time is divided between working with clients, mentoring, and writing. Her first book, A Tale of Two Horses: a passion for free-will teaching, was published in 2015, and she is currently writing her second book about bringing up a puppy using freewill teaching.
equine References
Berger, J. (1977). Organizational systems and dominance in feral horses in the Grand Canyon. Behavioral Ecology and Sociobiology (2) 2 131-146. Available at: link.springer.com/article/10.1007/BF00361898: bit.ly/2uwoWVf Feh, C. (1987). Etude du développement des relations sociales chez des étalons de race Camargue et de leur contribution à l’organisation sociale du groupe. University of Aix-Marseille, France: Thèse d’université Feist, J. & McCullough, D. (1976). Behaviour patterns and communications in feral horses. Zeitschrift für Tierpsychologie 41 (4) 337-71. Available at: bit.ly/2L7BFbi Kiley-Worthington, M. (1997). Communication in Horses: Cooperation and Competition. Eco Research Centre, University of Exeter, United Kingdom: Publication 19 Krueger, K., Flauger, B., Farmer, K., & Hemelrijkc, C. (2013). Movement initiation in groups of feral horses. Behavioural Processes (103) 91–101. Available at: bit.ly/2Ngf4Xw Linklater, W.L., Cameron, E.Z., Stafford, K.J., & Veltman, C.J. (2000). Social and spatial structure and range use by Kaimanawa wild horses (Equus caballus: Equidae). New Zealand Journal of Ecology 24 (2) 139152. Available at: bit.ly/2uunGln Pusey, A.E., & Packer, C. (1997). The ecology of relationships, in Krebs, J.R., and Davies, N.B., eds. Behavioral Ecology – An evolutionary approach p. 254–283. Malden, MA: Blackwell Publishing Ransom, J. I., & Cade, B. S., (2009). Quantifying Equid Behavior – A Research Ethogram for Free-Roaming Feral Horses. U.S. Department of the Interior U.S. Geological Survey. Available at: on.doi.gov/2IEO4lu Rees, L. (2017). Horses in Company. London, United Kingdom: J.A. Allen Syme, G.T., & Syme, L.A. (1979). Social Structure in Farm Animals. Amsterdam, Netherlands: Elsevier Tyler, S.J. (1972). Behaviour and Social Organisation of New Forest ponies. Animal Behaviour Monographs (5) 2 87-196. Available at: bit.ly/2LdMg1b
Resources. Available at: portals.iucn.org/library/efiles/documents/NS-024-1.pdf Skipper, L. (n.d.) The Myth of Dominance. Available at: ebta.co.uk/dominance-ls.html
BARKS from the Guild/September 2018
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pet care
Core and Non-Core Vaccinations In the second part of her two-part article, Lauri Bowen-Vaccare highlights specific
vaccinations, depending on the region, that are usually required to ensure dogs
I
stay healthy during a stay at a day care or boarding facility n the first part of this article, I discussed the importance of vaccination protocols and wellness exams in keeping dogs safe and healthy in boarding and day care environments. I will now go into further detail regarding the vaccinations that are usually required for a dog to attend a day care or boarding facility, as well as some of those that are region-dependent and are not usually required.
Core Vaccinations
These include: o Rabies (required to board and/or attend day care): • A severe and often fatal viral disease that causes acute inflammation of the brain and central nervous system in humans and other mammals. The primary way the rabies virus is transmitted to dogs in the United States is through a bite from a disease carrier: foxes, raccoons, skunks, and bats. • Rabies is zoonotic and can thus be transmitted to other species of animals and humans. o Distemper (required to board and/or attend day care): • A highly contagious and sometimes fatal viral disease that is seen in dogs worldwide and a wide variety of animal families, including domestic and wild species of dogs, coyotes, foxes, pandas, wolves, ferrets, skunks, raccoons, and large cats, as well as pinnipeds, some primates, and a variety of other species. • Animals usually become infected by direct contact with virus particles from the secretions of other infected animals (generally via inhalation). Indirect transmission (e.g. carried on dishes or other objects) is not common because the virus does not survive for long in the environment. The virus can be shed by dogs for several weeks after recovery. o Adenovirus (Hepatitis) (required to board and/or attend day care): • A viral disease that is caused by the canine adenovirus CAV-1, a type of DNA virus that causes upper respiratory tract infections. This virus targets the functional parts of the organs, notably the liver, kidneys, eyes and cells that line the interior surface of the blood vessels. • Type 2 (CAV-2) causes respiratory disease in dogs and is one of the infectious agents commonly associated with canine infectious tracheobronchitis, which is also known as “kennel cough.” Canine infectious tracheobronchitis is usually spread through coughing. o Parvo (required to board and/or attend day care): • A very contagious and potentially fatal viral disease seen in dogs. Most commonly, parvovirus causes gastroenteritis, or inflammation of the stomach and intestines. • Infection can occur directly through contact with infected dogs, but also through indirect contact with contaminated surfaces and objects. • It is estimated that parvovirus is fatal in 16-48 percent of cases. Consult your vet as soon as possible if your dog shows signs of parvovirus. • It can survive for several months (some experts say as long as two years) in the environment, and is also resistant to many disinfectants.
Non-Core Vaccinations
These include: o Bordetella (required to board and/or attend day care): • A highly contagious respiratory disease among dogs 42
BARKS from the Guild/September 2018
© Can Stock Photo/Feverpitched
Some vaccines are usually required for dogs to be able to attend a day care or stay in a boarding facility, while others are region-dependent and are not always required
that is typified by inflammation of the trachea and bronchi. This disease is found throughout the world. • Young puppies often suffer the most severe complications that can result from this disease since they have immature immune systems. Also at increased risk are older dogs, who may have decreased immune capabilities, pregnant bitches, who also have lowered immunity, and dogs with preexisting respiratory diseases. • Many veterinarians have begun recommending the oral form of this vaccination since it has proven effective and safe, and contains only the Bordetella antibodies. The oral vaccination is good for a year. • Some vets may also recommend the injectable form, which is also good for a year, although many have moved away from this form to prevent an abundance of injections that a dog receives. • The intranasal form is not recommended for dogs whose core vaccination protocols, as designed by their personal vet, include adenovirus and/or parainfluenza, since it also contains adenovirus and parainfluenza. • Over vaccinating does not provide extra protection. • The intranasal form has proven not as effective for dogs who have been previously exposed to or vaccinated for Bordetella, and future vaccination for Bordetella should be oral or injectable. • It is not uncommon for mild to severe health and/or behavioral problems to develop due to over vaccinating, including contracting the disease for which the animal has been vaccinated. • The intranasal form can irritate a dog’s nasal passages, causing sneezing, therefore expelling much of the vaccination into the air. o Parainfluenza (usually required to board and/or attend day care): • Often a regionally-specific vaccination that may or may not be part of a veterinarian’s core vaccination protocol for their patients. Owners should discuss their dog’s lifestyle with their vet about a customized vaccination protocol. • The virus that causes dog flu, Influenza Type A
Young puppies often suffer the most severe complications that can result from [Bordetella] since they have immature immune systems. (H3N8), was first identified in Florida in 2004. It primarily infects the respiratory system and is extremely contagious. • May or may not be necessary, depending on where you live, your dog’s lifestyle and the boarding facility. Speak with your vet about a customized vaccination protocol. • Often included in veterinarians’ individual vaccination protocols as needed. • Should not be given if the dog receives the intranasal form of the combo Bordetella vaccination which also contains parainfluenza and adenovirus. o Avian Influenza Virus (regionally-dependent as of August 2016: may be required to board and/or attend day care): • As of 2016, this is a regionally-specific vaccination that may or may not be part of a veterinarian’ core vaccination protocol for their patients. Owners should discuss their dog’s lifestyle with their vets about a customized vaccination protocol. • A highly contagious respiratory disease that was introduced to the United States in 2007, origins were traced back to dogs who were imported from Korea. • May or may not be necessary, depending on where you live, your dog’s lifestyle, and the boarding facility. Speak with your vet about a customized vaccination protocol. o Leptospirosis (may be regionally-dependent, but generally should not be required to board or attend day care because the risk of acquiring at a boarding facility should be extremely low): • Often a regionally-specific vaccination. Owners should discuss their dog’s lifestyle with their vets. • A bacterial infection which dogs acquire when subspecies of the Leptospira interrogans penetrate the skin and spread through the body by way of the bloodstream. • Mainly occurs in subtropical, tropical, and wet environments, and is more prevalent in marshy/muddy areas which have stagnant surface water and are frequented by wildlife. Heavily irrigated pastures are also common sources of infection.. • This bacteria is zoonotic, meaning it can be transmitted to humans and other species of animals. Children are most at risk of acquiring this bacterial infection from an infected pet. • May or may not be necessary, depending on where you live, and your dog’s lifestyle. Speak with your vet about a customized vaccination protocol. o Lyme (should not be required to board or attend day care): • Often a regionally-specific vaccination that may or may not be part of a veterinarian’s core vaccination protocol for their patients. Owners should discuss their dog’s lifestyle with their vet. • Lyme disease is transmitted by the deer tick (blacklegged tick) and a small group of other closely related ticks. The deer tick is small and may bite animals and people without being detected. Infection typically occurs after the Borrelia-carrying tick has been attached to the dog for at least two to three days. Ticks become infected with the bacteria by feeding on infected mice and other small animals. When an infected tick bites other animals, it can transmit the bacteria to these animals. • There is no evidence that Lyme disease is spread by direct contact with infected animals. However, keep in mind that ticks can hitch a ride home on your pets and move on to the humans in the household. • Risk Factors: Dogs that spend a lot of time outdoors, especially in the woods, bush, or areas of tall grass are most commonly infected with Lyme disease.
pet care
• May or may not be necessary, depending on where you live, and your dog’s lifestyle. Speak with your vet about a customized vaccination protocol. o Coronavirus (should not be required to board and/or attend day care): • A contagious intestinal disease found worldwide in dogs. Infection is generally considered to be a relatively mild disease with sporadic symptoms, or none at all. If an infection occurs simultaneously with a viral parvo infection or an infection caused by other intestinal pathogens, the consequences can be more serious. There have been some deaths reported in vulnerable puppies. • The most common source of a coronavirus infection is exposure to feces from an infected dog. The viral strands can remain in the body and shed into the feces for up to six months. • Stress caused by over-intensive training, overcrowding and generally unsanitary conditions increase a dog’s susceptibility to an infection. • Vaccination is not generally recommended. n
Resources
American Veterinary Medical Association: avma.org/Pages/home.aspx American Animal Hospital Association: aaha.org/default.aspx Dr. Jean Dodds: hemopet.org/education/jean-doddsveterinarian.html Dr. Ronald Schultz: vetmed.wisc.edu/vaccination-guidelines-2016 PetMD: petmd.com Lauri Bowen-Vaccare ABCDT is the owner of Warren, Kentuckybased Believe In Dog, LLC (believeindog.
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pet care
Behind the Scenes
In the first of a four-part article, Frania Shelley-Grielen addresses the lack of regulation in
the pet care and services industry, and wonders how standards can be improved for pets
and their owners
A
© Can Stock Photo/JB325
© Can Stock Photo/littlebell
Many pet owners contract out a portion of pet care responsibilities to try to ensure their pets’ needs are met as much as possible, but in an unregulated industry, standards of knowledge, skill and care may vary
In cases where regulations do exist for pet care facilities or breeding operations, they mainly address physical space, housing and sanitation as opposed to staff education or qualifications
mericans
44
BARKS from the Guild/September 2018. terri-
“
pet care A Constructional Approachconditioning protocols. “Humane, modern animal training relies on science-based protocols: ‘Within.”
- Pet Professional Guild (2016) Open Letter to Veterinarians on Referrals to Training and Behavior Professionals
tory. exBARKS from the Guild/September 2018
45
...have you ever wondered about the pet service providers? The people who work with your pets? How did they learn to do what they do? Are they as qualified and experienced as you expect or as they say they are? How would you know? How can you know? cellent. n
pet care References
American Pet Products Association. (2018). National Pet Owners Survey. Stamford, CT: APPA New York City Economic Development Corporation. (2012, February) nycedc.com/blog-entry/new-york-city-s-pet-population Pet Professional Guild. (2016). Open Letter to Veterinarians on Referrals to Training and Behavior Professionals. Available at: petprofessionalguild.com/Open-letter-to-veterinarians-on-referrals -to-training-and-behavior-professionals US Bureau of Labor Statistics. (2018). Animal Care and Service Workers. Available at: bls.gov/ooh/personal-care-and-service/animal-care-and-service -workers.htm
Resources
Pet Professional Guild. (2018). Professional Ethics and Guiding Principles. Available at: petprofessionalguild.com/PPGs-Guiding -Principles Pet Professional Guild Member Directory: petprofessionalguild.com/Zip-Code-Search Sherwin, N. (2016, September). The Right Environment. BARKS from the Guild (20) 39-41. Available at: issuu.com/petprofessionalguild/docs/bftg_sept_2016_online/39 Frania Shelley-Grielen is a New York City-based professional animal behavior consultant, dog trainer and educator who holds a Master’s in animal behavior from Hunter College, New York City, and a Master’s in urban planning from New York University. She is a licensed pet care technician instructor, a registered therapy dog handler, and a certified Doggone Safe bite safety instructor, and specializes in behavior modification work and training with cats, dogs and birds and humane management for urban wildlife. She is also the author of Cats and Dogs; Living with and Looking at Companion Animals from their Point of View and founded AnimalBehavior ASPCA in New York City.
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consulting
Critical to Success
In the first of a two-part article, Niki Tudge outlines her recommended training plan and
I
how she breaks down client visits into lessons within each individual session to ensure
maximum efficacy
n the client consulting process, no matter how you normally proceed or whatever your individual consulting process is, the first step will always be a client interview of some sort. Once you have completed this interview and reviewed all the anecdotal information, you will then either feel comfortable that you have a reliable contingency statement, or you will feel the need to further investigate what is reinforcing the problematic behavior specific to that case. It is critical to success that the evoking or eliciting antecedent and/or the pertinent consequences that are providing the reinforcement are known prior to embarking on a training plan. Feeling comfortable about your contingency statement will help you reliably discuss with your clients the potential scope and length of your training plan, what will be included, when it will take place, what the training will look like, and who will be responsible for which components. Your training plan will then be compartmentalized into individual lessons scheduled with the client across a given period. For example, I may structure my training plan to include eight lessons beginning with two lessons each week and then progressing to just © Can Stock Photo/mheim3011 one lesson per week as the client becomes more competent across For training to be professional and effective for both clients and their dogs, it needs the key skills and knowledge required. to be done correctly, with a full plan in place from the outset The topography of each lesson will be determined by the individual sessions required, both to build competency around the necLesson Plan essary skills and knowledge for the client and their pet, and to ensure We will now look at a typical lesson plan taken from our Six-Week Trainskills are introduced at the right time and in a clear and concise manner ing Plan (detailed in Figure 1-1 on page 49). Before we arrive at the to prevent confusion and blurring across the lines. For example, profesclient’s home we need to have any important documents ready and sionals often broach three or four topics in a lesson with a client but do make sure we have all the relevant training equipment. Preparation is not clearly define where each one starts and finishes. This can comessential. It is very unprofessional to arrive at a training appointment pound the difficulty of the training and lead to frustration and mistakes. and then realize we have forgotten the muzzle or handout we need to Scenarios such as training methods, capturing, targeting and luring, or conduct the lesson effectively. However, if it does happen, we have one dimensions such as distance and duration, can quickly become a blur to of two choices: a) omit that skill session from the lesson, or b) train the pet owners if our sessions are not clearly defined through subject matskill without all the necessary tools. Neither of these options is conter and the start and finish of each session. ducive to getting outstanding training results. In this article, I will focus on lesson and session planning. A training I firmly believe that, if training is to be professional and effective, it lesson is the period of time we, the pet professionals, are contracted to needs to be done correctly, and that means having all the necessary provide training services to our clients, while a lesson may contain sevtools and documents on hand and prepared. During our preparation we eral short training sessions on separate and/or interrelated topics. We need to try to picture the actual training lesson and the planned sesneed to make sure we run these sessions as effectively as possible. sions. What are the individual training tasks we will focus on? What will Most of our lessons are service products that we sell. They are inwe say, and how will we explain the “how,” “what” and “why” of our crements of time. They are generally 1-11⁄2 hours long. In some cases, training plan? How will we demonstrate the actual skill? What questions the service product may be sold as package, i.e. groupings of individual do we anticipate the client will ask and how will we answer them? How lessons. These should be prepaid, and I recommend that they qualify will we handle any problems that may arise? the client for a small, pre-pay discount. Finally, we must be sure we completely understand our material so Scenarios such as training methods, capturing, we can competently demonstrate everything we expect the client to targeting and luring, or dimensions such as learn. We cannot just wing it when teaching a paying client. This would distance and duration, can quickly become a blur be highly irresponsible and very unprofessional.
to our pet owners if our sessions are not clearly defined through subject matter and the start and finish of each session. 48
BARKS from the Guild/September 2018
Quick Preparation Checklist 1. 2.
Do we have your training road map? Do we have our training plan?
consulting Figure 1-1: The Six-Week Training Plan Detailing Skills and Theory
Session # 1
Location
Client home
Knowledge (Teaching Theory) x x
x x x x x x
x x x x x x x x
Review current cues and skill levels Overview of training philosophy o Management - purpose o Training - how o Relationship - why Review equipment use Theory of name game, hand feeding and mental stimulation exercises Theory for including play Theory for using harness Practical application of new skills Kongs and toys ʹ purpose and use Theory of muzzle training Theory of crate training dŚĞŽƌLJŽĨ͞ůĞƚ͛ƐŐŽ͟ Theory of leash walking
x x
x
Clicker mechanics, timing and purpose Hand feeding exercise Name game process Play activities Fitting and desensitizing a harness Practical application and context of new skills Practical application of Kongs and toys
x x x x x
Recap of homework Muzzle training Crate training >Ğƚ͛ƐŐŽ Walk nicely
Theory of sit and down acquisition Theory of maintain
x x x
Recap of homework Sit/down Maintain
x x
Theory of counterconditioning and desensitization Recap on leash walking ʹ Oops, what do I do now
x x
Practice trials Practice trials
x x
Theory of relax Recap of counterconditioning and desensitization Recap of sit/down/maintain
x x x
x x
Recap theory of counterconditioning Recap theory or conditioned relax
x
Relax game practice (end of session) Review of crate training On the road o >Ğƚ͛ƐŐŽ o Play with tug toys o Leash walking o Sit/down/maintain o Counterconditioning exercises On the road o Counterconditioning exercises o WƌĂĐƚŝĐĂůĂƉƉůŝĐĂƚŝŽŶŽĨůĞƚ͛ƐŐŽ͕ sit/down maintain
(2-hour session)
x x
2
Client home (2-hour session)
3
Client home (1-hour session) Client home and quiet area outdoors
4
Skills (Training Mechanics)
(1-hour session) Client home and quiet area outdoors
5
(1-hour session)
Outdoor area with light traffic and exposure to the problematic conditioned stimulus
6
(1-hour session)
3. 4. 5.
Have we prepared our individual lesson plan? How many skills sessions do we plan to execute in the lesson? Do we have our skill sessions planned? This means: a. Do we know what we will teach first and to what criteria? b. Have we developed our how, what and why? c. Do we have the necessary handouts to support knowledge transfer in conjunction with the skill training we have planned?
Graphic © Niki Tudge
d. Do we have all the correct equipment on hand? e. Are we dressed appropriately, i.e. do we look professional? The individual lesson plan document in Figure 1-2 (see page 50) highlights an example of an individual lesson from the six-week training plan. The lesson is then dissected into two components: 1. What knowledge will we be transferring to the client? 2. What skills will we need to teach the client so they can train BARKS from the Guild/September 2018
49
consulting Figure 1-2: Individual Lesson Plan Highlighting the Supporting Documentation Needed and Goal Criteria for the Skills Being Covered Knowledge (Teaching Theory) x x x
x x x
x
Overview of training philosophy Review equipment use Theory of name game, hand feeding and mental stimulation exercises Theory for including play Theory for using harness Practical application of new skills Kongs and toys ʹ purpose and use
Supporting Documents -
-
Four Skill Sessions
Handouts on training versus management versus relationships Handouts on each of the following skills: o play o harnesses vs. collars o Kong filler recipes
1.
2. x x x 3. 4.
Goal Criteria
Using a clicker, mechanics, timing and purpose Relationship Exercises Hand feeding exercise Name game process Play activities Fitting and desensitizing a harness Filling a Kong toy
-
-
-
their dog competently? In addition, we must identify what supporting documents are required for the knowledge transfer and what equipment is needed for the skill training. When training the skills what criteria do we hope to achieve? When we have multiple clients it is important to record this information so we know, when we arrive for a lesson, where we left off, where the client stands, and where this lesson plan should take us. Before we begin any individual training sessions within a lesson, we should be very clear about what exactly we will be training and to what criteria. Using a lesson plan like the one detailed in Figure 1-2 (above)
Charging the clicker, timing, position and treat delivery Hand feeding for seven days while playing the name game and making positive eye contact Identifying two play activities for inside the house and two for the yard Dressing and undressing the dog with a harness while eliciting a conditioned emotional response Three Kongs prepped for use
helps us to be sure we have all the necessary support and homework documentation. Note that in the lesson plan there would also be a column for goal criteria. This will ensure we know the exact criteria each skill will be trained to in any individual lesson and support our clients achieving their goals. As discussed previously, we may have three to five individual skill training sessions within one lesson, and we need to prepare for each one of them. As can be seen in Figure 1-2, there are multiple sessions in each single lesson.
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Graphic © Niki Tudge
Figure 1-3: Each training lesson should be conducted in the same way to ensure trainers guide students through the Experiential Learning Cycle
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Topics may include a particular aspect of training, ethology, learning theory, behavior specifics...anything at all your fellow pet professionals would find educational. We’ll even do some practice runs with you to help you along (if you need them!)
Learning Cycle
consulting
Each lesson should be conducted in the same way. This entails working to the same method every time to ensure we guide students through the Experiential Learning Cycle (see Figure 1-3, page 50, below left). The learning cycle involves moving from experience, to reflecting, to conceptualizing and, finally, to integrating the actual skills. 1. As we are learning, we first experience something new and immerse ourselves in it. We bring our own biases to the experience so we are caught up in our own individual meanings. 2. Next, we reflect on the experience. We begin to filter it through our own eyes based on our past experiences. As we move through this reflection we are able to dismiss our biases and rigidity to see and feel more objectively what we have just experienced. 3. Then we conceptualize, at which point we narrow our focus from individual reflections and move from perception to concept. We seek to understand what we have experienced so we can label it or classify it in a way that makes sense to us based on our previous experiences. 4. Finally, we take action once we understand the concept. For most of us though, action is not enough. We need to play around with the experience, tweak it and make it work for us. At this stage we have become part of the manipulation process. In other words, we can manipulate our actions based on our experiences, reflections and conceptualizations. These four components, experience, reflection, conceptualization and action, are the four cornerstones of professor of organizational behavior and educational theorist David A. Kolb’s Experiential Learning Cycle. There is a formula for moving through the Experiential Learning Cycle and, in the second part of this article, I will present an overview of the various steps involved, as well as what should be covered in each lesson. n
References
Kolb, D. A. (2015). Experiential Learning. 2nd edn. Upper Saddle River, NJ: Pearson Education Inc.
Niki Tudge PCBC-A AABP-CDBT AAPB – CDT is founder and president of the Pet Professional Guild (petprofessionalguild.com), The DogSmith (dogsmith.com), a national dog training and pet-care license, and DogNostics Career College (dognosticselearning.com), and president of Doggone Safe (doggonesafe.com). She has business degrees from Oxford Brookes University, UK and has achieved her DipABT and DipCBST. Recently, she has published People Training Skills for Pet Professionals – Your essential guide to engaging, educating and empowering your human clients, Training Big for Small Businesses, and A Kids’ Comprehensive Guide to Speaking Dog., PetProfessionalGuild.com/benefitinformation. Please be sure to log in first.
For people who are serious about their dogs!
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consulting
A Helping Hand
I
Sheelah Gullion starts a conversation on the value of mentorship in the pet industry
by inviting trainers with a variety of experience to weigh in with their thoughts n spite of its short history, dog training as a profession is evolving rapidly and those who take the profession seriously know that education and practical experience are equally important, no matter how you acquire them. But what is the best way to acquire education and experience? Do we need mentorships in our industry? Should they be formal, and long? Or informal and just long enough for a student to get his or her feet wet? What is the value of having a mentor and how do you know if yours is a good one? I posed these questions to some other trainers. All respondents were professional, working dog trainers in the United States who took my questions seriously and gave considered responses. There were a few surprises among the replies: while everyone agrees that having a mentor is a good thing, there was no clear agreement on how much experience a mentor should have or what kind of experience. Respondents agreed that, in their opinion, the sheer volume and variety of dog trainer programs currently available seem to be fragmenting our industry rather than building it up, but there was a surprising variation in how long everyone feels mentorships should last. In order to give the respondents the opportunity to be completely frank in their opinions, I have kept their replies anonymous. It is my hope that this will form the beginning of a conversation that will ultimately reach those who may eventually help draw up regulations for education requirements in our industry. Q: Have you ever been a mentor or a mentee, or did you come to training another way?
Respondent 1: I’ve been both mentor and mentee. I first started my puppy and dog training by assisting in classes at both a private school and at a shelter. At the private school, I assisted in puppy classes four hours a week for five years under one instructor, and occasionally subbed for other instructors. Then an opening came up and I was offered [the chance] to teach my own classes. I was very fortunate to have such exposure and hands-on experience. At the same time, I was volunteering at a shelter for three years, assisting in classes there two hours a week plus walking and/or training adoptable dogs for an additional hour. The shelter offered me a great variety of classes and dogs and I had several instructors there that mentored me. Both situations were incredibly valuable because I learned from hands-on experience with close observation and discussions with the primary instructors. Both situations were voluntary and informal, allowing me the luxury of time to decide if I really wanted to take this path. I have never formally mentored anyone in the dog training world. However, I have definitely had multiple assistants in my classes, including some that were going through internship programs, but my comments were never sought. I found that those in internship programs were more likely to ask questions and commit to the process, whereas those who were in training academies and wanted to observe or assist were never fully committed. I can think of one who, to this day, still contacts me to discuss issues and this gives me great joy. Respondent 2: I am a self-taught dog trainer. I would have loved to have had a mentor but there was no one in my area who was willing to men52
BARKS from the Guild/September 2018
© Can Stock Photo/focalpoint
Although the pet professionals interviewed for this article agreed that having a mentor is a good thing, there was no clear agreement on how much experience a mentor should have or even what kind of experience
tor me when I first started. Although I had a few trainers point me towards trade organizations and other resources, there were not any willing to let me shadow or learn from them, so I had to figure it out on my own through attending conferences, workshops, and watching popular dog training TV shows and YouTube videos - 12 years ago there wasn’t as much good YouTube content!. Respondent 3: I found it very valuable to observe and watch my mentor interact with the clients and their dogs. It also gave me the chance to practice reading dog body language and see my mentor’s reactions to what the dog was communicating in real time. I also find it valuable to have another person to mull over the more complicated cases with for new ideas or suggestions, or just affirmation of my thoughts. I was able to slowly take over more and more sessions with her support, which was a big confidence booster for me in the beginning.
Respondent 4: I would very much like to have a formal mentor. I often wish I had someone formal to bounce my ideas off of, give me pointers, and help confirm that I am indeed on the right track. I have a network of people that serve as mentors when I need a sounding board, but because it is not formal I worry about being a bother.
Respondent 5: I constantly wish that I was able to study under and be mentored by a trainer further along in my field. My only experience similar to being mentored was through a big box chain where I observed classes being taught by one of the trainers there a few times. As my own career started and grew, I ended up teaching the other trainers at this pet store how to train as well. It was a very short program so I’m not sure I would actually consider it mentoring. I’ve also helped coach other trainers throughout my career. I think that teaching other trainers is a really great way to learn and make sense of what it is you’re teaching. Q: Our industry is trending towards fixed-term, structured internships or combined programs of online learning followed by a formal internship. Do you feel this is better or worse?
Respondent 3: I do feel more structure is better. Mine was relatively unstructured, which worked okay for me, but it’s easy to get overwhelmed with information in the beginning and not know how or where to start with a dog. I would have liked more hands-on instruction from my mentor of my training skills and timing, and more discussion of hypothetical or real cases and formulating training plans. Respondent 5: I believe having a more formal way to have mentors and mentees will help bring more credibility to this industry. Respondent 4: I think this new trend has its pros and cons. I learned a huge amount from my structured internship and I am very thankful it was there as an option for me. Now that it is completed though, I am hungry for reassurance and guidance but I find that the people I would like to have as mentors are busy teaching their next class of interns.
Respondent 1: I think it will always depend on the individuals. I like the idea of a formal internship so feedback and timelines and goals exist to help the mentee get through the process, build confidence and develop skills. I do think most programs are probably not structured to be long enough in duration. I also think it is important not to have only one mentor, but rather to have at least two to three so you can really see what fits your way of learning best.
consulting. Q: How long should a mentorship go on (months, years)?
Respondent 2:.
Respondent 1: I don’t think they are usually long enough. It depends on how much experience the mentee has. If they are completely new, it may go on for a year or two. If they have already been in the industry and taken classes, then it may be less. Respondent 4: I think it depends. For example, there is a more experienced trainer that I frequently reach out to with questions and/or for reassurance who is happy to chat with me and guide me along. I think as long as I don’t abuse this, this type of relationship can go on for years. A formal mentorship is more of a time commitment. As long as mentor and mentee are in agreement, it could be beneficial to have a mentor for more than one year.
Respondent 5: I would say that an informal mentorship should last a minimum of three months. For a formal one, depending on the goal of
Respondent 2: I’ve served as a mentor for two online schools for dog trainers for a long time now. What I’ve found is that the school that offers more hands-on coaching combined with the classroom learning creates better-equipped students (future dog trainers). Yet nothing replaces a well-structured shadow program.
Q: Consider the following statement: The increasing number of programs that teach people how to become dog trainers run the risk of fragmenting our industry, in part because of a lack of standards across educational programs. What are your thoughts on this?
Respondent 1: Yes, there are so many different programs out there, each trying to compete with the other one for drawing students. [Some] of them lack comprehensive training and give the student a false sense of accomplishment and knowledge. Respondent 5: I would have to agree. However I think that mentoring should continue, but with standards of what makes someone considered a professional dog trainer and what does not.
Respondent 3: I do believe it would help to have a set standard for new dog trainer programs. What is deemed acceptable treatment of dogs varies from trainer to trainer and program to program, and I would like to see this changed.
© Can Stock Photo/Zuzule
Working alongside a mentor can help pet professionals practice reading dog body language and learn firsthand about canine communication
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consulting. the trainer, I think one year for a professional pet dog trainer would suffice, but for a behavior consultant, I would say at least one to three years of education, etc., or proof of testing and skills.
Respondent 3: It partly depends on the time commitment (hours per week) for an informal mentorship, but I’d say at least six months to a year would be ideal. For a formal program, I think a year is long enough, but in both cases, it depends on the individual’s ability to commit.
Q: Who should be mentoring and who should not? Should there be a minimum required time working in the industry? Would you mentor under someone with “only” 10 years of experience?
Respondent 5: Since the industry is unregulated, you have to look at several different areas of expertise, not just years in the field. I think that skills, proof of education, experience level and client/colleague testimonials would be a great way to determine if someone is qualified. Respondent 3: I believe a mentor should be certified, and have been working in the industry for at least five to six years, ideally more. It really depends on the mentor and their dedication to staying up-to-date with seminars and continued education. I would mentor under someone with 10 years of experience, depending on other factors as well. Someone who has been training for 10, 15, or 20 years but who has not attended a science-based education seminar or workshop in that time, I’d steer clear of. Respondent 1: Yes, I think 10 years of experience would be the minimum.
Respondent 4: I think it’s challenging to put a hard timeline on this. Everyone learns at different paces and potentially delves deeper into the industry at different rates.
Respondent 2: I think this comes down to how much experience a mentor trainer has versus how long they’ve been training. I know plenty of trainers who have 25 years of training experience under their belts yet don’t have half of the experience (privates, group, shelter, behavior, bite case work, expert witness, board and train, day train, multiple species, etc.) that some others have. I think if you’re going to be teaching someone else, it’s only fair that the mentor trainer actually has a broad range of experience in our industry in order to teach a new trainer. They have to have enough experiences to pull from in order Hands-on instruction from a mentor can be invaluable for trainers who are just starting out working with dogs
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© Can Stock Photo/halfpoint
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to grow and coach a new trainer. I don’t think there’s any specific length of time, but would suspect it can’t be less than three to five years before a trainer may be ready to start mentoring another trainer. Q: What downside do you see to being a mentee or mentor?
Respondent 2: The biggest downside of being a mentor is creating competition for your own business in your area. Respondent 1: None.
Respondent 4: Personally, I can see how I might feel indebted to my mentor for the amount of effort they’ve devoted to helping me. For a mentor, I can see how it might be challenging to create appropriate boundaries to ensure time is made for their own career goals. Respondent 3: I don’t see any downside. Personally, I wouldn’t have made it if not for my mentor.
Respondent 5: The only downsides are the time commitment and the cost of doing so. But if you’re committed to this industry, it would be well worth it.
Q: At this point in our industry, why do you think it’s a good/bad idea to have mentoring programs?
Respondent 5: I think having mentoring programs helps give our field more credibility. Having someone to vouch for your skills and knowledge. Respondent 3: I think it’s a fantastic idea and would love to see some standards put in place for our industry.
Respondent 4: I think they are essential. Especially for trainers who focus on positive reinforcement. Since there is so much misinformation out there around dog training and what methods should or shouldn’t be used, it is important that the right messages are spread. Respondent 2: I do think they are a good idea but there definitely needs to be some standardization put in place in our industry, education included. Respondent 1: It should be a requirement. Because dog training is real life. There is nothing like hands-on experience when working with animals. It may take months or typically longer for a variety of situations to ever cross your path. n
Sources
Respondent 1 is a self-employed dog trainer with 17 years in the industry. Respondent 2 is a dog trainer and business owner with 34 employees who has been in the industry for 12 years. Respondent 3 is a dog trainer and management-level employee at a dog training school and has been in the industry for four years. Respondent 4 is a self-employed dog trainer and part-time employee at a dog training school with 18 months in the industry. Respondent 5 is a self-employed dog trainer with seven years in the industry.
Sheelah Gullion CPDT-KA is an AKC Star Puppy and Canine Good Citizen Evaluator. She is interested in all facets of dog training and is currently focused on learning more about nose work and tracking with her three-year-old Rhodesian ridgeback, Jabu. She recently joined the training team at SmartyPup! (smartypup.com) in San Francisco, California as a day school and class trainer.
karen pryor ACADEMY for Animal Training & Behavior
DOG TRAINER PROFESSIONAL PROGRAM The standard of excellence. More than 1,300 dog trainers worldwide have earned our certification. Join them for one of the best career decisions you’ll ever make. Find out more at: karenpryoracademy.com
BARKS from the Guild/September 2018
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business
Ask the Experts: Optimizing Your Website Veronica Boutelle of dog*biz responds to pet professionals’ questions on all things
business and marketing
Q: Help! My new website isn’t working and I can’t figure out why. I’m frustrated. I just spent all this money and time and nothing seems to be happening. What am I doing wrong?
- A Frustrated Trainer in Texas
A: First, thanks for noticing our new name! Second, I’m sorry about the frustration with your new website. It’s a little hard to say what might be going on (or not going on!) without more information, but let’s go over the most common culprits responsible for an underperforming website. There are two main ways a site can fail. One is not being found, and the other is failing the user once found. Installing Google Analytics (or having a webmaster to do so for you) can help you determine which problem you’re having. If your site is brand new (i.e., you’ve never had a website at your current website address or URL), it may simply be that Google and the other search engines haven’t found you yet. That can take months, but you can help by submitting your site to the search engines (or having a webmaster or search engine optimization, aka SEO, specialist do so for you). Whether your site is brand new or you’ve replaced your old site on the same URL, you’ll want to engage in some good SEO to help search engines deliver your site higher on their list when someone goes looking for what you do in your area. SEO is a wide-ranging process with many aspects to it—too much to cover here, and requires specialized expertise and customized application—but there are a couple of simple things you can do to start the process. First, just read through the copy (i.e. the text) on your site to make sure you’ve got plenty of key words—the words someone might type into Google to find someone who does what you do where you do it. You want to do this on all of your pages, but the home page is most important. Focus on service words (dog training, dog trainer, puppy train-
BARKS from the Guild
© Can Stock Photo/adogslifephoto
Studies suggest that people take two to three seconds to decide whether to stay on any given website they land on
...look to add dynamic content to your site. A blog is a great way to do this. Google loves sites that continue to update content. And a blog creates continued opportunity to utilize key words, too. Plus it gives you a way to share valuable education with your community.
BARKS from the Guild is the 64-page bi-monthly pet industry trade magazine published by the Pet Professional Guild, available to Pet Professional Guild Australia members, supporters and the general public online (and in print, by monthly subscription). Widely read by pet industry professionals and pet owners alike, BARKS covers a vast range of topics encompassing animal behavior, pet care, training, education, industry trends, business AND MUCH MORE! If you would like to reach your target audience, BARKS is the perfect vehicle to achieve that goal. To contribute an article, please contact the editor, Susan Nilson: barkseditor@petprofessionalguild.com To advertise, please contact Kelly Fahey: Kelly@petprofessionalguild.com
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BARKS from the Guild/September 2018
business
ing classes, for example) and location words. If you don’t include where you operate, search engines won’t be able to match you with searchers. Second, look to add dynamic content to your site. A blog is a great way to do this. Google loves sites that continue to update content. And a blog creates continued opportunity to utilize key words, too. Plus it gives you a way to share valuable education with your community—you get to do good while building the strength of your website.
These are some of the most common mistakes we see on dog pros’ sites. I hope they give you some insights to work from. Bottom line: If you have an underperforming SEO is a wide-ranging process where key website, call in prowords and dynamic fessional help. Your content, such as a site is your most imblog, are essential © Can Stock Photo/26kot portant business tool, your primary business investment. It always pays to pay for its health. If you think it might be helpful to bring in an expert set of eyes to assess your site and make SEO recommendations, we love Judy Taylor at JT © Can Stock Photo/kbuntu Dataworks (jtdataworks.com). Timing Is Everything Good luck and best of success! n If people are finding your site but not reaching out once they do, you’ve got either a messaging problem or a usability issue. Studies suggest that people take two to three seconds to decide whether to stay on any given site they land on. Two to three seconds! That’s not a lot of time to convince someone they’re in the right place. So if someone can’t at a glance learn what you do and how it will make their lives better, you may well lose them. Take a look at your site to see if you’re getting your message across fast. Most dog pro sites I see fail in this regard. If you survive the initial two to three seconds, the average time you get to make your case is two to three minutes. Again, not much. So your site has to be easy to use. A visitor shouldn’t have to work hard to gather the basic info needed to make a decision. Is it easy to find my way to each of your services? Are the details about how it works, what I get, and how much it costs readily available? Can I scan through the information, or are you asking me to read long, heavy paragraphs?
Do you have a question for the business experts at dog*biz? Submit your question for consideration to: barkseditor@petprofessionalguild.com Learn how
can help your business:
Veronica Boutelle MA Ed CTC is founder and co-president of dog*biz (dogbizsuccess.com), and author of How to Run Your Dog Business and co-author of Minding Your Dog Business. dog*biz offers professionally-designed positive reinforcement dog training class curricula, including Open-Enrollment Puppy, Open-Enrollment Basic Manners, and short Topics classes built for retention.
BARKS from the Guild/September 2018
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business
Claiming for Injuries
David Pearsall of PPG corporate sponsor Business Insurers of the Carolinas discusses the
important issue of workers’ compensation insurance and urges all pet professionals to
A
consider whether they need to add this coverage
s a professional pet service provider, be it a dog trainer, pet groomer, pet sitter/dog walker or pet boarding facility, you are likely already aware of the need to carry general liability insurance to protect yourself and your business against lawsuits alleging bodily injury or property damage to others, including your clients and the dogs in your care/classes. But what about those injuries that you, your employees, or your subcontractors incur while on the job? Over the years our agency, Business Insurers of the Carolinas, has received many calls from clients who thought their medical injuries were covered by their general liability insurance, only to learn at the time of the claim that there was no coverage for injuries to themselves or anyone working on their behalf. It is important to note that the PPG liability policy is a general liability insurance policy that provides coverage for bodily injury or property damage claims to a third party caused by your negligence. There is absolutely no coverage whatsoever under the PPG liability policy (or any other general liability policy on the market) for injuries sustained by you or your employees.. All of these are claims we have received over the years. Unfortunately, unless you or one of your employees have been injured on the job, it might be hard to fathom carrying this insurance. However, I recommend you give careful consideration to the consequences of not carrying it, especially if you are hiring others to work in your business. Suppose you or one of your employees suffered a significant injury from a slip and fall or dog bite, and were unable to work for a number of weeks. Although you and your staff may have health insurance, you will find that health insurers typically look to exclude work-related injuries. And even if your health insurer does cover the medical portion, they most certainly will not cover your lost wages while you are unable to work. According to the National Council on Compensation Insurance (NCCI), as of December 31, 2016, the average medical costs on a lost time claim were approximately $29,100, while the average indemnity cost (lost wages/settlements) on a lost time claim was approximately $23,900. There is a good reason why all those workers’ comp attorneys advertise on television throughout the day, asking: “Have you been seriously injured on the job?”
According to the National Council on Compensation Insurance (NCCI), as of December 31, 2016, the average medical costs on a lost time claim were approximately $29,100, while the average indemnity cost (lost wages/settlements) on a lost time claim was approximately $23,900. 58
BARKS from the Guild/September 2018
© Can Stock Photo/chalabala
Under their general liability insurance, pet care service providers are not necessarily covered for injuries to themselves, their employees, or their subcontractors
Workers’ compensation covers all work-related injuries arising out of employment and occurring during the course of employment. It also covers occupational diseases resulting from employment, and employers’ liability that is excluded from employment. It is the exclusive remedy for workplace injuries, meaning the employee relinquishes the right to sue the employer in exchange for a guaranteed set of benefits. Workers’ compensation benefits include payment for medical expenses, disability (loss of income), rehabilitation, and death.
State Specific
Each individual state has its own workers’ compensation statute and the specific laws and benefit amounts vary from state to state. Coverage is compulsory in all states with the exception of Texas. But states do differ on the requirement based on the number of people you employ or in which you have an employee/employer relationship. This can be tricky so be sure to follow your state law. Some states require you to insure if you have even one employee, while others may say three employees. Even if you have less than the number required, you still may be liable. for an employee’s injuries, so be aware of your state requirements. Fines for not carrying coverage can vary anywhere from $250 a day up to $5,000 for every 10 days you neglect to purchase coverage. And many state laws will specify that failure to have coverage due to lack of knowledge is not a valid excuse for failure to insure, so please be aware if you hire or subcontract anyone to work for you or on behalf of your business. Furthermore, each state’s workers’ compensation statute also differs on how they view independent contractors and/or subcontractors. Some states will say you are responsible for injuries to your subcontractors if: 1) They do not have coverage in place and they are told how, when or where to perform the work. 2) They fail to meet certain criteria such as having the right to make a profit or loss, or having the ability to control the work. 3) They fail to provide you with proof they are insured for general liability and workers’ compensation. Other states, meanwhile, will hold you responsible for the subcontractor’s employees or helpers if they are injured (even if you didn’t know the subcontractor was hiring or using a helper) and that subcontractor failed to have a workers’ compensation policy in place.
business
If you utilize independent contractors/subcontractors in your business and are not 100 percent certain you are not liable for their injuries, I recommend contacting your state workers’ comp board/bureau/regulator, reading your state workers’ compensation statute (all typically define independent contractor/subcontractor relationships and can usually be found online), and/or contact an accomplished workers’ comp attorney in your area for consultation. It is always better to find out before the claim occurs! If it is determined that there is an employee/employer relationship, workers’ compensation is the only way to cover an employee. Therefore, if you do not wish to have an employee/employer relationship and purchase your own workers’ compensation policy, it is recommended that you consider requiring your independent contractors to purchase their own policy and provide you with proof via a certificate of insurance each year on the effective date of their policy. This not only strengthens the fact that they are a true independent contractor and keeps you from placing your business at risk, but it also insures that anyone the independent contractor hires or utilizes as a helper is covered. n
If you have additional insurance questions or concerns or want to know more about your individual state requirements, please feel free to contact David Pearsall: dp@business-insurers.com. See also ad on this page, below.
David Pearsall is a certified insurance counselor (CIC) and co-owner of Business Insurers of the Carolinas (business-insurers.com), a multiline commercial insurance agency specializing in insurance for pet service professionals since 1992. He has headed up association liability and bonding programs for national pet care service associations for over 20 years, including PPG. He is a licensed insurance agent in all 50 states and has held the CIC designation since 2002.
BARKS from the Guild/September 2018
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profile
Helping People Connect
In our ongoing series of PPG member profiles, this month BARKS features Tracey Prall
T
of Canine Connections Dog Training and Dog Hotel in Walterstone, Hereford, England racey Prall is a United Kingdom-based dog trainer who seeks to help owners build a solid foundation in their relationship with their dogs, therefore creating stronger bonds.
Q: Can you tell us a bit more about yourself, how you first got into animal behavior and training and what you are doing now?
A: I run Canine Connections Dog Training and Dog Hotel. I have been running the training for six years and the dog hotel for a year and a half. I also run puppy socialization classes at my local vets and puppy classes locally. Clients can continue on to adolescent classes with me too. I also run the Kennel Club Good Citizen Awards and have been doing so for a couple of years. With my location, I have a large paddock which I can use in the summer for some of the classes. I have just passed my teaching foundation to run Hoopers classes so I will be adding those to my list of available services soon. The Dog Hotel comprises two kennel suites modeled on the latest design from the Dogs Trust. They are situated in my garden and I spend a lot of time with the dogs, walking, play time, scent work, etc. The kennels are light and airy, there is a radio and calming Pet Remedy if needed, and if any of the dogs are really unsettled, I do sleep in there with them! I first got into training and behavior when I had problems with my two dogs about 10 years ago. Having just ended a relationship and moved home, my two dogs were suffering from separation anxiety and howling when I was not there. I engaged a trainer who spent time with me to understand why they were so stressed and anxious and how to help alleviate and work to make them feel comfortable. I was hooked in wanting to understand more about behavior and when money and time allowed, I started training courses (both practical and online), which took two years to complete. Some of the training I did used old fashioned methods which did not sit right with me, so I pursued all avenues of training that I could find that used only positive methods. I went on many courses, which included Kay Laurence seminar days with my dogs, the BAT training course with Grisha Stewart, a seminar with Patricia McConnell and also a seminar with the Helen Zulch at the University of Lincoln. Three years ago, I took my Association of Professional Dog Trainers (APDT) assessment and passed to become a full member. I adhere to strict codes of conduct and use only force-free methods, which I advocate in all my classes. I recently attended a two-day Kathy Sdao event and the Leslie McDevitt Control Unleashed seminar. Q: Tell us a little bit about your own pets.
A: I have a kelpie cross called Kilo. She was a rescue who had already had two failed attempts at rehoming and was being fostered when I saw her at 8 months old. She is now almost 4 years old and she is a lovely girl. She has frustration issues, which at the start were difficult for both of us, but together we have gradually worked to make her feel more comfortable. We have been doing scent work in the last year, which she is loving (me too!) with Scentwork Wales. It is a wonderful way for her to engage in a class environment and not get too aroused. We regularly compete in trials and she has just moved up to Novice Silver level. We have also been to Mantrailing sessions which we both enjoy. My wife Tina has a smooth collie called Cliffie who is 2 years old. He is a delight and both dogs get on superbly. Cliffie also does scent work and competes at trials organized by Scentwork Wales. He trains twice a week at agility classes too. We live on a smallholding with chickens, ducks and three alpacas plus a cria (baby alpaca), so it is always busy. Kilo and Cliffie always help with the morning routine of feeding everyone. At the time of writing, we have 60
BARKS from the Guild/September 2018
Photo © Tracey Prall
Tracey Prall with dogs (left to right) boarder dogs Otis and Crispin, own dog Kilo, and boarder dog Cosmo
just rehomed a 7-month-old border collie called Max who is settling in well.
Q: Are you a crossover trainer or have you always been a force-free trainer?
A:When I first owned dogs I didn't have a clue! I made a lot of mistakes (and still do) but I am always striving to learn more and continue with my professional development. I wish I had had the knowledge 20 years ago that I have now. When I took my dogs to classes in those early years, the training didn't seem right, fair or ethical so I really wanted to find a better way.
Q: What are some of your favorite positive reinforcement techniques for the most commonly encountered client-dog problems?
A: Reminding people that we can easily fall into the trap of reprimanding our dogs for undesirable behaviors and not praising the good behaviors. Changing people’s mindsets makes a big difference. Also, using a mat to help owners teach their dogs to settle for short periods of time, using a filled Kong, and teaching fun tricks like “find it,” “spin,” “twist,” or scent work to emphasize focus and fun. Q: What awards or competition placements have you and your dog(s) achieved using force-free methods?
A: All of my dogs have been rescues with difficult starts to life, but one of my collie crosses, Freya, helped me to achieve my CAP1 clicker training award and she also gained her Good Citizen Bronze Award. Another of my dogs, Lola, achieved her Bronze Good Citizen Award and was successful in becoming a Pets as Therapy Dog. My current dog, Kilo, has passed the Good Citizen Bronze Award, as has Cliffie. Both are currently working towards the Silver. We attend regular scent work classes where she has achieved her Scentwork Level 5, as well as gaining numerous clean sweep rosettes at trials, and has now moved up to Novice Silver level.
Q: What drives you to be a force-free professional and why is it important to you?
A: My dogs are my family and they have feelings and emotions too, of course. My drive is to make sure I do my level best to make sure they are safe and comfortable and learning new things in a force-free environment. This translates further into me being a professional trainer and helping other people. Sometimes, having a small conversation with an owner who thinks they have to “dominate” their dog, and being able to change that to bonding and working as a team, makes all the difference. If I can help people make small changes in the way they view their relationship with their dogs, then that is a step in the right direction. Q: Why did you become a dog trainer or pet care provider?
A: I wanted to learn more about my own dogs. With the knowledge that I have gained and continue to gain, I now want to share it with owners to help them have a better bond with their dogs. Q: What do you consider to be your area of expertise?
A: Early puppy socialization and training; adolescent training; Kennel Club Awards; and helping owners to understand their dogs’ emotions and what motivates them, as well as creating a strong connection with their puppy/dog.
Q: What is the funniest or craziest situation you have been in with a pet and their owner?
A: I have a Great Dane called Duke who attends my Kennel Club classes and he weighs 170 lbs. He will quite often sit his rear end on his owner’s lap when waiting his turn in class and it looks so funny. He is a gentle giant and has just passed his Silver Award. Q: What reward do you get out of a day's training?
A: My reward is seeing an owner smile when their dog has done his first down or hand touch and responded with a relaxed, happy tail. I thoroughly enjoy the process of helping people connect with their dog.
Pet Professional Guild has partnered with BarkBox to provide all members with a 20% discount.
profile
“I wish I had had the knowledge 20 years ago that I have now. When I took my dogs to classes in those early years, the training didn't seem right, fair or ethical, so I really wanted to find a better way.” - Tracey Prall Q: Who has most influenced your career and how?
A: Anything written by Patricia Mc Connell, Karen Pryor and the late Sophia Yin. All have influenced the way I have pursued my training with dogs, showing that there is another way, a more ethical, fun way to train your dog. Q: What is your favorite part of your job?
A: Meeting lots of lovely puppies and dogs; helping people build solid foundations in their relationship with their dogs.
Q: What advice would you give to a new trainer starting out?
A: Volunteer at local classes, do some credible courses and read a lot. Ask questions and practice your listening skills as it’s not all about dog training, it is people training too.
Q: How has PPG helped you to become a more complete trainer?
A: PPG has helped underline and confirm everything I do as a trainer. Fear and pain are not options in training; fairness and kind methods create a good bond and trust. n
Canine Connections Dog Training and Dog Hotel (canineconnections.co.uk) is located in Walterstone, Hereford, England To be featured in the BARKS Profile section, please complete this form: bit.ly/2y9plS1
* Order a monthly box of dog goodies for your canine friend! * Special rates available for gifts for dog friends * A portion of proceeds from each box will go to help dogs in need The promocode can be found in the Member Area of the PPG website: PetProfessionalGuild.com /benefitinformation BARKS from the Guild/September 2018
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books
From an Ethologist’s Perspective
I
Breanna Norris reviews How Dogs Work by Raymond Coppinger and Mark Feinstein purchased How Dogs Work a couple of years ago from a DogWise booth at an event and have been looking forward to finding the time to read it when it eventually made its way to the top of my pile. If this book has not made it to your pile yet or is way down at the bottom, then I can safely tell you it is time to move it toward the top. On the front cover there is a quotation from a review by Robert Bailey who says: “Be prepared to be challenged.” Now, when Bob Bailey says this, I listen! His statement is actually true of any of Coppinger’s work and How Dogs Work is no exception. Indeed, this book will get you pondering and your science-loving soul singing. How Dogs Work looks at the behavior of dogs, not as our pets but as a species from an ethologist’s perspective. The authors write: “The ethologist isn’t driven by a special interest in a particular type of behavior or a specific hypothesis – the idea is just to get a wide-angle picture of what is going on, to get a handle on what seems to be behaviorally significant in an essentially continuous stream of movement.” Behaviors discussed in the book are foraging behaviors (this one is fascinating, especially when they discuss puppies), intrinsic behaviors, emergent behaviors and, one of my favorites, play behaviors. Motor patterns are also an ongoing theme of the book and because of this the development of these patterns are noted. According to the authors: “The fact is that we normally think about animals in terms of the adult alone as if adult were the goal of growth.” Puppy motor patterns get a special in-depth look here, and I found these interesting and thought provoking. Wolf pups also get some attention. Part of this book could really have been called How Puppies Work. Coppinger often reflects on studies with dogs, mostly livestock guardian dogs, border collies and a few sled dogs through storytelling and research. Indeed, his storytelling is often what I find so memorable about his style. For those of us that have respected him from afar, I think these stories within his writings and talks are what has been so noteworthy. It is a rarity to see such a science-minded person relay research through storytelling in such a dynamic way. Stories like that of the Maremma named Lina appears in his 2001 book, Dogs: A Startling New Understanding of Canine Origin and he continues with more stories about her in How Dogs Work. I do not find data memorable (or sometimes even digestible) but the stories are memorable. This is the sign of a good writer and teacher, in my opinion. The information sticks with you. The authors continually explain that even from the ethologist perspective behavior is complicated. They write: “One of the greatest difficulties we have with dog breeders is that they believe their dogs’ behavior is entirely hardwired and therefore inevitable – all you have to do is buy a livestockguarding dog and it will guard your sheep from predators. We ethologists, who otherwise agree that genetic hard-wiring is a crucial dimension of behavior, find ourselves frustratingly saying over and over that farmers have to pay attention to the developmental context: if you don’t raise the dog in the proper environment, you ruin its adult working performance. It’s the na-
r g fo ? n i k Loo ething Som
ture/nurture conundrum all over again.” They go on to explain: “...we don’t mean to suggest that behavior of animals can’t be altered. Our machine metaphor notwithstanding, dogs aren’t fixed automata relentlessly carrying out pre-programmed routines and nothing more. Certainly they can learn to do a great deal that isn’t ‘written in the genes’.” This is a science book and any science loving reader will enjoy it, whether they enjoy the company of dogs or not. The authors give nods to the two founders of ethology and Nobel Peace Prize winners, How Dogs Work examines the behavior of Konrad Lorenz and Niko Tindogs, not as pets but as a species from an bergen, who I could only ethologist’s perspective imagine would be pleased with this new ethology classic. Reading this book made me want to reread Lorenz’s King Solomon’s Ring, which I have not read in 20 years but was frequently reminded of while reading this book. To illustrate the essence of this book, I must share with you one of my favorite quotes that science lovers like me particularly appreciate: “But all things being equal, science generally prefers the simplest explanations that cover observable facts, even if more complicated ones might appeal to us intellectually or sentimentally.” Following this book, Coppinger went on to write What Is a Dog? with Lorna Coppinger. In August 2017, Coppinger passed away. I am so grateful that he left us with so many good stories, books, research and, above all, a deeper understanding of canines and critical thinking skills. I leave you with this quote from the afterword: “Perhaps you find some of these ideas unsettling or contrary to your own experience with dogs. Good! As lifelong college professors, we think that the best way to teach and learn is to encourage active and critical inquiry.” n
The PPG Archive currently holds over 2,150 articles, studies, podcasts, blogs and videos and is growing daily!
How Dogs Work Raymond Coppinger and Mark Feinstein (2015) 224 Pages University of Chicago Press ISBN: 9780226128139
Categories include: canine / feline / equine / piscine / pocket pets / murine / avian / behavior / training / business / trends / PPG news / book reviews / member profiles / opinion
petprofessionalguild.com/Guild-Archives
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BARKS from the Guild/September 2018
BARKS from the Guild is the bi-monthly trade publication from the Pet Professional Guild covering all things animal behavior and training, p...
Published on Aug 14, 2018
BARKS from the Guild is the bi-monthly trade publication from the Pet Professional Guild covering all things animal behavior and training, p... | https://issuu.com/petprofessionalguild/docs/bftg_september_2018_digital_edition | CC-MAIN-2018-39 | refinedweb | 36,858 | 59.84 |
I'm trying to implement a Hadoop Map/Reduce job that worked fine before in Spark. The Spark app definition is the following:
val data = spark.textFile(file, 2).cache()
val result = data
.map(//some pre-processing)
.map(docWeightPar => (docWeightPar(0),docWeightPar(1))))
.flatMap(line => MyFunctions.combine(line))
.reduceByKey( _ + _)
MyFunctions.combine
def combine(tuples: Array[(String, String)]): IndexedSeq[(String,Double)] =
for (i <- 0 to tuples.length - 2;
j <- 1 to tuples.length - 1
) yield (toKey(tuples(i)._1,tuples(j)._1),tuples(i)._2.toDouble * tuples(j)._2.toDouble)
combine
combine
java.lang.OutOfMemoryError: GC overhead limit exceeded
tuples
Adjusting the memory is probably a good way to go, as has already been suggested, because this is an expensive operation that scales in an ugly way. But maybe some code changes will help.
You could take a different approach in your combine function that avoids
if statements by using the
combinations function. I'd also convert the second element of the tuples to doubles before the combination operation:
tuples. // Convert to doubles only once map{ x=> (x._1, x._2.toDouble) }. // Take all pairwise combinations. Though this function // will not give self-pairs, which it looks like you might need combinations(2). // Your operation map{ x=> (toKey(x{0}._1, x{1}._1), x{0}._2*x{1}._2) }
This will give an iterator, which you can use downstream or, if you want, convert to list (or something) with
toList. | https://codedump.io/share/3LPe5zwM7JjZ/1/why-does-spark-fail-with-javalangoutofmemoryerror-gc-overhead-limit-exceeded | CC-MAIN-2018-13 | refinedweb | 242 | 51.65 |
Native mobile app development is a difficult environment. There are different operating systems, a vast array of handset manufacturers and a huge range of screen resolutions to build for. Thankfully, Facebook has released React Native – a framework designed to extend the React approach to mobile application development.
In this tutorial, we're going to build a real-time weather app using OpenWeatherMap's free API. I will cover working with React Native components, imagery and styles, and loading and parsing JSON data.
Getting started
First, download the source files from GitHub. You will find a 'source-imagery' folder that contains the tutorial images, an 'article-steps' folder that contains the source code for each step (plus comments), and a 'completed-project' folder containing the final source project.
You'll need Xcode for compiling the iOS apps (available from the App Store) and the Homebrew OSX package manager. Once you have Homebrew installed, you can open a Terminal window and run the following commands (if you have issues, there a guide here):
- brew install node to install Node.js
- brew install watchman to install Watchman, a file-watching service
- brew install flow, a static data type checker
- npm install -g react-native-cli to install React Native
You can create the project by typing react-native init weatherapp. Make a note of the project folder and open it to see React Native's default folder structure. The iOS directory is where the iOS platform's project files reside. The file we're interested in at this point is 'index.ios.js'. Open this up in your editor of choice.
Let's take a look at the folder structure:
- Lines 8-11 include the React requires for this component of the app
- Lines 15-32 declare the default class for the weatherapp and its render methods
- Lines 34-51 define the styles used in the app
- Line 53 is this Component's export name
The first thing we need to do is to prepare a blank canvas. Change the render method to:
render: function() { return ( <View style={[styles.container, {backgroundColor: this.state.backgroundColor}]}> </View> ); }
This creates an empty view using an array of styles - the container style and a state variable called backgroundColor. We will change the backgroundColor variable based on the current temperature when we query the weather API for data. We can also set the container's style to use flex: 1 for centring.
container: { flex: 1 },
Now we're going to use React's getInitialState method. This is invoked automatically on any component when the app is run. We'll use it to declare state variables that are used later. Add this above the render method in the WeatherApp class:
getInitialState: function() { return { weatherData: null, backgroundColor: "#FFFFFF" }; },
Now is a perfect time to jump into Xcode and hit play on the simulator to see your application. One of React Native's fantastic features is its recompile speed. Edit #FFFFFF to another colour and hit 'cmd+R' to see the almost instant reload – pretty neat!
Declaring constants
Let's declare the constants used for the background colours, and another for the openweathermap.org URL that provides the weather data. Add the following just below the React requires:
var BG_HOT = "#fb9f4d"; var BG_WARM = "#fbd84d"; var BG_COLD = "#00abe6"; var REQUEST_URL = "";
We'll also need to use another of React's built-in methods, componentDidMount. This is invoked automatically when a component loads successfully. We'll use it to query the navigator to get the current geolocation. Add the following after getInitialState method and before the render method:
componentDidMount: function() { navigator.geolocation.getCurrentPosition( location => { var formattedURL = REQUEST_URL + "lat=" + location.coords.latitude + "&lon=" + location.coords.longitude; console.log(formattedURL); }, error => { console.log(error); }); },
When compiled, the simulator will ask you to allow the application access to your location. You should see the completed URL (the variable formattedURL) displayed in the Xcode output window. React Native uses console.log() to display content like this – very handy for debugging.
The next step is to send our latitude and longitude to the openweathermap.org API. Add the following code below componentDidMount and above render:
fetchData: function(url) { fetch(url) .then((response) => response.json()) .then((responseData) => { var bg; var temp = parseInt(responseData.main.temp); if(temp < 14) { bg = BG_COLD; } else if(temp >= 14 && temp < 25) { bg = BG_WARM; } else if(temp >= 25) { bg = BG_HOT; } this.setState({ weatherData: responseData, backgroundColor: bg }); }) .done(); },
The above code connects to the API to get the JSON response. It then parses the location's temperature and updates the state variable backgroundColor. When the app next renders, it uses this new colour.
Finally, you need to add a line that will call this new fetchData method from the componentDidMount method. The following code goes directly below the console.log we used to display the URL:
this.fetchData(formattedURL);
As there may be a delay in loading API data, we need to display a new view that will act as holding text. The following method will return a new view with loading text:
renderLoadingView: function() { return ( <View style={styles.loading}> <Text style={styles.loadingText}> Loading Weather </Text> </View> ); },
As the app renders, it needs to check its state to see if the weather data is available or not:
if (!this.state.weatherData) { return this.renderLoadingView(); }
Now, add your own custom loading and loadingText styling into the styles and this section is done.
When you test the app, you should briefly see the loading message and then a background colour that reflects the temperature.
Weather information
It's now time to create the component that displays the weather information. Create a new folder called 'App' in your project root. In this, create another folder called 'Views' , into which we'll copy the WeatherView template from the article steps.
You will notice it is almost identical to the main class. As it already contains placeholder text, we'll jump back to our main index.ios.js class and add a declaration for the component.
var WeatherView = require('./App/Views/WeatherView.js');
Then in the render method, we simply add:
<WeatherView />
Upon restarting the simulator with 'cmd+R' , you should see 'TEST' displayed in the centre of the screen. You've now loaded your new component.
Adding icons
Now we're going to add icons to our Xcode project for each of the weather types (codes are provided here). In Xcode, open 'Images.xcassets' and drag all of the images from the 'weather_icons' folder.
To save a lot of typing, go into the GitHub repo, and replace your current 'WeatherView.js' with the one in Step 7. The new code you can see is an array, indexed by the weather icon code returned from the API. Before we can use it, we need to pass the weather data into this component.
In order to achieve this, we can use state variables again, and – thanks to propTypes – we can declare the data-type we expect back. Add the following directly under the WeatherView class creation:
propTypes: { weather: React.PropTypes.string, temperature: React.PropTypes.int, city: React.PropTypes.string, country: React.PropTypes.string },
Let's amend the markup returned from WeatherView. The following code adds a weather image, plus text for the temperature and city and country. Notice how the tags reference the props variables and, for the image, the variable for the key of the array, so the correct image shows.
<View style={styles.centreContainer}> <Image source={weatherIconArray[this.props.weather]} style={styles.weatherIcon} /> <Text style={styles.weatherText}>{this.props.temperature}°</Text> <Text style={styles.weatherTextLight}>{this.props.city},</Text> <Text style={styles.weatherTextLight}>{this.props.country}</Text> </View>
The styles we need to add for this are:
weatherIcon: { width: 132, height: 132, }, weatherText: { fontSize: 62, fontWeight: "bold", color: "#FFFFFF", textAlign: "center" }, weatherTextLight: { fontSize: 32, fontWeight: "100", color: "#FFFFFF", textAlign: "center" }
Here we specify the weather icons' width and height. The weatherText style creates a large, heavy font for the temperature, and weatherTextLight creates a light font for the location fields.
Adding data
All that remains is to add some data. Head to your 'index.ios.js' and update the render method to:
var city = this.state.weatherData.name.toUpperCase(); var country = this.state.weatherData.sys.country.toUpperCase(); var temp = parseInt(this.state.weatherData.main.temp).toFixed(0); var weather = this.state.weatherData.weather[0].icon.toString(); return ( <View style={[styles.container, {backgroundColor: this.state.backgroundColor}]}> <WeatherView weather={weather} temperature={temp} city={city} country={country} /> </View> );
This parses the JSON response and takes the city, country and temperature data, and passes it to the component. Now if you 'cmd+R' to restart the simulator, you should see your final app.
This is the core of building a React Native application. It's that simple! I hope you enjoy working with it.
Words: Anton Mills
Anton Mills is a creative technologist who also specialises in game development. This article was originally published in issue 270 of net magazine.
Liked this? Read these!
- Rapid prototyping in mobile app design
- How to build an app: try these great tutorials
- Free graphic design software available to you right now! | https://www.creativebloq.com/web-design/build-native-mobile-app-react-native-121518147 | CC-MAIN-2021-10 | refinedweb | 1,515 | 58.08 |
One error you may encounter when using NumPy is:
ValueError: all the input arrays must have same number of dimensions
This error occurs when you attempt to concatenate two NumPy arrays that have different dimensions.
The following example shows how to fix this error in practice.
How to Reproduce the Error
Suppose we have the following two NumPy arrays:
import numpy as np #create first array array1 = np.array([[1, 2], [3, 4], [5,6], [7,8]]) print(array1) [[1 2] [3 4] [5 6] [7 8]] #create second array array2 = np.array([9,10, 11, 12]) print(array2) [ 9 10 11 12]
Now suppose we attempt to use the concatenate() function to combine the two arrays into one array:
#attempt to concatenate the two arrays np.concatenate([array1, array2]) ValueError: all the input arrays must have same number of dimensions, but the array at index 0 has 2 dimension(s) and the array at index 1 has 1 dimension(s)
We receive a ValueError because the two arrays have different dimensions.
How to Fix the Error
There are two methods we can use to fix this error.
Method 1: Use np.column_stack
One way to concatenate the two arrays while avoiding errors is to use the column_stack() function as follows:
np.column_stack((array1, array2)) array([[ 1, 2, 9], [ 3, 4, 10], [ 5, 6, 11], [ 7, 8, 12]])
Notice that we’re able to successfully concatenate the two arrays without any errors.
Method 2: Use np.c_
We can also concatenate the two arrays while avoiding errors using the np.c_ function as follows:
np.c_[array1, array2] array([[ 1, 2, 9], [ 3, 4, 10], [ 5, 6, 11], [ 7, 8, 12]])
Notice that this function returns the exact same result as the previous method.
Additional Resources
The following tutorials explain how to fix other common errors in Python:
How to Fix KeyError in Pandas
How to Fix: ValueError: cannot convert float NaN to integer
How to Fix: ValueError: operands could not be broadcast together with shapes | https://www.statology.org/numpy-all-input-arrays-must-have-same-number-of-dimensions/ | CC-MAIN-2021-39 | refinedweb | 336 | 58.62 |
SplineData.MakeLinearSplineLinear()
On 28/01/2013 at 04:30, xxxxxxxx wrote:
Hi guys.
I am using MakeLinearSplineLinear() in PYTHON, but this function is only implemented since R13. What function should I look in R12?
What I need to make, is in INIT stage I need to set 2 points on spline. Ho should this be done in R12?
Thank you.
On 28/01/2013 at 04:43, xxxxxxxx wrote:
Hi Tomas,
you can use the SplineData.SetKnot() method.
On 28/01/2013 at 04:47, xxxxxxxx wrote:
Isn't SplineData.SetKnot() implemented only since R13?
On 28/01/2013 at 04:50, xxxxxxxx wrote:
Originally posted by xxxxxxxx
Isn't SplineData.SetKnot() implemented only since R13?
Hi Tomas,
Yes, you should instead call SplineData.InsertKnots() and set the tension with SplineData.SetRound().
On 28/01/2013 at 04:55, xxxxxxxx wrote:
Originally posted by xxxxxxxx
Isn't SplineData.SetKnot() implemented only since R13?
You're right, my fault.
On 28/01/2013 at 05:33, xxxxxxxx wrote:
Thanks guys:), InsertKnot() seems to be working.
But maybe I am missing something else?
I am getting four point on the spline now :(
self.sizeSpline = c4d.SplineData()
self.sizeSpline.SetRound(0)
self.sizeSpline.InsertKnot(0, 1)
self.sizeSpline.InsertKnot(1, 0)
And it looks nothing as expected:)
On 28/01/2013 at 05:37, xxxxxxxx wrote:
Hi Tomas,
I'm sure you wanted to thank Yannick, he told you about the InsertKnot() method. ;-)
_> >> I am getting four point on the spline now :( _
You probably need to remove the points that are there by default. Use the DeleteAllKnots()
method before inserting your knots.
On 28/01/2013 at 05:47, xxxxxxxx wrote:
yeap, sorry about that Yannick:)
WOW - I removed points and now it works. Wo-Hoooo. Thank you everybody.
In case someone will find this topic useful, here's a code
spline = c4d.SplineData() spline.DeleteKnot(0) #Delete Knot 0 spline.DeleteKnot(0) #Delete Knot 1 spline.InsertKnot(0, 1) #Set the first knot's position spline.InsertKnot(1, 0) #Set the second knot's position print "Point Count: ", spline.GetKnotCount()
On 28/01/2013 at 05:53, xxxxxxxx wrote:
Hi Tomas,
Instead of using DeleteKnot() two times, you can just use DeleteAllKnots () to flush all knots
from the SplineData (as I suggested above).
On 28/01/2013 at 06:12, xxxxxxxx wrote:
Strage, but I get error "AttributeError: 'c4d.SplineData' object has no attribute 'DeleteAllKnots'"
if I use this:
spline = c4d.SplineData()
spline.DeleteAllKnots()
On 28/01/2013 at 06:21, xxxxxxxx wrote:
Hi Tomas,
I just tested it in R12 and I get the same error. The R12 documentation must be wrong then.
Alternatively, you can use this function:
def flush_splinedata(spl) : count = spl.GetKnotCount() for i in xrange(count) : spl.DeleteKnot(0) spl = c4d.SplineData() flush_splinedata(spl)
On 28/01/2013 at 06:23, xxxxxxxx wrote:
Niklas, you'r THE MAN!!!
Thank you. | https://plugincafe.maxon.net/topic/6892/7728_splinedatamakelinearsplinelinear | CC-MAIN-2021-17 | refinedweb | 485 | 77.64 |
Suppose we have two lists costs_from and costs_to of same size where each index i represents a city. It is making a one-way road from city i to j and their costs are costs_from[i] + costs_to[j]. We also have a list of edges where each edge contains [x, y] indicates there is already a one-way road from city x to y. If we want to go to any city from city 0, we have to find the minimum cost to build the necessary roads.
So, if the input is like costs_from = [6, 2, 2, 12] costs_to = [2, 2, 3, 2] edges = [[0, 3]], then the output will be 13, as we can go from 0 to 2 for a cost of 9. After that, we can go from 2 to 1 for a cost of 4. And we already have the road to go to 3 from 0. So total is 9 + 4 = 13.
To solve this, we will follow these steps −
Let us see the following implementation to get better understanding −
#include using namespace std; class Solution { public: int solve(vector& costs_from, vector& costs_to, vector>& g) { int n = costs_from.size(); int ret = 0; map> edges; map> redges; for (auto& it : g) { edges[it[0]].push_back(it[1]); redges[it[1]].push_back(it[0]); } int from_cost = INT_MAX; set visited; set reachable; queue q; reachable.insert(0); q.push(0); while (!q.empty()) { int node = q.front(); q.pop(); for (int i : edges[node]) { if (!reachable.count(i)) { reachable.insert(i); q.push(i); } } from_cost = min(from_cost, costs_from[node]); } int global_min = *min_element(costs_from.begin(), costs_from.end()); ret += from_cost - global_min; vector po; function dfs; dfs = [&](int i) { if (!visited.count(i) && !reachable.count(i)) { visited.insert(i); for (int j : edges[i]) { dfs(j); } po.push_back(i); } }; for (int i = 0; i < n; i++) dfs(i); reverse(po.begin(), po.end()); function dfs2; dfs2 = [&](int i) { if (visited.count(i)) return true; if (reachable.count(i)) return false; visited.insert(i); reachable.insert(i); bool ret = true; for (int j : redges[i]) { ret &= dfs2(j); } return ret; }; for (int i : po) { if (reachable.count(i)) continue; visited.clear(); bool initial = dfs2(i); if (initial) { int best = INT_MAX; for (int j : visited) { best = min(best, costs_to[j]); } ret += global_min + best; } } return ret; } }; int solve(vector& costs_from, vector& costs_to, vector>& edges) { return (new Solution())->solve(costs_from, costs_to, edges); } int main(){ vector costs_from = {6, 2, 2, 12}; vector costs_to = {2, 2, 3, 2}; vector> edges = {{0, 3}}; cout << solve(costs_from, costs_to, edges); }
{6, 2, 2, 12}, {2, 2, 3, 2}, {{0, 3}}
13 | https://www.tutorialspoint.com/program-to-find-minimum-number-of-roads-we-have-to-make-to-reach-any-city-from-first-one-in-cplusplus | CC-MAIN-2021-49 | refinedweb | 431 | 64 |
Scenario:We are loading data from source table to destination table. The data has to be converted to destination data types before we insert the data into Destination table. We are using Data Conversion to convert the data types of input columns. If data is not able to convert to data type we have specified in Data Conversion Transformation we want to redirect those records. After redirecting those records, we want to log the information with Column Name which became the reason for redirection.
Solution :
Let's create SSIS Package and see if we can get error column name without doing any custom coding.
Step 1:
Create SSIS Package and bring data flow task to Control Flow pane. Use the OLE DB Source to extract data for Source Table. Here is definition of our Source Table with couple of records
CREATE TABLE [dbo].[SourceTable](
[Name] [varchar](100) NULL,
[SaleDate] [varchar](50) NULL
)
Insert into dbo.SourceTable
Values
('Aamir','2013-12-03 10:19:56.887'),
('Raza','Test Date')
We want to convert SaleDate to DateTime before insert into Destination table. If any value will not be able to convert then we want to redirect the row from Data Conversion Transformation.
Let's create Data Flow Task with all transformation as shown below
Redirect the Rows If truncation or Error occur
Bring Multicast and connect to the Error Output of Data Conversion. After that put Data Viewer to see the redirected rows as shown below
After executing our package we can see that the one row was converted successfully and moved to destination but one row could not converted to required data types and it is redirect to multicast. In above snapshot we can see ErrorCode, ErrorColumn (Lineage ID) Number and ErrorCode Description but we can't really tell it happened because of SaleDate Column or Name column.
Read Package File to Get LineageIDs
Our goal is to get the column name, to do that we have to read the package file(.dtsx) and get the Lineage IDs for columns. The lineageID can be same for different columns in different Tasks. We will also read the Task Name so each record will be unique with combination of Task Name.
Step 2:
We will use Data Flow Task as our very first Task to read the Package definition and extract Lineage IDs, Column Names and Task Names and save these records in Cache Transformation. So we can use this data set anywhere in our package by using Lookup transformation to extract Error column Names by joining on Error Column( LineageID) and Task Name.
Let's drag data flow task to Control Flow pane and then bring Script Component. As we have to read the definition of SSIS Package. I created a variable and saved the location of same package I am working on.
Variable Name : VarPackagePath
Type : String
Value : Where ever you have saved your package.
Configure Script Component as Source and Provide the variable value for SSIS Package Path.
Go to Input and Output Columns and add columns as shown
Hit on Edit Script and paste below script , The only part I wrote is in Red
/* System.Collections;
using System.Xml;
CreateNewOutputRows()
{
//Declare Variables
String TaskName;
String ColName;
Int32 ColLineageID;
String ColKey;
//Read the Package File
XmlDocument PackageFile = new XmlDocument();
PackageFile.Load(Variables.VarPackagePath);
//Create Hash Table
Hashtable ColKeyTable = new Hashtable();
XmlNamespaceManager NameSpcMgr = new XmlNamespaceManager(PackageFile.NameTable);
NameSpcMgr.AddNamespace("DTS", "");
foreach (XmlNode childnode in PackageFile.SelectNodes("//*[@lineageId != '' and @name != '']"))
{
XmlNode ExecutableNode = childnode.SelectSingleNode("ancestor::DTS:Executable[1]", NameSpcMgr);
TaskName = ExecutableNode.SelectSingleNode("DTS:Property[@DTS:Name='ObjectName']", NameSpcMgr).InnerText;
ColName = childnode.Attributes["name"].Value;
ColLineageID = Convert.ToInt32(childnode.Attributes["lineageId"].Value);
ColKey = TaskName + ColName + ColLineageID;
if (!ColKeyTable.ContainsKey(ColKey))
{
ColKeyTable.Add(ColKey, DBNull.Value);
Output0Buffer.AddRow();
Output0Buffer.ColLineageID = ColLineageID;
Output0Buffer.ColName = ColName;
Output0Buffer.TaskName = TaskName;
}
}
}
}
Step 3:
Bring Cache Transformation and connect Script component to it and configure Cache Transformation as shown.
Put Data Viewer between Script component and Cache Transformation and see if LineageID,Column Name and Task Name is read correctly.
Step 4:
As we have the Task Name, Column Name and Lineage ID , we can use this information in our actually data flow where rows are redirecting and get the column Name by joining on Task Name and Lineage ID.
Add Derived Column and Add Column "DER_DFT_Name". The value of this column will be the name of Data Flow it is in. We will be using this in Lookup to find out Error Column Name for any record which is redirected in this data flow.
Final Output :
Connect the Matching output of Lookup to Multicast and put Data Viewer. Now we should be able to find out the Column Name which produces error for redirection of row.
Summary:
Quick Summary, we have to read our Package file in First Data flow and then use that information ( Task Name, Column Name, LienageID) where ever we need that in our SSIS Package. We can create a template package with First Data Flow to read package file and save information in Cache Transformation for us to use later.
OR
we can create a meta data table and read our all packages and save LineageIDs,Column Names and Task Names and then we do not have to read the package file inside the package.
OR
we can create a meta data table and read our all packages and save LineageIDs,Column Names and Task Names and then we do not have to read the package file inside the package. | http://www.techbrothersit.com/2013/12/ssis-how-to-get-error-column-name-in.html | CC-MAIN-2017-04 | refinedweb | 916 | 54.42 |
This section illustrates you how to find the second largest number from an array. For this purpose, we have allowed the user to enter the array elements of their choice and determine the largest among them. Pulls the largest number out from the array and again check for the largest one i.e. for the second largest and display it.
Here is the code:
import java.util.*; class ArrayExample { public static void main(String[] args) { int secondlargest = 0; int largest = 0; Scanner input = new Scanner(System.in); System.out.println("Enter array values: "); int arr[] = new int[5]; for (int i = 0; i < arr.length; i++) { arr[i] = input.nextInt(); if (largest < arr[i]) { secondlargest = largest; largest = arr[i]; } if (secondlargest < arr[i] && largest != arr[i]) secondlargest = arr[i]; } System.out.println("Second Largest number is: " + secondlargest); } }
Output:
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Posted on: July | http://www.roseindia.net/tutorial/java/core/findsecondLargestNumber.html | CC-MAIN-2017-30 | refinedweb | 142 | 60.21 |
A practical guide to TypeScript decorators
Information drawn from
We can all agree that JavaScript is an amazing programming language that allows you to build apps on almost any platform. Although it comes with its own fair share of drawbacks, TypeScript has done a great job of covering up some gaps inherent in JavaScript. Not only does it add type safety to a dynamic language, but it also comes with some cool features that don’t exist yet in JavaScript, such as decorators.
What are decorators?
Although the definition might vary for different programming languages, the reason why decorators exist is pretty much the same across the board. In a nutshell, a decorator is a pattern in programming in which you wrap something to change its behavior.
In JavaScript, this feature is currently at stage two. It’s not yet available in browsers or Node.js, but you can test it out by using compilers like Babel. Having said that, it’s not exactly a brand new thing; several programming languages, such as Python, Java, and C#, adopted this pattern before JavaScript.
Even though JavaScript already has this feature proposed, TypeScript’s decorator feature is different in a few significant ways. Since TypeScript is a strongly typed language, you can access some additional information associated with your data types to do some cool stuff, such as runtime type-assertion and dependency injection.
Getting started
Start by creating a blank Node.js project.
$ mkdir typescript-decorators $ cd typescript decorators $ npm init -y
Next, install TypeScript as a development dependency.
$ npm install -D typescript @types/node
The @types/node package contains the Node.js type definitions for TypeScript. We need this package to access some Node.js standard libraries.
Add an npm script in the package.json file to compile your TypeScript code.
{ // ... "scripts": { "build": "tsc" } }
TypeScript has labeled this feature as experimental. Nonetheless, it’s stable enough to use in production. In fact, the open source community has been using it for quite a while.
To activate the feature, you’ll need to make some adjustments to your tsconfig.json file.
{ "compilerOptions": { "target": "ES5", "experimentalDecorators": true } }
Create a simple TypeScript index.ts file to test it out.
console.log("Hello, world!");
$ npm run build $ node index.js Hello, world!
Instead of repeating this command over and over, you can simplify the compilation and execution process by using a package called ts-node. It’s a community package that enables you to run TypeScript code directly without first compiling it.
Let’s install it as a development dependency.
$ npm install -D ts-node
Next, add a start script to the package.json file.
{ "scripts": { "build": "tsc", "start": "ts-node index.ts" } }
Simply run npm start to run your code.
$ npm start Hello, world!
For reference, I have all the source code on this article published on my GitHub. You can clone it onto your computer using the command below.
$ git clone
Types of decorators
In TypeScript, decorators are functions that can be attached to classes and their members, such as methods and properties. Let’s look at some examples.
Class decorator
When you attach a function to a class as a decorator, you’ll receive the class constructor as the first parameter.
const classDecorator = (target: Function) => { // do something with your class } @classDecorator class Rocket {}
If you want to override the properties within the class, you can return a new class that extends its constructor and set the properties.
const addFuelToRocket = (target: Function) => { return class extends target { fuel = 100 } } @addFuelToRocket class Rocket {}
Now your Rocket class will have a fuel property with a default value of 100.
const rocket = new Rocket() console.log((rocket).fuel) // 100
Method decorator
Another good place to attach a decorator is the class method. Here, you’re getting three parameters in your function: target, propertyKey, and descriptor.
const myDecorator = (target: Object, propertyKey: string, descriptor: PropertyDescriptor) => { // do something with your method } class Rocket { @myDecorator launch() { console.log("Launching rocket in 3... 2... 1... 🚀") } }
The first parameter contains the class where this method lives, which, in this case, is the Rocket class. The second parameter contains your method name in string format, and the last parameter is the property descriptor, a set of information that defines a property behavior. This can be used to observe, modify, or replace a method definition.
The method decorator can be very useful if you want to extend the functionality of your method, which we’ll cover later.
Property decorator
Just like the method decorator, you’ll get the target and propertyKey parameter. The only difference is that you don’t get the property descriptor.
const propertyDecorator = (target: Object, propertyKey: string) => { // do something with your property }
There are several other places to attach your decorators in TypeScript, but that’s beyond the scope of this article. If you’re curious, you can read more about it in the TypeScript docs.
Use cases for TypeScript decorators
Now that we’ve covered what decorators are and how to use them properly, let’s take a look at some specific problems decorators can help us solve.
Calculate execution time
Let’s say you want to estimate how long it takes to run a function as a way to gauge your application performance. You can create a decorator to calculate the execution time of a method and print it on the console.
class Rocket { @measure launch() { console.log("Launching in 3... 2... 1... 🚀"); } }
The Rocket class has a launch method inside of it. To measure the execution time of the launch method, you can attach the measure decorator.
import { performance } from "perf_hooks"; const measure = ( target: Object, propertyKey: string, descriptor: PropertyDescriptor ) => { const originalMethod = descriptor.value; descriptor.value = function (...args) { const start = performance.now(); const result = originalMethod.apply(this, args); const finish = performance.now(); console.log(`Execution time: ${finish - start} milliseconds`); return result; }; return descriptor; };
As you can see, the measure decorator replaces the original method with a new one that enables it to calculate the execution time of the original method and log it to the console.
To calculate the execution time, we’ll use the Performance Hooks API from the Node.js standard library.
Instantiate a new Rocket instance and call the launch method.
const rocket = new Rocket(); rocket.launch();
You’ll get the following result.
Launching in 3... 2... 1... 🚀 Execution time: 1.0407989993691444 milliseconds
Decorator factory
To configure your decorators to act differently in a certain scenario, you can use a concept called decorator factory.
Decorator factory is a function that returns a decorator. This enables you to customize the behavior of your decorators by passing some parameters in the factory.
Take a look at the example below.
const changeValue = (value) => (target: Object, propertyKey: string) => { Object.defineProperty(target, propertyKey, { value }); };
The changeValue function returns a decorator that change the value of the property based on the value passed from your factory.
class Rocket { @changeValue(100) fuel = 50 } const rocket = new Rocket() console.log(rocket.fuel) // 100
Now, if you bind your decorator factory to the fuel property, the value will be 100.
Automatic error guard
Let’s implement what we’ve learned to solve a real-world problem.
class Rocket { fuel = 50; launchToMars() { console.log("Launching to Mars in 3... 2... 1... 🚀"); } }
Let’s say you have a Rocket class that has a launchToMars method. To launch a rocket to Mars, the fuel level must be above 100.
Let’s create the decorator for it.
const minimumFuel = (fuel: number) => ( target: Object, propertyKey: string, descriptor: PropertyDescriptor ) => { const originalMethod = descriptor.value; descriptor.value = function (...args) { if (this.fuel > fuel) { originalMethod.apply(this, args); } else { console.log("Not enough fuel!"); } }; return descriptor; };
The minimumFuel is a factory decorator. It takes the fuel parameter, which indicates how much fuel is needed to launch a particular rocket.
To check the fuel condition, wrap the original method with a new method, just like in the previous use case.
Now you can plug your decorator to the launchToMars method and set the minimum fuel level.
class Rocket { fuel = 50; @minimumFuel(100) launchToMars() { console.log("Launching to Mars in 3... 2... 1... 🚀"); } }
Now if you invoke the launchToMars method, it won’t launch the rocket to Mars because the current fuel level is 50.
const rocket = new Rocket() rocket.launchToMars() Not enough fuel!
The cool thing about this decorator is that you can apply the same logic into a different method without rewriting the whole if-else statement.
Let’s say you want to make a new method to launch the rocket to the moon. To do that, the fuel level must be above 25.
Repeat the same code and change the parameter.
class Rocket { fuel = 50; @minimumFuel(100) launchToMars() { console.log("Launching to Mars in 3... 2... 1... 🚀"); } @minimumFuel(25) launchToMoon() { console.log("Launching to Moon in 3... 2... 1... 🚀") } }
Now, this rocket can be launched to the moon.
const rocket = new Rocket() rocket.launchToMoon() Launching to Moon in 3... 2... 1... 🚀
This type of decorator can be very useful for authentication and authorization purposes, such as checking whether a user is allowed to access some private data or not.
Conclusion
It’s true that, in some scenarios, it’s not necessary to make your own decorators. Many TypeScript libraries/frameworks out there, such as TypeORM and Angular, already provide all the decorators you need. But it’s always worth the extra effort to understand what’s going on under the hood, and it might even inspire you to build your own TypeScript framework.
------------------------------------------------------------------------
Last update on 26 Apr 2022
--- | https://codersnack.com/typescript-decorators-a-practical-guide/ | CC-MAIN-2022-33 | refinedweb | 1,586 | 58.69 |
Barry deFreese, le Wed 27 May 2009 23:09:29 -0400, a écrit : > This block of code in Src/cond.c seems to be the initial issue with > zsh-beta: Yes it is. > #if defined(GET_ST_MTIME_NSEC) && defined(GET_ST_ATIME_NSEC) > if (!(st = getstat(left))) > return 1; > return (st->st_atime == st->st_mtime) ? > GET_ST_ATIME_NSEC(*st) > GET_ST_MTIME_NSEC(*st) : > st->st_atime > st->st_mtime; > #else > return !((st = getstat(left)) && st->st_atime <= st->st_mtime); > #endif The GET_ST_* macros use the st_atim field, which we do provide (as we should and as Linux does) when __USE_MISC gets defined by <features.h>. IIRC the configure script of zsh properly sets some _BSD_SOURCE to get it but apparently it is not propagated up to here, that's what should be tracked. Samuel | https://lists.debian.org/debian-hurd/2009/05/msg00071.html | CC-MAIN-2015-40 | refinedweb | 121 | 65.12 |
After a solution is accepted it would be very helpful to know how to make it run faster looking at better performing solution(s).
int maxDepth(TreeNode* root) { if (root == NULL) return 0; stack<TreeNode*> myStack; stack<int> depthStack; if (root != NULL) myStack.push(root); int maxDepth = 0; depthStack.push(0); while (!myStack.empty()) { TreeNode *p = myStack.top(); int d = depthStack.top(); if (d > maxDepth) maxDepth = d; myStack.pop(); depthStack.pop(); if (p->left != NULL) {myStack.push(p->left); depthStack.push(d + 1);} if (p->right != NULL) {myStack.push(p->right); depthStack.push(d + 1);} } return maxDepth + 1; }
Sometimes one's solution is of top performing just because the server was at very good form when he's coding. Leetcode's server configurations are probably changing as well, as I found my old solution would have poorer performance in new submissions.
int maxDepth(TreeNode* root) { if(root == NULL){ return 0; } int depth_left = maxDepth(root->left) + 1; int depth_right = maxDepth(root->right) + 1; return depth_left > depth_right ? depth_left : depth_right; }
@rainhacker I agree this would be awesome to see (and learn). But the OJ times are very inconsistent, something might score in top 25% on one submission and then submitting the exact same solution a minute later might score in bottom 25%. It's hard to derive much meaning from the OJ times.
I would love to see some actual measurement of the number of cycles or calculations or something not dependent on time or maybe just running your solution 100 times and getting an average may make the number more meaningful. It's not easy to figure out the best way to "measure" a solution quantitatively and in the absence people tend to place a lot of value on the brevity of their solution "3 lines!" which to me doesn't seem to be a good indicator of anything really.
@jdrogin
On top of this discussion.
I wonder if the run time is the TOTAL of run time for each individual testcase.
If this is the case (and I believe so), we could just randomly generate some big testcases pools.
Especially for algorithm questions that operations on integers / array of integers / etc.
Segmenting the runtime in the bandwidth of 1 ms could be meaning less when you have just a handful of testcases.
I imagine, even with the same time / space complexity, depending on the way people code, the run time could still vary a bit.
And the only way to distinguish would be to have a big pool of testcases.
public class Solution {
public int maxDepth(TreeNode root) {
int left=1;int right=1;
if (root==null) return 0;
else{
if(root.left!=null){
left=maxDepth(root.left)+1;
}
if(root.right!=null){
right=maxDepth(root.right)+1;
}
}
return Math.max(left,right); }
}
@Patrick1993 I think this answer is better than mine because I called the recursive function in my return value, which doubles my runtime. Thx
@muzhou @Patrick1993 my solution is very similar to Patrick1993's solution except that I save on one addition by first comparing the values return by recursive call and then only adding to the one that is greatest.
public int maxDepth(TreeNode root) { if (root == null) return 0; int maxL = maxDepth(root.left); int maxR = maxDepth(root.right); if ( maxL > maxR) return maxL + 1; else return maxR + 1; } }
Looks like your connection to LeetCode Discuss was lost, please wait while we try to reconnect. | https://discuss.leetcode.com/topic/7139/can-leetcode-share-top-performing-solution-s-of-problems-for-each-supported-language | CC-MAIN-2017-47 | refinedweb | 569 | 63.39 |
My experiments with asp.net mvc, jquery, wpf, silverlight, sharepoint, tdd and design patterns.
Welcome back readers! This blog post is about a small tip that may make working with WCF servicehost a bit easier, if you have lots of services and you need to quickly host them for testing.
Recently I was encountered a situation where we were faced to create multiple service host quickly for testing. Here is the code snippet which is pretty self explanatory. You can put this code in your service host which in this case is a console application.
class Program { static void Main(string[] args) { // Stores all hosts List<ServiceHost> hosts = new List<ServiceHost>(); try { // Get the services element from the serviceModel element in the config file var section = ConfigurationManager.GetSection("system.serviceModel/services") as ServicesSection; if (section != null) { foreach (ServiceElement element in section.Services) { // NOTE : If the assembly is in another namespace, provide a fully qualified name here in the form // <typename, namespace> // For e.g. Business.Services.CustomerService, Business.Services var serviceType = Type.GetType(element.Name); // Get the typeName var host = new ServiceHost(serviceType); hosts.Add(host); // Add to the host collection host.Open(); // Open the host } } Console.ReadLine(); } catch (Exception e) { Console.WriteLine(e.Message); Console.ReadLine(); } finally { foreach (ServiceHost host in hosts) { if (host.State == CommunicationState.Opened) { host.Close(); } else { host.Abort(); } } } } }
I hope you find this useful. You can make this as a windows service if required.
Skin design by Mark Wagner, Adapted by David Vidmar | http://geekswithblogs.net/rajeshpillai/archive/2011/02/24/wcf-automatically-create-service-hosts.aspx | CC-MAIN-2014-10 | refinedweb | 248 | 52.46 |
Difference between revisions of "Welcome STEM Developers"
Revision as of 11:29, 1 February 2007
Contents
- 1 Introduction
- 2 STEM Installation Instructions
- 3 Software Engineering
- 3.1 Coding Conventions and Guidelines
- 3.2 Source Code Control
- 3.3 Plans to move STEM to Open Source repository
- 3.4 Subversion Source Code Control System
- 3.5 Getting Access to the STEM Source Code Repository
- 3.6 Accessing the STEM Source Code Repository with Subclipse
- 3.7 Creating a project in the STEM Source Code Repository with Subclipse
- 3.8 Software Engineering Documentation To Do's
- 4 STEM subprojects
- 5 STEM Data
- 6 Other Information
- 7 Books OHF STEM developers
- Read this article.
- When you find missing, confusing, erroneous information please contribute, by fixing the problem. This Wiki allows any registered user to update content. Please do!
- Visit the OHF project page. Bookmark it.
- Subscribe to the project mailing list. The mailing list is used for all internal developer communication. It is preferred to send private Emails.
- Install Java 5.0 and Eclipse 3.2]
- Obtain the source code for the STEM project from the CVS repository.
STEM Installation Instructions
Installing Java™ 5 JVM
STEM requires Java Version 1.5. IBMers should obtain the IBM version of Java 1.5. Others can use either IBM's Java 1.5 or the Sun Java 1.5 [
Running Stem as a standalone application If you want to first tryout STEM as an application then we provide a standalone version of STEM that only requires that you have Java 1.5 or higher installed.
You can get the file by going to the project page: and then clicking on . that.stem;
/******************************************************************************* * Copyright (c) 2006 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/
import ... ;
National Language Support
STEM supports languages other than English. The basic process is to provide properly named properties files that mirror the "native" English properties files. These files are grouped into a "plug-in fragment" which acts as an "add on" to a plug-in and adds the files of the fragment to the plug-in as if they were there originally. We separate them so that additional languages can be added without changing the original plug-in.
If a native file is named "messages.properties", then the corresponding file with Spanish translations for the messages would be named "messages_es.properties". It is also possible to provide translations that are specific to a particular country, for instance, for Canadian English, the corresponding file would be "messages_en_CA.properties". For Californian English it would be "messages_en_US_CA.properties". This follows the regular Java conventions.
To get us started, I've created one new plug-in fragment called "org.eclipse.ohf.stem.ui.nl1" which contains the properties files for the main UI component of STEM in the plug-in "org.ecliopse.ohf.stem.ui". Each of the other plug-ins with translatable strings will require their own (yet to be created) plug-in fragment. I also created properly named, untranslated, properties files for Californian English, Canadian English, Spanish, Hebrew, Tamil and Chinese in the new fragment.
To start STEM (Eclipse) in a language different from the working language of the operating system, you need to use the "-nl" command line parameter. For example, use "-nl en_US_CA" to start STEM in Californian English, or "-nl es" to start it in Spanish. You might find it useful to create a new launch configuration in Eclipse with the parameter specified. I have one for each language.
1) Use the "Run..." menu item to open the "Create, manage, and run configurations" dialogue. 2) Duplicate the Eclipse application you use to launch STEM and rename the new one to reflect the language (e.g., "STEM Californian") 3) Select the "Arguments" tab 4) In the "Program arguments" text box enter the command line parameter (E.g., "-nl en_US_CA" without the quotes, for Californian English). 5) Apply 6) Run
Open the Active Simulations View and you should see a different title than normal.
Here are some good resources for more detailed information:
"Building Commercial Quality Plug-ins", Clayberg,
"The Java Developer's Guide to ECLIPSE", D'Anjou, et al.
Source Code Control
<P [[2]]
Books
[3]Java in a Nutshell, Fifth Edition Flanagan, D., O'Reilly, 2005, ISBN 0-596-00773-6. This is a great reference for Java™. Indispensable.
[4]Eclipse Modeling Framework Budinsky, F., et al, Addison-Wesley. 2003. ISBN 0131425420. This is THE book on the eclipse modeling framework (EMF). Note- a second edition is due out very soon, and is available for pre-order
[5]Official Eclipse 3.0 FAQs Arthorne, J., Laffra, C., Addison-Wesley, 2004, ISBN 0321268385. This is an excellent source of quick answers to great questions.
[6]Eclipse:Building Commercial-Quality Plug-Ins Clayberg, E., Rubel, D., Addison-Wesley, 2004. ISBN: 0321228472. Good reference, but starts out a bit too simply.
[7.
[8]Eclipse Rich Client Platform: Designing, Coding, and Packaging Java™ Applications McAffer, J., et al., Addison-Wesley, 2005, ISBN 0321334612.
[9]Eclipse Cookbook Holzner, S., O'Reilly, 2004, ISBN 0-596-00710-8. Good “how to” guide to use eclipse, less for eclipse plug-in development itself.</P> [10]>
[11]UML for Java™ Programmers Martin, R., Prentice Hall, 2003, ISBN 0131428489. Good “what you need to know” introduction to UML.
[12 | http://wiki.eclipse.org/index.php?title=Welcome_STEM_Developers&diff=next&oldid=25533 | CC-MAIN-2020-34 | refinedweb | 912 | 59.8 |
In this tutorial, you will learn how to build a chat widget powered by CometChat. You will make use of the Wolox Chat widget. The end goal is to provide a means of communication between you and your users without them necessarily leaving the website to contact you. You can find the entire code for this project on this repo.
Here is a demo of what you will build
Go to your CometChat dashboard and create a new app called wolox-chat-widget-cometchat. After creating your new app, make sure the badge on card says v2 as the API you’ll be using is a bit different from v1 apps.
Next, click on the explore link and go to the API Keys tab. You should see an already generated API key and APP ID. Copy them as you’ll need them shortly. After copying out your keys, create a new user on the users tab. Use admin as the uid and Admin as the name. Note this down as well because you’ll need it soon enough.
First, create a project folder called wolox-chat-widget-cometchat for your project. In this folder, create two other folders. One called backend and the other called frontend. As mentioned earlier, this app requires a Node.js backend and a React frontend. In the backend, you'll set up a REST API that will communicate with the CometChat API and serve data to the frontend.
Next, open the backend folder in your terminal and run this command:
npm init -y
This command generates a package.json file in your backend folder. Next, install dependencies for your backend by running this command:
npm install axios cors dotenv express uuid
Here is a rundown of the dependencies you just installed:
Next, you need to setup your environment variables. Create a new .env file in the backend folder and paste this snippet:
COMETCHAT_API_KEY=YOUR_COMETCHAT_API_KEY
COMETCHAT_APP_ID=YOUR_COMETCHAT_APP_ID
Replace the placeholders in this file with the corresponding credentials from the CometChat app you created earlier. Note that you should never commit your env file to version control.
Next, you need to create a script to run your application. Open your package.json file and add a scripts key for running a Node server. The scripts JSON object already exists, so add the server property like so:
# backend/package.json
"scripts": {
...
"server": "node index.js"
}
The index.js file referenced here does not exist yet, so create an index.js file in the backend folder. Inside the file, paste this snippet:
// backend/index.js
require('dotenv/config')
const express = require('express')
const uuidv4 = require('uuid/v4')
const axios = require('axios')
const cors = require('cors')
Here, you imported the dependencies you installed earlier, The dotenv package should be required at the topmost level as possible.
Next, add this snippet:
// backend/index.js
const PORT = process.env.PORT || 4000
const app = express()
app.use(cors())
const headers = {
appid: process.env.COMETCHAT_APP_ID,
apikey: process.env.COMETCHAT_API_KEY,
'content-type': 'application/json',
accept: 'application/json'
}
const adminUID = 'admin'
const baseUrl = ''
The baseUrl depends on the region you selected. If you selected Europe, this is the correct URL. If you selected USA instead, the correct thing should be.
Here, you created a dedicated port for the server to run if none is specified in the environmental variables. You also initialized an express app and added the cors middleware. Because you're going to be making multiple axios requests, the headers variables contain all the necessary headers for those requests to avoid repetition.
Lastly, the adminUID and baseUrl variables are extracted at the top. This is good in case you decide to change the admin uid or use the base URL for v1. In the next steps, you will create three endpoints to be used on the frontend.
One of such is the endpoint for creating new users when they visit the homepage of the website. Add this snippet to your index.js file:
// backend/index.js
app.get('/api/create-user', async (_, res) => {
const randomUUID = uuidv4()
const newUser = {
uid: randomUUID,
name: randomUUID
}
try {
const response = await axios.post(baseUrl, JSON.stringify(newUser),
{ headers }
)
const uid = await response.data.data.uid
const user = await createAuthToken(uid)
res.status(200).json({ user })
} catch (err) {
console.log({ 'create-user': err })
}
})
The primary function of this endpoint is to create new users and that is done by making a POST request to CometChat API with information about the new user, such as the UID and name. For simplicity, a random id is generated and used for both the uid and the name of the user. If this request is successful, what is returned is the UID of the user.
You then use that UID to create a token for that user to use for logging in. You'll notice that a function createAuthToken is called. Paste the function just below your global variables and before the endpoint:
// backend/index.js
async function createAuthToken(uid) {
try {
const response = await axios.post(`${baseUrl}/${uid}/auth_tokens`, null,
{ headers }
)
return response.data.data
} catch (err) {
console.log({ 'create-auth-token': err })
}
}
This function takes in a UID of the user and returns JSON containing an authToken and the UID of the user. In other words, this is the final data returned after a new user is created.
Next, you will create another endpoint that will return an auth token for the admin. Paste the snippet below the first endpoint like so:
// backend/index.js
app.get('/api/authenticate-user', async (req, res) => {
const uid = await req.query.uid
const user = await createAuthToken(uid)
res.status(200).json({ user })
})
In this endpoint, the UID of the admin is gotten from the query string, all you have to do now is pass it to the createAuthToken function in order to return an authentication token for the admin.
The next endpoint you will create is one that will return all the users. Add this snippet below the second endpoint:
// backend/index.js
app.get('/api/get-users', async (_, res) => {
try {
const response = await axios.get(baseUrl, {
headers
})
const users = await response.data.data.filter(user => user.uid !== adminUID)
res.status(200).json({ users })
} catch (err) {
console.log({ 'get-users': err })
}
})
Before returning the users returned from the axios request, the admin UID is filtered to prevent returning the information about the admin since it is not necessary.
Finally, for the backend, add this snippet at the end of the file:
// backend/index.js
app.listen(PORT, () => {
console.log(`Server listening on port ${PORT}`)
})
This snippet will take care of running the server on the port you defined earlier. To run the server all you need to do now is open your terminal and run the following:
npm run server
If everything goes well, you should now see a message in the console that reads "Server listening on port 4000".
You can test this out in the browser by visiting each of those endpoints and making sure data is returned. That concludes the backend for this app. In the next section, you'll start working on the frontend.
You will use the create-react-app package to scaffold a new React project for the frontend. Open another terminal window, make sure you're in the wolox-chat-widget-cometchat directory, then run this command:
npx create-react-app frontend
This step installs all the necessary dependencies needed to start this project. This process can take a couple of minutes to complete depending on your internet speed.
The next thing you will do is to install dependencies peculiar to the project. For this project, you need the following:
To install the above dependencies, move into the frontend directory and run this command:
npm install @cometchat-pro/chat react-router-dom react-chat-widget uuid
The next step is not entirely necessary but will help avoid confusion in this tutorial. So, go ahead and delete the following files in the src directory namely, serviceWorker.js, logo.svg, index.css , App.test.js, and App.css. Deleting these files will break the app at this point but that will be fixed as you progress.
To give this app a decent look, you will add Bootstrap for styling. You can add a link to bootstrap CDN by adding this snippet in the head tag of public/index.html as follows:
"
/>
While you're here, change the title of this app to Wolox Chat Widget CometChat.
Next, go ahead and create a file called .env at the root of the frontend folder and add this code to it:
REACT_APP_COMETCHAT_APP_ID=YOUR_COMETCHAT_APP_ID
Replace the placeholders with the actual credentials from your CometChat dashboard. Also, note that you should not commit this file to version control.
Next, create a config.js file in the src directory and paste this snippet:
// frontend/src/config.js
const config = {
adminUID: 'admin',
adminName: 'Admin',
appID: process.env.REACT_APP_COMETCHAT_APP_ID
};
export default config;
Now open src/index.js file replace everything in it with this snippet:
// frontend/src/index.js
import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import { CometChat } from '@cometchat-pro/chat';
import config from './config';
CometChat.init(config.appID).then(
() => {
console.log('Initialized cometchat');
},
() => {
console.log('Failed to initialize cometchat');
}
);
ReactDOM.render(<App />, document.getElementById('root'));
This will ensure that CometChat is initialized in your application.
For this project, there you’re going to need three routes, one for the user and two for the admin. The / route will load the wolox chat widget for the user to start chatting. The other two routes will pertain to the admin. The /admin route will load up the admin component containing the list of users which will navigate to /admin/:uid where individual messages can then be fetched and replies can be sent.
To begin, open src/App.js and replace the default code with this snippet:
// frontend/src/App.js
import React from 'react';
import { BrowserRouter as Router, Route } from 'react-router-dom';
import User from './components/user';
import Admin from './components/admin';
function App() {
return (
<Router>
<Route exact path='/' component={User} />
<Route exact path='/admin' component={Admin} />
<Route exact path='/admin/:uid' component={Admin} />
</Router>
);
}
export default App;
If you've used react router before, you'd know this is a familiar setup. A Router component is used to wrap the entire app and individual Routes that map to paths in the browser. What you'll notice is that the Admin component is used to match to paths, that's because its mostly the same content they both render. In the next step, you're going to create each of these components.
As mentioned earlier, this component handles the display of the chat widget. I have also added a few extra styling to this component to make it a bit presentable, but nothing too fancy to take away the point of this tutorial.
Create a file called user.js in the src/components directory and add this snippet:
// frontend/src/components/user.js
import React, { useEffect } from 'react';
import { CometChat } from '@cometchat-pro/chat';
import { Widget, addResponseMessage, dropMessages } from 'react-chat-widget';
import 'react-chat-widget/lib/styles.css';
import { Link } from 'react-router-dom';
import config from '../config';
The CometChat module should seem familiar by now because you used it in src/index.js when you initialized the SDK. Whenever you need to handle authentication or messages, you're going to need that module. The Widget, component will be used to display a floating action button that will pop up a chat widget. The addResponseMessage and dropMessages are used for displaying messages to the user and deleting messages respectively.
You also imported the CSS file necessary for styling the widget appropriately.
The next thing you need to do is define a functional component called User and export it. Paste this snippet below the imports:
// frontend/src/components/user.js
function User() {
// custom functions and hooks go here...
return (
<div style={{ background: '#000', height: '100vh' }}>
<header>
<div className='container py-2'>
<div>
<h1 className='text-center text-white'>ACME.</h1>
</div>
<ul
className='nav nav-tabs'
style={{ background: '#000', border: 'none' }}
>
<li className='nav-item'>
<Link
style={{ color: '#fff', borderBottom: '3px solid #fff' }}
</Link>
</li>
<li className='nav-item'>
<Link style={{ color: '#ccc' }}
Features
</Link>
</li>
<li className='nav-item'>
<Link style={{ color: '#ccc' }}
</Link>
</li>
</ul>
</div>
</header>
<div
className='jumbotron text-white'
style={{
backgroundColor: '#000'
}}
>
<div className='container text-center'>
<h1 className='display-4'>ACME.</h1>
<p className='lead'>
ACME is a San Francisco based design agency. We build amazing web
experiences
</p>
<Link className='btn btn-light btn-lg' to='/' role='button'>
Learn more
</Link>
</div>
</div>
<Widget handleNewUserMessage={handleNewUserMessage} title={`ACME Chat`} />
</div>
);
}
export default User;
In this snippet, you created the User function and rendered the JSX. You will now add other functions and hooks to the component.
Add this snippet just before the return statement:
// frontend/src/components/user.js
useEffect(() => {
addResponseMessage(
'Hi, if you have any questions, please ask them here. Please note that if you refresh the page, all messages will be lost.'
);
const createUser = async () => {
try {
const userResponse = await fetch(
''
);
const json = await userResponse.json();
const user = await json.user;
await CometChat.login(user.authToken);
} catch (err) {
console.log({ err });
}
};
createUser();
}, []);
This useEffect hook will run as soon as the component is mounted. In this hook, you first called the addResponseMessage function imported earlier. This function will display a default message to the user. Next, the createUser function will handle the creation of a new user by making a request to the API in the backend and logging in with the authToken returned.
Now that a new user can be created and logged in, the logical step is to allow the user to chat with the admin. CometChat provides a way for this to happen by setting up a message listener on this component to handle the sending and receiving of new messages. Paste this snippet just below the first useEffect hook:
// frontend/src/components/user.js
useEffect(() => {
const listenerId = 'client-listener-key';
CometChat.addMessageListener(
listenerId,
new CometChat.MessageListener({
onTextMessageReceived: message => {
addResponseMessage(message.text);
}
})
);
return () => {
CometChat.removeMessageListener(listenerId);
CometChat.logout();
dropMessages();
};
}, []);
This second useEffect function is responsible for setting up a message listener on this component. CometChat provides hooks inside the message listener to enable you only listen for functions you care about. One of such hook is the onTextMessageReceived. This hook gets triggered whenever a new text message is received. Once a new text message is received, that message will then be displayed to the user by calling the addResponseMessage function again.
The other significant part of this useEffect hook is the return function that is called when this component is unmounted. You can think of it as componentWillUnmount in terms of class components. The message listener must be removed and the user logged out to prevent a memory leak.
The last function in this component will handle what happens when the user submits the chat form. Create a new function handleNewUserMessage just below the last useEffect hook like so:
// frontend/src/components/user.js
const handleNewUserMessage = async newMessage => {
const textMessage = new CometChat.TextMessage(
config.adminUID,
newMessage,
CometChat.RECEIVER_TYPE.USER
)
try {
await CometChat.sendMessage(textMessage);
} catch (error) {
console.log('Message sending failed with error:', error);
}
};
This function is hooked up to the widget component and will be called anytime the user submits the form. In this function, the message typed by the user is passed as an argument and a new text message object is created containing metadata about the type of message it is and who the message is for. In this case, the message is for the admin. Finally, the message is sent by calling the sendMessage function provided by CometChat.
If there are no errors, the messages sent will be received by the admin. In the next section, you're going to set up the admin component.
Create a file called admin.js in src/components directory and paste this in the file:
// src/components/admin.js
import React, { useEffect, useState } from 'react';
import { Link } from 'react-router-dom';
import { CometChat } from '@cometchat-pro/chat';
import config from '../config';
import uuid from 'uuid';
Here, you are importing the dependencies you will need for this component. Now define a functional component called Admin in this file by adding this snippet:
// src/components/admin.js
function Admin({
match: {
params: { uid }
}
}) {
// state variables
// custom functions and useEffects
// return statement
}
export default Admin;
So far, the only thing happening here is that the UID is destructured from this component. Initially, this value will return undefined because the /admin route does not expect any parameters containing a UID. It is only when we visit /admin/:uid that the UID will have a valid value.
Also, you could have easily just written props in the function declaration instead of destructuring the UID and referenced by writing props.match.params.uid. But, I did it this way because the UID is used in multiple places and as such will seem repetitive by writing out the entire props hierarchy.
Next, you need to define some state variables for this component. Paste this snippet inside the Admin functional component:
// frontend/src/componsnets/admin.js
const [users, setUsers] = useState([]);
const [messages, setMessages] = useState([]);
const [message, setMessage] = useState('');
const [isLoggedIn, setIsLoggedIn] = useState(false);
Here is a brief overview of the state variables you have declared:
I only explained the initial values destructured from each useState hook. The second destructured values are state updater functions that will be used to update the initial values. Learn more about React hooks here.
Now that you have set up the state variables. You need to also set up some useEffect hooks that will be called on different instances. From here on out, all the useEffect hooks will go under the state variables you just declared.
Add the first useEffect hook under the state variables like so:
// frontend/src/components/admin.js
useEffect(() => {
const createAuthToken = async () => {
try {
const response = await fetch(
`{config.adminUID}`
);
const json = await response.json();
const admin = await json.user;
await CometChat.login(admin.authToken);
setIsLoggedIn(true);
} catch (err) {
console.log({ err });
}
};
createAuthToken();
}, []);
Much like what you did in the user component, this effect runs when this component mounts and requests from the backend an authentication token that will be used to log in the admin. When this is successful, the isLoggedIn state variable is updated to true so that now this component is aware that the admin has logged. The next useEffect hook following this one will make it clearer why this is important.
Define another useEffect hook below this one like so:
// frontend/src/components/admin.js
useEffect(() => {
const getUsers = async () => {
const response = await fetch('');
const json = await response.json();
const users = await json.users;
setUsers([...users]);
};
getUsers();
}, [isLoggedIn]);
In this snippet, you will notice that the dependency array contains isLoggedIn variable. What this means is that this useEffect hook will run when the component first mounts and when the value of isLoggedIn changes. On these two occasions, the getUsers function will be called to updates the users state variable.
Simple enough right? The next useEffect function will handle setting up of a message listener on this component. It is just like what you did earlier in the User component. Whenever a new message is sent or received, the function within this effect will run. Paste this code snippet below the last useEffect function:
// frontend/src/components/admin.js
useEffect(() => {
const listenerId = 'message-listener-id';
const listenForNewMessages = () => {
CometChat.addMessageListener(
listenerId,
new CometChat.MessageListener({
onTextMessageReceived: msg => {
setMessages(prevMessages => [...prevMessages, msg]);
}
})
);
};
listenForNewMessages();
return () => {
CometChat.removeMessageListener(listenerId);
CometChat.logout();
};
}, []);
Just like it was in the user component. This useEffect hooks gets called when the component mounts.
When a new message is received, the onTextMessageReceived function present in the message listener will capture it and update the messages state variable with the new message. When this component unmounts, the return function is called which in turn removes the message listener and logs out the admin.
You could have easily put this functionality into the first useEffect hook and it would still work but, this is to avoid clutter and keep the code readable. Besides, there's no limit to the number of useEffect hooks that can live in a given component.
You will add another useEffect hook. This time, to check when users come online or go offline. Paste this snippet below the previous useEffect:
// frontend/src/components/admin.js
useEffect(() => {
const listenerID = 'user-listener-id';
CometChat.addUserListener(
listenerID,
new CometChat.UserListener({
onUserOnline: onlineUser => {
const otherUsers = users.filter(u => u.uid !== onlineUser.uid);
setUsers([onlineUser, ...otherUsers]);
},
onUserOffline: offlineUser => {
const targetUser = users.find(u => u.uid === offlineUser.uid);
if (targetUser && targetUser.uid === offlineUser.uid) {
const otherUsers = users.filter(u => u.uid !== offlineUser.uid);
setUsers([...otherUsers, offlineUser]);
const messagesToKeep = messages.filter(
m =>
m.receiver !== uid &&
m.sender.uid !== config.adminUID &&
m.receiver !== config.adminUID &&
m.sender.uid !== uid
);
setMessages(messagesToKeep);
}
}
})
);
return () => CometChat.removeUserListener(listenerID);
}, [users, messages, uid]);
The listener listens to know when a user comes online or goes offline. What happens here is that users that are online are placed at the top of the list. When a user goes offline, that user is pushed to the bottom of the users list.
In the dependency array, you'll notice that there are several dependencies, namely: users, messages, and UID. This is because this effect is in sync with those state variables. Therefore, whenever those state variables change, React will re-render this component.
Now, you're going to handle a case where a patricular user is selected from the users list. In the beginning, when you created this admin component, you destructed the UID from props. Now, you're going to use that UID to fetch previous messages for a particular user. Paste this snippet under the previous useEffect function:
// frontend/src/components/admin.js
useEffect(() => {
const fetchPreviousMessages = async () => {
try {
const messagesRequest = new CometChat.MessagesRequestBuilder()
.setUID(uid)
.setLimit(50)
.build();
const previousMessages = await messagesRequest.fetchPrevious();
setMessages([...previousMessages]);
} catch (err) {
console.log('Message fetching failed with error:', err);
}
};
if (uid !== undefined) fetchPreviousMessages();
}, [uid]);
This useEffect hook is designed to only run when a user is selected from the users list. Basically, when the URL in the address matches something of this nature: /admin/:uid, where :uid represents a user identity. That's why there is a condition to only fetch previous messages if the UID is present.
In the body of the useEffect hook, a message request containing that UID is sent to retrieve all messages with that user and then used to update the messages state variable. Next, you will create a function to enable the admin send messages. The function will be attached to the onSubmit event handler in the JSX portion of this component.
Add the following code snippet under the last useEffect hook:
// frontend/src/components/admin.js
const handleSendMessage = async e => {
e.preventDefault();
const _message = message;
setMessage('');
const textMessage = new CometChat.TextMessage(
uid,
CometChat.RECEIVER_TYPE.USER
)
try {
const msg = await CometChat.sendMessage(textMessage);
setMessages([...messages, msg]);
} catch (error) {
console.log('Message sending failed with error:', error);
}
};
When the admin submits the form, the message typed is used to construct a text message and then sent by calling the sendMessage function. If the message is sent successfully, a new message object is returned and then used to update the messages state variable.
Now, you will add the JSX to your component. Add this snippet below the handleSendMessage function:
// frontend/src/component/admin.js
return (
<div style={{ height: '100vh' }}>
<header
className='bg-secondary text-white d-flex align-items-center'
style={{ height: '50px' }}
>
<h3 className='px-3'>
<Link to='/admin' className='text-white'>
Dashboard
</Link>
</h3>
{uid !== undefined && (
<span>
{' - '}
{uid}
</span>
)}
</header>
<div style={{ height: 'calc(100vh - 50px)' }}>
<div className='d-flex' style={{ height: '100%' }}>
<aside
className='bg-light p-3'
style={{ width: '30%', height: '100%', overflowY: 'scroll' }}
>
<h2 className='pl-4'>Users</h2>
{users.length > 0 ? (
users.map(user => (
<li
style={{
background: 'transparent',
border: 0,
borderBottom: '1px solid #ccc'
}}
className='list-group-item'
key={user.uid}
>
<Link className='lead' to={`/admin/${user.uid}`}>
{user.name}
</Link>
</li>
))
) : (
<span className='text-center pl-4 mt-4'>Fetching users</span>
)}
</aside>
<main
className='p-3 d-flex flex-column'
style={{
flex: '1',
height: 'calc(100vh - 60px)',
position: 'relative'
}}
>
<div className='chat-box' style={{ flex: '1', height: '70vh' }}>
{uid === undefined && !messages.length && (
<div>
<h3 className='text-dark'>Chats</h3>
<p className='lead'>Select a chat to load the messages</p>
</div>
)}
{messages.length > 0 ? (
<ul
className='list-group px-3'
style={{ height: '100%', overflowY: 'scroll' }}
>
{messages.map(m => (
<li
className='list-group-item mb-2 px-0'
key={uuid()}
style={{
border: 0,
background: 'transparent',
textAlign: m.sender.uid === uid ? 'left' : 'right'
}}
>
<span
className='py-2 px-3'
style={{
background:
m.sender.uid === uid ? '#F4F7F9' : '#A3EAF7',
borderRadius: '4px'
}}
>
{m.text}
</span>
</li>
))}
</ul>
) : (
<p className='lead'>No messages</p>
)}
</div>
{uid !== undefined && (
<div
className='chat-form'
style={{
height: '50px'
}}
>
<form
className='w-100 d-flex justify-content-between align-items-center'
onSubmit={e => handleSendMessage(e)}
>
<div className='form-group w-100'>
<input
type='text'
className='form-control mt-3'
placeholder='Type to send message'
value={message}
onChange={e => setMessage(e.target.value)}
/>
</div>
<button className='btn btn-secondary' type='submit'>
Send
</button>
</form>
</div>
)}
</main>
</div>
</div>
</div>
);
From this snippet, the Admin component consists of a two column layout, what you usually refer to as a sidebar and a content area. On the sidebar is where the users are mapped over and displayed as list items containing links to each UID of the user. On the content area, a default text is shown directing the admin to select a user from the list to start chatting.
When a user is selected, this component re-renders and displays the chat form for the admin to start an interaction. In the message container, only messages exchanged between the admin and the user is displayed when any user is selected, if there are no messages, nothing is displayed.
Finally, in the chat form, the handleSendMessage, and setMessage functions are hooked up to be called when the admin submits the form and when the admin types in the input respectively.
At this point, you are done with your app! Since you already have your Node server running, you just need to run the frontend part of your application. Navigate to the frontend folder in your terminal and run this command:
npm run start
Then go to localhost:3000 to start testing your application.
In this article, you built a chat app using the Wolox chat widget, Bootstrap, and Node.js. You learned how to utilize some CometChat functionalities such as creating new users, authenticating them, sending and receiving messages in realtime, etc. There is a ton of things you can still do with CometChat. For example, you can enable push notifications or add end-to-end encryption to messages in your app to provide an added layer of security. Learn more about CometChat JavaScript SDK here. | https://www.cometchat.com/tutorials/make-cometchat-work-with-wolox-chat-widget | CC-MAIN-2020-34 | refinedweb | 4,499 | 57.67 |
Content-type: text/html
getpgid - Gets process group ID
Standard C Library (libc.a)
#include <sys/types.h>
#include <unistd.h>
pid_t getpgid(
pid_t pid);
Specifies the process ID of the target process; zero implies the calling process.
The getpgid() function returns the process group ID of the process specified by the process ID pid. Specifying a pid of 0 (zero) returns the process group ID of the calling process.
The getpgid() function returns the process group ID of the process specified. If there was an error, a value of -1 is returned and errno is set to indicate the error.
If any of the following conditions occurs, the getpgid() function sets errno to the corresponding value: The specified process is not in the same session as the calling process, and the calling process lacks sufficient privilege to read the specified process. As released, Tru64 UNIX does not check the privilege. No process has been found that has a process ID identical to that specified by the pid parameter.
Functions: exec(2), fork(2), setpgid(2) delim off | http://backdrift.org/man/tru64/man2/getpgid.2.html | CC-MAIN-2016-50 | refinedweb | 178 | 74.08 |
2014-07-21 17:19:17 8 Comments
I have noticed very poor performance when using iterrows from pandas.
Is this something that is experienced by others? Is it specific to iterrows and should this function be avoided for data of a certain size (I'm working with 2-3 million rows)?
This discussion on GitHub led me to believe it is caused when mixing dtypes in the dataframe, however the simple example below shows it is there even when using one dtype (float64). This takes 36 seconds on my machine:
import pandas as pd import numpy as np import time s1 = np.random.randn(2000000) s2 = np.random.randn(2000000) dfa = pd.DataFrame({'s1': s1, 's2': s2}) start = time.time() i=0 for rowindex, row in dfa.iterrows(): i+=1 end = time.time() print end - start
Why are vectorized operations like apply so much quicker? I imagine there must be some row by row iteration going on there too.
I cannot figure out how to not use iterrows in my case (this I'll save for a future question). Therefore I would appreciate hearing if you have consistently been able to avoid this iteration. I'm making calculations based on data in separate dataframes. Thank you!
---Edit: simplified version of what I want to run has been added below---
import pandas as pd import numpy as np #%% Create the original tables t1 = {'letter':['a','b'], 'number1':[50,-10]} t2 = {'letter':['a','a','b','b'], 'number2':[0.2,0.5,0.1,0.4]} table1 = pd.DataFrame(t1) table2 = pd.DataFrame(t2) #%% Create the body of the new table table3 = pd.DataFrame(np.nan, columns=['letter','number2'], index=[0]) #%% Iterate through filtering relevant data, optimizing, returning info for row_index, row in table1.iterrows(): t2info = table2[table2.letter == row['letter']].reset_index() table3.ix[row_index,] = optimize(t2info,row['number1']) #%% Define optimization def optimize(t2info, t1info): calculation = [] for index, r in t2info.iterrows(): calculation.append(r['number2']*t1info) maxrow = calculation.index(max(calculation)) return t2info.ix[maxrow]
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@Vandana Sharma 2019-04-13 19:40:25
Yes, Pandas itertuples() is faster than iterrows(). you can refer the documentation:
"To preserve dtypes while iterating over the rows, it is better to use itertuples() which returns namedtuples of the values and which is generally faster than iterrows."
@chrisaycock 2014-07-21 17:41:18
Vector operations in Numpy and pandas are much faster than scalar operations in vanilla Python for several reasons:
Amortized type lookup: Python is a dynamically typed language, so there is runtime overhead for each element in an array. However, Numpy (and thus pandas) perform calculations in C (often via Cython). The type of the array is determined only at the start of the iteration; this savings alone is one of the biggest wins.
Better caching: Iterating over a C array is cache-friendly and thus very fast. A pandas DataFrame is a "column-oriented table", which means that each column is really just an array. So the native actions you can perform on a DataFrame (like summing all the elements in a column) are going to have few cache misses.
More opportunities for parallelism: A simple C array can be operated on via SIMD instructions. Some parts of Numpy enable SIMD, depending on your CPU and installation process. The benefits to parallelism won't be as dramatic as the static typing and better caching, but they're still a solid win.
Moral of the story: use the vector operations in Numpy and pandas. They are faster than scalar operations in Python for the simple reason that these operations are exactly what a C programmer would have written by hand anyway. (Except that the array notion is much easier to read than explicit loops with embedded SIMD instructions.)
@Jeff 2014-07-21 17:39:48
Generally,
iterrowsshould only be used in very very specific cases. This is the general order of precedence for performance of various operations:
Using a custom cython routine is usually too complicated, so let's skip that for now.
1) Vectorization is ALWAYS ALWAYS the first and best choice. However, there are a small set of cases which cannot be vectorized in obvious ways (mostly involving a recurrence). Further, on a smallish frame, it may be faster to do other methods.
3) Apply involves can usually be done by an iterator in Cython space (this is done internally in pandas) (this is a) case.
This is dependent on what is going on inside the apply expression. e.g.
df.apply(lambda x: np.sum(x))will be executed pretty swiftly (of course
df.sum(1)is even better). However something like:
df.apply(lambda x: x['b'] + 1)will be executed in python space, and consequently is slower.
4)
itertuplesdoes not box the data into a Series, just returns it as a tuple
5)
iterrowsDOES box the data into a Series. Unless you really need this, use another method.
6) updating an empty frame a-single-row-at-a-time. I have seen this method used WAY too much. It is by far the slowest. It is probably common place (and reasonably fast for some python structures), but a DataFrame does a fair number of checks on indexing, so this will always be very slow to update a row at a time. Much better to create new structures and
concat.
@KieranPC 2014-07-21 17:53:07
Yes, I used number 6 (and 5). I've got some learning to do. It seems like the obvious choice to a relative beginner.
@IanS 2016-03-09 10:46:18
In my experience, the difference between 3, 4, and 5 is limited depending on the use case.
@Dimgold 2017-07-06 10:48:37
I've tried to check the runtimes in this notebook. Somehow
itertuplesis faster than
apply:(
@jpp 2018-10-17 10:35:32
pd.DataFrame.applyis often slower than
itertuples. In addition, it's worth considering list comprehensions,
map, the poorly named
np.vectorizeand
numba(in no particular order) for non-vectorisable calculations, e.g. see this answer.
@cs95 2019-04-14 05:21:17
@Jeff, out of curiosity, why have you not added list comprehensions here? While it is true that they do not handle index alignment or missing data (unless you use a function with a try-catch), they are good for a lot of use cases (string/regex stuff) where pandas methods do not have vectorized (in the truest sense of the word) implementations. Do you think it is worth mentioning LCs are a faster, lower overhead alternative to pandas apply and many pandas string functions?
@Polor Beer 2017-08-15 14:42:51
Another option is to use
to_records(), which is faster than both
itertuplesand
iterrows.
But for your case, there is much room for other types of improvements.
Here's my final optimized version
Benchmark test:
Full code:
The final version is almost 10x faster than the original code. The strategy is:
groupbyto avoid repeated comparing of values.
to_recordsto access raw numpy.records objects.
@Jeff 2014-07-21 17:55:57
Here's the way to do your problem. This is all vectorized.
@KieranPC 2014-07-21 21:34:56
Very clear answer thanks. I will try merging but I have doubts as I will then have 5 billion rows (2.5million*2000). In order to keep this Q general I've created a specific Q. I'd be happy to see an alternative to avoid this giant table, if you know of one: here:stackoverflow.com/questions/24875096/…
@Jeff 2014-07-22 00:15:24
this does not create the Cartesian product - it is a compressed space and is pretty memory efficient. what you are doing is a very standard problem. give a try. (your linked question has a very similar soln) | https://tutel.me/c/programming/questions/24870953/does+pandas+iterrows+have+performance+issues | CC-MAIN-2019-30 | refinedweb | 1,531 | 57.06 |
Hello i need your help.
i tried simple_traker_experiment.py in pygaze official site.
but
Traceback (most recent call last):
File "/home/kmucs/문서/캡스톤/simple_tracker_experiment.py", line 6, in <module>
import constants
ImportError: No module named constants
so i tried download 'constants' module in python , but not cleared. i need your help.
The examples on the Pygaze website can't be replicated 1:1 in OpenSesame since those are "pure" Python without a GUI, so that you have to program everything manually, while OpenSesame has a GUI and tons of built-in functionality. "Constants" isn't a module, it's a script: in Python, you'd usually create two scripts (one with constants, the other with the experimental procedure) and import whatever you define in constants.py into your main script. This isn't necessary in OpenSesame since you can define constant variables in the main experiment item. The most common variables you'd define in a constants script would be the screen resolution and the backend/disptype (psychopy, pygame etc), which can both conveniently be found there :)
Hope this helps!
thx problem is cleared. | http://forum.cogsci.nl/index.php?p=/discussion/4998/hello-i-need-your-help | CC-MAIN-2019-30 | refinedweb | 185 | 57.16 |
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Messages on the Web carry three levels of information: Structure Semantics, Protocol Semantics, and Application Semantics. No matter the implementation style, all three of these are needed for any successful communication between client and server. This threesome (S-P-A) forms the …
Developer Christophe Lauret recently commented: "A schema is like an aircraft: it can be designed for stability or maneuverability but not both." I recently have been trying a different method for designing intermediate schemas in publication chains. It is an exercise in taking the three-layer model for XML with Schematron to an extreme. The best name I can think of this is Highly Generic Schemas..
Fans of nerdy men with beards will enjoy the InfoQ website. Watching Freeman and Feather's TDD - Ten years later, a few things stuck out relevant to standards-makers and to Schematron.
Paul Hermans has kindly set up a process (I believe an XProc pipeline using Calabash and SAXON 9) to test the XML Schema to Schematron converter I have been documenting in this blog over the last few years. Here are some results.
I have recently being doing some more work on the XML Schema to Schematron converter, and one of the first issues to come up is more proper handling of namespaces.
The beta release of my open source XML Schema validator is available now, from Schematron.com.
Dennis Sosnoski has a good article Schema for Web Services - Part I: Basic Datatypes up at InfoQ. It looks like being a series, and Dennis knows his stuff. It is about some gotchas with data binding.... There are many parts of XSD which don't play well for use in automated data binding systems, but I suspect many of Dennis' gotchas in this article are just intrinsic to exchange rather than being flaws in XSD datatypes, necessarily.
This article sketches out how to implement the same functionality as XSD's integrity constraints in Schematron.
I have not written anything about converting Schematron schemas to XML Schemas in the 12 months since the last little article. So here is another approach for schemas that were not written to be XSD-conversion friendly: it is just brute force and ignorance (BFI) pattern matching.
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All trademarks and registered trademarks appearing on oreilly.com are the property of their respective owners. | http://oreilly.com/blogs/tags.csp?tag=xsd | CC-MAIN-2014-41 | refinedweb | 404 | 61.87 |
Since the majority of the code we've demonstrated so far in this book has been written in VBScript, you may be wondering why we are going to talk about Visual Basic.NET (VB.NET). Unfortunately, one of the drawbacks with the .NET Framework is that it currently does not provide native support for VBScript. It does support JScript, but since Visual Basic is a much more powerful language than JScript, we will use VB.NET in our examples. It is still unclear what Microsoft's future direction is in regard to providing native support for scripting languages like VBScript in .NET. Until that happens, you should get more familiar with the .NET class library and gain some experience with Visual Basic, which will ultimately increase your capabilities as a programmer. As we mentioned earlier, one of the design goals for the .NET Framework was simplicity. With the .NET Framework class library, Microsoft has made developing Windows-based applications significantly easier. As far as Active Directory goes, it will not take long at all to map your ADSI knowledge to the classes, properties, and methods in the System.DirectoryServices namespace.
To get started using VB.NET, you'll need to get an integrated development environment (IDE) such as Visual Studio.NET (VS.NET), which is available from. Once you have VS.NET, you should download the latest .NET Framework SDK, which is available from. Once you have both of those installed, you are ready to start programming with the .NET Framework.
To start a new project in VS.NET, select File New Project from the menu. At that point you'll see a screen similar to the one in Figure 28-1.
Click on Visual Basic Projects and select Console Application from the Templates window. Now you have started a new project and are ready to start writing code in a file called Module1.vb, which contains the following code by default:
Module Module1 Sub Main( ) End Sub End Module
If you are inexperienced with VB, you can create usable programs simply by adding code to the Main( ) subroutine. Once you become more experienced, you can start creating your own classes, subroutines and functions, and reference them within Main( ).
To start using the System.DirectoryServices classes to query and manipulate Active Directory, you must add a reference to it in your project. From the menu, select Project Add Reference, then under Component Name click on System.DirectoryServices. Click the Select button and click OK. Figure 28-2 shows what this window looks like in VS.NET.
You are now ready to start writing Active Directory applications with the .NET Framework, so let's take a look at the System.DirectoryServices namespace. | http://etutorials.org/Server+Administration/Active+directory/Part+III+Scripting+Active+Directory+with+ADSI+ADO+and+WMI/Chapter+28.+Getting+Started+with+VB.NET+and+System.Directory+Services/28.2+Using+VB.NET/ | CC-MAIN-2019-09 | refinedweb | 451 | 66.74 |
MRML node to represent camera node. More...
#include <Libs/MRML/Core/vtkMRMLCameraNode.h>
MRML node to represent camera node.
Camera node uses vtkCamera to store the state of the camera
Definition at line 29 of file vtkMRMLCameraNode.h.
Definition at line 33 of file vtkMRMLCameraNode.h.
Events
Definition at line 167 of file vtkMRMLCameraNode.h.
Definition at line 178 of file vtkMRMLCameraNode.h.
Enum identifying the parameters being manipulated with calls to InteractionOn() and InteractionOff(). Identifiers are powers of two so they can be combined into a bitmask to manipulate multiple parameters. The meanings for the flags are:
Definition at line 240 of file vtkMRMLCameraNode.h.
Definition at line 187 of file vtkMRMLCameraNode.h.
Definition at line 193 of file vtkMRMLCameraNode.h.
Copy the node's attributes to this object
Reimplemented from vtkMRMLNode.
MRMLNode methods.
Implements vtkMRMLTransformableNode.
Deprecated. Use SetLayoutName instead. Set the camera active tag, i.e. the tag for which object (view) this camera is active.
This is the transform that was last applied to the position, focal point, and up vector (for any new transforms, the incremental difference is calculated and applied to the parameters)
vtkCamera
Get the focal point of the camera in world coordinates.
Get node XML tag name (like Volume, Model)
Implements vtkMRMLTransformableNode.
Definition at line 61 of file vtkMRMLCameraNode.h.
Set camera ParallelProjection flag
Set camera Parallel Scale
Get the position of the camera in world coordinates.
Get the camera view angle
Get camera Up vector
alternative method to propagate events generated in Camera nodes
Reimplemented from vtkMRMLNode.
Read node attributes from XML file
Reimplemented from vtkMRMLNode.
Reset the camera If resetRotation is true, the camera rotates to the closest direction If resetTranslation is true, the focal point is moved to the center of the renderer props not changing the rotation. If resetDistance is true, the camera to moved to make sure the view contains the renderer bounds.
Reset the clipping range just based on its position and focal point.
Utility function that rotates of 15 degrees around an axis. Call RotateAround 6 times to make a right angle
15 degrees by default
Moves the camera toward a position. Keeps the same distance to the focal point.
Set the focal point of the camera in world coordinates. It is also the point around which the camera rotates around.
Definition at line 285 of file vtkMRMLCameraNode.h.
Get/Set a flag indicating whether this node is actively being manipulated (usually) by a user interface. This flag is used by logic classes to determine whether state changes should be propagated to other nodes to implement linked controls. Does not cause a Modified().
Get/Set a flag indicating what parameters are being manipulated within calls to InteractingOn() and InteractingOff(). These fields are used to propagate linked behaviors. This flag is a bitfield, with multiple parameters OR'd to compose the flag. Does not cause a Modified().
Name of the layout widget that this camera is used in. Must be unique between all the slice composite nodes because it is used as a singleton tag. Must be the same as the slice node. No name (i.e. "") by default. Typical names are numbers: "1", "2", ... to uniquely define the 3D view node.
Set camera ParallelProjection flag
Set camera Parallel Scale
Set the position of the camera in world coordinates. It is recommended to call ResetClippingRange() after calling this to ensure that all objects that should be visible are rendered.
Definition at line 278 of file vtkMRMLCameraNode.h.
Set the camera view angle
Set camera Up vector
Definition at line 292 of file vtkMRMLCameraNode.h.
Translate the camera and focal point of a 6th of the screen width. Call TranslateAround 6 times to not see what was on screen before.
Copy node content (excludes basic data, such as name and node references).
Write this node's information to a MRML file in XML format.
Reimplemented from vtkMRMLNode.
Definition at line 271 of file vtkMRMLCameraNode.h.
Definition at line 267 of file vtkMRMLCameraNode.h.
Definition at line 273 of file vtkMRMLCameraNode.h.
Definition at line 274 of file vtkMRMLCameraNode.h.
Definition at line 269 of file vtkMRMLCameraNode.h. | https://apidocs.slicer.org/master/classvtkMRMLCameraNode.html | CC-MAIN-2021-25 | refinedweb | 689 | 51.24 |
Find Questions & Answers
Can't find what you're looking for? Visit the Questions & Answers page!
Hi All,
I am facing an issue in the calculation of open sales order quantity in BI. I am using 2lis_11_v_ssl data source.
Scenario:
One particular sales order is open i.e. it has order qty = 200, confirmed qty = 200 and deliver qty = 200 but there is no goods issued against the delivery so we should have 200 open quantity.
2 lines are appearing in 2lis_11_v_ssl data source,
I am removing all the closed items from the data source i.e. code is written in start routine to pass Reverse image ('R') to all those records which have Lowest GI status = 'C'.
So, in this case as Lowest GI status is blank or 'A', record mode is not changed here.
In my target DSO, required and confirmed qty is getting to 400 rather as per function rule it should be 200 only. Please help me here, how to get the correct quantities.
Hi Sameer,
As per the DSO property it should return the value 200. Could you please debug this and check the value coming in the source package.
Also kindly check the aggregation property in the transformation level for the keyfigures it should be summation.
Regards
Vivek
Hi Vivek,
Yes, the key figure at transformation level is summation. As per the technicalities, it is working fine i.e. summation of 2 records will return (200+200) = 400.
However, from functional point of view it should return 200 only. I have followed standard BW content for backorder functionality. I thought, SAP must have taken care of this scenario.
In this case, I don't know if I am doing something wrong or do I need to take care of this scenario.
Because in other scenarios, schedule line confirmed quantity is split into 2 lines. first line will have 200 qty and second line will have 0 quantities. So, summing 2 line will give correct 200 quantities.
In this special case, both schedule line have same 200 quantities. So, please help in treating this kind of scenario. | https://answers.sap.com/questions/72340/issue-in-the-calculation-of-backorder.html | CC-MAIN-2018-05 | refinedweb | 352 | 74.9 |
!
Settings – adding custom class
Have you ever wondered how you enter custom classes into the new vs2005 (and vs2008) settings editor?
Or like me, desperately tried to do so and couldn’t the information anywhere.
A little information as to what I’m blathering about.
In the VS2005/VS2008 settings editor, you can specify the type of the setting from a drop down list. Also at the bottom you can choose browse to view all types. That has all the assemblies listed that you have referenced as non project references. However it doesn’t have any types listed from your project based references – annoying.
Then by accident I discovered it!
You simply type into the combo box after choosing browse, and lo and behold, it will find your types. You do have to type in your whole namespace as well though.
Items
Missing controls
I believe there are a number of missing controls from WPF as of November 2007, despite the RTM of Visual Studio 2008, by comparison with Windows Forms v2.
- NumericUpDown (aka Spinner) – is a serious omission as it’s not simple to replicate
- DomainUpDown – is also a serious omission
- MaskedTextBox – can be replicated relatively easily using the KeyDown event, but it is a bit of a
- LinkLabel – can be easily replicated by using a hyperlink inside a TextBlock
- DateTimePicker – another serious omission, as it is a serious undertaking to write
- MonthCalendar – again, a lengthy process to provide a replacement
- CheckedListBox – this can be replicated by using a custom item template
How do you get around these problems, well you have a number of options
- Write your own versions
- Buy in a third party library
- Use a freeware libary
- Wait for Microsoft to implement
Of these, option 4 looks like it will be a long wait (but why? why?) as can be seen by how long it took them to provide proper menus and toolbars in winforms.
Option 3 has some appeal, especially since one of the WPF main people Kevin Moore has provided just such an item with NumericUpDown, DateTimePicker and MonthCalendar – but as with all freeware they have problems. To be fair, he provides them as is and as building blocks only.
Option 2 is expensive obviously, and most places I’ve worked are opposed on many grounds (cost, maintenance, red tape)
That leaves option 1, which isn’t what I thought WPF was going to be about
List
ListBox – multi column example
A listbox can easily be used as a multi-column list in WPF. To do that, you need firstly, a listbox:
<Listbox x:
Then, you need to define a couple of templates, one for the headers and one for the items to be drawn. The header one needs to style the buttons that you will use to action header clicking:
<ControlTemplate x:
<Border Background="Silver" TextBlock.
<ContentPresenter/>
</Border>
</ControlTemplate>
Then the template for the items, i’m using a custom object with 4 properties, but it can be anything of course:
<DataTemplate x:
<Grid ShowGridLines="True" >
>
<TextBlock Grid.
<TextBlock Grid.
<TextBlock Grid.
<TextBlock Grid.
</Grid>
</DataTemplate>
Note, we use shared size grouping on the columns, that’s so that the grids containing the headers and the items size the same.
Then we need to apply these templates to the listbox, which we do via a style:
<Style x:
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Border Grid.
<Border Margin="10" BorderThickness="1" BorderBrush="Black">
<DockPanel Grid.
<ScrollViewer HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Auto" DockPanel.
<Grid DockPanel.
>
<Button Grid. Name </Button>
<Button Grid. Width </Button>
<Button Grid. Auto fit </Button>
<Button Grid. Visible </Button>
</Grid>
</ScrollViewer>
<ScrollViewer HorizontalScrollBarVisibility="Visible" Name="Master">
<StackPanel IsItemsHost="True"/>
</ScrollViewer>
</DockPanel>
</Border>
</Border>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
List
Ac…
Drag and drop – checking mouse button
If you are doing drag and drop by hand (rather than using Josh Smith’s excellent DragAndDropManager –) for whatever reason, one thing to be careful is to to allow existing functionality to carry on working.
For example, in a listview, you want the ability to drag and drop column headers (to move columns around) to continue, if it has been turned on by setting AllowsColumnReorder=”True”.
Therefore you need to check that when the left mouse button is pressed, you only specify it as a drag and drop button click if you are sure it’s a listviewitem being selected, rather than a scrollbar or a header.
You could walk up the visual tree looking for the right type of control, or look for a property being set somewhere in the visual tree. However, what I have found useful is to check that the originating element’s datacontext is set to the type of the listviewitem’s bound type. This only works if you’re using databinding and an itemscontrol or descendent (listbox or listview), but is quick and easy
An example:
private void lv_PreviewMouseLeftButtonDown(object sender, MouseEventArgs e)
{
// check to see if drag can be done
FrameworkElement ele = e.OriginalSource as FrameworkElement;
if(ele != null && ele.DataContext != null && ele.DataContext.GetType() == typeof(xxx))
{
m_StartPoint = e.GetPosition(null); // save mouse position
m_IsDragging = false;
}
else
m_IsDragging = true;
}
where m_IsDragging is a boolean indicating whether you can do drag and drop operation, and m_StartPoint is used by the drag and drop operation to test whether to start doing it, and xxx is your object that is bound to the listview
Ac) | http://itknowledgeexchange.techtarget.com/wpf/page/9/ | CC-MAIN-2016-07 | refinedweb | 904 | 57.5 |
The official source of information on Managed Providers, DataSet & Entity Framework from Microsoft
A while ago we blogged about EF7 targeting new platforms and new data stores. In that post we shared that our EF6.x code base wasn’t setup to achieve what we wanted to in EF7, and that EF7 would be a “lightweight and extensible version of EF”.
That begs the question, is EF7 the next version of EF, or is it something new? Before we dig into the answer, let’s cover exactly what’s the same and what’s changing.
When it comes to writing code, most of the top level experience is staying the same in EF7.
An example
For example, this code looks exactly the same in EF6.x and EF7.
using (var db = new BloggingContext()){ db.Blogs.Add(new Blog { Url = "blogs.msdn.com/adonet" }); db.SaveChanges(); var blogs = from b in db.Blogs.Include(b => b.Posts) orderby b.Name select b; foreach (var blog in blogs) { Console.WriteLine(blog.Name); foreach (var post in blog.Posts) { Console.WriteLine(" -" + post.Title); } }}
While the top level API remains the same (or very similar), EF7 does also include a number of significant changes. These changes can be grouped into a series of buckets.
One of the key motivations behind EF7 is to provide a code base that will allow us to more quickly add new features. While many of these will come after the initial RTM, we have been able to easily implement some of them as we build out the core framework.
Some examples of features already added to EF7 include:
EF6 and earlier releases have some unintuitive behavior in the top level APIs. While the APIs are staying the same, we are taking the opportunity to remove some limitations and chose more expected behavior.
An example of this is how queries are processed. In EF6.x the entire LINQ query was translated into a single SQL query that was executed in the database. This meant your query could only contain things that EF knew how to translate to SQL and you would often get complex SQL that did not perform well.
In EF7 we are adopting a model where the provider gets to select which bits of the query to execute in the database, and how they are executed. This means that query now supports evaluating parts of the query on the client rather than database. It also means the providers can make use of queries with multiple results sets etc., rather than creating one single SELECT with everything in it.
Under the covers EF7 is built over the top of a lighter weight and more flexible set of components. Many of these provide the same functionality as components from EF6.x, but are designer to be faster, easier to use, and easier to replace or customize. To achieve this they are factored differently and bare varying resemblance to their counterparts from EF6.x.
A good example of this is the metadata that EF stores about your entity types and how they map to the data store. The MetadataWorkspace from EF6.x (and earlier versions) was a complex component with a difficult API. MetadataWorkspace was not built with a lightweight and performant O/RM in mind and achieving basic tasks is difficult. For example here is the code to find out which table the Blog entity type is mapped to:
using (var context = new BloggingContext()){ var metadata = ((IObjectContextAdapter)context).ObjectContext.MetadataWorkspace; var objectItemCollection = ((ObjectItemCollection)metadata.GetItemCollection(DataSpace.OSpace)); var entityType = metadata .GetItems<EntityType>(DataSpace.OSpace) .Single(e => objectItemCollection.GetClrType(e) == typeof(Blog)); var entitySet = metadata .GetItems<EntityContainer>(DataSpace.CSpace).Single() .EntitySets .Single(s => s.ElementType.Name == entityType.Name); var mapping = metadata.GetItems<EntityContainerMapping>(DataSpace.CSSpace).Single() .EntitySetMappings .Single(s => s.EntitySet == entitySet); var table = mapping .EntityTypeMappings.Single() .Fragments.Single() .StoreEntitySet; var tableName = (string)table.MetadataProperties["Table"].Value ?? table.Name;}
In EF7 we are using a metadata model that is simple to use and purpose built for the needs of Entity Framework. To highlight this point, here is the EF7 code to achieve the same thing as the EF6.x code listed above.
using (var db = new BloggingContext()){ var tableName = db.Model.GetEntityType(typeof(Blog)).Relational().Table;}
Removing features is always a tough decision, and not something we take lightly. Given the major changes in EF7 we have identified some features that we will not be bringing forward.
Most of the features not coming forwards in EF7 are legacy features that are only used by a very small number of developers.
Some of the features we are retiring because there is already another (we believe better) way of doing things. While we’d love to continue pulling everything forward, we need to balance time, resources, and the cost of adding support for highly requested features as we move forward. To be able to continue devloping and improving the stack we need to shed some of the baggage.
Because much of the core of EF7 is new, the first release of EF7 isn’t going to have all the features that are required for all applications. There is always a tension between wanting to ship quickly and wanting to have more features in a given release. As soon as we have the core framework and basic functionality implemented we will provide a release of EF7 for folks to use in applications with simpler requirements. We’ll then provide a series of quick releases that add more and more features.
Of course, this means EF7 isn’t going to be usable for every application when it is first released, and for that reason we are continuing development of EF6.x for some time and expect many of our customers to remain on that release.
An example of this is lazy loading support, we know this is a critical feature for a number of developers, but at the same time there are many applications that can be developed without this feature. Rather than making everyone wait until it is implemented, we will ship when we have a stable code base and are confident that we have the correct factoring in our core components. To be clear, it's not that we are planning to remove lazy loading support from EF7, just that some apps can start taking advantage of the benefits of EF7 before lazy loading is implemented.
The answer is both. There were actually three options we discussed in terms of naming/branding for EF7:
We decided that once you start writing code, this feels so much like Entity Framework that is really isn’t something new (that ruled out option #3). While there are going to be some nuances between the v6 and v7 transition that need to be documented and explained, it would ultimately be more confusing to have two different frameworks that have almost identical APIs and patterns.
Options #1 and #2 both seem valid to us. Our ultimate conclusion was that #1 is going to cause some confusion in the short term, but make the most sense in the long term. To a lesser extent we’ve tackled similar hurdles in the past with the introduction of DbContext API and Code First in EF4.1 and then the move out of the .NET Framework in EF6 (and subsequent duplications of types, namespace changes, etc.). While these were confusing things to explain, in the long term it seems to have been the correct decision to continue with one product name.
Of course, this is a somewhat subjective decision and there are no doubt folks who are going to agree and some who will disagree (there are even mixed opinions within our team). | http://blogs.msdn.com/b/adonet/archive/2014/10/27/ef7-v1-or-v7.aspx | CC-MAIN-2016-30 | refinedweb | 1,281 | 62.78 |
PHP Cookbook/Functions
From WikiContent
Introduction
Functions help you create organized and reusable code. They allow you to abstract out details so your code becomes more flexible and more readable. Without functions, it is impossible to write easily maintainable programs because you're constantly updating identical blocks of code in multiple places and in multiple files.
With a function you pass a number of arguments in and get a value back:
// add two numbers together function add($a, $b) { return $a + $b; } $total = add(2, 2); // 4
To declare a function, use the function keyword, followed by the name of the function and any parameters in parentheses. To invoke a function, simply use the function name, specifying argument values for any parameters to the function. If the function returns a value, you can assign the result of the function to a variable, as shown in the previous example.
You don't need to predeclare a function before you call it. PHP parses the entire file before it begins executing, so you can intermix function declarations and invocations. You can't, however, redefine a function in PHP. If PHP encounters a function with an identical name to one it's already found, it throws a fatal error and dies.
Sometimes, the standard procedure of passing in a fixed number of arguments and getting one value back doesn't quite fit a particular situation in your code. Maybe you don't know ahead of time exactly how many parameters your function needs to accept. Or, you do know your parameters, but they're almost always the same values, so it's tedious to continue to repass them. Or, you want to return more than one value from your function.
This chapter helps you use PHP to solve these types of problems. We begin by detailing different ways to pass arguments to a function. Recipe 6.2 through Recipe 6.6 cover passing arguments by value, reference, and as named parameters; assigning default parameter values; and functions with a variable number of parameters.
The next four recipes are all about returning values from a function. Recipe 6.7 describes returning by reference, Recipe 6.8 covers returning more than one variable, Recipe 6.9 describes how to skip selected return values, and Recipe 6.10 talks about the best way to return and check for failure from a function. The final three recipes show how to call variable functions, deal with variable scoping problems, and dynamically create a function. There's one recipe on function variables located in Recipe 6.2; if you want a variable to maintain its value between function invocations, see Recipe 5.6.
Accessing Function Parameters
Problem
You want to access the values passed to a function.
Solution
Use the names from the function prototype:
function commercial_sponsorship($letter, $number) { print "This episode of Sesame Street is brought to you by "; print "the letter $letter and number $number.\n"; } commercial_sponsorship('G', 3); commercial_sponsorship($another_letter, $another_number);
Discussion
Inside the function, it doesn't matter whether the values are passed in as strings, numbers, arrays, or another kind of variable. You can treat them all the same and refer to them using the names from the prototype.
Unlike in C, you don't need to (and, in fact, can't) describe the type of variable being passed in. PHP keeps track of this for you.
Also, unless specified, all values being passed into and out of a function are passed by value, not by reference. This means PHP makes a copy of the value and provides you with that copy to access and manipulate. Therefore, any changes you make to your copy don't alter the original value. Here's an example:
function add_one($number) { $number++; } $number = 1; add_one($number); print "$number\n"; 1
If the variable was passed by reference, the value of $number would be 2.
In many languages, passing variables by reference also has the additional benefit of being significantly faster than by value. While this is also true in PHP, the speed difference is marginal. For that reason, we suggest passing variables by reference only when actually necessary and never as a performance-enhancing trick.
See Also
Recipe 6.4 to pass values by reference and Recipe 6.7 to return values by reference.
Setting Default Values for Function Parameters
Problem
You want a parameter to have a default value if the function's caller doesn't pass it. For example, a function to draw a table might have a parameter for border width, which defaults to 1 if no width is given.
Solution
Assign the default value to the parameters inside the function prototype:
function wrap_html_tag($string, $tag = 'b') { return "<$tag>$string</$tag>"; }
Discussion
The example in the Solution sets the default tag value to b, for bold. For example:
$string = 'I am some HTML'; wrap_html_tag($string);
returns:
<b>I am some HTML</b>
This example:
wrap_html_tag($string, 'i');
returns:
<i>I am some HTML</i>
There are two important things to remember when assigning default values. First, all parameters with default values must appear after parameters without defaults. Otherwise, PHP can't tell which parameters are omitted and should take the default value, and which arguments are overriding the default. So, wrap_html_tag( ) can't be defined as:
function wrap_html_tag($tag = 'i', $string)
If you do this and pass wrap_html_tag( ) only a single argument, PHP assigns the value to $tag and issues a warning complaining of a missing second argument.
Second, the assigned value must be a constant — a string or a number. It can't be a variable. Again, using wrap_html_tag( ) as our example, you can't do this:
$my_favorite_html_tag = 'i'; function wrap_html_tag($string, $tag = $my_favorite_html_tag) { ... }
If you want to assign a default of nothing, one solution is to assign the empty string to your parameter:
function wrap_html_tag($string, $tag = '') { if (empty($tag)) return $string; return "<$tag>$string</$tag>"; }
This function returns the original string, if no value is passed in for the $tag. Or, if a (nonempty) tag is passed in, it returns the string wrapped inside of tags.
Depending on circumstances, another option for the $tag default value is either 0 or NULL. In wrap_html_tag( ), you don't want to allow an empty valued-tag. However, in some cases, the empty string can be an acceptable option. For instance, join( ) is often called on the empty string, after calling file( ) , to place a file into a string. Also, as the following code shows, you can use a default message if no argument is provided but an empty message if the empty string is passed:
function pc_log_db_error($message = NULL) { if (is_null($message)) { $message = 'Couldn't connect to DB'; } error_log("[DB] [$message]"); }
See Also
Recipe 6.6 on creating functions that take a variable number of arguments.
Passing Values by Reference
Problem
You want to pass a variable to a function and have it retain any changes made to its value inside the function.
Solution
To instruct a function to accept an argument passed by reference instead of value, prepend an & to the parameter name in the function prototype:
function wrap_html_tag(&$string, $tag = 'b') { $string = "<$tag>$string</$tag>"; }
Now there's no need to return the string because the original is modified in-place.
Discussion
Passing a variable to a function by reference allows you to avoid the work of returning the variable and assigning the return value to the original variable. It is also useful when you want a function to return a boolean success value of true or false, but you still want to modify argument values with the function.
You can't switch between passing a parameter by value or reference; it's either one or the other. In other words, there's no way to tell PHP to optionally treat the variable as a reference or as a value.
Actually, that statement isn't 100% true. If the configuration directive allow_call_time_pass_reference is enabled, PHP lets you optionally pass a value by reference by prepending an ampersand to the variable's name. However, this feature has been deprecated since PHP 4.0 Beta 4, and PHP issues explicit warnings that this feature may go away in the future when you employ call-time pass-by-reference. Caveat coder.
Also, if a parameter is declared to accept a value by reference, you can't pass a constant string (or number, etc.), or PHP will die with a fatal error.
See Also
Recipe 6.7 on returning values by reference.
Using Named Parameters
Problem
You want to specify your arguments to a function by name, instead of simply their position in the function invocation.
Solution
Have the function use one parameter but make it an associative array:
function image($img) { $'; return $tag; } $image = image(array('src' => 'cow.png', 'alt' => 'cows say moo')); $image = image(array('src' => 'pig.jpeg'));
Discussion
While using named parameters makes the code inside your functions more complex, it ensures the calling code is easier to read. Since a function lives in one place but is called in many, this makes for more understandable code.
When you use this technique, PHP doesn't complain if you accidentally misspell a parameter's name, so you need to be careful because the parser won't catch these types of mistakes. Also, you can't take advantage of PHP's ability to assign a default value for a parameter. Luckily, you can work around this deficit with some simple code at the top of the function:
function image($img) { if (! isset($img['src'])) { $img['src'] = 'cow.png'; } if (! isset($img['alt'])) { $img['alt'] = 'milk factory'; } if (! isset($img['height'])) { $img['height'] = 100; } if (! isset($img['width'])) { $img['width'] = 50; } ... }
Using the isset( ) function, check to see if a value for each parameter is set; if not, assign a default value.
Alternatively, you can write a short function to handle this:
function pc_assign_defaults($array, $defaults) { $a = array( ); foreach ($defaults as $d => $v) { $a[$d] = isset($array[$d]) ? $array[$d] : $v; } return $a; }
This function loops through a series of keys from an array of defaults and checks if a given array, $array, has a value set. If it doesn't, the function assigns a default value from $defaults. To use it in the previous snippet, replace the top lines with:
function image($img) { $defaults = array('src' => 'cow.png', 'alt' => 'milk factory', 'height' => 100, 'width' => 50 ); $img = pc_assign_defaults($img, $defaults); ... }
This is nicer because it introduces more flexibility into the code. If you want to modify how defaults are assigned, you only need to change it inside pc_assign_defaults( ) and not in hundreds of lines of code inside various functions. Also, it's clearer to have an array of name/value pairs and one line that assigns the defaults instead of intermixing the two concepts in a series of almost identical repeated lines.
See Also
Recipe 6.6 on creating functions that accept a variable number of arguments.
Creating Functions That Take a Variable Number of Arguments
Problem
You want to define a function that takes a variable number of arguments.
Solution
Pass an array and place the variable arguments inside the array:
// find the "average" of a group of numbers function mean($numbers) { // initialize to avoid warnings $sum = 0; // the number of elements in the array $size = count($numbers); // iterate through the array and add up the numbers for ($i = 0; $i < $size; $i++) { $sum += $numbers[$i]; } // divide by the amount of numbers $average = $sum / $size; // return average return $average; } $mean = mean(array(96, 93, 97));
Discussion
There are two good solutions, depending on your coding style and preferences. The more traditional PHP method is the one described in the Solution. We prefer this method because using arrays in PHP is a frequent activity; therefore, all programmers are familiar with arrays and their behavior.
So, while this method creates some additional overhead, bundling variables is commonplace. It's done in Recipe 6.5 to create named parameters and in Recipe 6.8 to return more than one value from a function. Also, inside the function, the syntax to access and manipulate the array involves basic commands such as $array[$i] and count($array).
However, this can seem clunky, so PHP provides an alternative and allows you direct access to the argument list:
// find the "average" of a group of numbers function mean() { // initialize to avoid warnings $sum = 0; // the number of arguments passed to the function $size = func_num_args(); // iterate through the arguments and add up the numbers for ($i = 0; $i < $size; $i++) { $sum += func_get_arg($i); } // divide by the amount of numbers $average = $sum / $size; // return average return $average; } $mean = mean(96, 93, 97);
This example uses a set of functions that return data based on the arguments passed to the function they are called from. First, func_num_args( ) returns an integer with the number of arguments passed into its invoking function — in this case, mean( ). From there, you can then call func_get_arg( ) to find the specific argument value for each position.
When you call mean(96, 93, 97), func_num_args( ) returns 3. The first argument is in position 0, so you iterate from 0 to 2, not 1 to 3. That's what happens inside the for loop where $i goes from 0 to less than $size. As you can see, this is the same logic used in the first example in which an array was passed. If you're worried about the potential overhead from using func_get_arg( ) inside a loop, don't be. This version is actually faster than the array passing method.
There is a third version of this function that uses func_num_args( ) to return an array containing all the values passed to the function. It ends up looking like hybrid between the previous two functions:
// find the "average" of a group of numbers function mean() { // initialize to avoid warnings $sum = 0; // load the arguments into $numbers $numbers = func_get_args(); // the number of elements in the array $size = count($numbers); // iterate through the array and add up the numbers for ($i = 0; $i < $size; $i++) { $sum += $numbers[$i]; } // divide by the amount of numbers $average = $sum / $size; // return average return $average; } $mean = mean(96, 93, 97);
Here you have the dual advantages of not needing to place the numbers inside a temporary array when passing them into mean( ), but inside the function you can continue to treat them as if you did. Unfortunately, this method is slightly slower than the first two.
See Also
Recipe 6.8 on returning multiple values from a function; documentation on func_num_arg( ) at, func_get_arg( ) at, and func_get_args( ) at.
Returning Values by Reference
Problem
You want to return a value by reference, not by value. This allows you to avoid making a duplicate copy of a variable.
Solution
The syntax for returning a variable by reference is similar to passing it by reference. However, instead of placing an & before the parameter, place it before the name of the function:
function &wrap_html_tag($string, $tag = 'b') { return "<$tag>$string</$tag>"; }
Also, you must use the =& assignment operator instead of plain = when invoking the function:
$html =& wrap_html_tag($string);
Discussion
Unlike passing values into functions, in which an argument is either passed by value or by reference, you can optionally choose not to assign a reference and just take the returned value. Just use = instead of =&, and PHP assigns the value instead of the reference.
See Also
Recipe 6.4 on passing values by reference.
Returning More Than One Value
Problem
You want to return more than one value from a function.
Solution
Return an array and use list( ) to separate elements:
function averages($stats) { ... return array($median, $mean, $mode); } list($median, $mean, $mode) = averages($stats);
Discussion
From a performance perspective, this isn't a great idea. There is a bit of overhead because PHP is forced to first create an array and then dispose of it. That's what is happening in this example:
function time_parts($time) { return explode(':', $time); } list($hour, $minute, $second) = time_parts('12:34:56');
You pass in a time string as you might see on a digital clock and call explode( ) to break it apart as array elements. When time_parts( ) returns, use list( ) to take each element and store it in a scalar variable. Although this is a little inefficient, the other possible solutions are worse because they can lead to confusing code.
One alternative is to pass the values in by reference. However, this is somewhat clumsy and can be nonintuitive since it doesn't always make logical sense to pass the necessary variables into the function. For instance:
function time_parts($time, &$hour, &$minute, &$second) { list($hour, $minute, $second) = explode(':', $time); } time_parts('12:34:56', $hour, $minute, $second);
Without knowledge of the function prototype, there's no way to look at this and know $hour, $minute, and $second are, in essence, the return values of time_parts( ).
You can also use global variables, but this clutters the global namespace and also makes it difficult to easily see which variables are being silently modified in the function. For example:
function time_parts($time) { global $hour, $minute, $second; list($hour, $minute, $second) = explode(':', $time); } time_parts('12:34:56');
Again, here it's clear because the function is directly above the call, but if the function is in a different file or written by another person, it'd be more mysterious and thus open to creating a subtle bug.
Our advice is that if you modify a value inside a function, return that value and assign it to a variable unless you have a very good reason, such as significant performance issues. It's cleaner and easier to understand and maintain.
See Also
Recipe 6.4 on passing values by reference and Recipe 6.12 for information on variable scoping.
Skipping Selected Return Values
Problem
A function returns multiple values, but you only care about some of them.
Solution
Omit variables inside of list( ) :
// Only care about minutes function time_parts($time) { return explode(':', $time); } list(, $minute,) = time_parts('12:34:56');
Discussion
Even though it looks like there's a mistake in the code, the code in the Solution is valid PHP. This is most frequently seen when a programmer is iterating through an array using each( ), but cares only about the array values:
while (list(,$value) = each($array)) { process($value); }
However, this is more clearly written using a foreach:
foreach ($array as $value) { process($value); }
To reduce confusion, we don't often use this feature, but if a function returns many values, and you only want one or two of them, this technique can come in handy. One example of this case is if you read in fields using fgetcsv( ) , which returns an array holding the fields from the line. In that case, you can use the following:
while ($fields = fgetcsv($fh, 4096)) { print $fields[2] . "\n"; // the third field }
If it's an internally written function and not built-in, you could also make the returning array have string keys, because it's hard to remember, for example, that array element 2 is associated with 'rank':
while ($fields = read_fields($filename)) { $rank = $fields['rank']; // the third field is now called rank print "$rank\n"; }
However, here's the most efficient method:
while (list(,,$rank,,) = fgetcsv($fh, 4096)) { print "$rank\n"; // directly assign $rank }
Be careful you don't miscount the amount of commas; you'll end up with a bug.
See Also
Recipe 1.10 for more on reading files using fgetcsv( ).
Returning Failure
Problem
You want to indicate failure from a function.
Solution
Return false:
function lookup($name) { if (empty($name)) { return false; } ... } if (false !== lookup($name)) { /* act upon lookup */ }
Discussion
I n PHP, non-true values aren't standardized and can easily cause errors. As a result, it's best if all your functions return the defined false keyword because this works best when checking a logical value.
Other possibilities are '' or 0. However, while all three evaluate to non-true inside an if, there's actually a difference among them. Also, sometimes a return value of 0 is a meaningful result, but you still want to be able to also return failure.
For example, strpos( ) returns the location of the first substring within a string. If the substring isn't found, strpos( ) returns false. If it is found, it returns an integer with the position. Therefore, to find a substring position, you might write:
if (strpos($string, $substring)) { /* found it! */ }
However, if $substring is found at the exact start of $string, the value returned is 0. Unfortunately, inside the if, this evaluates to false, so the conditional is not executed. Here's the correct way to handle the return value of strpos( ):
if (false !== strpos($string, $substring)) { /* found it! */ }
Also, false is always guaranteed to be false — in the current version of PHP and forever more. Other values may not guarantee this. For example, in PHP 3, empty('0') was true, but it changed to false in PHP 4.
See Also
The introduction to Chapter 5 for more on the truth values of variables; documentation on strpos( ) at and empty( ) at; information on migrating from PHP 3 to PHP 4 at.
Calling Variable Functions
Problem
You want to call different functions depending on a variable's value.
Solution
Use variable variables:
function eat_fruit($fruit) { print "chewing $fruit."; } $function = 'eat_fruit'; $fruit = 'kiwi'; $function($fruit); // calls eat_fruit( )
Discussion
If you have multiple possibilities to call, use an associative array of function names:
$dispatch = array( 'add' => 'do_add', 'commit' => 'do_commit', 'checkout' => 'do_checkout', 'update' => 'do_update' ); $cmd = (isset($_REQUEST['command']) ? $_REQUEST['command'] : ''); if (array_key_exists($cmd, $dispatch)) { $function = $dispatch[$cmd]; $function(); // call function } else { error_log("Unknown command $cmd"); }
This code takes the command name from a request and executes that function. Note the check to see that the command is in a list of acceptable command. This prevents your code from calling whatever function was passed in from a request, such as phpinfo( ) . This makes your code more secure and allows you to easily log errors.
Another advantage is that you can map multiple commands to the same function, so you can have a long and a short name:
$dispatch = array( 'add' => 'do_add', 'commit' => 'do_commit', 'ci' => 'do_commit', 'checkout' => 'do_checkout', 'co' => 'do_checkout', 'update' => 'do_update', 'up' => 'do_update' );
See Also
Recipe 5.5 for more on variable variables.
Accessing a Global Variable Inside a Function
Problem
You need to access a global variable inside a function.
Solution
Bring the global variable into local scope with the global keyword:
function eat_fruit($fruit) { global $chew_count; for ($i = $chew_count; $i > 0; $i--) { ... } }
Or reference it directly in $GLOBALS:
function eat_fruit($fruit) { for ($i = $GLOBALS['chew_count']; $i > 0; $i--) { ... } }
Discussion
If you use a number of global variables inside a function, the global keyword may make the syntax of the function easier to understand, especially if the global variables are interpolated in strings.
You can use the global keyword to bring multiple global variables into local scope by specifying the variables as a comma-separated list:
global $age,$gender,shoe_size;
You can also specify the names of global variables using variable variables:
$which_var = 'age'; global $$which_var; // refers to the global variable $age
However, if you call unset( ) on a variable brought into local scope using the global keyword, the variable is unset only within the function. To unset the variable in the global scope, you must call unset( ) on the element of the $GLOBALS array:
$food = 'pizza'; $drink = 'beer'; function party( ) { global $food, $drink; unset($food); // eat pizza unset($GLOBALS['drink']); // drink beer } print "$food: $drink\n"; party( ); print "$food: $drink\n"; pizza: beer pizza:
You can see that $food stayed the same, while $drink was unset. Declaring a variable global inside a function is similar to assigning a reference of the global variable to the local one:
$food = &GLOBALS['food'];
See Also
Documentation on variable scope at and variable references at.
Creating Dynamic Functions
Problem
You want to create and define a function as your program is running.
Solution
Use create_function( ):
$add = create_function('$i,$j', 'return $i+$j;'); $add(1, 1); // returns 2
Discussion
The first parameter to create_function( ) is a string that contains the arguments for the function, and the second is the function body. Using create_function( ) is exceptionally slow, so if you can predefine the function, it's best to do so.
The most frequently used case of create_function( ) in action is to create custom sorting functions for usort( ) or array_walk( ):
// sort files in reverse natural order usort($files, create_function('$a, $b', 'return strnatcmp($b, $a);'));
See Also
Recipe 4.18 for information on usort( ); documentation on create_function( ) at and on usort( ) at. | http://commons.oreilly.com/wiki/index.php?title=PHP_Cookbook/Functions&oldid=7318 | CC-MAIN-2016-40 | refinedweb | 4,089 | 51.18 |
Prior
1607768450
In this article, you will learn what are hooks in React JS? and when to use react hooks? React JS is developed by Facebook in the year 2013. There are many students and the new developers who have confusion between react and hooks in react. Well, it is not different, react is a programming language and hooks is a function which is used in react programming language.
Read More:-
#react #hooks in react #react hooks example #react js projects for beginners #what are hooks in react js? #when to use react hooks
React hooks ra đời đã giúp functional component trở nên powerful hơn bao giờ hết! 😍Trước đây khi cần dùng đến các tính năng của React như state, life cycle thì mình bắt buộc phải dùng class component. Nhưng giờ thì đã khác, có hooks, functional component như hổ mọc thêm cánh, có thể xử lý được state, life cycle và những thứ khác của React một cách êm đềm.
Cùng mình xem hết videos để khám phá những điều thú vị từ React hooks nhé! 😉
Link tham khảo:
#reactjs #react-hook #hook #javascript #web-development
Prior
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If you are a React developer, and haven’t learned about React hooks yet, it is the perfect time to start learning now. In this post, we are specifically going to learn about the React Hook, the useEffect.
In this article, let’s dive in and get started with the next hook, _useEffect. _This article assumes that you have already learned about the _useState _hook.
Note: If you are new to React, I would recommend learning Hooks first, and then learn older way of doing things.
Hooks were introduced in React version 16.8 and now used by many teams that use React.
Hooks solves the problem of code reuse across components. They are written without classes. This does not mean that React is getting rid of classes, but hooks is just an alternate approach.
In React, you can soon end up with complex components with stateful logic. It is not easy to break these components because within the class you are dependent on the React Lifecycle Methods. That’s where React Hooks come in handy. They provide you a way to split a component, into smaller functions. Instead of splitting code based on the Lifecycle methods, you can now organize and split your code into smaller units based on functionality.
This is a huge win for React developers. We have always been trained to write React classes which adhere to the confusing lifecycle methods. Things are going to get better with the introduction of hooks to React.
‘Hooks are functions that let you “hook into” React state and lifecycle features from function component. They do not work within a class. They let you use React without a class.’ – React Official Blog post.
_useEffect _hook essentially is to allow side effects within the functional component. In class components, you may be familiar with lifecycle methods. The lifecycle methods, _componentDidMount, componentDidUpdate _and componentWillUnmount, are all all handled by the useEffect hook in functional components.
Before the introduction of this hook, there was no way to perform these side-effects in a functional component. Now the useEffect hook, can provide the same functionality as the three lifecycle methods mentioned above. Let’s look at some examples to learn this better.
import React from "react"; class TraditionalComponent extends React.Component { state = { buttonPressed: "", }; componentDidMount() { console.log("Component did mount", this.state.buttonPressed) } componentDidUpdate() { console.log("Component did update", this.state.buttonPressed) } onYesPress() { this.setState({ buttonPressed: "Yes" }); } onNoPress() { this.setState({ buttonPressed: "No" }); } render() { return ( <div> <button onClick={() => this.onYesPress()}>Yes</button> <button onClick={() => this.onNoPress()}>No</button> </div> ); } } export default TraditionalComponent;
In the example above we have coded a traditional class React component. In class components, we have access to the lifecycle methods. Here I am using _componentDidMount() _and _componentDidUpdate() _with console logs in each of them. When you run this above code, and look at the console you will initially see the following message:
Component did mount ""
_**componentDidMount() **_is called as soon as the component is mounted and ready. This is a good place to initiate API calls, if you need to load data from a remote endpoint.
Now if we press the Yes button or the _No _button, the button state is updated. At this point you should see the following on the console:
Component did update Yes Component did update Yes
The _componentDidUpdate()_method is called when the state changes. This lifecycle method is invoked as soon as the updating happens. The most common use case for the _componentDidUpdate() _method is updating the DOM in response to state changes.
Alright, now what does the _useEffect _hook really do?
Let’s now re-write our example into a functional component.
import React, { useState, useEffect } from "react"; const UseEffectExample = () => { const [button, setButton] = useState(""); //useEffect hook useEffect(() => { console.log("useEffect has been called!", button); }); const onYesPress = () => { setButton("Yes"); }; const onNoPress = () => { setButton("No"); }; return ( <div> <button onClick={() => this.onYesPress()}>Yes</button> <button onClick={() => this.onNoPress()}>No</button> </div> ); }; export default UseEffectExample;
We have now rewritten our class component into a functional component.
Note: The first thing we need to do to get the useEffect to work is, import the _useEffect _from React.
import React, { useEffect } from "react";
Notice here that the useEffect hook has access to the state. When you run this code, you will initially see that the useEffect is called which could be similar to the componentDidMount. After that every time the state of the button changes, the useEffect hook is called. This is similar to the componentDidUpdate lifecycle.
// Console useEffect has been called! "" // comparable to componentDidMount useEffect has been called! Yes // comparable to componentDidUpdate useEffect has been called! No // comparable to componentDidUpdate
I hope you are with me so far. Let’s look into some more details about the _useEffect _hook.
You can optionally pass an empty array to the useEffect hook, which will tell React to run the effect only when the component mounts.
Here is the modified useEffect hook from the previous example, which will occur at mount time.
//useEffect hook useEffect(() => { console.log("useEffect has been called!", button); }, []);
When you run this on the console you will only see the _useEffect _being called once at mount.
// Console useEffect has been called! "" // comparable to componentDidMount
An interesting feature of the _useEffect _hook is that, you can separate them into multiple hooks, based on the logic. With lifecycle methods, this was not possible. Often, unrelated logic was combined within the same lifecycle method, because there could only be one of each lifecycle method within the class component.
If you have multiple states in your functional component, you can have multiple _useEffect _hooks. Let’s extend the previous example, by adding another state within the component, that display the titles of blog posts. Now this is unrelated to the yes and no button we had. We can create multiple useEffect hooks, to separate the concerns as shown below:
import React, { useState, useEffect } from "react"; import { default as UUID } from "uuid"; const UseEffectExample = () => { const [button, setButton] = useState(""); const [blogPosts, setBlogPosts] = useState([ { title: "Learn useState Hook", id: 1 }, { title: "Learn useEffect Hook", id: 2 } ]); useEffect(() => { console.log("useEffect has been called!", button); }, [button]); useEffect(() => { console.log("useEffect has been called!", blogPosts); }, [blogPosts]); const onYesPress = () => { setButton("Yes"); }; const onNoPress = () => { setButton("No"); }; const onAddPosts = () => { setBlogPosts([...blogPosts, { title: "My new post", id: UUID.v4() }]); }; return ( <div> <button onClick={() => this.onYesPress()}>Yes</button> <button onClick={() => this.onNoPress()}>No</button> <ul> {blogPosts.map(blogPost => { return <li key={blogPost.id}>{blogPost.title}</li>; })} </ul> <button onClick={() => onAddPosts()}>Add Posts</button> </div> ); }; export default UseEffectExample;
In the example above, we have a button state and a blog post state within the component. We have separated the unrelated logic into two different effect hooks. With the lifecycle methods, this would have not been possible. Hooks let us split the code based on what it is doing rather than a lifecycle method name. React will apply every effect used by the component, in the order they were specified.
When we run this code, when the component is mounted both the useEffect hooks are run as follows:
You can see how the effects have been separated for each state. This is done by passing the state within an array to the _useEffect _hook.
Now if the Yes/No button is pressed, you should see this on the console.
Notice here, that the useEffect for the blogPosts has not been invoked here. This tells React which effect to apply, without bundling them all within a call. Now if we clicked on adding a blog post button, we would see its effect take place.
You get the idea!
If you have you are used to the class components with lifecycle methods, you would have tried to optimize when the _componentDidUpdate _is called by passing the _prevProps _or _prevState _and compare it with the current state. Only if they don’t match the componentDidUpdate will happen. Now with _useEffect _hook, you can achieve the same optimization by simply passing the state in an array as a parameter as we have seen in the example above. This will ensure that the hook is run when the state passed to the effect changes.
Congratulations, you have stayed with me so far! Hooks is a fairly newer concept in React, and the official React documentation does not recommend that you rewrite all your components using Hooks. Instead, you can start writing your newer components using Hooks.
If you want to play with the code samples I used in this blog post, they are available on my GitHub Repo below:
#reactjs #react #reach-hooks #hooks #webdev
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Hooks are a new addition in React 16.8. They let you use state and other React features without writing a class.
#reactjs #react-js #hooks #react-hooks #javascript | https://morioh.com/p/b4d2ea7f5cdf | CC-MAIN-2021-39 | refinedweb | 1,647 | 57.77 |
With the new fullscreen behaviour, it is not possible to hide the tab bar. This was very useful for presentations. (Or maybe it is possible but I don't know how) I can hide most of the toolbars from the view menu (but that's a bit annoying cause you need to reset everything when leaving fullscreen). I suggest adding a menu item while in full mode to allow top toolbars to hide and only show when you hover the top of the browser.
We're ignoring the browser.fullscreen.autohide preference on 10.7 now, which is what controlled the previous behavior. We can't reasonably overload that preference for Lion, so maybe we should have a new preference for Lion only? It would default to false but could be enabled through about:config. I'll give it a go. I know Chrome has a separate "Presentation Mode" which hides the toolbar. If I had to guess though, they're doing that at the Cocoa layer (I think there's an option for that) though I could be wrong.
My questions are mostly curiosity, I'm not implying you're wrong: (In reply to Paul O'Shannessy [:zpao] (no longer moco, slower to respond) from comment #1) > We're ignoring the browser.fullscreen.autohide preference on 10.7 now, which > is what controlled the previous behavior. Why ignoring the preference ? Couldn't have it been possible to set this preference key to "false" at update time on Lion? > We can't reasonably overload that preference for Lion, I don't really understand the concept of "overloading a preference", can you be more explicit. > so maybe we should have a new preference for Lion only? > It would default to false but could be enabled through about:config. I'll > give it a go. That would be awesome! François.
There are two ways to fix this bug quickly: 1) Provide a non-default option to use the "old" (non-Lion) fullscreen mode on OS X Lion and above. 2) Provide a non-default option to obey the browser.fullscreen.autohide setting even on OS X Lion and above. I currently prefer #1, because I'm afraid #2 is a Frankenstein's monster (that it mixes UI elements that don't really belong together). But it's hard to choose unless you have some kind of testcase to play with. So I've created a patch that just stops our Lion fullscreen mode from ignoring browser.fullscreen.autohide. I'll start a tryserver build, which should be available by tomorrow morning. This is *not* a finished work. At the very least we'll need to add another setting that governs this behavior. But I hope it will give people who think they prefer choice #2 above a better idea of whether or not this is what they really want. (I'll post the patch when I post the tryserver build.)
(Following up comment #4) Anything besides (or between) these two choices will be more work (perhaps a *lot* more work). Which means that it (probably) won't be finished anytime soon.
Hi, Thanks for you work, I'll give it a try when it's ready. I suppose that 774685 may be a blocker if we want it to work correctly "Lion style". What would be nice (if not too Frankenstein-ish) would be to have the same kind of behaviour as in Apple Preview : both the application menu and the toolbars drop down at the same time. Cheers.
Created attachment 643861 [details] [diff] [review] Obey browser.fullscreen.autohide in Lion fullscreen mode (for testing, not a fix) Here's the patch I promised in comment #4. As I said there it's not finished -- it's just for people to test option #2 from comment #4. I already know it's not ideal -- so you needn't bother telling us that it isn't. The questions that need answering for both options from comment #4 are: 1) Is it better than what we have now? 2) Is it worth landing now as an interim patch?
Oops, forgot the tryserver build for my patch from comment #7:
I tried your build in comment #8. From a user point of view, and apart from bug #738335 getting in the way a little bit, it's perfect and I don't see what's wrong with that. Again, still from my user point of view, I think it's better than what we have now (to answer your question in comment #7), and I really don't see what is so evil about it (comment #4). Thanks..
The tryserver build in comment 8 only solves half the Air Mozilla problem described in comment 10.
(In reply to comment #10 and comment #11) Sounds like what you mean by "presentation mode" is choice #1 from comment #4 (the "old", non-Lion-specific fullscreen mode). My tryserver build (partially) implements choice #2.
(In reply to Richard A Milewski[:richard] from comment #10) >. Mountain Lion will solve this by allowing one fullscreen apps per screen.
>. In it please address the issue on both Lion and Mountain Lion. I'm on vacation next week. But I should have a chance to look at it when I get back.
(In reply to Steven Michaud from comment #14) > >. Please note that all applications in fullscreen will behave like this. It is Lion specific behavior.
Keynote seems to be able to manage something that at least looks like full-screen dual-display behavior on Lion.
What's possible in the near future is described in comment #4. Anything more should be the subject of other bugs (like bug 738335).
I am very anxious to restore the true full screen functionality in Lion 10.7.4 lost with today's upgrade to Firefox 14.0.1. I have wasted this whole day trying to find a way to do this until I came across this bug thread. As a user, how can I download and install the patch (temporary fix or not) in Comment #7? Alternately, how can I get rid of today's upgrade and download the previous version of Firefox? My Mac worked exactly the way I wanted it to yesterday, but since this morning it no longer does.
Tom, The link in comment #8 is the version with the temporary fix. You can find older versions of firefox at: (Along with information on why using them might be a really bad idea).
Tom, also note that I've been asking people to make a choice between the two options listed in comment #4. I assume you'd choose option #1 (provide a non-default option to use the "old" (non-Lion) fullscreen mode on OS X Lion and above). It's always a good idea to read the whole bug before commenting :-)
I'm going to be on vacation (and mostly away from the internet) all of next week.
Steven, I've spent over two hours reading the bug, and you're right, option #1 is the one I would choose. I downloaded and installed the patch in Comment #8, but I can't find the triggering option, so it has no effect. Help please? Tom
> I can't find the triggering option I don't understand. With the tryserver build from comment #8 (which *partially* implements option #2 from comment #4), the only "trigger" you need (once you're in fullscreen mode) is to mouse up to the top of the page. That should make Firefox's toolbars and menus appear, both at the same time. (Though the menus do overlap the tab bar, which is the uppermost toolbar -- that's bug 738335.) Note that this build is for testing, not for everyday use. For example it doesn't give you the option to go back to the previous Lion-style fullscreen mode (which didn't hide any of FF's toolbars). (I assume you haven't used about:config to change browser.fullscreen.autohide to "false" from its default setting of "true".)
You're right, I didn't use about:config to change browser.fullscreen.autohide to "false" from its default setting of "true" because I can't find it. About Firefox in my Firefox menu is apparently the wrong place to look. Remember, I am just a user. My objective is to restore the Lion full screen display to a pure image almost identical to the screen saver image.
> My objective is to restore the Lion full screen display to a pure > image almost identical to the screen saver image. I don't understand this, either. This bug is a real bug, but we can't fix it instantly. For now your only options (if you're running on OS X 10.7 or above) are to a) go back to FF 13.0.1 (not recommended because FF 14.0.1 contains security fixes) or b) use my tryserver build from comment #8. The tryserver build from comment #8 should "just work". If it doesn't, we're probably not going to be able to figure out why.
Sorry, I didn't understand either. I thought the FirefoxNightly download was a patch or upgrade to Firefox, which was installed when I dragged the icon into the Applications folder as with other upgrades. Therefore, I expected Firefox to "just work" as you say after restarting it. After I finally figured out that FirefoxNightly is a stand alone application, I found that it works exactly as I expected it to. Thank you! But I would suggest that you consider adding some minimal instructions to future "non-standard" Mac downloads.
Tom, The other thing I think you missed is how to use about:config. Type that into the address bar. CAUTION: It's generally safer to look but not touch.
Richard, Thanks, I'll tuck that away for future reference. I have my Mac working the way I want it to now, so I think I'll just leave well enough alone for the time being. Tom
Upgrading to OS X 10.8 Mountain Lion makes Firefox 14.0.1 revert to the (good & desired) behavior of Firefox 13. Not sure why that makes any sense, but I'm happy. However, comment 135 of bug 639705 seems to imply that this is unintended, which is too bad.
Here's another tryserver build made from my (testing) patch from comment #7: Someone asked for it. Note that tryserver builds are only available for a week or two.
Thanks for reposting a build. So when trying this, I feel like it's not something you'd like on a setting. People using their browser fullscreen want toolbars to always be visible. But sometimes you need a presentation mode. It just depends on the context. So I think two entries in the View menu is the best option.
I disagree with Anthony Ricaud. When I use my browser in fullscreen I do not want any toolbars to be visible. I consider fullscreen and presentation mode to be the same thing. I am still using the Nightly build with the original (testing) patch from comment #7, and will continue to do so until Firefox is upgraded with the identical behavior. If some users want a partial fullscreen with toolbars (name it what you like), I agree it should be a separate option. I suspect that such an arrangement would be difficult to implement.
Obeying browser.fullscreen.autohide and showing the a context menu for toggling it should be flexible enough for those who want to permanently hide toolbars and those who want it temporarily.
(In reply to tom.etheridge from comment #32) > I disagree with Anthony Ricaud. When I use my browser in fullscreen I do not > want any toolbars to be visible. I consider fullscreen and presentation mode > to be the same thing. Yeah, I really would like to know where this assertion of "People using their browser fullscreen want toolbars to always be visible" comes from. Especially since with the toolbars visible, one is almost not gaining any space on the screen, which is the point of running full screen! Especially, I don't understand the point of disabling the functionality allowing to hide toolbars. If people want to keep their toolbars on, even by default, fair enough. But why would one remove the possibility completely? Maybe it's just me presenting it in a negative way, but I'm yet to find someone who finds the new full screen mode better than the old one (apart from OS integration).
Tom: I think your use-case would still be possible with two options in the view menu. You'll just use presentation mode all the time. What I tried to (poorly) say in comment 31 is that it's not only a matter of a user preference. It's also a matter of context. I don't prefer "tabs visible" or "tabs hidden", I prefer the mode that makes more sense depending on the context. When doing presentations or running WebGL demos, I'll certainly use the "presentation mode". But then when I'm at my desk, maybe I prefer tabs to be visible or not.
With the "fixing" of bug 639705 in 15.0, we're now back at a stage when a full-on presentation mode is impossible in the main release of Firefox. Any chance of fixing that. Now that the keystroke has been standardized to the usual OS X cmd-control-F, I think the best way to handle presentation mode is to mimic Preview.app. It has Enter Full Screen at cmd-control-F and Slideshow at cmd-shift-F. We can add Presentation Mode at cmt-shift-F by analogy.
the absence of a presentation mode render firefox useless for HTML(5) based presentations and also slideshows. :-(
(In reply to Anthony Ricaud (:rik) from comment #13) > Mountain Lion will solve this by allowing one fullscreen apps per screen. ...doesn't seem to. A Firefox CMD-SHIFT-F on one monitor replaces the wallpaper on the second monitor with the linen pattern.
Hello, Could we please have an update on Mozilla's *intentions* on the matter? It's really irritating that we've lost a functionality and that it's taking months to make a decision about how to re-implement it. Whichever way you do it, I don't care any more, please just do it... Cheers,
Firefox is so poor on OS X. I prefer Gecko and I like FF but it's bugs like this that make it hard to use on OS X. I can't believe that anybody desires the functionality how it is now. In full screen mode the tabs (at least) should auto hide. It's the only functionality that makes sense.
recent Opera, Safari and Chrome all provide fullscreen aka presentation mode in Mountain Lion, with no UI toolbars showing. What is the holdup on fixing this regression bug?
Does anyone know of an add-on that can solve it while this bug is still open? Having to run full-screen presentations in Chrome when talking on Firefox/Mozilla topics is pretty hilarious.
Ah! I finally found it after many searches
tried that, doesn't work for me on ML and latest FF :-(
First of all, the name of this bug should not be "Allow hiding toolbars for presentations." It should be "Restore fullscreen mode," which was the original intention. Fullscreen mode is useful in far more situations than merely presentations. For example, reading on-line magazines, maximizing the size of on-line artwork, and watching HD videos. Words mean things, and implying that this problem only affects presentations diminishes its importance. I just installed Firefox 19.0.2 (the latest version) and the problem is still there. That is inexcusable. This problem was completely fixed in Nightly 17.0a1 (2012-07-18), which I am still using, and will continue to use until the obstinate developers at Mozilla get off their stubborn butts and fix it in Firefox. They obviously know how, they just won't.
Here's a working add-on that reverts to the old custom-built fullscreen mode: Looking under the covers it's astonishingly simple...
when fix it ???
The addons: and provide a full screen, but can be considered a PARTIAL FIX. Because using these we cannot access the menu bar while in full screen. Anyway, is better than without them. NOFS addon don't show the navigation bar when hoovering the mouse on top, so I recommend using Old Lion FS addon.
The original intent can be fixed by using the DOM Fullscreen API. Now, I do think that having the option to (A) autohide the browser chrome in (browser, not DOM API) fullscreen mode is something many people (myself included) might like (when moving the mouse to the top, the chrome should slide in like, and with the menu bar). There's also the "mobile" solution (B) which slides out the chrome while scrolling down (and sliding back in when scrolling up, not necessarily only when scrolling all the way to the top), so that's another option to solve this problem. As I understand, solution (A) is what this bug is about. Or how about investigating solution (B)? Either way, can somebody please clarify the title, then?
This problem has not been fixed for almost two years now, why is it still not possible to have a working full-screen mode with Firefox v24? I can see where the problem is, however one would expect that the Mozilla developers can come up with a solution within two years - yes, the OSX full-screen mode intends to only hide the system UI elements like menu bar and notifications, nevertheless Mozilla can still change the way Firefox behaves in that mode. Seeing how this ridiculous bug has not been fixed yet I do believe that this won't change in the future. Well done.
I have to use Chrome and Firefox simultaneously for web app compatibility reasons and I feel as though my Firefox user experience is lessened by the amount of screen I can use. Seems like an easy fix and weird that it has gone unfixed for so long.
I thought maybe they were saving this fix for Australis, but I just tried the nightly and fullscreen still doesn't hide the bars. Very disappointing...
Running Nightly 29.0a1 (2014-01-03) on 10.9 Maverick and experiencing the same issue. Would love to see a fix for this as well.
Confirm. Still not working with Firefox 26.0 under MacOS X 10.9.1 Mavericks. There is no option in Firefox to get a real Firefox-Fullscreen (no bars or Menue) any more since Apple introduced "Fullscreen-Function"?
If anyone is interested, I wrote a very simple fix using Stylish.; }
This add-on has been working great for me to get fullscreen back: (it was buried up above in this thread but lost in the sands of time by now)
I still using the old-lion-fullscreen addon but it has some bugs. If i move the mouse up to the top of the screen it often doesn't show the menu or bars.
Confirming this -- using Mavericks 10.9.2 and Firefox 28. When one goes into full-screen mode, the tabs and navigation bar are still visible. (NB: browser.fullscreen.autohide is set to true. Also, I use the firefox menu rather than the OS X control to go into full-screen, if that makes a difference.) (I see there's an add-on to get round this but it seems better not to need an add-on, especially if the latter is buggy.)
Will this ever be fixed? Chrome is able to provide a presentation mode in OS X native fullscreen that works, for a long time already.
It has been years of this regression. Why no mozilla developer cares to fix such useful feature?
I've been just sitting here using old-lion-fullscreen for Firefox, which requires its own desktop to work, for years, hoping this would get fixed. It wasn't.
I'm currently using Chrome to public talks about Mozilla. That's kind of contradictory but that's what we have. I agree with Francisco. This bug deserves better attention.
(In reply to Sergio Oliveira Campos from comment #65) > I'm currently using Chrome to public talks about Mozilla. That's kind of > contradictory but that's what we have. I agree with Francisco. This bug > deserves better attention. Hi Sergio, please keep doing that, if people get to ask why you're doing that, it's one more way to explain and complain about it =)
Like the other posters have commented, it is crazy that this is still a bug, and drives me insane when I use fullscreen mode. Again the fact that there is even a setting - browser.fullscreen.autohide - but it is just ignored seems nuts. I don't have enough FF internal knowledge to understand why it simply can't just be set to default to false on Mac OS X, and then allow the user to change the value when desired? Why would that be a problem?
I'm using the following userChrome.css to work around this bug: @namespace url(""); #main-window[inFullscreen="true"] #nav-bar, #main-window[inFullscreen="true"] #TabsToolbar { display: none !important } It could use some more work, e.g. there's no popup for CMD-L, but it's enough for me.
(In reply to kAton from comment #48) > The addons: > and > provide a full screen, but can be considered a PARTIAL FIX. Because using > these we cannot access the menu bar while in full screen. Recently bought a new laptop, so I moved from 10.4 to 10.10.4, and now I'm being effected by this bug, too (was using TenFourFox on the old laptop). Have you tried this extension? Seems to be working for me. Removes the toolbars that Firefox's fullsceen mode is not, and I can still access the menubar if I mouse to the top, along with the address bar, tab bar, and bookmarks bar.
For those landing on this bug who are looking for a workaround that will hide everything in full-screen mode on Mac OS X, including the address and tab bars, here is an extension I have found to work reasonably well. The extension mentioned in comment #69 is no longer available.
So it's been two years since the last comment on this bug. I just created a new profile on the current Firefox (54.0). Going to full-screen mode leaves the tab bar and main toolbar still. The only thing that's really being hidden is the menu bar and window control buttons in the upper-left. While we have some extensions that work *right now* for getting a true full screen mode, will any of those still work after Firefox 57 or whenever you change to the WebExtensions API? I'm still using the extension I mentioned in Comment #69, and the "Old Lion Fullscreen" extension appears abandoned since its GitHub hasn't seen changes since 2012. It's been a long time since OSX Lion (10.7). Isn't it about time for a real solution on this? | https://bugzilla.mozilla.org/show_bug.cgi?id=740148 | CC-MAIN-2017-34 | refinedweb | 3,902 | 73.58 |
I understand that the problem explicitly asks for a constant space solution, however I found this algorithm that allows you to find duplicates in linear time using just sqrt(n) memory.
One of the advantages of this algorithm is that is also decides if there are no duplicates in the array (in this case I returned -1).
Explanation
Split the numbers from 1 to n in sqrt(n) ranges so that range i corresponds to [sqrt(n) * i .. sqrt(n) * (i + 1)).
Do one pass through the stream of numbers and figure out how many numbers fall in each of the ranges.
At least one of the ranges will contain more than sqrt(n) elements.
Do another pass and process just those elements in the oversubscribed range.
Using a hash table to keep frequencies, you’ll find a repeated element.
This is O(sqrt(n)) memory and 2 sequential passes through the stream.
public class Solution { public int findDuplicate(int[] a) { int bucketLen = (int)Math.sqrt(a.length); int[] freq = new int[bucketLen + 1]; for(Integer i : a) { freq[Math.min(i/bucketLen - (i%bucketLen == 0?1:0), bucketLen)]++; } int i = 0; while(i < bucketLen && freq[i] <= bucketLen) i++; Set<Integer> found = new HashSet<Integer>(); for(Integer v : a) { if(i*bucketLen < v && (i==freq.length-1 || v <= (i+1)*bucketLen)) { if(found.contains(v)) return v; found.add(v); } } return -1; } }
Hope you find this helpful :) | https://discuss.leetcode.com/topic/75765/my-o-n-time-o-sqrt-n-space-solution | CC-MAIN-2017-39 | refinedweb | 237 | 67.35 |
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RPC with new v8 API (Call Python function from JavaScript examples) Odoo 8
in the new API, if you've to deal with ids/recordsets then for python function definition choose decorator:
@api.multi -to get recordset in your function
@api.one -to get browse_records one by one in your function
in examples I'll use @api.multi but @api.one also may be used to deal with ids, depending on requirements.
if it's simple function that does not have to deal with records/ids then for python function choose decorator:
@api.model -Allows to be polite with old style api
@api.multi -you can use it as well, just pass [ ] (empty array) as first argument in javascript...
an example model:
class my_model(models.Model):
_name = "my.model"
name = fields.Char('Name')
@api.multi
def foo_manipulate_records_1(self):
""" function returns list of tuples (id,name) """
return [(i.id,i.name) for i in self]
@api.multi
def foo_manipulate_records_2(self, arg1, arg2)
#here you can take advantage of "self" recordset and same tie use aditional arguments "arg1", "arg2"
pass
@api.model
def bar_no_deal_with_ids(self, arg1, arg2):
""" concatenate arg1 and arg2 """
return unicode(arg1) + unicode(arg2)
Odoo RPC examples:
assume that "list_of_ids" variable contains list(array) of ids of existing records of my.model model.
- call of function foo_manipulate_records_1 decorated with @api.multi:
new instance.web.Model("my.model")
.call( "foo_manipulate_records_1", [list_of_ids])
.then(function (result) {
// do something with result
});
-call of function foo_manipulate_records_2 decorated with @api.multi:
new instance.web.Model("my.model")
.call( "foo_manipulate_records_2", [list_of_ids, arg1, arg2])
.then(function (result) {
// do something with result
});
-call of function bar_no_deal_with_ids decorated with @api.model:
new instance.web.Model("my.model")
.call( "bar_no_deal_with_ids", [arg1, arg2])
.then(function (result) {
// do something with result
});
also if it has some sense depending on implementation, then you can call function decorated with @api.multi even if you have not to deal with ids (just pass empty array in place of ids, as firs element of argument list):
new instance.web.Model("my.model")
.call( "foo_manipulate_records_2", [[], arg1, arg2])
.then(function (result) {
// do something with result
});
this way may be useful in some cases, as undecorated function in v8.0 api is considered as @api.multi (as @api.multi is a default decorator)
except of two parameters to RPC call that I've used in examples (the function name and argument list), you can use third parameter -a dictionary of keyword arguments. it's highly recommended to turn around the context, as it may change behavior of remote procedure (localization, etc.). below I'll rewrite the last example with context argument in rpc call (same may be applied to all examples)
var self = this;
new instance.web.Model("my.model")
.call("foo_manipulate_records_2", [[], arg1, arg2], {'context':self.session.user_context})
.then(function (result) {
// do something with result
});
(of course you can use custom context as well instead of turning around the existing one, if that's a requirement.)
references: Odoo RPC documentation, Odoo new API method decorators
Originally were posted here as answer.
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