text stringlengths 454 608k | url stringlengths 17 896 | dump stringclasses 91
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value | word_count int64 101 114k | flesch_reading_ease float64 50 104 |
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Details
- Type:
Improvement
- Status: Resolved
- Priority:
Minor
- Resolution: Fixed
- Affects Version/s: 1.3-rc1
-
-
- Labels:None
- Environment:Operating System: All
Platform: All
Description
Support for Static Utility Classes is:
1) define namespaces
context.defineNamespace("Math").add( java.lang.Math.class ) ;
used as $Math.sin(0)
2) Add / Replace / remove methods in namespace :
context.getNamespace("Math").add(MyRandom.class.getMethod("randomString",new
Class[]
))
used as $Math.randomString(12)
3) "union" on namespaces
context.defineNamespace("Utils")
.add(context.getNamespace("Math"))
.add(context.defineNamespace("Collections",Collections.class ) );
used as:
$Utils.sin(0)
$Utils.sort($list)
4) Global namespace
context.getGlobalNamespace().add( Math.class );
used as $sin(0)
5) inline namespaces:
#use java.lang.Math as Math
$Math.sin(0)
#end
#with Math
$sin(0)
#end
Activity
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- Work Log
- History
- Activity
- Transitions
No "automatic names" and nothing changed in Context
I think I'll change some things in uberspector, nothing more(at least based on what I remember about this functionality).
I've always wanted something like this, so if there are not objections I will give it a try.
java.lang.Math seems like a good enough general example. At least, everyone knows it and its static nature, so the problem is apparent. Though i'm not entirely sure how Adrian intends to do this, I don't think this is likely to take more code than something along the lines of Jim Seach's tweak to UberspectImpl.getMethod above (just fixed to maintain backwards compatibility). Seems like a pretty small code effort (new docs and tests aside) for a feature that appears sufficiently desired by people. As long as someone who wants it does the work, i have no problem with the basic idea. I only object to the "automatic names" idea, as that does open up new complications and implies a change to Context (a very public interface).
Christopher,
I agree java.lang.Math was not a good example for what I was trying to explain, anyway on second thought letting the user to choose the name is more appropriate. Sometime it is good to enforce users to follow a specific path, but this one is not the right case.
So I will go with context.put(String, Class) and we will so how it goes after first implementation.
Adrian,
If you are willing to subclass a certain class to change its "automatic" name, then why not also subclass said class to provide methods to access the static members and methods from a concrete instance of that class?
I tend to agree with Nathan that custom tools are a good way to go, here. It's unfortunate that you can't create an instance of java.lang.Math (nor can you extend it), but this class was simply not designed to be used in any way other than statically.
Are we picking java.lang.Math as a truly representative class of useful items in the Java universe? I feel like that example is a bit contrived, and leads us down a path requiring lots of code and special cases to handle a situation that has minimal applicability.
It's fine with me, anyway the users can java-isms their templates if they want
at least I think I will do it
For me, having a java look-a-like version of accessing static members is preferable, but it is more like a matter of taste.
I can't say i'm fond of the idea for a few reasons. First, the very reasons that i like context.put("math", Math.class) are that it keeps control of the name fully in the hands of the context creator, and that when working on the template, you don't really need to know that $math is anything special.
I've long been an advocate of hiding java-isms (like the difference between arrays and lists) from templates. Despite the fact that it is java-powered and allows java methods to be called, VTL is not java. When we do things that make it more like java, then it complicates it and makes it more difficult to swap things around on the java side. So, i prefer the ignorance that comes with something like $view.CONTEXT, as it allows $view to be almost anything and CONTEXT to refer to getCONTEXT() or get("CONTEXT"). This loose binding provides a lot of implementation flexibility that a tighter binding would not. The class can evolve a lot without ever needing to update the template.
So, i actually think keeping things to $view.CONTEXT simplifies things. No worries about classes with same name and different package, no need to consider if something is accessed through a class or an instance, as there is no actual difference between the way the two behave.
Sorry, I meant to say "scan for static methods/fields of any object present in context and not only for a Class object".
For example I have a tool ViewTool and I'm using this tool as : context.put("view", new ViewTool()).
I also have some public static fields and methods : ViewTool.CONTEXT or ViewTool.getPath() and I would like to have those accessible in my templates.
Maybe even to introduce in Context something like void put(Class staticTool) to allow automatic name creation. In my opinion it would be better to have in templates ViewTool.CONTEXT instead of view.CONTEXT cause you will "know" it is a static member access.Allowing the users to name the tool in the context could lead to some confusion when reading a template. Right now you know that every access to a member is done against an instance but if we introduce access to static members and static access will look like instance access could be confusing.
Of course it can creates conflicts, two classes with the same name but in different package cannot be used with this automatic naming but on the other hand not every class in your project actually goes in the context.
As a workaround you can extend the class with static members and provide a different name to be used in the context.Also an exception could be threw in case of conflicts like this one.
Any thoughts?
I also liked context.put("math", Math.class). I'm not sure what you mean by scanning instances for static classes, but public static field support is another conversation and an old one at that. I'm open to it, but let's save it for another bug.
Anyway, i think if you are going to implement this, then you should go on whichever path you prefer. "Them that do the work make the decisions", as they say. Do what seems best to you.
I think Geir proposal (context.put("math", Math.class)
it's the cleanest possible solution for the end user. I will go even further and even for instances we could scan for static classes/fields(just once per class). The solution should definitely go in the current uberspect implementation.
I could take a look, but I need to know which path to go...
Is anyone still interested in following through on this? Seems like a good fit for a custom uberspect, especially if chaining support gets finished (see
VELOCITY-588). Of course, i'm perfectly happy just using VelocityTools. Shouldn't be too hard to implement. I like the StaticWrapper idea. Schedule it for 1.6
"#with" macro ( idea from Pascal )
This is not static method specific and can be used
for bean properties too :
#with math, formatUtils, bean
$format( $sin($x) )
$format( $cos($x/2) )
#end
becomes this :
$formatUtils.format( $math.sin( $bean.x ) )
$formatUtils.format( $math.cos( $bean.x/2 ) )
"#with .. as" form:
#with math, formatUtils, bean as t
$t.format( $t.sin($t.x) )
$t.format( $t.cos($t.x/2) )
#end
I am not sure about "use/uses" macro it loads class from template and it is not
very secure and can be problems with ClassLoaders:
#use java.lang.Math as math
Some code generation tools provide Velocity templates and it is possible to
replace them with custom templates, but API working with context is private.
I know "properties" can help to add tools, but I like this way too.
I like "StaticClassWrapper" idea, namespace stuff can be implemented this
way too, StaticClassWrapper can be container for static methods :
public StaticClassWrapper defineNamespace( String name ){ StaticClassWrapper namespace = new StaticClassWrapper(); put( name, namespace ); return namespace; }
public class StaticClassWrapper{
List methods = new Vector();
public StaticClassWrapper add( Class c ){ copyStaticMethods( methods, c.getMethods() ); return this; }
..........................
}
methods can be added/removed this way and used like :
$math.sin(2)
$math.median($var)
some reserved name can be used for "global" methods.
Jim, that's exactly what I was suggesting. I originally brought it up on the
commons-dev list as what you'd do to an extension Uberspector which you could
plug into Velocity. However, it might be reasonable to include this sort of
functionality in the core. Geir, do you have any thoughts on this?
Daniel, when I first read your email about the wrapper, I didn't understand
what you were getting at, but I think I do now. In other words, create a
wrapper class something like:
public class StaticClassWrapper {
private Class userClass;
public StaticClassWrapper(Class userClass){ this.userClass = userClass; }
public StaticClassWrapper(String className) throws ClassNotFoundException{ this(Class.forName(className)); }
public Class getUserClass(){ return userClass; }
}
check for that class in UberspectImpl.getMethod(), and pass its wrapped class
to the introspecter, rather than checking for java.lang.Class and using that
object as I had suggested earlier.
Taking it one step further, if we anticipate that others may have a need to
extend this class, we may want to define an interface, a default wrapper class
implementing that interface, and a way to override which wrapper class to look
for with a configuration option, as you suggested. (Of course, we could always
just make the class final and privatize all the methods in order to avoid the
maintenance headaches
If one of the committers thinks this is a reasonable approach, I can try to
implement it and post a patch this weekend. Let me know.
Geir, I'm totally in favor of that and have given my +1 on your vote.
I'm looking at this issue as a new feature, where one has only an instance of a
Class object and can't create an instance of the object it represents. This
would be useful for some classes in the JDK which also have private constructors.
Combining my suggestion with Jim Seach's code above would produce a backwards
compatible solution for this issue.
Irregardless of what happens with this issue, I am firm on StringUtils having a
public ctor.
or they could put the CTOR back
Alternately, the Invoker suggestion I made on the Commons dev list could be
used. It may be trading one special case for another in the
uberspector/introspector, but it preserves backwards compatibility and could be
handled as a configuration option.
Why not first look in the methods of java.lang.Class and then, only if not
found, look into the static methods of the targeted class
?
A static tool is not meant to contain methods like toString or newInstance...
(still some forbidden names among the possibly usefull ones for your static
methods, like 'getResourceAsStream' since it exists in java.lang.Class, but at
least it
is backward compatible)
CloD
The problem with my previous suggestion is that it is not 100% backwards
compatible. If someone has a template that calls methods of a java.lang.Class
object it will no longer work, unless a utility class is created to call
methods of java.lang.Class.
I haven't tested this, but would changing UberspectImpl.getMethod() to
something like this work:
public VelMethod getMethod(Object obj, String methodName,
Object[] args, Info i)
throws Exception
{
if (obj == null)
return null;
Class c = obj.getClass();
Method m = null;
if (c == java.lang.Class)
{
m = introspector.getMethod(obj, methodName, args);
if (!java.lang.reflect.Modifier.isStatic(m.getModifiers()))
}
else
return (m != null) ? new VelMethodImpl(m) : null;
}
Wow.
I assume this is part of the organized resistance to public CTORs in commons-land?
Why so complicated a solution? Couldn't something like :
context.put("math", Math.class):
and then if we find a Class in the context, we find static public methods and invoke them?
I wonder if we can do that.
Looks ok to me. Thanks Nathan. | https://issues.apache.org/jira/browse/VELOCITY-102 | CC-MAIN-2016-26 | refinedweb | 2,082 | 64.61 |
How to Write POGOs
In the Java programming language a Java bean is often referred to as a "Plain Old Java Object", or "POJO". The equivalent concept in Groovy is referred to as a "POGO", or "Plain Old Groovy Object". It is the equivalent of the Java bean. Therefore, the POGO permits you to store properties for a business entity such as an order, a customer, a vendor or a person. In this lesson we will focus on a common application of POGOs by creating a Person bean.
To learn how to use POGOs in Groovy follow these 5 steps:
- First, you will create the Person POGO. Open your text editor and type in the following lines of Groovy code:Very straightforward, just like a Java bean. If you're a Java developer, however, you may well be asking, "Where are the getters and setters?" The answer is Groovy provides those for you! Therefore, explicit
// Person POGO (Plain Old Groovy Object) class Person { String fullName String emailAddress public String toString() { "Name: $fullName Email: $emailAddress" } }
getXXXand
setXXX(where "XXX" is the property name) are not required in Groovy but may be provided in those cases where you want to tailor getter or setter implementation. Note that a
toStringmethod has been provided as a convenience for object state display.
- Save your file as
Person.groovy.
- Open a command prompt and navigate to the directory containing your new Groovy POGO. Then type in the command to compile your source:
- Now, let's create a tester in the same directory. Open your text editor and type in the following lines of Groovy code:Note that we are required to import the
import Person def person = new Person( fullName: "Stephen Withrow", emailAddress: "sfw@coolMail.com") println ("Person data: \n $person") println ("Our new person's name is $person.fullName") person.emailAddress="stephen@coolestMail.com" println ("Updated person data: \n $person")
Personclass. The program instantiates a Person object using the
newkeyword. The Person constructor is called and parameter data is provided using the parameter names defined in the POGO. This constructor is provided by Groovy and is not a part of the Person source that you created in the first step of this topic. The program displays the full object state (i.e., the values of full name and email address) and also the
fullNameproperty only. The final step is to change the email address and then display the object state again to verify the email address was successfully updated.
- In the command prompt, type in the command to interpret and run your script:
The program output verifies the correct object state before and after the email address update. | https://www.webucator.com/how-to/how-write-pogos.cfm | CC-MAIN-2020-16 | refinedweb | 443 | 61.87 |
0
I have set up a code in a class but i am not sure if this is the class that i would use.I have to put the logic of the game in a Class and then use the methods from the class to run the game.Right now i have some methods in a class but i am not sure on how i would go on getting it to work and calling the functions.I would like help on Possible telling me if i need another class and how to fix my methods in the class.Also if you would point me in the right direction on how i would use the methods and then call them in another file so i can make the BlackJack Program work. please and thanks for the help
from random import * class DeckOfCards: def __init__(self): #Make the Deck Of Cards self.__cards = [2,3,4,5,6,7,8,9,10,10,10,10,11] * 4 #keeps the score for the player and computer playerScore = 0 computerScore = 0 #holds the cards player = [] computer =[] #boolean to see who wins PlayerLoser = False ComputerLoser = False def drawCard(self): #draw a card for the player player.append(choice(self.__cards)) def drawCardComp(self): #draw a card for the computer computer.append(choice(self.__cards)) def totalOfPlayer(self): #the total the player has in his hands self.__totalOfP = total(player) return self.__totalOfP def totalOfComputer(self): #the total the computer has in his hands self.__totalOfC = total(computer) return self.__totalOfC def playGame(self):#i dunno if this is the method i am going to use here while True: #i want it to call the function in the class to draw a card drawCard() drawCard() if self.__totalOfP > 21: print 'You Lost' playerLoser = True elif self.totalOfP == 21: print 'hey congrats you got BlackJack :)' else: goAgain = raw_input("Hit or Stand (h or s): ").lower() if goAgain == 'h': #i want it to call the function in the class to get another class drawCard() while True: # loop for the computer's play #draw the computer cards drawCardComp() drawCardComp() while True: if totalOfC < 18: #draw the card if its less than 18 print "the computer has %s for a total of %d" % (computer, self.__totalOfComputer) # now figure out who won ... if self.__totalOfComputer > 21: print "The computer is busted!" ComputerLoser = True if PlayerLoser == False: print 'The Player Wins' playerScore += 1 elif totalOfC > totalOfP: print 'the Computer wins' computerScore += 1 elif totalOfC == totalOfP: print 'TIE' elif totalOfP > totalOfC: if PlayerLoser == False: print 'The Player Wins' playerScore += 1 elif ComputerLoser == False: print 'The Computer Wins' computerScore += 1 print print "Wins, player = %d computer = %d" % (playerScore, computerScore) exit = raw_input("Press Enter (q to quit): ").lower() print | https://www.daniweb.com/programming/software-development/threads/159799/blackjack-game-help | CC-MAIN-2017-39 | refinedweb | 454 | 58.11 |
startService ProblemsMike Karrys Apr 4, 2003 12:04 PM
I am having trouble getting my code to run in the startService and stopService routines. When my MBean starts it will not log or run routines in the startService but after the server starts I can run these routines successfully by getting the MBean from the MBean server and then running them but I can't seem to figure out why my startServcie won't run them or even why the log.info() doesn't write to the server log.
1. Re: startService ProblemsAdrian Brock Apr 4, 2003 1:31 PM (in response to Mike Karrys)
Do you extend ServiceMBeanSupport?
start() invokes startService()
Does your interface extend Service or expose
void start();
void stop();
start/stop are the real methods invoked by
the service controller.
Regards,
Adrian
2. Re: startService ProblemsMike Karrys Apr 4, 2003 2:43 PM (in response to Mike Karrys)
Yes. I do the following "public class MobileWebUpdateQuery extends org.jboss.system.ServiceMBeanSupport implements MobileWebUpdateQueryMBean
and my startService starts with " public void startService() throws Exception". My interface files starts with "public interface MobileWebUpdateQueryMBean extends org.jboss.system.ServiceMBean" and I do not define start() or stop(). I am running jboss 3.0.6 under Linux 2.4.18. I have tried changing startService() to start() without any change.
3. Re: startService ProblemsMike Karrys Apr 4, 2003 5:11 PM (in response to Mike Karrys)
Just for the record. The problem seemed to be that my jboss-service.xml had a depends on a Message bean. When I took out the depends the system runs the startService(). The message bean works fine in both configurations so I am not sure what is not starting.
4. Re: startService Problemscptnkirk Apr 15, 2003 3:07 AM (in response to Mike Karrys)
I too am having this problem.
I'm implementing Service and extending ServiceMBeanSupport.
The MBean get's configured and is visible via the JMX Web Agent.
The problem is that create(), start(), createService(), startService() methods are never called.
Could anyone start me in the right direction of tracking this problem down?
5. Re: startService Problemscptnkirk Apr 15, 2003 3:21 AM (in response to Mike Karrys)
BTW: I'm registering the MBean via the following in user-service.xml.
No, depends or anything, so I don't think I'm getting hung up there.
6. Re: startService ProblemsAdrian Brock Apr 15, 2003 11:10 AM (in response to Mike Karrys)
You have not exposed create/start
on TestMBean (the management interface)
Add extends ServiceMBean to it.
Regards,
Adrian
7. Re: startService Problemscptnkirk Apr 15, 2003 11:48 AM (in response to Mike Karrys)
That does indeed fix the problem. Thank you for the quick response. | https://developer.jboss.org/thread/50494 | CC-MAIN-2018-51 | refinedweb | 455 | 65.62 |
This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.
Matt Austern <austern@apple.com> writes: > FYI, here are the results of a fairly crude test that I did > using one of the Apple performance tools. > > This table shows where the L3 cache misses are coming from. > Our performance tool shows which instruction causes a cache > miss, and then I found which function each of those > instructions came from. > > Using cc1plus: 7257 samples > 10.5% 0x0003eb8c cp_tree_node_structure > 4.3% 0x00016fec walk_namespaces_r > 3.5% 0x00016e88 vtable_decl_p > 3.2% 0x90074224 memset Does Apple's memset use dcbz? I'm curious why memset should cause any cache misses at all. > 2.7% 0x0024a15c ht_lookup > 2.7% 0x0014403c list_length > 2.2% 0x0003fd34 gt_ggc_mx_lang_tree_node > 1.4% 0x0024a150 ht_lookup > 1.2% 0x0015e7e4 wrapup_global_declarations > 1.2% 0x0015e820 wrapup_global_declarations > ... > > Using cc1: 3814 samples > 8.9% 0x00017164 lookup_tag > 6.9% 0x00023310 gt_ggc_mx_lang_tree_node > 3.6% 0x000699d4 ht_lookup > 3.5% 0x90074224 memset > 2.5% 0x000699c8 ht_lookup > 2.3% 0x000239ec gt_ggc_mx_lang_tree_node > 1.7% 0x000af9a8 check_global_declarations > 1.7% 0x0008b500 list_length > 1.7% 0x000afe44 compile_file > 1.6% 0x00069bc0 ht_expand > > As these numbers suggest, using cc1plus takes much longer than > using cc1. > > The fact that list_length and ht_lookup and cp_tree_node_structure > are so high suggests that we've got poor locality in tree node > allocation. The fact that cp_tree_node_structure is so high > suggests that we're probably getting a lot of cache misses > during garbage collection. Yes, cp_tree_node_structure is the first time each tree is looked at in GC. It's not surprising that GC will have a lot of cache misses. GC looks at every tree (and every pointer) exactly once, so for GC locality is irrelevant; there is no re-use. -- - Geoffrey Keating <geoffk@geoffk.org> <geoffk@redhat.com> | https://gcc.gnu.org/legacy-ml/gcc/2002-08/msg01204.html | CC-MAIN-2021-39 | refinedweb | 292 | 72.53 |
Collaborator's New API Feature - Part 1
Collaborator's New API Feature - Part 1
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How to Transform Your Business in the Digital Age: Learn how organizations are re-architecting their integration strategy with data-driven app integration for true digital transformation. of guys around the office had mentioned possibly creating an Add-In for Microsoft Word. I overheard, and soon after I was off to the races. I knew enough about Microsoft Word’s architecture to be dangerous, as I had written several Office plugins in a former life. This was going to be easy! Or was it?
Before creating a Word plugin, I needed to know what was involved; more specifically I needed to know how to send requests to Collaborator’s new API. Beyond just sending a request, I needed to understand the authentication mechanism and I needed to know how to send the appropriate commands to create a review with a document attached. That also required that I get the document from my local copy of Word to Collaborator, which meant uploading it.
But how would I send a file to this new web service?
Here’s the story of my journey, and the creation of a simple Office plugin, revolving around the Collaborator JSON/RPC API.
The story begins with JSON. What is it? It’s an acronym for JavaScript Object Notation. How is it implemented? Well, that’s not so straight forward.
After reading the API documentation, I learned that Collaborator accepts HTTP POST requests at /services/json/v1. The request needs to be a list of commands paired with the arguments for each.
[ {"command" : "ServerInfoService.getVersion" }, {"command" : "Examples.echo", "args" : {"echo" : "Some text."} }, ]
The server will then return a list of response objects which correlate to the requests. Each response object is either an error message, or the result data from the request command.
[ { "result" : { "version" : "9.1.9100" } }, { "result" : { "echo" : "Some text." } }, ]
In theory, it sounds simple enough, but implementing it required a bit of thought. What’s the easiest way to generate the JSON request string? What is the easiest way to process the JSON response from the server?
I could just build the strings by hand, substituting in appropriate values for the variables, but that wasn’t robust enough. It wasn’t simple enough to maintain, and it was going to be error prone. I needed something better.
The answer was quite simple: JSON serialization. Almost all modern languages provide this mechanism in one way or another, either natively, or with the help of open source or commercially available libraries. JavaScript supports it natively, but you can’t write a Word plugin in JavaScript, it needs to be C#. Microsoft provides the System.Runtime.Serialization.Json namespace as a part of the .NET framework which can do just that. However, it’s a bit complicated to use, so I chose to use the Json.NET third party library from Newtonsoft.
With Json.NET, I could take a vanilla C# class, instantiate it, and then turn it into a JSON string with ease.
public class JsonRequest { string command; List args; }
JsonRequest myRequest = new JsonRequest(); myRequest.command = "ServerInfoService.getVersion"; string json = JsonConvert.SerializeObject(myRequest);
The resulting JSON string was exactly what I needed:
{ "command" : "ServerInfoService.getVersion" }
Inverting this process was equally simple, if I had this string variable full of JSON:
string json = "{'command' : 'ServerInfoService.getVersion'}";
Then, I could turn it into a JSONRequest object like this:
JsonRequest myRequest = JsonConvert.DeserializeObject<JsonRequest>;
Simple! I would then find that the MyRequest object had its command value set to “ServerInfoService.getVersion.”
This would become one of the foundational building blocks of the plug in. The ability to predefine my data contract in the form of .NET classes provided the flexibility, and the simplicity that I needed. It’s a simple and elegant solution that is easy to extend.
In the next installment we’ll be diving deeper into how you put the serialized JsonRequests into action. You can see this in action on GitHub. }} | https://dzone.com/articles/collaborators-new-api-feature | CC-MAIN-2019-09 | refinedweb | 682 | 58.89 |
A module for collecting internal application/library performance statistics
Stats is a utility module which provides an API to collect internal application statistics for your programs and libraries. It is very thin and lite when running so as to not alter the performance of the program it is attempting to observe. Most importantly it provides Histograms of the stats it is observing to help you understand the behavior of your program.
Specifically, for example, you can set up a stat for measure the time elapsed between sending a request and receiving a response. That stat can be fed into a Histogram to aid your understanding of the distribution of that request/response stat.
Here is a sketched out example code of using stats, histograms, and namespaces.
var Stats = require('stats') , stats = Stats() //a singleton NameSpace for all your stats, histograms, // and namespaces //returns a singleton via `new Stats()` as well , myns = stats.createNameSpace('my app') myns.createStat('rsp time', Stats.TimerMS) myns.createStat('rsp size', Stats.Value, {units:'bytes'}) myns.createHistogram('rsp time linLogMS', 'rsp time', Stats.linLogMS) myns.createHistogram('rsp size logBytes', 'rsp size', Stats.logBytes) ... done = myns.get('rsp time').start() conn.sendRequest(req, function(err, rsp) { ... done() myns.get('rsp size').set(rsp.size) }) ... console.log(myns.toString()) console.log(stats.get('my app').toString()) //works the same console.log(stats.toString()) //works as well with additional indentation
The output might look like this:
STAT rsp time 705 ms STAT rsp size 781 HOG rsp time linLogMS %14 %14 %14 %28 %28 4 10 ms 4 10^2 ms 5 10^2 ms 6 10^2 ms 7 10^2 ms HOG rsp size logBytes %57 %42 512-1024 bytes 1-2 KB
Sure it could be prettier, but you get the gist of the data.
For Histograms there is also an output mode that tries to semi-graphically display the output in bars of '#' characters. File sizes of my home directory looks like this:
console.log(myns.toString({hash:true})) STAT file_sz 88 HOG file_sz SemiLogBytes 0-64 bytes %35 : ################################### 64-192 bytes %10 : ########## 192-448 bytes %16 : ################ 448-1024 bytes %10 : ########## 0-64 KB %24 : ######################## 448-1024 KB %2 : ##
There are three big kinds of things: Stats, Histograms, and NameSpaces. Stats represent things with a single value (sorta). Histograms are, well, histograms of Stat values, and NameSpaces are collections of named Stats, Histograms, and other NameSpaces. Stats, Histograms, and NameSpaces are all EventEmitters, but this mostly matters just for Stats.
The core mechanism for how this API works is that Stats emit 'value' events when their value changes. Histograms and other Stat types consume these change events to update their own values. For instance, lets say your base Stat is a request size. We create a Stat for request size either directly or within the context of a NameSpace:
var req_size = new Value({units: 'bytes'}) myns.set('req_size', req_size)
or
myns.createStat('req_size', Stats.Value, {units:'bytes'})
When a new request comes in we just set the value for 'req_size' like so:
req_size.value = req.size //setting .value causes an event
or
myns.get('req_size').value = req.size //setting .value causes an event
[Note: From this point on I am just going to use the NameSpace version of this API because that is how you should be using this API.]
I could consume this Stat for another stat like a RunningAverage, AND for a Histogram.
myns.createStat('req_size_ravg', Stats.RunningAverage, {nelts:10}) myns.createHistogram('req_size', 'req_size', Stats.LogBytes)
Both the RunningAverage and Histogram will be automagically be updated when
we set the value of the 'req_size' Stat. Also, not that the Histogram can
have the same name as the Stat ('req_size'). This is because all names
exists in a unified namespace regardless of kind (
Stat,
Histogram,
or
NameSpace).
For Histograms there is an additional object called the Bucketer (I
considered calling them Bucketizers but that was longer:P). The Bucketer,
takes the value and generates a name for the Histogram bucket to increment.
The Bucketer is really just a pair of functions: the
bucket() function which
takes a value and returns a bucket name; and a
order() function which takes
a bucket name and returns a arbitrary number used to determine the order each
bucket is display in. The Bucketer maintains no state so there are a number
of already instantiated
Bucketer() classes which are just a stateless pair of
bucket()/
order() functions.
Stat
Has no internal state.
Inherits from
EventEmitter.
publish(err, value)
if errelse
reset()
Emit a
reset event.
Value([opt])
opt is a optional object with only one property 'units' which is used
in
toString()
Inherits from Stat.
_value
Internal, aka private, storage variable for the value of a stat.
value
Assigning to
value causes a publish. (ssh! its magic)
units
String describing what is stored.
set(value)
Stores and publishes
value
get()
Returns what is stored in
value property.
reset()
Set
_value to
undefined and emit a
reset event.
toString([opt])
opt.sigDigitsnumber of significant digits of value displayed. Default: 6
opt.commifyboolean that specifies wheter to put commas in the integer part of the displayed value. (Sorry for all those in different locales) Default: false
TimerMS()
Measures to time between when the
start() method is called and when the
function
start() returned is executed. This time delta is measured in
milliseconds via
Date.now().
Inherits from
Value.
start()Returns a function closed over when
start()was called. When that function is called (no args), it stores & publishes the current time versus the time when
start()was called. Its return the difference in milliseconds. If it is called with an arg, that arg is published as the error and the time delta as the second argument.
TimerNS()
Measures to time between when the
start() method is called and when the
function
start() returned is executed. This time delta is measured in
nanoseconds via
process.hrtime().
Inherits from
Value.
start()Returns a function closed over when
start()was called. When that function is called (no args), it stores & publishes the current time versus the time when
start()was called. Its return the difference in nanoseconds. If it is called with an arg, that arg is published as the error and the time delta as the second argument.
Count(opt)
opt is a object with only one required property 'units' which is used in
toString(). The second property
stat provides a Stat object.
When the Stat object emits a value
inc(1) is called.
Inherits from Value which inherits from Stat. So there is
publish(),
set(),
get(),
toString()
units(required)
stat(optional) If provided the Count object will call
inc()on every 'value' event.
inc([i])
Increments the internal value by
i and publishes
i. If no argument is
provided
i = 1.
reset()
Sets the count to 0. Emits a
reset event. Returns the old count value.
reset() set internal value to 0, and emit a 'reset' event. Return the old
value.
Rate(opt)
opt is a required object with the following properties:
stat(required) Stat object. When the Stat object emits a
'value'Rate will accumulate the
valueto its' internal
accproperty.
period(default: 1) number of
intervalmilliseconds between publishes of the calculated rate. Additionally, we calculate rate by dividing the internal
accproperty by
period(eg.
value = acc / period).
interval(default: 'sec') a string ('ms','sec','min','hour', or 'day') sets number of milliseconds per
period. Additionally it sets the
unitsproperty to be
stat.units+"/"+interval.
add(value) Add
value to the internal value of Rate
reset() set internal accumulator value to 0, and emit a 'reset' event.
Return with the old value.
MovingAverage(opt)
opt is a required object with one required property
stat and two optional
units and
nelts.
opt.stat must be a object of type Stat.
'opt.units' is optional. If it is provided it will be used instead of
opt.stat.units . Mostly,
opt.units is not needed.
nelts ioptional and defaults to 10. It is the number of values stored to
calculate the moving average. see Wikipedia's Simple moving average definition
add(v) adds a value
v to the MovingAverage's fixed internal array of
the last
nelts values.
toString() returns
format("%s %s", mavg, units) where
mavg is the
last calculated moving average or the average of the values accumulated so
far if the number of values is less than
nelts.
reset() sets the internal
_value to 0. Deletes the internal list of the
nelts values. Emit a 'reset' event. Returns the old
_value.
RunningAverage(opt)
opt is a required object with one require property 'stat' and two optional
properties:
units and
nelts.
opt.stat must be a object of type Stat.
'opt.units' is optional. If it is provided it will be used instead of
opt.stat.units . Mostly,
opt.units is not needed.
opt.nelts is optional and defaults to 10. It is the number used to calculate
the running average. see Wikipedia's Running moving average definition
add(v)uses the value
vto calculate the RunningAverage
Bucketer(bucketFn, orderFn)
The Bucketer base class.
The
bucketFn takes a value and returns a "bucket" string.
The
orderFn takes a "bucket" string and returns an number that is only used
for greater-than/less-than ordering comparisons for display purposes. For
exampele bucket strings: "1 foo" "2 foos" "3 foos" "many foo", "1 bar",
"2 bars", "3 bars", "many bar", etc could map to 1.0, 1.0001, 1.002, 1.03,
1.4, 2.0001, 2.002, 2.03, and 2.4. And that would work perfectly well.
LinearBucketer(base, units)
This is close to useless, but I included it for completeness.
base is used
as a divisor for the values passed to the
linear.bucket(v) function. Often
one would use 10 as the base resulting in a bucket for every 10, 20, 30,
etcetra values.
These objects are really just pairs of functions as the bucketizing functions are algorithmic and the units are built in.
linearMS
LinearBucketer order=10 units="ms"
linearNS
LinearBucketer order=10 units="ns"
linearByes
LinearBucketer order=10 units="bytes"
logMS
The buckets are "ms", "10 ms", "100 ms", "sec", "10 sec", "100 sec",
"10^3 sec", "10^4 sec", "10^5 sec", "10^6 sec", "lot-o-sec".
These buckets should read "single digit milliseconds", "tens of milliseconds", "hundreds of millisecons", "single digit seconds", "tens of seconds", "hundreds of seconds", "thousands of seconds", "millions of seconds" and "a whole shit-load of seconds".
semiLogMS
buckets map to "1-2 "+logMS(v), "2-4 "+logMS(v), "5-10"+logMS(v) where
"x-y" means a range inclusive of x and exclusive of y aka
[x,y).
These bucket names should be read at "one or two ms", "two thru 4 ms",
"five thru ten ms".
"1-2" is 2 wide, "2-4" is 3 wide, 5-10 is 5 wide; with a progression of 2, 3, 5. That is what "semiLog" means. It sorta makes sence if you look at it from the right direction and cock you head to the side.
linLogMS
The buckets map to n+" "+logMS(v) where n is an integer.
They are read as "one ms", "two ms", "three ms", etcetra.
logNS
Same as logMS but with 'ns' (nanosecond) and 'us" (microsecond) on the
low-end.
semiLogNS
ditto with
logNS
linLogNS
ditto with
logNS
bytes
The buckets are "bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB", and
"lots-o-bytes".
These are classic orders of 10s of bytes ie 2^10, 2^20, 2^30, etc. KiB, MiB, GiB are crap created to appease marketroids and their lickspittle lackeys. Grrr... don't get me going ;)
They are kilobytes, megabytes, gigabytes, terabytes, petabytes, exabytes, zettabytes, yottabytes, and shit-load-of-bytes.
semiBytes
The buckets are "1-64 "+bytes(v), "64-192 "+bytes(v), "192-448 "+bytes(v),
and "448-1024 "+bytes(v)
The width of each bucket is progressively bigger "1-64" is 64 wid", "64-192" is 128 wide, "192-448" is 256 wide, and "448-1024" is 576 wide. So the progression is 64, 128, 256, 576 to cover a 1024 range. That fuzzy-ness is what "semi" means.
logBytes
The buckets are "0-2 "+bytes(v), "2-4 "+bytes(v), "4-8 "+bytes(v),
"8-16 "+bytes(v), "16-32 "+bytes(v), 32-64 "+bytes(v), "64-128 "+bytes(v),
"12-256 "+bytes(v), "256-512 "+bytes(v), and "512-1024 "+bytes(v).
So first we cut the ranges down by the 2^(n*10), then by plain log2() for the 0-1024 remainder.
best choice for mentally visualizing your data.
Every toString() of every Stat type, Histogram, and NameSpace takes an optional "Options" object. These settings intentionally have different names, and a given name means the same thing anywhere it is used. | https://www.npmjs.com/package/stats-api | CC-MAIN-2016-36 | refinedweb | 2,132 | 65.93 |
How to Tell a SWF What File(s) to Load — From the Outside
A number of people have asked how I handled the microphone icons in my last post, Papi’s Wah-feh (An Audio Guide). Did I simply use Save As a bunch of times to create eight separate SWFs, each with its own imported audio? I certainly could have done that, but I decided instead to create one single SWF that could be told from the outside which MP3 to play. Not only does this mean I can re-use that SWF as often as I like — without recompiling, by the way! — but it also reduces download time, because the SWF is only retrieved once (only 407 bytes, at that!), and the MP3s only load as needed.
The following technique can be used for graphics, too — really, for any file a SWF can load at runtime, from CSS to video (FLV), to other SWFs. Let’s take a look.
An answer, moderately long and sweet (and how it works)
It’s a good idea in general to load external files for audio, unless you need tight synchronization, such as for cartoon lipsynching. Why? Well, again, a SWF by itself has a much smaller footprint without the extra weight of imported sound files. Besides, if the user happens not to venture down a particular path in your movie, why force the download for that section? Let the user download files as they’re needed.
Under normal circumstances, I might have programmed the microphone graphic (a button symbol) with my ActionScript in a keyframe like this:
var s:Sound = new Sound(); iconButton.onRelease = function():Void { s.loadAudio("path/to/audio/sound.mp3", true); }
Note: For a look at this code in the AS3, see “How to Retrieve FlashVars Data in ActionScript 3.0.”
In the first line, an arbitrarily named variable,
s, is declared and set to an instance of the
Sound class. In line 2, a function literal is assigned to the
Button.onRelease event of a button symbol whose instance name is
iconButton. This function literal calls the
Sound.loadSound() method on the
s instance and supplies the path to an external MP3 file. The second parameter,
true, tells Flash to start playing the audio as soon as enough data are available — even if the file isn’t yet completely downloaded.
But clearly, this approach is hard coded. In order to open up the possibilities, replace the path reference with a variable — let’s just call it
audio.
var s:Sound = new Sound(); iconButton.onRelease = function():Void { s.loadAudio(audio, true); }
Note, the quotation marks are gone, because the
audio variable now contains that string. But wait, where is this variable declared? Currently, it’s
undefined, right? Right. We’re going to pass in the desired string from outside the SWF.
There are a number of ways to do this, but in this article, we’ll look at the FlashVars approach. SWF files are embedded into HTML via the
<object> and
<embed> elements. The
<object> element contains several child
<param> elements, and these contain attributes that set various properties of the SWF, such as where the SWF file is located, its width and height, quality settings, and so forth. Internet Explorer reads the
<object> element and other browsers read
<embed>, so if you look carefully at a working sample, you’ll notice that
<object>’s
<param> attributes are basically mirrored in the
<embed> attributes. With FlashVars, you simply need one additional
<param> element and one additional
<embed> attribute to match, both of which can be tossed into the mix wherever you please.
Here’s the skeleton of a typical
<object>/
<embed> pair.
<object [several attributes, including width and height] > <param name="movie" value="movie.swf" /> <embed [attributes, including width, height, and src]></embed> </object>
FlashVars effectively allow you to declare a SWF’s variables from the HTML. Note: these will be strings only, so if you want to pass in a number, you’ll have to cast it as such inside the SWF (
parseInt() or
parseFloat(), for example). These variables will be scoped to the main timeline, so using FlashVars is the equivalent of typing …
var audio:String = "path/to/file/audo.mp3";
… in frame 1 of the main timeline. Here it is.
<object [attributes] > <param name="movie" value="movie.swf" /> <param name="FlashVars" value="audio=path/to/file/audio.mp3" /> <embed [attributes]</embed> </object>
Again, note that both the
<param> and
<embed> elements need the same information. The above creates a string variable
audio in the main timeline — which is the variable reference in the
Button.onRelease handler above! So there it is.
If you want to pass in a number of variables, separate each name/value pair with an ampersand (&).
audio1=aaa.mp3&audio2=bbb.mp3&audio3=ccc.mp3
What about SWFObject?
If you’re using Geoff Stearns’ SWFObject to get around the IE “click to activate” issue, simply use his object’s
addParam() method to add your FlashVars virtually.
<script type="text/javascript"> var so = new SWFObject( "movie.swf", "mymovie", "200", "100%", "7", "#336699" ); so.addParam("FlashVars", "audio=music.mp3"); so.write("flashcontent"); </script>
Update! Here‘s a sample file (thanks for the suggestion, Amy!) to illustrate what‘s shown above. The sample shows an MP3 file specified from the HTML, using traditional embed and SWFObject. The SWFObject example uses
addVariable() instead of
addParam(), as shown above.
August 22nd, 2006 at 4:09 pm
Also, SWFObject has a custom method called addVariable() for adding FlashVars, so you could also easily add several variables like this:
so.addVariable(”audio1″, “music1.mp3″);
so.addVariable(”audio2″, “music2.mp3″);
so.addVariable(”audio3″, “music3.mp3″);
August 22nd, 2006 at 4:13 pm
Good point, ImagicDigital! I’m so used to FlashVars that I tend to overlook that feature of SWFObject. Thanks for bringing it up.
I think that approach may “gel” better for some people.
August 25th, 2006 at 6:52 am
Hi David,
Great site.
Total newbie to Flash 8, but learning quickly.
Let’s say we have an html file where player.swf file is embedded (linked to 1 flv in the same folder via contentpath in flvplayback component). I have several flv’s in the same folder that i want to see using the same swf player. How can I code for changing the `contentpath’ in the swf without republishing? Can I change the contentpath of the swf by editing the html alone?
If this does not make sense, dont shoot the messenger lol.
Thx.
August 25th, 2006 at 7:10 am
Bert,
Your question makes sense. No need to shoot anyone.
The answer to your question is spelled out in the article above. Just think to yourself: how would I set the
contentPathproperty by hand? — I assume you’re using the FLVPlayback Component? — and when you get that squared away, just replace the hard-coded file path with a variable, and feed in the variable as described.
For example, give your FLVPlayback Component instance, on the Stage, the instance name
video(or whatever you like). Don’t use the contentPath parameter in the Component Inspector, but rather, in a keyframe type
video.contentPath = "sample.flv";. It’s really that simple. Once you test that proof of concept, change the string “sample.flv” to a variable and set that variable from your HTML.
August 25th, 2006 at 7:56 am
Wonderful,
This is the missing step. When I said I was a newbie, I lied. I only started Flash and HTML yesterday
Many thanks, this will get me started on my project.
kl.
September 25th, 2006 at 2:59 pm
Hi David - My question pertains to the above q. regarding ‘How to Tell a SWF What File(s) to Load — From the Outside’. My issue is similar…but different. I’ve got ‘main.swf’ that loads various .swfs from within the same directory. One of those .swfs is a video page that has a FLVplayback component that is ‘bound’ to a comboBox that calls 19 different 2 minute videos. I followed a well written tutorial I found and when I test the video .swf by itself, it works beautifully. However, when testing from the ‘main.swf’, the video.swf shows up, as well as the first video in the comboBox, but does not allow access to any of the other videos. No menu drop down is available now. WHERE DID I GO WRONG??!! I’ve tried everything I can think of — so any help/insight is greatly appreciated. Thanks so much!
Senan
September 26th, 2006 at 7:03 am
senan,
Similar but different, eh?
I’m glad to help when I can, but in this case, the possibilities are pretty wide open. You’ve described quite a bit without going into any details. To find the exact place you went wrong (or possibly the many places), you’ll have to narrow things down. This calls for classic troubleshooting. It sounds like you should start with the video SWF, since the others seem to be working. Embed the video SWF in an HTML page and check if it works while running in the browser on its own. Start a new FLA and use that to load the video SWF in its own, and so on. As it is, you’re stuck with too many places to look. Clear the fog.
September 26th, 2006 at 7:53 am
david - I much appreciate the feedback and will begin packing for my troubleshooting journey. Wish me luck - bonvoyage - will keep you posted. Thanks again!
auf Wiedersehen! : )
September 26th, 2006 at 9:15 am
Hmmm - Getting the same results. From the standalone video test page, I’ve uploaded the 1st 3 videos and they work nicely - however, calling it from the new .fla/swf embedded in an html page, no dice - nor from the ‘main.swf’ — Here are a few links to show you what’s going on. Again, I appreciate any help on this - overall, it’s for a good cause —
– Player on its own:
– New .fla created to call vid page:
Here’s the code I’m using to call the video page from the video button inside the ‘main.swf’:
on (release) {
empty.loadMovie(”nsp_videopage.swf”, 1);
}
Is it something to do with the contentPath and needing to AS it vs. use the component inspector? Thanks David!!
September 28th, 2006 at 10:24 am
senan,
I can only guess that you’re using paths that don’t translate well when the working SWF is loaded into another. Maybe you’re referencing
_rootin your paths? That’s a gotcha (explained here). Given the complexity of your technique, here — ComboBox databinding, loading into another SWF — the error (or errors) could be in a number of places. Have you experimented with the Debugger panel or other Output panel debugging approaches? You need to “see what’s under the hood,” so to speak.
October 30th, 2006 at 11:06 pm
How about passing the volume level to a swf to control the volume of an flv using SWFObject? Possible? SOmething special needed in the swf file to account for it or can it be controled through a flash var that is inhereant with flashscript???
October 31st, 2006 at 8:29 am
Robert,
Volume shouldn’t be a problem — in fact, I can’t think of an example that couldn’t somehow be handled through FlashVars, even by way of SWFObject. In addition to any other name/value pairs you might have, just include a variable for volume. If you like, call it something like
extVolume(for “external volume”), and whenever you would have hard coded a number to set the FLVPlayback component’s volume (or whatever other approach you’re using), use the variable instead.
November 16th, 2006 at 11:12 am
Hello,
I am an absolute noob when it comes to flash and I am totally lost. I am trying to have my swf load a FLV, but I want only to have 1 swf file. Basically I want to have one swf load a FLV file based upon the URL (ex: player.php?video=somevideo) and have it play that file and when i change it to player.php?video=anothervideo have it play that. So far everything I’ve tried has failed and I’m at an absolute loss. Please help
November 16th, 2006 at 11:18 am
Seth,
Your question is actually answered on the trail between the original post and some of the other comments. The post covers a general approach to getting outside variables — such as from a URL — into the SWF. Once in the SWF, you can use the variable to load whatever you like. Where are you getting stuck?
November 16th, 2006 at 1:40 pm
Im getting stuck on the whole process of actionscript and associating it with php to load the video.
November 16th, 2006 at 2:00 pm
Seth,
There are a number of ways you could go. You could use PHP to write out the
FlashVarsattribute of the
<object>…
<param>/
<embed>HTML tags — that seems like a straightforward way to go.
Check out this info-packed tutorial: Passing Variables from HTML to Flash via FlashVars. It shows you how to grab data from a query string and get it into Flash (example #3).
November 16th, 2006 at 3:19 pm
Not working for me…
This is what I have:
PHP:
.flv”>
”
bgcolor=#99CC33 WIDTH=488 HEIGHT=390
TYPE=”application/x-shockwave-flash”>
ActionScript:
onClipEvent (load) {
loadMovie(_video.file, “”);
}
Im still at a loss, if it helps in using Proxus FLV Player 2.0.1 sorry, i don’t know any action script what so ever…
November 16th, 2006 at 3:20 pm
It didnt show up…. goto:
November 16th, 2006 at 3:34 pm
Seth,
Bro, I’m at something of a loss here, too.
If you don’t know any ActionScript whatsoever, I can only recommend that you start from scratch and learn the basics. I wouldn’t try to build a cabinet for my dining room until I knew a bit about carpentry. You know?
November 16th, 2006 at 3:39 pm
Well, I do know php fairly well. Its just that I want to change my contentPath (in my component its called: _video i think) and ive tried going about his in every way shape and form and no luck towards it. Is there any referece you can give me? Or in actuality can i give you the files to look at? I’ve yet to find somebody that could help…
November 16th, 2006 at 4:02 pm
Seth,
Here’s something that works for me: when I’m faced with a goal that just stands in my way — something that seems insurmountable to me — I try to break it down into smaller pieces. In a case like this, I would probably save my work and start a brand new FLA, without the “clutter” or “distraction” of the Video object, that Proxus player, or anything else. I would focus on simply getting a variable into my SWF from the outside. Start without any external programming at all: start by adding a dynamic text field to your FLA, giving it an instance name, and setting its
TextField.textproperty to a string.
With me so far, right? It doesn’t get any more basic than that. Now, change that literal string to a variable:
Each one of these small steps is an encouragement. Next, move that variable from inside the SWF to a FlashVars attribute in the HTML:
Still with me? At this point, keep going. Instead of hard coding the FlashVars part, use PHP to write the value after the equals sign. After that, set some other property of the text field (see the
TextFieldclass in the ActionScript 2.0 Language Reference for available properties). Just keep in mind that any data you pass in are strings, so you might need to convert or cast to other datatypes. Eventually, all these baby steps lead you toward setting the necessary property of the Proxus player (which I haven’t heard of).
I did give you a reference.
I pointed you to an external tutorial that shows you several ways to get variables into a SWF (even with PHP). I’m here to help, but I strongly believe in helping people help themselves.
November 23rd, 2006 at 6:16 am
Hello,
I have been looking thru these threads - every little bit of information is helpful - however I am unable to find anywhere if you can after loading in Flashvars can you reference them via an array type senario like you can args in a js function … arguments[0] … hopefully something like FlashVars[0] … does anyone know of the syntax I could use to achieve this. I am stuck with a dynamic string where I do not know how many paired params will be supplied.
Thank you in advance
Markus
November 27th, 2006 at 3:05 am
Markus,
Use a
for..inloop to run through the main timeline — that’s your best bet. All FlashVars variables are strings, and they all appear in the main timeline.
The array access operator,
[], allows you to reference these objects by strings. Use in cahoots with the
typeofoperator to make sure the dynamically reference objects are strings, and not other variables (of other datatypes, perhaps) that you declared internally.
December 31st, 2006 at 2:35 am
Okay.. So.. I too have looked through all the code and I think I am okay up to a point. Nothing really addressed the issue the way I am using it. I can see how to reuse the parameters to utilize the same swf to call different videos/files, but there wasn’t anything in here about how to tell the swf what flv to load from a hyperlink.
Take a look at my page.
Inside the swf, I followed your methods and have (on its own layer)
1 videoPlayer.contentPath = video;
when I change this to mass05.flv it does play the video so I know that I was on the right track
so video is my variable…right?
so now I want to have the user click on any of the links and have the swf be told what flv to load.
So call me clueless, but I am just not seeing how to do this in any of the posts above.
Thanks for your help. You really seem to be giving people a real hand.
December 31st, 2006 at 12:30 pm
Dax,
By the looks of it, that’s right. Your variable seems to be
In the context of this article, it would occur by way of a FlashVars name/value pair. In your HTML, you would set the name
video. If that’s the case, you need to provide that variable a value, otherwise it’s just a variable that doesn’t mean anything. The way in which set the value of a variable is up to you, of course.
videoto the value
mass05.flv. Have you done that yet? I ask, because it looks like your hyperlinks are linking to SWFs rather than HTML documents that embed SWFs. Without the parent HTML document, you’d have to feed your variable in with a query string.
January 28th, 2007 at 6:11 pm
Thankyou so much! I’ve been googling how to do this for a while now, but I only get answers to getting the variables from .html links. This code works perfectly
January 28th, 2007 at 6:34 pm
Sorry for the double-reply, but I have a problem. I have a hyperlink in Flash, using the getURL method, and I link directly to a .swf file. Is it possible to add variables onto that link? I’ve tried it normally, but it didn’t work. Any suggestions?
January 29th, 2007 at 10:27 pm
Ben,
You can indeed pass variables into a directly linked SWF. Rather than FlashVars, which would of course require HTML, just append a query string after your SWF reference.
<a href="myMovie.swf?myVar=string%20here">Flash!</a>
February 27th, 2007 at 1:25 pm
I have a main swf.I want to see my other swf file by clicking the button but not in my main swf.thanks for your help.
February 27th, 2007 at 2:50 pm
osman,
You have a main SWF. You want to see another SWF by clicking on “the button” — where is this button?
March 19th, 2007 at 7:33 am
[…] There’s theres the basis of the information needed about passing the value of an flv file into the player (so you have your flash video player, and just tell it which video to play) at quip.net. […]
April 4th, 2007 at 4:41 am
Hi David,
I will first say thank you for your help so far. I managed to get a file loading using FlashVars embedded in my webpage with your help.
However, it seems that it only works when the flash file, HTML file & flash video are all in the same directory. As soon as I try and populate a web address into the embed code (either referencing the SWF or FLV in a folder) the video stops working.
Is there any chance you could point me in the right direction as I am completely lost with this flash stuff.
Thanks in advance.
G
April 4th, 2007 at 7:12 am
G,
There’s a bit of a trick to file paths when it comes to SWFs and relative file paths. You can either use absolute paths (fully qualified domain name preceding each file) or relative, but if you use relative paths, be aware that the SWF’s “point of view” isn’t its own location, but that of the HTML file that holds it. With the exception of FLV files — for those, the point of view is relative to the SWF.
So, if you’re loading the FLVPlayback Component, for example, and you want to specify a skin, use a file path relative to the HTML document (because skins are SWFs), but when you’re specifying the FLV, use a file path relative to to the SWF that contains the FLVPlayback instance.
April 5th, 2007 at 5:48 pm
Hi David-
Is there a sample flash file we can view? I’ve used Flash before but it was mainly for basic animations and VERY basic actionscripting like button states and what not.
My only problem with this whole thing is, I’m not sure where all the codes is suppose to go in the flash file and what codes needs to be in there. I’ve been searching the net but nothing close to helping me except your article here! =)
Thanks,
Amy
April 6th, 2007 at 1:59 pm
Amy,
Once you see it all in place, I think it’ll gel for you right away. See the very bottom of the original article for a sample file.
April 6th, 2007 at 3:08 pm
Greetings,
First off I just wanted to say thanks for all the useful information you’ve posted through out your sites, I’ve learned a lot. So I’ve built a video player ala, gotoandlearn.com, and I want to control what FLV’s are playing by using HTML links, much like previous posts here, but I’m not using any components.
So I have player.swf playing an external FLV using NetStream and the player is in an HTML page. An inital video is set to play
ns.play(”video1.flv”);
I want to have three text links on the page that tell player.swf to play three different movies. I tried a few different methods but I can’t seem to get it all to work. The latest experiment involved the PassFlash function in JavaScript were I would send a variable from HTML to a dynamic text box in player.swf. I added a textfield listener and setup a onChanged function to just play ns.play(”video2.flv”);
So when I test the page and click on the link it sends the variable, “2″ to player.swf and it appears in the text box but the video2.flv does not start. Now if I change the text box to an Input Text type box and test the page I can type a “2″ in the box and the second video will play. I don’t know if PassFlash will really work for what I’m trying to do or if I need to use FlashVars or something else but any guidance would be appreciated.
Thanks,
Matt
April 10th, 2007 at 10:53 am
Hi -
Is there a way to use a hyperlink containing only an URL to open an FLV player in a popup window? Thanks.
April 10th, 2007 at 11:12 am
To Matt …
I’ve never heard of PassFlash, so I’m guessing that’s somebody’s API for handling data transfer between a SWF and outside JavaScript. If that’s what you’re after — “live” updates via hyperlinks — you may want to check out the
ExternalInterfaceclass. That lets you trigger completely custom ActionScript functions from JavaScript any time you like. I’ve added that to my to-do list for this blog.
Your
TextField.onChangedapproach isn’t a bad idea, but check out the ActionScript 2.0 Language Reference for the entry on that event:
To Steven …
If your hyperlink contains a query string with name/value pairs and directly opens a SWF file, those variables will be place in the SWF’s main timeline. If the same hyperlink opens a new HTML window, you’ll have to acquire those variables from the loaded page. The JavaScript
searchproperty, described here at DevGuru, will do that for you. I’ll add your question to my to-do list as well.
April 13th, 2007 at 4:00 pm
David,
As you can see, I’m making the most of your blog. OK.Two more questions:
1. can you use FlashVars to pass a boolean value? If so, what is the syntax of that?
2. What I can’t figure out anywhere (and I’m sure I just haven’t looked hard enough) is what the url that contains multiple variables looks like? In my case, it would include the variables: VIDCHOICE, VIDMENU & JUMPFRAME(boolean).
Thanks!
April 13th, 2007 at 6:50 pm
Kevin,
I love to hear that, man.
It feels good to know that my rambling can be helpful.
Yes. Well, yes and no. In your name/value pair, just use the word “true” or “false” for the value …
e.g.
FlashVars="booleanA=true&booleanB=false"
… but, keep in mind, all FlashVars are actually strings, so you’ll need to treat your “Boolean” data carefully once inside Flash. In your code that checks the value of these strings, use the
Boolean()function to convert the strings to actual
true/
falsevalues. (See A Tip on the Boolean() Function (Casting as Boolean) for some pointers.)
April 18th, 2007 at 7:11 pm
David.
I can’t possibly have done this right, but what the heck. Maybe I have? And, if by some miracle I have done it right, do I need to use placeholder variables to receive the variables (frameLink & vidLink) or can I just put it right into the variables I already use (vidFrame & vidChoice). I assumed I would need to use temps because I am otherwise initializing the variables in the first frame. Does this make any sense?!
//This links to the submenu
var frameLink:String = “”;
// This is the video they were sent
var vidLink:String =”";
//This tells me that they’ve hyperlinked in
var sentLink:String = “False”;
var placeHolder:LoadVars = new LoadVars();
placeHolder.onLoad = function (success:Boolean):Void {
if (success) {
//menuChoice, vidName & referred would be in the html
frameLink = menuChoice;
vidLink = vidName;
sentLink = referred;
}
}
var deepLinked:Boolean = (sentLink==”false”) ? false:true;
//This would tell me that I should jump ahead.
if (deepLinked) function() {
vidFrame = x;
vidChoice = y;
gotoAndStop([vidFrame]);
};
April 24th, 2007 at 11:43 am
Hi David,
First, thanx for this blog, that’s very helpful
I would like to know if you ever worked using ASP, because I’m currently working for a programmer that uses ASP. Our problem is that we use SWF Object to load the SWF, but I cannot pass any variable to Flash using the so.addVariable property, and I cannot figure out why..
Everything works fine if I just save my .asp in a .htm file or if I use the embed tag instead of SWF Object, but since the website we’re working on is huge and we’re only updating it, we cannot simply transfer the code from ASP to HTML.
Any help would be more than appreciated!
April 24th, 2007 at 4:38 pm
Problem solved.
I had to leave a blank keyframe at the beginning of my SWF. It looks like asp processes javascript slower than HTML does, or something like that…
April 26th, 2007 at 7:32 am
To Kevin …
Your sample code uses the
LoadVarsclass, which is certainly a way to load data from outside the SWF, but it’s different in that the SWF is doing the asking, whereas here, the variables are being “forced” on the SWF from the outside as it loads (or arguably, before it loads). Now, you may very well be combining techniques — using FlashVars-supplied variables in cahoots with
LoadVars— and if that’s so, you don’t need to “prep” any of your variables, but it may make sense to declare the
LoadVarsvariables outside the
onLoadfunction, which it looks like you’ve done.
But honestly, you don’t have to do that either, because the
placeHoldervariable (your
LoadVarsinstance) has the data you want — once those data are loaded. Part of what confuses me here is that you haven’t used any of the
LoadVarsmethods that actually do anything. You’ve instantiated an object (
placeHolder), you’ve prepared an
onLoadevent handler, but you haven’t loaded anything (
placeHolder.load()or
placeHolder.sendAndLoad()).
I’m guessing you’ll want your
if (deepLinked)statement inside the
onLoadevent, but I’m not sure. You don’t need to declare a function (after that
if) to get the
if’s contents to perform. Then, too, what are
xand
y? And also, watch out for capitalization! You’ve set
setLinkto “False” but are later checking for “false”.
To Jasmin …
Yay! Glad you got it working. I’m not sure I’ve encountered what you saw — that ASP processes JavaScript slower (once the ASP is processed, the browser sees it as plain old HTML) — but success is good, in any case.
May 6th, 2007 at 3:31 pm
Hi David,
I’ve been trying to get variable passing to work between HTML and the FLVPlayback component using the SWFObject and I seem to be stuck. I’ve looked at your example and I can’t seem to figure out what I’m doing wrong. I’m wondering if you can help, please?
Here’s my script HTML code:
Get the Flash Player to see the Flash Movie.
var so = new SWFObject(””, “MyTube”, “355″, “275″, “9″, “”);
so.addParam(”allowFullScreen”,”true”);
so.addParam(”vidPath”, “”);
so.write(”Test”);
Then the code I’m using in the swf (which I believe is where it’s breaking is:
import fl.video.*;
var flvControl = Display; //named instance of FLVPlayback Component
var flvSource = vidPath;
flvControl.source = flvSource;
This is all the code I’m using. This is actionscript 3 on Flash CS3.
Any glaring easily correctable errors? If I put the direct path to the flv into the flvSource variable, it works fine.
Thanks, Craig
May 10th, 2007 at 1:22 am
@David
That was an hypothesis, but I’m glad what I said makes sense (or does it?) A friend of mine who is in programming told me it might be possible, but that I shouldn’t bother too much about it as long as it works lol
If you want to experience what I did, just save any html file you have to .asp and then upload it to an IIS server (or create a local IIS server), make sure your swf uses the variable on the first frame (in my case, it is a variable used to tell the swf if he has to load an introduction animation) and then load your swf with swfObject. I just left the 1st frame blank and moved my AS to the 2nd keyframe and everything worked fine from that time (I found this solution on a forum, it was a suggestion made by the guy who created SWFObject to solve a similar issue with HTML).
@Craig
Read my post, it might help you out!
May 13th, 2007 at 8:03 pm
To Craig …
There’s nothing glaringly wrong with your code. You’re using more lines than you need to — for example, you could simply put
Display.source = vidPath— but your three lines aren’t doing anything wrong. Jasmin’s suggestion to leave a blank keyframe at the beginning might be worth a shot, though I couldn’t explain why.
To make sure your information is indeed getting into the SWF, I would try a few
trace()statements …
e.g.
trace(vidPath);
… because if you get undefined or an empty string, you’ll at least know the first obstacle lies elsewhere.
To Jasmin …
Sooner or later, I’ll have to give that a shot. Thanks again for the input!
May 14th, 2007 at 10:15 am
Hi Jasmin,
I’m not sure how your example relates to mine. Am I missing something?
Thanks, Craig
May 14th, 2007 at 10:27 am
Craig,
I’m think Jasmin is suggesting you try a blank keyframe or two at the beginning of your movie to let the SWF “catch up,” in a sense, with the incoming variable(s). I can’t deny that such a trick might work, but then again, I couldn’t explain why if it did, and I don’t see anything inherently wrong with your code. Have you tried a
trace()yet, to see if the variable has truly made its way into your movie?
In order for the
trace()to be visible when you test in an HTML document, you’ll have to use remote debugging, as described in this Adobe article (start with page 4/4 to jump right into it). You might also route that variable to a dynamic text field for testing, if you don’t want to go to the expense of remote debugging.
May 16th, 2007 at 12:21 pm
Thanks David! I’ll give the trace() a try using your article and see what happens. Thanks for explaining what Jasmin was referring to and verifying that my code was OK. That’s exactly what I needed to get ‘unstuck’.
I appreciate your help!
Craig
May 18th, 2007 at 1:41 pm
Craig,
Sure thing! Best of luck.
August 20th, 2007 at 8:47 am
Craig,
Did you ever figure this problem out? I’m having the exact same problem now and I can’t get it. I would appreciate any help.
Thanks,
Mark
August 28th, 2007 at 4:02 pm
Hello David,
First, THANK YOU! this blog helped me several times. Today my problem is partially solved by this post, but I’m still not sure how to make it happend. I want to call from SWF1 an HTML popup window that holds SWF2 which will load content depending on what the user select in SWF1. I already know how to popup the HTML window using “getURL(”javascript:Launch(’…” The part that I don’t know how is: How to pass the variables from SWF1 to SWF2. You showed in this post how SWF2 will retrive the vars from the HTML, but how SWF1 will put them in the right place of the HTML that holds SWF2 still a mystery for me.
Thank you.
Carlos Palacio
August 31st, 2007 at 8:55 am
Carlos,
Ah, that’s a really good question, actually. The concept goes like this: when you just JavaScript to open a new window, you’re ultimately using the
window.open()method (native to the JavaScript API). That method accepts a number of parameters, the first of which is tells the browser what HTML document to open. The second allows you to specify a reference to the opened window. The third allows you to specify characteristics of the opened window, such as width, height, position, and so forth.
It’s the second parameter that matters in this scenario. The reference name you give the new window is essentially equivalent to an instance name in ActionScript: it gives you a way to speak to the new object directly. Using the name you provide, you can reference the new window, then refer to the SWF in that window by way of the
idor
nameattribute given to its
<object>/
<embed>tags. Once you’ve referenced the SWF itself, you should be able to interact with it via the
ExternalInterfaceclass or the approach described on this Adobe link:
Scripting with Flash 5 (which still works just fine)
In any case, though, this would make a great blog entry, so I’ve added it to my list. Thanks for the idea, Carlos! I’ll mention your name in the article whenever I get to it.
September 10th, 2007 at 5:31 am
I was wondering how the same thing could be done with flash video. There’s 1 small thing I don’t see to understand. I’m also trying out the full screen function that’s new in flash 9. My code looks like the following:
import fl.video.*;
// 1. Video component instance name
var flvControl = display;
var f:FLVPlayback = new FLVPlayback();
flvSource = fl.video.FLVPlayback(fideo, true);
// 2. Set video parametes
flvControl.fullScreenButton = fullScrn_btn;
flvControl.align = VideoAlign.CENTER;
flvControl.scaleMode = VideoScaleMode.MAINTAIN_ASPECT_RATIO;
flvControl.source = flvSource;
Any help, much appreciated.
Huw
September 24th, 2007 at 6:59 pm
Huw,
The principle is the same for video files as it is for any other: a particular loading mechanism, at some point, is going to ask for a file. In terms of the FLVPlayback component, if you’re using ActionScript 3.0, the mechanism is the
FLVPlayback.sourceproperty, as you’ve shown.
The trick is that AS3 looks for passed-in variables in a different location from AS2 — which isn’t at all obvious if you don’t know to look for it. Rather than populating variables in the root (main timeline), ActionScript 3.0 SWFs look for their variables in the
LoaderInfoinstance of the main timeline — specifically, the
parametersproperty of that instance — which may be referenced via the
DisplayObject.rootproperty of the main timeline like this:
Since the main timeline is a
DisplayObject, it has access to the
DisplayObject.loaderInfoproperty, which points to the
LoaderInfoinstance associated with the main timeline (perhaps a bit confusing, but roll with it, if you can). From there. the next part of the expression,
parameters.flvSourceleads to the
flvSourceproperty (your variable) of the
parametersproperty of the previously described expression.
This complex approach is only necessary in ActionScript 3.0, which you’ll need if you’re after the fullscreen functionality of Flash Player 9.
October 5th, 2007 at 8:36 am
Hi, david great deal with this site. I have a question for you, i´m developing a web site with trendyflash site builder, and everthing its seems to work good, but when i publish the site on my local computer the hyperlinks made inside don´t work i think is because my OS its windows XP SP2 and the browser IE6 sp2 i think its protecting the active content, could please give some tips.
October 5th, 2007 at 12:32 pm
Artur,
Gosh, I don’t know how valuable my suggestions may be — I have no personal experience with Trendy Flash! Recent versions of Flash Player feature tighter security restrictions than they used to, so regardless of your browser, you’re likely to see warnings when accessing online content while testing a SWF from your hard drive (unless you’re in the Flash IDE itself; and even then, sometimes). If you upload your SWF to a server and test from there, you should see improvement, because at that point the Flash content is being tested from an online context.
Internet Explorer, running in Windows XP (Service Pack 2) or higher, refuses to play active content or scripting unless you put something called “the mark of the web” in your HTML document. See this Adobe TechNote for details. This might just be your best bet, because I know how convenient it is to test content locally.
TechNote 19578
October 11th, 2007 at 10:19 pm
Hello David, I need major help, How can i put in the variables when I’m using this (custom (FLV) flash player)
ns.play(”URL”);? please answer my question I really need this. Thanks
October 12th, 2007 at 1:18 pm
Eduardo,
First, decide on the name of your variable. If your intent is to play video, you might, for example, name the variable
videoFile. This would be the variable that you pass into Flash from the outside. In ActionScript 2.0, a
videoFilevariable will automatically be declared for you as soon as the SWF loads, so in your call to
NetStream.play(), you would supply your variable instead instead of a quoted file path:
ns.play(videoFile);
In ActionScript 3.0 — just in case that’s what you’re using — you would retrieve the variable from a different location, as described here:
How to Retrieve FlashVars Data in ActionScript 3.0
October 12th, 2007 at 6:09 pm
So I would have to add this –> [ns.play(videoFile);] to this ——>
[[[ var s:Sound = new Sound();
iconButton.onRelease = function():Void {
s.loadAudio(audio, true);
} ]]]]]
I’m really confused LOL. And I’m using actionscript 2.0 (flash 8 professional)
October 12th, 2007 at 6:38 pm
Nevermine I figured out Yay! I’m jumping with joy hahaha this might make my life a lil’ easier now. Thanks so much your tutorials are such great help.
October 15th, 2007 at 7:42 pm
Eduardo,
I’m glad to hear that! It sure does feel good when a solution presents itself!
January 8th, 2008 at 12:26 pm
David-
I am trying to load a variable using LoadVars from a text file and I want to use this variable in loadSound. The variable loads correctly but will not work inside loadSound. Your help is appreciated.
var myData = new LoadVars();
myData.onLoad = function() {
var s:Sound = new Sound();
s.loadSound(this.myAudio, true);
};
myData.load(”text.txt”);
My text file looks like this:
myAudio=radio.mp3
January 8th, 2008 at 3:52 pm
I have a problem with flashvars when using multiple instances of same swf file.
They all have and also parameters in embed tag.
Every instance has different value for the variable City.
I coded actionscript just to output value of the City and on IE,safari,opera,firefox 1.0 it works perfectly but on firefox 2.0 it works only for first instance while the rest outputs “undefined”.
Here is the url.
Any help is appriciated
January 8th, 2008 at 4:48 pm
Just discovered the problem.
One of the add-ons was making this bug.
Now that this addon is disabled it works perfectly.
January 13th, 2008 at 2:03 pm
To Marc …
You’ve scoped your
Soundinstance inside the
LoadVarsinstance by virtue of declaring the
svariable inside the
onLoadevent handler. That might be what you’re running into. Try declaring
soutside the function. When referencing the loaded data from outside the
LoadVarsinstance — such as in a later frame, if that’s what you’re after — you’ll have to use the
LoadVarsinstance (
myData) as your prefix instead of
this. Does that make sense?
To msmuser …
Hey, glad you solved it!
February 5th, 2008 at 4:44 pm
Hi David,
I’m still deciding whether to start with Actionscript 3 or 2. (Newbie) I have Flash CS3 and using all it’s bits and bobs (components) and learning slowly. I want to create a basic vid player using the FLVplayback component, with no skin and pass the streaming vid content to it via FlashVars. I haven’t seen one example of a path, using variables etc, going to a streaming server address, ie RTMP://myserver/myvid.flv. My query is that when pointing to a file the whole thing seems to be wrapped in speech marks. ie “myvariable=../path/to/file.flv”. I can’t get it working. (I only got the example shipped with flash working after someone on a blog said the AC js script had to be ammended also in html. Basically I want to Flashvars flv’s from a FMS streaming server?? Many thanks for your time, will keep plugging away..
February 6th, 2008 at 9:13 pm
Ed,
Any variable that comes into Flash is a string, so that explains the quotation marks you’d have to use in your HTML. If you’re using Adobe’s Active Content JavaScript (AC_RunActiveContent.js), then yes, you’ll have to edit the JavaScript code as well as the
<param>and
<embed>tags in your HTML. You’ll have to add a
<param>tag that looks like this:
You’ll also have to add an attribute to your
<param>tag that looks like this:
Finally, you’ll have to add a set of parameters somewhere in the lengthy list that exists inside the JavaScript:
Without that change to the JavaScript, you won’t ever get the variable(s), because the JavaScript overrides the
<object>and
<embed>tags — purposefully so. The complexity of the AC_RunActiveContent.js implementation is enough to keep me away from it, personally. It works perfectly fine, mind you, but I I found SWFObject so much easier on the eyes.
February 7th, 2008 at 5:42 am
Hi David, Everything working now thanks very much!! With regards to AS3, (don’t know if I should put this in this thread?!) when declaring a variable, if you want to have more than one, do you have to write a line for each, ie loaderInfo.parameters.audio, loaderInfo.parameters.video, loaderInfo.parameters.boxheight etc ??
Many thanks again
February 7th, 2008 at 8:39 am
Ed,
Glad to hear everything works!
I’m not sure what you mean by writing a line for each variable. In ActionScript 3.0, every variable you add becomes another property of the
parametersproperty of that
loaderInfoinstance. In ActionScript 2.0, every variable you add because another referenceable variable in the main timeline. I think you’re asking about the HTML/JavaScript itself, and if so, you need to put everything in the same line. If you have more than one variable, each name/value pair goes into the single string that comprises your FlashVars parameter:
Each name/value pair is separated by an ampersand (&).
February 7th, 2008 at 9:04 am
Hi David, at the moment I am trying to get to variables into the swf. Using AS3 and in the fla have done the following -
player.source=root.loaderInfo.parameters.myvideo;
player.skinBackgroundColor=root.loaderInfo.parameters.ctrlcolour;
then in the html, entering the strings as you have mentioned. this half seems to work in the sense it takes one parameter, but not the other. In the html AC js part, do you list the string the same as you do for the object and embed part?
I’ve had both of these parameters working using flashvars, just not together….still plugging..
February 7th, 2008 at 9:13 am
Hi David, I have it working now, must have been a typo! I guess I’m asking in AS3 if you can just specify all the parameters you want to include in one line,
ie, loaderInfo.parameters.myvideo.myaudio.myboxsize etc
Thanks you for all your help, and articles, it’s a slow uphill struggle but enjoyable! (I’m still working out the difference between symbols, objects et al!)
February 7th, 2008 at 9:41 am
Ed,
Aha! No, the line you showed …
loaderInfo.parameters.myvideo.myaudio.myboxsize
… would theoretically reference the
myboxsizeproperty of a
myaudioobject, which in turn is a property of a
myvideoobject, which in turn is a property of the
parametersproperty of the
loaderInfoobject — all in the house that Jack built. Think of these object hierarchies in terms of folders and files on your hard drive. What you’re after is comparable to a series of files in a folder structure that goes loaderInfo/parameters.
February 7th, 2008 at 11:11 am
Hi David,
Many thanks for your patience, I swear I will leave you alone soon, just to summarise then, I would have to list each variable as so
In the fla, AS3
loaderInfo.parameters.myvideo
loaderInfo.parameters.myaudio
loaderInfo.parameters.myboxsize
so I that I can reference them in html?
February 7th, 2008 at 11:24 am
Ed,
No worries.
What you’ve shown will do it — but you’ll be referencing them from values supplied by HTML, not really referencing them “in” HTML (I just don’t want you to think the communication goes both ways: you can’t read these values back out of the SWF into HTML).
You’ll reference these on separate lines, like you showed in your 9:04 am post.
February 7th, 2008 at 3:59 pm
That’s great, once again many thanks for your patience and for your help, cheers Ed
February 13th, 2008 at 12:14 am
Ed,
You’re sure welcome.
February 17th, 2008 at 12:46 pm
how can i publish an embedded code contain swf video into flash video..i just have this code :-
can u show me how to publish this file into flash video. not in website platform. TQ
February 22nd, 2008 at 9:31 pm
rahim,
I’m afraid I don’t understand what you’re asking. Can you try to rephrase your question?
June 10th, 2008 at 3:01 am
David,
Thanks heaps for this. I have encountered a rather annoying problem and can’t quite put my finger on the solution (i’m sure it’s an easy one).
I’m using swfobject and using flashvars for a button to link to a URL defined from the HTML. The code is the same inside flash, outside it looks like:
so.addParam(”FlashVars”, “variable=”);
This seemed to have worked so I finished the page, then did the same for a different flash file on a different page, and then the buttons started linking to an ‘undefined’ page. Went page to the original page to check code differences and the original page started to link to the ‘undefined’ page as well without touching the code.
Can’t figure it out!
June 10th, 2008 at 3:02 am
Sorry, I forgot to add, inside flash the button has a simple on (release) getURL statement.
June 10th, 2008 at 7:54 am
I think i fixed it. I had 3 separate parameters for 3 different variables, and didnt read your bit where it mentions multiple variables separated by a “&”.
Thanks anyway!!
June 13th, 2008 at 9:17 am
Brett,
Yes, sounds like you got it! Three variables would be separated with &s, as in …
variable=
June 26th, 2008 at 1:35 pm
Maybe I’m missing something but instead of this line:
var audio:String = “path/to/file/audo.mp3″;
Shouldn’t it be the following?
var audio:String = _root.audio;
Your article seems to miss the main point which I thought was referencing flashvars in ActionScript 2.0.
Scott
June 26th, 2008 at 1:52 pm
Scott,
I think you are missing something — or I wasn’t clear enough (which wouldn’t be the first time!).
The variable declaration you mentioned is just an example of what FlashVars is doing.
You wouldn’t need the suggested replacement either. Scratch the
var audio:String = _root.audio;. By virtue of the passed-in FlashVars, that
audiovariable doesn’t need to be declared at all.
Does that clear it up?
June 26th, 2008 at 2:11 pm
Yep, I got it, thanks.
June 26th, 2008 at 6:55 pm
I know it’s not really related to the flashvars topic but would you happen to know how to reference the allowscriptaccess parameter in a flash movie with ActionScript 2.0?
Scott
June 26th, 2008 at 7:06 pm
Scott,
That’s communication in the opposite direction — from the SWF out, rather than from the HTML in. If your HTML is formatted as XHTML, you can pass the URL of that very page to the SWF itself, as described here:
There’s more to it than that first article, but the first one (which is free) contains enough information to get you started. From that point, it’s a matter of locating the node that contains your parameter (actually, a tag attribute) and evaluating its value.
June 26th, 2008 at 8:44 pm
So there is no easy function you can use to read the value? I only need to read the value and determine if the value is set to always.
Scott
June 26th, 2008 at 8:54 pm
Scott,
Difficulty is a relative term, but I hear what you’re saying. There really isn’t an easy way to read any value in the HTML outside of FlashVars. In a sense, that’s why FlashVars is there. You could certainly use JavaScript to create a FlashVars variable on the fly, passing in the value of the parameter/attribute you’re after.
July 28th, 2008 at 9:10 am
David
You’ve been a major source of help in the past, I am hoping you can give me some advice on a new project:
I searched your site for anything on COMPONENTS or SCROLLBAR, and found nothing - forigve me if I am posting in an inaccurate area of your site or if perhaps I have overlooked any postings on this subject matter.
I am utilizing Flash VARS, loading .txt files into a dynamic text box to which I have added a scrollbar from components. It is working well, however I noticed that when I move from one area of my site to another, the scrollbar does not reset itself in a ‘default’ position each time a different text file is loaded. I have narration audio loading on each external SWF; the text box loads the text form of the narrative for those who either do not have speakers or are hearing impared.
I have several frames on a main timeline, and on each individual frame I have an external SWF file loading into the main (index.swf) SWF; the textbox is located on the index.swf.
On the index.swf file, in the first frame to load a text file, I have this code for the scrollbar:
—————————————————————————-
this.createTextField(”my_txt”, 10, 10, 20, 200, 100);
loadedInfo.wordWrap = true;
this.createClassObject(mx.controls.UIScrollBar, “my_sb”, 20);
// Set the target text field.
my_sb.setScrollTarget(loadedInfo);
// Size it to match the text field.
my_sb.setSize(12, loadedInfo._height);
// Move it next to the text field.
my_sb.move(loadedInfo._x + loadedInfo._width, loadedInfo._y);
—————————————————————————–
Each individual external SWF is coded like this on it’s last frame:
—————————————————————————–
onEnterFrame = gotoAndStop(_level0.nextFrame())
—————————————————————————–
This moves the program to the next frame, which loads the next external SWF and the text for the text box -
The code for each frame on the index.swf is:
—————————————————————————–
stop();
unloadMovieNum(5);
onEnterFrame = _root.myMCL.loadClip(”assets/SWFs/fileName.swf”, 5);
// Load text to display and define onData handler.
var my_lv:LoadVars = new LoadVars();
my_lv.onData = function(src:String) {
if (src != undefined) {
loadedInfo.text = src;
} else {
loadedInfo.text = “Error loading text.”;
}
};
my_lv.load(”assets/vars/fileName.txt”);
——————————————————————————–
This loads the appropriate text file into the text box, which corrosponds to the external SWF file currently playing.
Basically, I want the scrollbar to reset to the top of the text file each time a new text file is loaded - at present, when the scrollbar is utilized to read the loaded text, it remains at the bottom of the text file when a new file is loaded into the dynamic text box, (so that the user is reading the last line of the text file instead of the first line). The user has to manually scroll up in order to read the first line of the text file.
Is there a simple way to set a default for the scrollbar to reset to the top of the text file each time a new file is loaded?
August 6th, 2008 at 1:18 pm
David
Okay, I found the solution online elsewhere, and it is a lot more simple than I expected:
September 18th, 2008 at 1:49 pm
Hi, David
Have you tried to change Flashvar on the a fly? I tried, something like after clicking a HTML button, changed the Flashvar value, but somehow, Flash still read the original value of Flashvar? Any suggestion? Thanks.
//—— my code, it shows the new value of Aname, but Flash always reads the value in embed tag –//
September 18th, 2008 at 1:57 pm
To Kelley …
Sorry for the late reply! Sounds like you found a solution, though, and that’s the most important part. Glad to hear it!
To Richard …
You nailed it: FlashVars feed in their values at the time the SWF loads, and not afterward. If you want to pass values into (or out of) the SWF after it loads, use either the
LoadVarsclass or — probably better suited to this scenario — the
ExternalInterfaceclass.
ExternalInterfacelets you call functions inside the SWF from outside code (i.e., JavaScript). You can pass in parameters, too, so set up some “receiver functions in your FLA and call those with JavaScript.
September 24th, 2008 at 8:31 pm
Ok this may not be related to the topic. But you seems to know stuff…so i ask a basic question on problem i am facing.
I am using FLVplayback for playing video.
When i assign
//display is flvplayback instance.
display.source=””
it works.
But when i make it streamable using the following statement it do not like it. It does not like ? in the URL.
display.source=””;
There are two issues here. One it expects flv extension for source.
two it does not like ? in the url.
it throws this error.
VideoError: 1005: Invalid xml: URL: “″ No root node found; if url is for an flv it must have .flv extension and take no parameters
If you can solve this…you solve many people problem in the whole world.
thanks in advance. | http://www.quip.net/blog/2006/flash/how-to-tell-swf-from-outside | crawl-002 | refinedweb | 9,811 | 72.26 |
ActiveScriptEventConsumer class
The ActiveScriptEventConsumer class runs a predefined script in an arbitrary scripting language when an event is delivered to it. This class is one of the standard event consumers that WMI provides. For more information, see Monitoring and Responding to Events with Standard Consumers.
Mofcomp -n:root\<namespace> scrcons.mof
You can configure the performance of all instances of ActiveScriptEventConsumer on a system by setting the values of either the Timeout or MaximumScripts property in the single instance of ScriptingStandardConsumerSetting.
Syntax
[AMENDMENT] class ActiveScriptEventConsumer : __EventConsumer { uint8 CreatorSID[] = {1,1,0,0,0,0,0,5,18,0,0,0}; uint32 KillTimeout = 0; string MachineName; uint32 MaximumQueueSize; string Name; string ScriptingEngine; string ScriptFileName; string ScriptText; };
The ActiveScriptEventConsumer class has these types of members:
Properties
The ActiveScriptEventConsumer class has these properties.
CreatorSID
Data type: uint8 array
Access type: Read-only
Array that represents the security identifier (SID), which uniquely identifies the creator of the Active Script Event consumer. This property is inherited from __EventConsumer.
KillTimeout
Data type: uint32
Access type: Read-only
Number, in seconds, that the script is allowed to run. If 0 (zero), which is the default, the script is not terminated.
MachineName
Data type: string
Access type: Read-only
Name of the computer to which WMI sends events. By convention of Microsoft standard consumers, the script consumer cannot be run remotely. Third-party consumers can also use this property. This property is inherited from __EventConsumer.
MaximumQueueSize
Data type: uint32
Access type: Read-only
Maximum queue, in bytes, for the Active Script Event consumer. This property is inherited from __EventConsumer.
Name
Data type: string
Access type: Read/write
-
Unique identifier for the event consumer. If you rename the consumer, the result is two equal consumers that have different names.
ScriptFileName
Data type: string
Access type: Read-only
Name of the file from which the script text is read, intended as an alternative to specifying the text of the script in the ScriptText property. This property must be NULL if the ScriptText property is not NULL.
Note
When you specify the ScriptFileName, it is important to secure the executable that you are launching. If the executable is not in a secure location or secured with a strong access control list (ACL), anyone can replace the executable with a different one. For more information about ACLs, see Creating a Security Descriptor (SD) for a New Object in C++.
ScriptingEngine
Data type: string
Access type: Read-only
Name of the scripting engine to use, for example, "VBScript". This property cannot be NULL.
ScriptText
Data type: string
Access type: Read-only
Text of the script that is expressed in a language known to the scripting engine. This property must be NULL if the ScriptFileName property is not NULL.
Remarks
This class is derived from the __EventConsumer abstract class. It is located in the root\subscription namespace.
When the text of a script is specified in the event consumer instance, the script has access to the event instance in the script environment variable TargetEvent.
The scripts run in the LocalSystem security context. As a security measure, only a local system administrator or a domain administrator can configure the scripting consumer. Access rights are not checked until run time. After the consumer is configured, any user can trigger the event that causes the script to .
Failure to load the scripting engine or parse and validate the script is considered a failure. Error return codes from the script and terminating the script by using a time-out are also considered failures.
Either ScriptText or ScriptFileName must be not NULL. If both properties are NULL or not NULL, an error is generated.
When WMI is run as a service, scripts run by ActiveScriptEventConsumer do not generate screen output. Scripts that use MsgBox do run, but they do not display information on the screen. Running the WMI service as an executable file is not supported, but WMI allows scripts that use the MsgBox function to display output or accept user input. None of the methods provided by the WScript object can be used because ActiveScriptEventConsumer does not use Windows Script Host (WSH).
Examples
The Create Permanent WMI Event registration to monitor files PowerShell example on TechNet Gallery uses ActiveScriptEventConsumer as part of a complex script to set up a permanent WMI event registration. | https://docs.microsoft.com/en-us/windows/win32/wmisdk/activescripteventconsumer?redirectedfrom=MSDN | CC-MAIN-2019-39 | refinedweb | 715 | 55.24 |
Pool-Aware Scheduler Support¶
Man.
Problem Description¶:
After the scheduler selects a backend on which to place a new share, the backend may have to make a second decision about where to place the share within that backend. This logic is driver-specific and hard for admins to deal with.
The capabilities that the backend reports back to the scheduler may not apply universally. A single backend may support both SATA and SSD-based storage, but perhaps not at the same time. Backends need a way to express exactly what they support and how much space is consumed out of each type of storage.
Therefore, it is important to extend manila so that it is aware of storage pools within each backend and can use them as the finest granularity for resource placement.
Proposed change¶
A pool-aware scheduler will address the need for supporting multiple pools from one storage backend.
Terminology¶
- Pool
A logical concept to describe a set of storage resources that can be used to serve core manila requests, e.g. shares/snapshots. This notion is almost identical to manila Share Backend, for it has similar attributes (capacity, capability). The difference is that a Pool may not exist on its own; it must reside in a Share Backend. One Share Backend can have multiple Pools but Pools do not have sub-Pools (meaning even if they have them, sub-Pools do not get to exposed to manila, yet). Each Pool has a unique name in the Share Backend namespace, which means a Share Backend cannot have two pools using same name.
Design¶
The workflow in this change is simple:
Share Backends report how many pools and what those pools look like and are capable of to scheduler;
When request comes in, scheduler picks a pool that fits the need best to serve the request, it passes the request to the backend where the target pool resides;
Share driver gets the message and lets the target pool serve the request as scheduler instructed.
To support placing resources (share/snapshot) onto a pool, these changes will be made to specific components of manila:
Share Backends reporting capacity/capabilities at pool level;
Scheduler filtering/weighing based on pool capacity/capability and placing shares/snapshots to a pool of a certain backend;
Record which backend and pool a resource is located on.
Data model impact¶
No DB schema change involved, however, the host field of Shares table will now include pool information but no DB migration is needed.
Original host field of Shares:
HostX@BackendY
With this change:
HostX@BackendY#pool0
REST API impact¶
Notifications impact¶
Host attribute of shares now includes pool information in it, consumer of notification can now extend to extract pool information if needed.
Other end user impact¶.
Performance Impact¶.
Developer impact¶', } ] } | https://docs.openstack.org/manila/latest/contributor/pool-aware-manila-scheduler.html | CC-MAIN-2021-25 | refinedweb | 465 | 54.66 |
Many simple “for loops” in Python can be replaced with list comprehensions. You can often hear that list comprehension is “more Pythonic” (almost as if there was a scale for comparing how Pythonic something is, compared to something else 😉). In this article, I will compare their performance and discuss when a list comprehension is a good idea, and when it’s not.
Filter a list with a “for loop”
Let’s use a simple scenario for a loop operation - we have a list of numbers, and we want to remove the odd ones. One important thing to keep in mind is that we can’t remove items from a list as we iterate over it. Instead, we have to create a new one containing only the even numbers:
# filter_list.py MILLION_NUMBERS = list(range(1_000_000)) def for_loop(): output = [] for element in MILLION_NUMBERS: if not element % 2: output.append(element) return output
if not element % 2 is equivalent to
if element % 2 == 0, but it’s slightly faster. I will write a separate article about comparing boolean values soon.
Let’s measure the execution time of this function. I’m using Python 3.8 for benchmarks (you can read about the whole setup in the Introduction article):
$ python -m timeit -s "from filter_list import for_loop" "for_loop()" 5 loops, best of 5: 65.4 msec per loop
It takes 65 milliseconds to filter a list of one million elements. How fast will a list comprehension deal with the same task?
Filter a list with list comprehension
# filter_list.py MILLION_NUMBERS = list(range(1_000_000)) def list_comprehension(): return [number for number in MILLION_NUMBERS if not number % 2]
$ python -m timeit -s "from filter_list import list_comprehension" "list_comprehension()" 5 loops, best of 5: 44.5 msec per loop
“For loop” is around 50% slower than a list comprehension (65.4/44.5≈1.47). And we just reduced five lines of code to one line! Cleaner and faster code? Great!
Can we make it better?
Filter a list with the “filter” function
Python has a built-in filter function for filtering collections of elements. This sounds like a perfect use case for our problem, so let’s see how fast it will be.
# filter_list.py MILLION_NUMBERS = list(range(1_000_000)) def filter_function(): return filter(lambda x: not x % 2, MILLION_NUMBERS)
$ python -m timeit -s "from filter_list import filter_function" "filter_function()" 1000000 loops, best of 5: 284 nsec per loop
284 nanoseconds?! That’s suspiciously fast! It turns out that the filter function returns an iterator. It doesn’t immediately go over one million elements, but it will return the next value when we ask for it. To get all the results at once, we can convert this iterator to a list.
# filter_list.py MILLION_NUMBERS = list(range(1_000_000)) def filter_return_list(): return list(filter(lambda x: not x % 2, MILLION_NUMBERS))
$ python -m timeit -s "from filter_list import filter_return_list" "filter_return_list()" 2 loops, best of 5: 104 msec per loop
Now, its performance is not so great anymore. It’s 133% slower than the list comprehension (104/44.5≈2.337) and 60% slower than the “for loop” (104/65.4≈1.590).
While, in this case, it’s not the best solution, an iterator is an excellent alternative to a list comprehension when we don’t need to have all the results at once. If it turns out that we only need to get a few elements from the filtered list, an iterator will be a few orders of magnitude faster than other “non-lazy” solutions.
filterfalse()
We could use the filterfalse() function from the itertools library to simplify the filtering condition.
filterfalse returns the opposite elements than
filter. It picks those elements that evaluate to False. Unfortunately, it doesn't make any difference when it comes to performance:
from itertools import filterfalse
def filterfalse_list():
return list(filterfalse(lambda x: x % 2, MILLION_NUMBERS))
$ python -m timeit -s "from filter_list import filterfalse_list" "filterfalse_list()"
2 loops, best of 5: 103 msec per loop
More than one operation in the loop
List comprehensions are often faster and easier to read, but they have one significant limitation. What happens if you want to execute more than one simple instruction? List comprehension can’t accept multiple statements (without sacrificing readability). But in many cases, you can wrap those multiple statements in a function.
Let’s use a slightly modified version of the famous “Fizz Buzz” program as an example. We want to iterate over a list of elements and for each of them return:
- “fizzbuzz” if the number can be divided by 3 and 5
- “fizz” if the number can be divided by 3
- “buzz” if the number can be divided by 5
- the number itself, if it can’t be divided by 3 or 5
Here is a simple solution:
# filter_list.py def fizz_buzz(): output = [] for number in MILLION_NUMBERS: if number % 3 == 0 and number % 5 == 0: output.append('fizzbuzz') elif number % 3 == 0: output.append('fizz') elif number % 5 == 0: output.append('buzz') else: output.append(number) return output
Here is the list comprehension equivalent of the fizz_buzz():
['fizzbuzz' if x % 3 == 0 and x % 5 == 0 else 'fizz' if x % 3 == 0 else 'buzz' if x % 5 == 0 else x for x in MILLION_NUMBERS]
It’s not easy to read - at least for me. It gets better if we split it into multiple lines:
[ "fizzbuzz" if x % 3 == 0 and x % 5 == 0 else "fizz" if x % 3 == 0 else "buzz" if x % 5 == 0 else x for x in MILLION_NUMBERS ]
But if I see a list comprehension that spans multiple lines, I try to refactor it. We can extract the “if” statements into a separate function:
# filter_list.py def transform(number): if number % 3 == 0 and number % 5 == 0: return 'fizzbuzz' elif number % 3 == 0: return 'fizz' elif number % 5 == 0: return 'buzz' return number def fizz_buzz2(): output = [] for number in MILLION_NUMBERS: output.append(transform(number)) return output
Now it’s trivial to turn it into a list comprehension. And we get the additional benefit of a nice separation of logic into a function that does the “fizz buzz” check and a function that actually iterates over a list of numbers and applies the “fizz buzz” transformation.
Here is the improved list comprehension:
def fizz_buzz2_comprehension(): return [transform(number) for number in MILLION_NUMBERS]
Let’s compare all three versions:
$ python -m timeit -s "from filter_list import fizz_buzz" "fizz_buzz()" 2 loops, best of 5: 191 msec per loop $ python -m timeit -s "from filter_list import fizz_buzz2" "fizz_buzz2()" 1 loop, best of 5: 285 msec per loop $ python -m timeit -s "from filter_list import fizz_buzz2_comprehension" "fizz_buzz2_comprehension()" 1 loop, best of 5: 224 msec per loop
Extracting a separate function adds some overhead. List comprehension with a separate
transform() function is around 17% slower than the initial “for loop”-based version (224/191≈1.173). But it’s much more readable, so I prefer it over the other solutions.
And, if you are curious, the one-line list comprehension mentioned before is the fastest solution:
def fizz_buzz_comprehension(): return [ "fizzbuzz" if x % 3 == 0 and x % 5 == 0 else "fizz" if x % 3 == 0 else "buzz" if x % 5 == 0 else x for x in MILLION_NUMBERS ]
$ python -m timeit -s "from filter_list import fizz_buzz_comprehension" "fizz_buzz_comprehension()" 2 loops, best of 5: 147 msec per loop
Fastest, but also harder to read. If you run this code through a code formatter like black (which is a common practice in many projects), it will further obfuscate this function:
[ "fizzbuzz" if x % 3 == 0 and x % 5 == 0 else "fizz" if x % 3 == 0 else "buzz" if x % 5 == 0 else x for x in MILLION_NUMBERS ]
There is nothing wrong with black here - we are simply putting too much logic inside the list comprehension. If I had to say what the above code does, it would take me much longer to figure it out than if I had two separate functions. Saving a few hundred milliseconds of execution time and adding a few seconds of reading time doesn’t sound like a good trade-off 😉.
Clever one-liners can impress some recruiters during code interviews. But in real life, separating logic into different functions makes it much easier to read and document your code. And, statistically, we read more code than we write.
Conclusions
List comprehensions are often not only more readable but also faster than using “for loops.” They can simplify your code, but if you put too much logic inside, they will instead become harder to read and understand.
Even though list comprehensions are popular in Python, they have a specific use case: when you want to perform some operations on a list and return another list. And they have limitations - you can’t
break out of a list comprehension or put comments inside. In many cases, “for loops” will be your only choice.
I only scratched the surface of how useful list comprehension (or any other type of “comprehension” in Python) can be. If you want to learn more, Trey Hunner has many excellent articles and talks on this subject (for example, this one for beginners). | https://switowski.com/blog/for-loop-vs-list-comprehension | CC-MAIN-2020-50 | refinedweb | 1,516 | 58.52 |
I engaged a problem with inherited Controls in Windows Forms and need some advice on it.
I do use a base class for items in a List (selfmade GUI list made of a panel) and some inherited controls that are for each type of data that could be added to the list.
There was no problem with it, but I now found out, that it would be right, to make the base-control an abstract class, since it has methods, that need to be implemented in all inherited controls, called from the code inside the base-control, but must not and can not be implemented in the base class.
When I mark the base-control as abstract, the Visual Studio 2008 Designer refuses to load the window.
Is there a way to get the Designer work with the base-control made abstract?
I KNEW there had to be a way to do this (and I found a way to do this cleanly). Sheng's solution is exactly what I came up with as a temporary workaround but after a friend pointed out that the
Form class eventually inherited from an
abstract class, we SHOULD be able to get this done. If they can do it, we can do it.
We went from this code to the problem
Form1 : Form
public class Form1 : BaseForm ... public abstract class BaseForm : Form
This is where the initial question came into play. As said before, a friend pointed out that
System.Windows.Forms.Form implements a base class that is abstract. We were able to find...
Inheritance Hierarchy:
public **abstract** class MarshalByRefObject)
public class Form1 : MiddleClass ... public class MiddleClass : BaseForm ... public abstract class BaseForm : Form ...
This actually works and the designer renders it fine, problem solved.... except you have an extra level of inheritance in your production application that was only necessary because of an inadequacy in the winforms designer!
This isn't a 100% surefire solution but its pretty good. Basically you use
#if DEBUG to come up with the refined solution.
Form1.cs
#if DEBUG public class Form1 : MiddleClass #else public class Form1 : BaseForm #endif ...
MiddleClass.cs
public class MiddleClass : BaseForm ...
BaseForm.cs
public abstract class BaseForm : Form ...
What this does is only use the solution outlined in "initial solution", if it is in debug mode. The idea is that you will never release production mode via a debug build and that you will always design in debug mode.
The designer will always run against the code built in the current mode, so you cannot use the designer in release mode. However, as long as you design in debug mode and release the code built in release mode, you are good to go.
The only surefire solution would be if you can test for design mode via a preprocessor directive. | https://codedump.io/share/RXvfPjFVtKlo/1/how-can-i-get-visual-studio-2008-windows-forms-designer-to-render-a-form-that-implements-an-abstract-base-class | CC-MAIN-2017-39 | refinedweb | 467 | 63.39 |
More than one PCH file might apply to a given compilation. If so, the compiler uses the largest PCH file.
Support for Precompiled Header (PCH) files is deprecated from ARM Compiler 5.05 onwards on all platforms. Note that ARM Compiler on Windows 8 never supported PCH files.
That is, the compiler uses the PCH file representing the most preprocessing directives from the primary source file.
For example, a primary source file might begin with:
#include "xxx.h" #include "yyy.h" #include "zzz.h"
If there is one PCH file for xxx.h and a second for xxx.h and yyy.h, the latter PCH file is selected, assuming that both apply to the current compilation. Additionally, after the PCH file for the first two headers is read in and the third is compiled, a new PCH file for all three headers is created if the requirements for PCH file creation are met. | http://infocenter.arm.com/help/topic/com.arm.doc.dui0472m/chr1359124218307.html | CC-MAIN-2018-05 | refinedweb | 153 | 69.38 |
Forum:On bumping old topics
From Uncyclopedia, the content-free encyclopedia
Attention, everyone. I am getting sick of people who are editing old forum topics, bringing them back to the top of the page and making everyone irritated. Thus, the following rule is now in effect:
(Meaning, offense #1 = 1 day, offense #2 = 2 days, etc.) I'm getting fucking sick of this shit. Thank you. —RT. HON. HINOA, KNIGHT COMMANDER OF THE ORDER (BEG FOR MERCY)17:23, 12 May 2007 (UTC)
- Also, I will be reporting to Ban Patrol anyone that bumps an old forum topic without a damn good reason. -- 17:25, 12 May 2007 (UTC)
- Can't you simply archive and lock old topics? -- herr doktor needsAcell
[scream!] 17:28, 12 May 2007 (UTC)
- ... No. No we:29, 12 May 2007 (UTC)
- Well, there is a way to get it off the forum list.. but it will be harder to find topics that people want to read (that's read, not edit) —Braydie 17:30, 12 May 2007 (UTC)
- I'm with Insineratehymn on this. All ban patrollers should be watching out for pointless forum bump 17:31, 12 May 2007 (UTC)
- I agree, as long we have a big, nasty and colorful template above, as we have on VFD... (that brings me bad memories...). -- herr doktor needsAcell [scream!] 17:33, 12 May 2007 (UTC)
- Well, we can archive topics; it's just that they'll all show the last editor as the admin who archived it and the last edit time as right then. Once DPLforum 3.0 is installed, we'll be able to display the author of each topic and the time it was created, so archiving may become a more attractive option. --Algorithm 22:16, 12 May 2007 (UTC)
- Yeah, but I was thinking of adding a category when the message comes up spang put in. So if it hasn't been edited in a week it removes it from the forum lists via notcategory=. That's possible right? —Braydie 22:19, 12 May 2007 (UTC)
- It's possible, but it wouldn't be very practical, since the category database only gets refreshed when pages are edited (so you'd have to null-edit the forumheader every day). --Algorithm 22:25, 12 May 2007 (UTC)
- Hmm. Is that only null editing the forumheader, or the topics that are over a week old as well? —Braydie 22:27, 12 May 2007 (UTC)
- I'm really not sure; Mediawiki doesn't seem to have any hard-and-fast behavior in this area. All I know is, starting with 1.7, page categories are often refreshed when they contain a newly-edited template (this is why we had to stop using category timestamps with NRV and its ilk). However, I've also seen pages take a long time to update their categories (e.g. with PFP), so it may be based on whether the pages are viewed or purged as well. Go ahead and try it if you want; just be aware that it may not work the way you want it to. --Algorithm 22:34, 12 May 2007 (UTC)
One question...
How exactly are people finding these old topics? Would trar and other recent offenders mind saying? Because you must have to click pretty far back into the forum archive to find them - that admins topic was last edited in August 2006, and to get to it you'd have to skip over several other discussions of the same thing...???
Another suggestion: I think for long topics especially people skip over the "unedited in x days" warning. (At least, I assume they're not doing it deliberately...) Would it be possible to bring it up above the text box when editing such a page? --Whhhy?Whut?How? *Back from the dead* 00:03, 13 May 2007 (UTC)
- I think they are searching in the "Forum:" namespace and getting hits and then replying to the topic and bumping it up. I doubt anyone has the time to scroll through months of forum postings to find one topic they want to reply to, unless they have too much time on their hands. I mean nobody would be that
stupiddedicated because most people are lazy and just use tools like the search feature to save time anyway. What we might need is a script that locks pages from being edited after a month or so in the "Forum:" namespace. --Lt. Sir Orion Blastar (talk) 03:06, 13 May 2007 (UTC)
- No, couldn't do anything like that to the edit page, because in the editing page mediawiki assumes that the last edited date is the current time. Neither can you protect them, as the act of protecting adds a new revision, bumping the topic.
- A more extreme solution: It should be relatively simple to knock together a javascript that will disable edit tab/links on old forum topics. It wouldn't stop someone going to the edit screen directly if the really wanted to edit it, but it should be enough to give nearly everyone the hint. • Spang • ☃ • talk • 06:49, 13 May 2007
- Groovy idea - stops the n00bs in their tracks and allows the rest of us to bump things if we really need to. Out of curiousity, would such a thing be disable-able in our personal javascripts? --Whhhy?Whut?How? *Back from the dead* 23:16, 13 May 2007 (UTC)
Would it be possible to make it so someone could edit an old forum without bumping it? Like, I dunno... maybe an "edit without bumping" button, or something? I know that the answer's probably no, or "yes, but only if you hack up about two years' worth of programming and fix it all yourself," but I just thought I'd throw it out there. --Wehpudicontok--Welcome to Vaporstory! 02:59, 14 May 2007 (UTC)
- Not without taking them out of the forum category so they don't appear in the list at all. That was suggested at some point, but I don't think most people liked that idea.
- You could always create the edit on a different wiki with the date set just after the topic's last post, then export it from there and import it here, and that would probably do what you suggested. It may not though, it's just a guess. Not that you'd want to do that anyway, but what the hey. • Spang • ☃ • talk • 03:57, 14 May 2007
Cause trouble here
/me makes mental note to bump this topic in November.--<<
>> 14:23, 14 May 2007 (UTC)
- But if we make sure that it's edited at least twice a week, it will never be an old topic. Win! -- sannse (talk) 16:40, 14 May 2007 (UTC)
- Well it's old now sannse has edited it. Note to sannse: slap Braydie on IRC. —Braydie 18:45, 14 May 2007 (UTC)
- sannse wants the topic to be like her; well used. Note to sannse: slap Olipro on IRC --:49, 14 May 2007 (UTC)
- Oh, I think I'll wait until I suddenly appear out of nowhere in glorious 3D and slap you then -- sannse (talk) 19:11, 14 May 2007 (UTC)
- We're getting Uncyc in 3D next? I look forward to that update. Will I need special glasses? -- Whhhy?Whut?How? *Back from the dead* 23:14, 14 May 2007 (UTC)
- This is special for Olipro and Braydie and others
that I'm stalking. -- sannse (talk) 10:03, 15 May 2007 (UTC)
- What kind of trouble does the header refer to, funny or just dumb? I can provide the dumb kind ANY TIME!!! Besides, I think bumping old topics requires penisary counteraction. --:40, 7 July 2009 (UTC)
Sooo.....
Whatever happened with this initiative? EugeneKay wuz here (whine thank) 21:04, Thursday 02 July 2009
- 21:06, 2 July 2009 TheLedBalloon (Talk | contribs | block) blocked EugeneKay (Talk | contribs) with an expiry time of 1 day (this) (unblock | change block) -:06, Jul 2
- Lulz. :12, 2 July 2009 (UTC)
- But, couldn't you just protect old forum posts? --Mn-z 04:35, 3 July 2009 (UTC)
- Yes, but that would require doing it. It's far less effort to ban:42, Jul 3
Haaaaa
I cheated!!!-- 17:48, 20 July 2009 (UTC)
- How about commenting a topic for no reason just to keep it from going over 7 days without an edit? Is that allowed? --Mn-z 05:42, 25 July 2009 (UTC)
- Technically, yes; realistically, no. Sartorially, Tuesday. --Algorithm 23:05, 26 July 2009 (UTC)
- Your mother's technical! ... I don't even know what I mean by that... MegaPleb • Dexter111344 • Complain here 23:26, 26 July 2009 (UTC)
This really needs a response.?) 22:36, October 27,. --Pleb SYNDROME CUN medicate (butt poop!!!!) 23:52, October 27,)}" >
What do you mean by bumping?
I had to do it. But serious note - there are forums that really should be archived, and by that I mean moved out of Category:Village Dump and into Category:Archived forum or something of that ilk. I'm thinking anything over a year. Also, with the no bumping - there are a few forums that that rule is not as significant on. (Can't think of them off the top of my head, but the one about why the user name. Or what your real name is. Or that INS one that was mentioned on Chief's page recently.) So I was thinking:
- Have the forums automatically move to Category:Archived forum once they are 120 days+
- Keep the current js thingy Spang had in place.
- Have an
archive=notag added on the forum header template, so that those forums that shouldn't have any issue being bumped are free to remain active
Just to try and keep forum history a little cleaner. And so weirdos who go through old forums and decide to bump them like this are less inclined. • Puppy's talk page • 12:29 29 Mar
- (Block log); 09:10 . . Zombiebaron (talk | contribs | block) blocked PuppyOnTheRadio (talk | contribs) with an expiry time of 1 day -- Brigadier General Sir Zombiebaron 13:10, March 29, 2012 (UTC)
This whole forum
#REDIRECT Irony :24, March 31, 2012 (UTC)
I think there should be an exception.
For Forum:Count to a million because it is ongoing and will hopefully never end. Also, people forget to edit it a lot. ~Pleb 02:47, 04/01/2012 | http://uncyclopedia.wikia.com/wiki/Forum:On_bumping_old_topics?direction=prev&oldid=5467931 | CC-MAIN-2015-27 | refinedweb | 1,742 | 79.7 |
Hello! The attached patch against the CVS version of GRUB (it should apply to GRUB-0.5.92 as well) makes it possible to use the GRUB shell on OS'es other than Linux. Limitations: - Only floppy disks are supported - All floppy disks are assumed to be 1.44 Mb in size (80 cylinders, 2 heads, 18 sectors) - The floppy disk should not be mounted during the installation I have successfully created a bootable floppy under GNU Hurd (i.e. without rebooting) I'm not experienced in low-level file operations, so one may want to use a better method for checking the result of lseek() ChangeLog: * grub/asmstub.c [!__linux__]: compare the result of lseek with the requested position Pavel Roskin
--- grub/asmstub.c Wed Sep 1 10:01:17 1999 +++ grub/asmstub.c Fri Sep 10 02:24:19 1999 @@ -755,7 +755,7 @@ return -1; } #else - if (lseek (fd, sector * SECTOR_SIZE, SEEK_SET)) + if (lseek (fd, sector * SECTOR_SIZE, SEEK_SET) != sector * SECTOR_SIZE) return -1; #endif /* __linux__ */ | https://lists.debian.org/debian-hurd/1999/09/msg00104.html | CC-MAIN-2016-44 | refinedweb | 167 | 63.39 |
C Programming/stdbool.h
< C Programming(Redirected from C Programming/C Reference/stdbool.h)
The header stdbool.h in the C Standard Library for the C programming language contains four macros for a Boolean data type. This header was introduced in C99.
The macros as defined in the ISO C standard are :
- bool which expands to _Bool
- true which expands to 1
- false which expands to 0
- __bool_true_false_are_defined which expands to 1
which can be used in an example
#include <stdio.h> #include <stdlib.h> #include <stdbool.h> int main(void) { bool keep_going = true; // Could also be `bool keep_going = 1;` while(keep_going) { printf("This will run as long as keep_going is true.\n"); keep_going = false; // Could also be `keep_going = 0;` } printf("Stopping!\n"); return EXIT_SUCCESS; }
which will output
This will run as long as keep_going is true. Stopping!
External links[edit]
stdbool.h: boolean type and values – Base Definitions Reference, The Single UNIX® Specification, Issue 7 from The Open Group | https://en.wikibooks.org/wiki/C_Programming/C_Reference/stdbool.h | CC-MAIN-2017-39 | refinedweb | 160 | 51.04 |
C# Sharp Exercises: Find the leap years between to specified years
C# Sharp DateTime : Exercise-28 with Solution
Write a C# Sharp program to find the leap years between 1994 and 2016.
Note : Use IsLeapYear method.
Sample Solution:-
C# Sharp Code:
using System; public class Example28 { public static void Main() { for (int year = 1995; year <= 2016; year++) { if (DateTime.IsLeapYear(year)) { Console.WriteLine("{0} is a leap year.", year); DateTime leapDay = new DateTime(year, 2, 29); DateTime nextYear = leapDay.AddYears(1); Console.WriteLine(" One year from {0} is {1}.", leapDay.ToString("d"), nextYear.ToString("d")); } } } }
Sample Output:
1996 is a leap year. One year from 2/29/1996 is 2/28/1997. 2000 is a leap year. One year from 2/29/2000 is 2/28/2001. 2004 is a leap year. One year from 2/29/2004 is 2/28/2005. 2008 is a leap year. One year from 2/29/2008 is 2/28/2009. 2012 is a leap year. One year from 2/29/2012 is 2/28/2013. 2016 is a leap year. One year from 2/29/2016 is 2/28/2017.
Flowchart :
C# Sharp Code Editor:
Improve this sample solution and post your code through Disqus
Previous: Write a C# Sharp program to determine the type of a particular object.
Next: Write a C# Sharp program to convert the specified string representation of a date and time to its DateTime equivalent using the specified array of formats, culture-specific format information, and style.
What is the difficulty level of this exercise?
New Content: Composer: Dependency manager for PHP, R Programming | https://www.w3resource.com/csharp-exercises/datetime/csharp-datetime-exercise-28.php | CC-MAIN-2019-18 | refinedweb | 266 | 77.84 |
compilation warning with Min
GW32 in pratom .h
RESOLVED FIXED in 4.8.1
Status
--
trivial
People
(Reporter: gk, Assigned: wtc)
Tracking
Firefox Tracking Flags
(Not tracked)
Details
Attachments
(1 attachment)
User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; de; rv:1.9.0.13) Gecko/2009080200 SUSE/3.0.13-0.1.2 Firefox/3.0.13 Build Identifier: NSPR 4.8.0 Since MinGW32 also defines _WIN32 line 113 of pratom.h gives this warning: include/nspr4/pratom.h:113:71: warning: "_MSC_VER" is not defined the following simple patch fixes this warning: --- pratom.h.orig 2009-07-01 00:11:46.000000000 +0200 +++ pratom.h 2009-09-07 16:51:39.000000000 +0200 @@ -110,7 +110,7 @@ ** the macros and functions won't be compatible and can't be used ** interchangeably. */ -#if defined(_WIN32) && !defined(_WIN32_WCE) && (_MSC_VER >= 1310) +#if defined(_WIN32) && !defined(_WIN32_WCE) && defined(_MSC_VER) && (_MSC_VER >= 1310) long __cdecl _InterlockedIncrement(long volatile *Addend); #pragma intrinsic(_InterlockedIncrement) IMO the first check for _WIN32 can be ommited because the check for _MSC_VER should be sufficient. Reproducible: Always Steps to Reproduce: 1. compile a source which includes nspr.h with MinGW32. Actual Results: include/nspr4/pratom.h:113:71: warning: "_MSC_VER" is not defined Expected Results: no warnings.
Thanks for the bug report and the patch. It is legal to use an undefined macro in a conditional expression like "MSC_VER >= 1310". The undefined macro gets the value 0L. Do you know why MinGW32 warns about this? Are you compiling with a very strict warning flag?
Status: UNCONFIRMED → ASSIGNED
Ever confirmed: true
Hi Wan-Teh, (In reply to comment #1) > Do you know why MinGW32 warns about this? Are you compiling > with a very strict warning flag? yes, -Wundef triggers it; but if I develop I think its a valid desire to see as much warnings as possible; sure I know that I can ignore the warning in this case. But think of doing autobuilds of a project from cvs / svn / git repository - then you want to see if any recent commits made something break, and then you want to get an automatic message if the autobuild was not warning-free. This is currently not possible with an app which is a NSS consumer. thanks, Günter.
Thanks for the info. I checked the GCC 4.4.1 manual: -Wundef is not turned on by either -Wall or -Wextra. So it is a rarely used compiler flag. Are you sure you want to use -Wundef? We write _MSC_VER >= 1310 intentionally, taking advantage of C preprocessor's rule of giving an undefined macro a value of 0L in an #if conditional expression. I am sure we're not alone. -Wundef also warns about the following code: #if HAVE_FOO extern int foo(void); #endif I think this kind of code is also common (we write #ifdef HAVE_FOO for such code). So I think you'll get a lot of warnings if you turn on -Wundef. In summary, I will check in your patch, but this kind of code is likely to creep back in, and I suggest that you not compile with -Wundef. Do you control the makefile that uses -Wundef?
Hi Wan-Teh, (In reply to comment #3) > So it is a rarely used compiler flag. Are you sure > you want to use -Wundef? yes. It is very useful to detect typos. > We write _MSC_VER >= 1310 > intentionally, taking advantage of C preprocessor's > rule of giving an undefined macro a value of 0L in > an #if conditional expression. I am sure we're not > alone. from what I currently see you are: no other SSL library, and no kernel headers have such; and the reason why you dont get more BZs is simply because this problem only occurs with MinGW32, and no other compiler; I bet that you would get BZs about such a thing if it would be triggered on any Linux platform. > -Wundef also warns about the following code: > > #if HAVE_FOO > extern int foo(void); > #endif correct, and that is also bad coding style - instead use: #if defined(HAVE_FOO) && (HAVE_FOO > 0) if you want to test for the value of HAVE_FOO ... > I think this kind of code is also common (we write > #ifdef HAVE_FOO for such code). So I think you'll > get a lot of warnings if you turn on -Wundef. nope, only the one in the NSPR header I mentioned in this BZ so far. > In summary, I will check in your patch, but this thank you! > kind of code is likely to creep back in, and I no prob - I file another BZ then :) > suggest that you not compile with -Wundef. Do > you control the makefile that uses -Wundef? well, I'm member of a couple of projects, and such things would then be proposed, and commonly decided - but since I personally dont agree that removing -Wundef is a good idea since it helped already in the past to catch macro typos I will not suggest such a change. What downside do you see to let the pre-processor first check if a macro is defined before you check for its value? Also it might the true for gcc that undefined macros are automatically assigned 0L - but are you 100% sure that this is true for each and every compiler in the wild? Again, thanks for changing it.
The default value of 0L for an undefined macro is specified by the C language. For example, in K & R's "The C Programming Language," 2nd Ed., it is specified in Section A 12.5 on page 232: Any identifiers remaining after macro expansion are replaced by 0L. We write expressions like (_MSC_VER >= 1310) because they're more concise than defined(_MSC_VER) && (_MSC_VER >= 1310) Sometimes, this allows us to stay within 80 characters and avoid wrapping a long line.
I checked in this patch on the NSPR trunk (NSPR 4.8.1). Checking in pratom.h; /cvsroot/mozilla/nsprpub/pr/include/pratom.h,v <-- pratom.h new revision: 3.12; previous revision: 3.11 done
Attachment #400316 - Flags: review+
Severity: normal → trivial
Status: ASSIGNED → RESOLVED
Closed: 10 years ago
Resolution: --- → FIXED
Target Milestone: --- → 4.8.1 | https://bugzilla.mozilla.org/show_bug.cgi?id=515064 | CC-MAIN-2019-30 | refinedweb | 1,027 | 74.39 |
Meet self
In Python we have functions and methods.
Function definitions in Python look like this:
def sloganify(x): return "{} or bust!".format(x)
And method definitions look like this:
class Person: def sloganize(self, x): return "{} or bust!".format(x)
Classes are buckets of functions
When we write Python code, we don’t really write methods; we write class statements which contain function definitions.
Class statements look like this:
class Person: greeting = 'hello' x = 4 + 3
which is syntactic sugar for something like this:
Person = type("Person", (), {'greeting': 'hello', 'x': 4 + 3})
So writing a class with a method
class Foo: def bar(x, y, z): return 7
is about the same as writing
def bar_function(x, y, z): return 7 Foo = type("Foo", (), {'bar': bar_function}) del bar_function
We can also write this as
def bar_function(x, y, z): return 7 Foo = type("Foo", (), {}) Foo.bar = bar_function del bar_function
Method objects in Python
Despite all those examples trying to show that we write functions, not methods in Python, both function and method objects do exist:
>>> f = Foo() >>> f.bar <bound method bar_function of <__console__.Foo object at 0x113644128>> >>> bar_function # if we forgo the `del bar_function` above <function bar_function at 0x1135e66a8>
Besides having different names, these two different versions of the function we wrote take different numbers of arguments!
>>> import inspect >>> inspect.signature(bar_function) <Signature (x, y, z)> >>> inspect.signature(f.bar) <Signature (y, z)>
Is this some kind of class definition-time transformation? No, the function is indeed what gets stored in the class!
>>> Foo.bar <function bar_function at 0x1135e66a8>
Besides, the method objects we get from different instances are completely different:
>>> f.bar <bound method bar_function of <__console__.Foo object at 0x113644128>> >>> g.bar <bound method Foo.bar of <__console__.Foo object at 0x10a41a710>>
Maybe the method object is created when we create an instance of the class, and stored on the instance object!
>>> vars(f) {}
Hm, I don’t see it anywhere…
Partial Application
The “one less argument” thing is familiar to people who use Python classes and have seen this perplexing error message:
>>> f.bar(1, 2, 3) Traceback (most recent call last): File "<input>", line 1, in <module> f.bar(1, 2, 3) TypeError: bar() takes 3 positional arguments but 4 were given
But I did pass three arguments! Perhaps you see where this is going. A method is a version of a function that takes one less argument, an example of the technique of “partial application.” Say we have the general rectangle drawing function below:
def draw_rect(color, width, height, x, y): """Draws a rectangle""" ...
If we wanted to make a specialized version of this function for drawing small blue square, we might write a new function that calls this old version:
def draw_small_blue_square(x, y): """Draws a small blue square at the passed coordinates""" draw_rect('blue', 2, 2, x, y)
To be more concise and to avoid the extra layer of call stack in our error message stack traces we could use partial application instead:
>>> import functools >>> draw_large_red_square = functools.partial(draw_rect, 'red', 100, 100)
In this version we didn’t write a docstring or a new signature ourselves.
inspect.signature is smart enough to tell how to use this function:
>>> inspect.signature(draw_large_red_square) <Signature (x, y)>
but unfortunately our error message still refers to the original version of the function:
>>> draw_large_red_square(1, 2, 3) Traceback (most recent call last): File "<input>", line 1, in <module> draw_large_red_square(1, 2, 3) TypeError: drawRect() takes 5 positional arguments but 6 were given
Partial application can be really convenient!
>>> force_print = functools.partial(print, file=sys.stderr, flush=True) >>> intdict = functools.partial(collections.defaultdict, int)
Based on the similarity of these error messages, you might thing that this
method version of the function is implemented with by using
functools.partial to partially apply the
instance to the first parameter of the original function object. Good guess!
I looked at the CPython code and it’s not. But the behavior is similar, it’s sort
of a special, written-in-C, optimized version of this.
Method binding rocks
So that’s what’s going on: Python is creating a method object that takes one less argument (and now holds a reference to the instance from which we got it) from our our original Python function.
So method binding lets us write what could have been the clunky
f = Foo() Foo.bar(f, 2, 3)
as
f = Foo() f.bar(2, 3)
with both namespacing (the
f instance looks up to its class to find
this function) and method binding (we don’t have to re-specify the first
argument of
f.
This is creation of a bound method at attribute lookup time isn’t the only way
to make methods work: in JavaScript, to transformation of the function occurs
at function lookup time. To which object
this (JavaScript’s
self) refers
depends on the syntax used to call it instead. This is often undesirable,
so the function is often transformed with
bind.
Why is Python’s behavior preferable?
>>> distances = {'5k': 5000, 'mile': 1609.34, 'marathon': 42195} >>> distances.keys().sort(key=distances.get) >>> import threading >>> t = threading.thread(target=crawler.crawl) >>> t.start()
Because callbacks - one of the words used to describe passing a function as a value.
Sometimes Python apis expect a something callable as a passed argument.
We could wrap it in another layer of function,
.sort(lambda x: distance.get(x))
in the first example above, but it’s nice not to have to.
That pattern is more common in JavaScript:
> setTimeout(foo.bar) # bar won't be called correctly > setTimeout(function(){ foo.bar() });
How it happens: the descriptor protocol
So method binding is cool. And a bit mysterious: somehow attribute lookup is
more complicated that we suspected, because it’s somehow causing a method
to be created!
It seems like looking for the attribute
bar on an instance
f would require traversing a chain like
instance -> class -> parent class -> ... -> object
and returning the first matching attribute on one of these objects. I remember being stunned to discover this simple model did not reflect reality.
In fact the value returned from this process may instead be the result of arbitrary code by implementing something known as the descriptor protocol. Although the code for creating methods is written in C, the power of descriptors is available to use in Python, so let’s explore it from that direction.
If an attribute implements the descriptor protocol, it will have
a
__get__() method defined which will be called with information
about the lookup and the result returned as the result of the
attribute lookup.
>>> class ImADescriptor(): # because I have a __get__ method ... def __get__(self, instance, owner): ... return 7 ... >>> class Foo(): ... bar = ImADescriptor() ... >>> f = Foo() >>> f.bar 7
The
__get__ method is called by Python infernal (whoops, internal)
attribute lookup logic in
ceval.c
with a reference to the object that the attribute lookup started on so
it can be used to create our bound method.
It turns out that functions implement this descriptor protocol!
Take a look at the
__get__ method on a function:
>>> drawRect.__get__ <method-wrapper '__get__' of function object at 0x114414268>
If we were writing out that method in Python, it might look something like
class Function(): def __get__(self, instance, owner): return functools.partial(self, instance)
So that’s how methodization works in Python! | http://ballingt.com/python-methods/ | CC-MAIN-2018-34 | refinedweb | 1,229 | 63.09 |
Thanks.
So it seems I have to write my own code, there in nothing like I can set some flag.
So if that is the case shouldn't I just be gzipping and unzipping data write and read to request object.
rgds anurag
----- Original Message ---- From: David Bolen db3l.net@gmail.com To: twisted-python@twistedmatrix.com Sent: Friday, October 19, 2007 1:02:21 AM Subject: [Twisted-Python] Re: Content Encoding : gzip ?
anurag uniyal anuraguniyal@yahoo.com writes:
Is it possible to send and recieve compressed content using twisted.web?
I have set Accept-encoding to gzip but it doesn't make any difference. Will I have to cater for this myself?
Yes, in twisted.web. In twisted.web2, there's a filter that supports it.
Here's a small wrapper class I wrote recently that I've used to handle this in twisted.web, with the goal of minimal changes to existing resource code. I use it by noticing, in the original request handler, the ability to handle gzip encodings, and then wrap the original request in this class (since there's no built-in filtering of the output stream in twisted.web).
It's worked fine in my tests to date, and in limited production use, but to be honest it hasn't seen large scale, long term use because my original use case only yielded ~15% compression (multimedia files) and using this negates the ability to know the full length in advance, thus clients can't give projected download times. (My files are large enough that compressing twice is high overhead, and it wouldn't play well with the wrapper approach anyway).
In any event, hopefully it'll be a useful starting point for you.
Here's the wrapper:
- - - - - - - - - - - - - - - - - - - - - - - - -) if cdata: self.request.write(cdata) elif self.request.producer: # Simulate another pull even though it hasn't really made it # out to the consumer yet. self.request.producer.resumeProducing()
def finish(self): remain = self.compress.flush() self.csize += len(remain) if remain: self.request.write(remain) self.request.write(struct.pack('<LL', self.crc & 0xFFFFFFFFL, self.size & 0xFFFFFFFFL)) self.request.finish()
- - - - - - - - - - - - - - - - - - - - - - - - -
and here's a sample of using it. This code is from one of my Resource objects - if I were to use it more generally in my site I'd extract that into a mix-in class of some sort - currently there was only one specific resource (the multimedia files) I wanted to support it for:
def render_GET(self, request):
# (... argument validation ...)
accept_encoding = request.getHeader('accept-encoding') if accept_encoding: encodings = accept_encoding.split(',') for encoding in encodings: name = encoding.split(';')[0].strip() if name == 'gzip': request = GzipRequest(request) break
# At this point, use 'request' as normal
-- David
_______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com
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Data Structures for Drivers
no-involuntary-power-cycles(9P)
usb_completion_reason(9S)
usb_other_speed_cfg_descr(9S)
usb_request_attributes(9S)
- SPARC DMA limits structure
#include <sys/ddidmareq.h>
Solaris SPARC DDI specific (Solaris SPARC DDI). These interfaces are obsolete.
This page describes the SPARC version of the ddi_dma_lim structure. See ddi_dma_lim_x86(9S) for a description of the x86 version of this structure.
A ddi_dma_lim structure describes in a generic fashion the possible limitations of a device's DMA engine. This information is used by the system when it attempts to set up DMA resources for a device.
uint_t dlim_addr_lo; /* low range of 32 bit addressing capability */ uint_t dlim_addr_hi; /* inclusive upper bound of address. capability */ uint_t dlim_cntr_max; /* inclusive upper bound of dma engine address limit * / uint_t dlim_burstsizes; /* binary encoded dma burst sizes */ uint_t dlim_minxfer; /* minimum effective dma xfer size */ uint_t dlim_dmaspeed; /* average dma data rate (kb/s) */
The dlim_addr_lo and dlim_addr_hi fields specify the address range the device's DMA engine can access. The dlim_addr_lo field describes the lower 32–bit boundary of the device's DMA engine, the dlim_addr_hi describes the inclusive upper 32–bit boundary. The system allocates DMA resources in a way that the address for programming the device's DMA engine (see ddi_dma_cookie(9S) or ddi_dma_htoc(9F)) is within this range. For example, if your device can access the whole 32–bit address range, you may use [0,0xFFFFFFFF]. If your device has just a 16–bit address register but will access the top of the 32–bit address range, then [0xFFFF0000,0xFFFFFFFF] is the right limit.
The dlim_cntr_max field describes an inclusive upper bound for the device's DMA engine address register. This handles a fairly common case where a portion of the address register is only a latch rather than a full register. For example, the upper 8 bits of a 32–bit address register can be a latch. This splits the address register into a portion that acts as a true address register (24 bits) for a 16 Mbyte segment and a latch (8 bits) to hold a segment number. To describe these limits, specify 0xFFFFFF in the dlim_cntr_max structure.
The dlim_burstsizes field describes the possible burst sizes the device's DMA engine can accept. At the time of a DMA resource request, this element defines the possible DMA burst cycle sizes that the requester's DMA engine can handle. The format of the data is binary encoding of burst sizes assumed to be powers of two. That is, if a DMA engine is capable of doing 1–, 2–, 4–, and 16–byte transfers, the encoding ix 0x17. If the device is an SBus device and can take advantage of a 64–bit SBus, the lower 16 bits are used to specify the burst size for 32–bit transfers and the upper 16 bits are used to specify the burst size for 64–bit transfers. As the resource request is handled by the system, the burstsizes value can be modified. Prior to enabling DMA for the specific device, the driver that owns the DMA engine should check (using ddi_dma_burstsizes(9F)) what the allowed burstsizes have become and program the DMA engine appropriately.
The dlim_minxfer field describes the minimum effective DMA transfer size (in units of bytes). It must be a power of two. This value specifies the minimum effective granularity of the DMA engine. It is distinct from dlim_burstsizes in that it describes the minimum amount of access a DMA transfer will effect. dlim_burstsizes describes in what electrical fashion the DMA engine might perform its accesses, while dlim_minxfer describes the minimum amount of memory that can be touched by the DMA transfer. As a resource request is handled by the system, the dlim_minxfer value can be modified contingent upon the presence (and use) of I/O caches and DMA write buffers in between the DMA engine and the object that DMA is being performed on. After DMA resources have been allocated, the resultant minimum transfer value can be gotten using ddi_dma_devalign(9F).
The field dlim_dmaspeed is the expected average data rate for the DMA engine (in units of kilobytes per second). Note that this should not be the maximum, or peak, burst data rate, but a reasonable guess as to the average throughput. This field is entirely optional and can be left as zero. Its intended use is to provide some hints about how much of the DMA resource this device might need.
See attributes(5) for descriptions of the following attributes:
ddi_dma_addr_setup(9F), ddi_dma_buf_setup(9F), ddi_dma_burstsizes(9F), ddi_dma_devalign(9F), ddi_dma_htoc(9F), ddi_dma_setup(9F), ddi_dma_cookie(9S), ddi_dma_lim_x86(9S), ddi_dma_req(9S) | http://docs.oracle.com/cd/E23824_01/html/821-1478/ddi-dma-lim-9s.html | CC-MAIN-2014-15 | refinedweb | 761 | 51.78 |
KmPlot
#include <function.h>
Detailed Description
Uniquely identifies a single plot (i.e.
a single curvy line in the View).
Definition at line 589 of file function.h.
Constructor & Destructor Documentation
Definition at line 981 of file function.cpp.
Member Function Documentation
The color that the plot should be drawn with.
Definition at line 1151 of file function.cpp.
Converts the plotMode to the derivative number, e.g.
Function::Derivative1 -> 1, and Function::Integral -> -1
Definition at line 1175 of file function.cpp.
Changes the plotMode equivalent to differentiating.
Definition at line 1097 of file function.cpp.
- Returns
- a pointer to the function with ID as set by setFunctionID
Definition at line 609 of file function.h.
Definition at line 605 of file function.h.
Changes the plotMode equivalent to integrating.
Definition at line 1124 of file function.cpp.
Generates a name appropriate for distinguishing the plot from others.
Definition at line 1014 of file function.cpp.
Definition at line 992 of file function.cpp.
- Returns
- the value of the parameter associated with this plot.
Definition at line 1055 of file function.cpp.
Definition at line 1001 of file function.cpp.
- Returns
- the differential state for the plot (or 0 if no state).
Definition at line 1196 of file function.cpp.
Definition at line 1008 of file function.cpp.
Updates the current working parameter value in the function that this plot is for and the plus-minus signature for the function's equations.
Definition at line 1040 of file function.cpp.
Member Data Documentation
Cached pointer to function.
Definition at line 671 of file function.h.
ID of function.
Definition at line 670 of file function.h.
Definition at line 625 of file function.h.
Which derivative.
Definition at line 629 of file function.h.
Assigned when Function::allPlots() is called.
The plots for each plotMode are numbered 0 to *.
Definition at line 639 of file function.h.
The total number of plots of the same plotMode as this.
Definition at line 643 of file function.h.
For equations containing a plus-minus symbols, this indicates whether to take the plus or the minus for each one.
The list is for each equation of the function (so typically, the list will only be of size one, but parametric functions will have two).
Definition at line 665 of file function.h.
For differential equations, which state to draw.
It's probably easier to use the function differentialState(), however.
Definition at line 654 of file function.h.
The documentation for this class was generated from the following files:
Documentation copyright © 1996-2020 The KDE developers.
Generated on Fri Jan 17 2020 03:39:07 by doxygen 1.8.7 written by Dimitri van Heesch, © 1997-2006
KDE's Doxygen guidelines are available online. | https://api.kde.org/4.x-api/kdeedu-apidocs/kmplot/kmplot/html/classPlot.html | CC-MAIN-2020-05 | refinedweb | 461 | 53.68 |
Documentazione di Drawing
Questa pagina documenta la comprensione del modulo Drawing di jcc242. Il modulo include i file e le funzioni su cui sta lavorando attualmente e non può ancora essere inserita nel ramo master. La fonte di questi file è il suo Github, ma fate attenzione in quanto è molto instabile!
Base (Mod/Drawing)
gdtsvg.py
Python script that generates svg snippets for things such as gd&t symbols, dimension symbols, and basic svg elements such as lines, circles, and paths.
It has several support files that don't really do much. Run DrawingTest.py to create a bunch of svg icons in the icon directory that previews various icons in the gdtsvg.py file. settingslist.py and dimesettings, and convert.py are all deprecated from older settings methods and should probably be removed as the Drawing branch approaches merging into master.
DrawingAlgos.py
Creates svg lines from a list of vertices, supports both hidden and visible edges. Should probably be merged with gdtsvg.py as that file matures.
createSVG
Accepts part as an argument, projects the part into lines from the Drawing.project object and then draws creates the svg for each line.
App
Contains the backend side of the drawing module.
AppDrawing.cpp
Initializes the various namespaces and modules and stuff used in the drawing module. Will throw an error if it cannot load the Part module.
DrawingExport.cpp
Two classes: SVGOutput and DXFOutput. They both contain methods to put out the code in their respective language. Typically require an object of the appropriate typedef, and sometimes some additional identifier information.
FeatureClip.cpp
Callback (?) methods for the feature clipping gui, so it would seem. Called alone it will create the clip path, if ShowFrame.getValue is TRUE set it will show the frame border as well.
FeaturePage.cpp
Manages the views.
onChanged() for doing stuff when properties get changed.
execute() for recalculating a feature view, or so it claims. It seems to have stuff for checking for editable texts and saving drawings. Need to investigate further.
getEditableTextsFromTemplate() for retrieving text that can be edited by FreeCAD from an SVG file.
FeatureProjection.cpp
Flattens object to a 2D image?
FeatureView.cpp
Defines the properties for views.
FeatureViewAnnotation.cpp
Defines properties for annotations (right now just text), has an execute method to update the text if changed/moved.
FeatureViewPart.cpp
Constructor to add properties. Gets appearance stuff for projected parts.
PageGroup.cpp
Just adds a property for a list of pages, does not much else.
Precompiled.cppp
Just #include "PreCompiled.h"
ProjectionAlgos.cpp
The constructor just runs the execute() method to update it's stuff
invertY: since SVG does its y-axis backwards to every other coordinate system in the world, we must invert it when converting from a FreeCAD part to an SVG projection for the Drawing view.
getSVG: fetches the SVG code from the DrawingExport stuff. Formats depending on type of line (hidden or not and some other stuff I need to figure out).
getDXF: same as getSVG except for DXF format.
Gui
AppDrawingGui.cpp
Initializes the drawing gui.
AppDrawingGuiPy.cpp
Provides opening, importing, and exporting interfaces? Looks like it is python accessible.
Command.cpp
Handles commands (from the toolbar?) such as creating new drawings and stuff. It looks like this handles QT calls from clicking the button to whatever command it needs to go to e.g. clicking the CmdDrawingOrthoViews button will show the Ortho views gui in the task dialog spot.
DrawingView.cpp
Does a bunch of qt gui stuff, need to read more on it.
TaskDialog.cpp
Creates the task dialog thing on the side and probably switches to it from the tree view, as appropriate.
TaskOrthoViews.cpp
Creates the task dialog for placing the orthographic views!
Does a lot of the calculations for where to position stuff (automatic calculations as well, it seems).
Takes the input from the TaskOrthoViews gui and does stuff with it. Uses the single inheritance method talked about on the qt website.
ViewProviderPage.cpp
Constructor adds some properties for the view stuff. Destructor does nothing. Attaches something (attaches what? attaches the view to the page?) sets and gets display modes (what are display modes? what do they do and what are possible options?) Does something about updating some kind of data has a context menu that says "Show drawing", figure out what this means Has a thing for double clicking to select the view (I think?)
showDrawingView seems to do some work on settings things up: gets the current document, sets the window icon and title, adds it to the main window (of FreeCAD?)
ViewProviderView.cpp
Doesn't seem to do much, though I am sure it is important.
Workbench.cpp
Adds the icons to the toolbars and stuff.
Workflow
Program Flow
CanvasView is the actual QGraphicsScene object and DrawingView processes a list of FeatureView that are linked by reference in /App/FeatureViewPage. DrawingView then chooses the appropriate QGraphicsItem class (QGraphicsItemViewPart or QGraphicsItemViewDimension) and then calls a function in CanvasView to create this and add it to the scene.
Adding commands to the Drawing Workbench
4 simple steps:
- Add a class to Command.cpp. Follow the others for an example of the formatting.
- Add a title, icon, tooltip, etc., again, follow the existing classes in command.cpp
- Add your class to the bottom of Command.cpp
- Add your information to Workbench.cpp, this will tell FreeCAD/Drawing module where to place the icons defined in command.cpp in the actual freecad interface (the toolbars, dropdowns, etc.) | https://wiki.freecadweb.org/Drawing_Documentation/it | CC-MAIN-2021-49 | refinedweb | 917 | 59.4 |
import "github.com/gobuffalo/plush/plush/cmd"
var RootCmd = &cobra.Command{ Use: "plush", Short: "A brief description of your application", RunE: func(cmd *cobra.Command, args []string) error { if len(args) == 0 { return errors.New("you must pass in at least 1 plush file") } for _, a := range args { b, err := ioutil.ReadFile(a) if err != nil { return err } err = plush.RunScript(string(b), plush.NewContext()) if err != nil { return err } } return nil }, }
RootCmd represents the base command when called without any subcommands
Execute adds all child commands to the root command and sets flags appropriately. This is called by main.main(). It only needs to happen once to the rootCmd.
Package cmd imports 6 packages (graph) and is imported by 1 packages. Updated 2019-05-13. Refresh now. Tools for package owners. | https://godoc.org/github.com/gobuffalo/plush/plush/cmd | CC-MAIN-2019-30 | refinedweb | 133 | 70.39 |
Suppose we have an array A of numbers, we have to find all indices of this array so that after deleting the ith element from the array, the array will be a good array. We have to keep in mind that −
So, if the input is like [10, 4, 6, 2], then the output will be [1,4] as when we remove A[1], the array will look like [4, 6, 2] and it is good, as 6 = 4+2. If we delete A[4], the array will look like [10, 4, 6] and it is also good, as 10 = 4+6.
To solve this, we will follow these steps −
Let us see the following implementation to get better understanding −
from collections import defaultdict def find_indices(A): n = len(A) add = 0 my_map = defaultdict(lambda:0) for i in range(n): my_map[A[i]] += 1 add += A[i] for i in range(n): k = add - A[i] if k % 2 == 0: k = k >> 1 if k in my_map: if ((A[i] == k and my_map[k] > 1) or (A[i] != k)): print((i + 1)) A = [10, 4, 6, 2] find_indices(A)
[10, 4, 6, 2]
1 4 | https://www.tutorialspoint.com/find-all-good-indices-in-the-given-array-in-python | CC-MAIN-2021-25 | refinedweb | 196 | 69.59 |
24 March 2010 16:28 [Source: ICIS news]
SAO PAULO (ICIS new)--Europe needs to develop its own production of biofuels and not rely on imports of ethanol from Brazil to meet its renewable fuels targets, the European Bioethanol Fuel Association (eBio) said on Wednesday.
“Don't send your ethanol to Europe...we don't need it,” said e-Bio director Robert Vierhout during a presentation at FO Licht’s Sugar and Ethanol Brazil 2010 in Sao Paulo (see video below).
The remark echoed a statement Vierhout made in 2009, when he said ?xml:namespace>
The statement last year drew an immediate reaction by Unica, which said e-Bio was fundamentally wrong on trade.
Unica has waged a fierce campaign against trade barrier imposed by the US and Europe, but Vierhout has downplayed that, saying at an industry event last month that Brazil already has access to every market and holds 50% of the international trade.
It is also an agricultural issue and a matter of promoting technological development in
The 2010 Sugar | http://www.icis.com/Articles/2010/03/24/9345539/biofuels-group-tells-brazil-to-keep-ethanol-out-of-eu-video.html | CC-MAIN-2014-23 | refinedweb | 173 | 56.18 |
Discover node properties with node-set-provision-state¶
Blueprint URL:
This proposal adds the ability to perform out-of-band node inspection and automatically update node properties using node-set-provision-state (new target ‘inspect’) process. The same set of APIs can be used by in-band properties discovery too.
Problem description¶
Today, Ironic is unable to automatically detect node properties which are required for scheduling or for deploy (ports creation).
The properties required by scheduler/deploy:
memory size
Disk Size
CPU count
CPU Arch
NIC(s) MAC address
Proposed change¶
The spec proposes to add these abilities:
Discover the hardware properties and update the node.properties. It update all the properties with the new set values, even if the values were already set.
Create ports for the NIC MAC addresses discovered. This will be done automatically after the NICS are discovered with above step. If a port already exists, it will not create a new port for that MAC address. It will take care of adding as well as deleting of the ports for the NIC changes. The ports no longer associated with the node at the time of discovery will be auto deleted. Ideally the ports shall be created for PXE enabled mac addresses, however it is each driver responsibility to get list of pxe enabled mac addresses from the hardware.
Following would be done to achieve properties inspection:
A new target ‘inspect’ would be added to the end point provision /v1/nodes/<uuid>/states/provision
When inspection is finished, puts node.provision_state as MANAGED and node.target_provision_state as None.
The possible new states are: INSPECTING, INSPECTFAIL, MANAGED, INSPECTED.
Refer to [1] for more details on each state.
Initial state : node.provision_state = INSPECTING node.target_provision_state = INSPECTED
On Success: Final State : node.provision_state = MANAGED node.target_provision_state = None
On Failure: Final State: node.provision_state = INSPECTFAIL node.target_provision_state = None And the error is updated at the last error.
The provision state will be marked as INSPECTFAIL if any of the properties (scheduler required properties) could not be inspected. In this case, no properties will be updated. So its either all or none.
A node must be in MANAGED state before initiating inspection.
The properties values will be overwritten with every invocation of discovery APIs. It is done so because there may be addition/deletions in the hardware between two invocations of the discovery CLI/APIs.
Implement timeouts for inspection. There should be a periodic task in the conductor, checking that every mapped node is not in INSPECTING state for more then
inspect_timeout. This will be added as a config option in /etc/ironic/ironic.conf.
The Node.properties introspected properties will be updated whenever introspection is executed.
Hardware properties to be discovered:¶
The following properties would be discovered :
NICs mac addresses
cpus
cpu_arch
local_gb
memory_mb
The NICs data would be used to auto-create the ports. The other properties are mandatory properties for the scheduler, hence will be updated in Node.properties field.
Alternatives¶
The discovery can be initiated by node-create with single request to the API as below:
POST /v1/nodes/?discover=true :
In this, it requires the Nodes.post to be completely asynchronous. This would be a compatibility break for node-create as it requires a node object to be returned back. On the other hand, if discovery is done synchronously then Nodes.post will become slow. In this if Nodes.post still returns the node object without properties updated to the CLI and still do discovery in the background then Nodes.post becomes half synchronous and half asynchronous, then it will be wrong for REST API structure as the REST API shall be either synchronous or asynchronous. Hence, here node-create becomes partly synchronous and partly asynchronous. Given above reasons, this approach is not chosen.
The auto-discovery can also be used for discovering node properties but it also doesn’t provide the ability to discover properties at node-create and node-set-provision-state.
Data model impact¶
The discovered properties will be stored as part of the ‘properties’ field of the node. It will add two fields to the nodes table:
last_inspected: It will be updated with time (when last inspection finished).
inspection_started_at: It will store the start time of invocation of inspection. This will be required to calculate the inspection_timeout. It shall be cleared out after inspection finishes or timeout.
Ironic CLI impact¶
The node-set-provision-state target ‘inspect’ need to be defined. The synopsis will look like:
usage: ironic node-set-provision-state <UUID> inspect
REST API impact¶
The endpoint ‘provision’ will be enhanced with a new target:
PUT /v1/nodes/<uuid>/states/provision {“target”: “inspect”}
Changes provision_state as INSPECTING.
Changes target_provision_state as INSPECTED.
Method type: PUT
Normal response code: 202
Expected errors:
404 if the node with <uuid> does not exist.
400 if a conductor for the node’s driver cannot be found.
409 CONFLICT, if the node cannot be transitioned to INSPECTING state.
URL: /v1/nodes/<uuid>/states/provision {“target”: “inspect”}
URL parameters: None.
Response body is empty if successful.
When inspection is finished, puts node.provision_state as MANAGED and node.target_provision_state as None.
RPC API impact¶
A new rpcapi method inspect_hardware() will be added. It will be synchronous call to the conductor and will spawn a worker thread to perform discovery. This will allow the API service to receive the acknowledgement from the conductor that the inspecting has been initiated and returns status 202 to the client.
Driver API impact¶
It will add new interface InspectInterface with the method inspect_hardware():
def inspect_hardware(self, task): """Inspect hardware. :param task: a task from TaskManager. """
A driver may choose to implement the InspectInterface.
Since InspectInterface is a standard interface, following methods will also be added:
validate()
get_properties()
Other end user impact¶
This feature will improve user experience as users no longer need to manually update the node properties info.
Other deployer impact¶
The
inspect_timeout is introduced in the ironic.conf under
conductor. The default value for same shall be 1800 secs as
required by in-band implementations.
Implementation¶
Assignee(s)¶
- Primary assignee:
Nisha Agarwal (launchpad ID: agarwalnisha1980, IRC login ID: Nisha)
- Other Contributors:
Wan-Yen Hsu (launchpad ID : wan-yen-hsu, IRC login ID: wanyen)
Work Items¶
A new rpcapi method inspect_hardware() is added which will invoke the InspectInterface for discovering, updating node properties and creating/updating ports.
Add a new interface as InspectInterface to ironic driver.
Adding new method inspect_hardware to class InspectInterface.
Add new elements
last_inspectedand
inspection_started_atto the nodes table. Ironic cli will be changed to show these fields while running
ironic node-show.
The node.last_inspected will be updated with the last discovered time.
The node.inspection_started_at will be updated with the time when inspection was initiated. This will help to check the timeout for inspection. The periodic task needs to be created for the same.
The reference implementation will be done for iLO drivers.
Add a new target ‘inspect’ to node-set-provision-state for updating the hardware properties for already registered node.(ironic-client changes)
Dependencies¶
Requires implementation of for the states MANAGED, INSPECTED, INSPECTING and INSPECTFAIL.
Testing¶
Unit tests will be added conforming to ironic testing requirements. The test suites for tempest can be written for specific implementations.
References¶
[1] All possible states for a ironic node spec: | https://specs.openstack.org/openstack/ironic-specs/specs/kilo-implemented/ironic-node-properties-discovery.html | CC-MAIN-2020-10 | refinedweb | 1,211 | 50.02 |
Characters, Encodings, and Globalization
“I don’t know, but it works on my machine!!” Ever said that? Ever heard that? Ever wondered why it happens? Characters and Encodings are the basic concepts, which every developer must know, no matter what. In this information era when the entire world has shrunk, globalization has emerged as one of the key requirements from any product, because it is being sold and used across the globe by people from different countries, different languages and different cultures. A character or a text string doesn't get translated from one language to another, automatically; and globalization is not just about using resource bundles, if you are thinking that.
In this article, you will learn the basic concepts of Character, Glyph, Encoding, Font, and rendering, which are essential for every developer to know no matter what the platform, no matter what the program, no matter what the language that the developer works with. Then we clear the myths around ASCII, and move to Unicode. We will see what Unicode is, what Unicode is not, its architecture, and the three popular encoding schemes provided by Unicode – UTF-8, UTF-16, and UTF-32. Then we move on to the Unicode support in XML and Java* language. Finally, we talk about the Globalization concepts (Internationalization, Localization, and Translation) in general, as well as how they apply to Java.
Basic Concepts
Character and Glyph
A character is a platonic abstract entity which exists in theoretical space. Since a character is platonic, it is usually referred to by its name. For example, the “English Letter A” – ‘A’. What we see however, is the visual representation of the character, called its glyph.
A single character can have multiple glyphs. For example, the abstract character ‘A’ can have, but not limited to the following glyphs (but all mean the same thing – the character ‘A’):
(Figure: An abstract character in the Abstract Character Space maps to many glyphs in the Character Glyph Space)
The Abstract Character Space is the set of all characters in this world. Every abstract character in the Abstract Character Space maps to multiple glyphs in the Character Glyph Space. All such possible glyphs for every abstract character is called the Character Glyph Space. Let’s see some of the characteristics of character and glyphs.
Upper and lower case characters
The English language (and some other languages as well, for example Latin) has the concept of upper case and lower case characters, but not all languages (for example, Devanagari and many other East Asian languages) in this world have this concept. Even though the abstract character (upper case) ‘A’ semantically means the same thing as the abstract character (lower case) ‘a’, but for sake of simplicity, both (the upper case and the lower case characters) are treated as two different characters in the machine world.
Ligatures
One character can have multiple glyphs, but it is also true that some glyphs represent multiple characters. For example, the glyph ‘æ’ is a combination of two different glyphs ‘a’ and ‘e’ corresponding to the characters ‘a’ and ‘e’ respectively. Such glyphs, which get combined to change shape based on its adjacent characters, are called ligatures. Examples of other ligatures are ‘fi’, ‘fl’, ‘ff’, etc.
(Figure: A ligature broken into individual characters)
Decomposable characters
Decomposable characters (also called composite or precomposed characters) are ones which can be decomposed into multiple smaller characters. For example, the French letter é with the acute (or aigu) accent is one such character, which can be broken down into the character ‘e’, and the ‘character of the acute accent’.
(Figure: A decomposable character broken into individual characters)
The acute accent and other such marks like circumflex (^), grave accent (`), cedilla (¸), macron (¯), diaeresis (¨), etc are called diacritical marks. When more than one diacritical mark is used on a single base character, they all usually either stack up on the top of the base character or stack down on the bottom of the base character in the order in which they appear with respect to the base character.
Technically a ligature can also be called as a composite character, because they too can be decomposed into individual characters. But there is a subtle difference between the two. The individual characters in a ligature are complete and independent characters and can also exist on their own, but it is not the same for decomposable characters. For example, the acute accent (and other diacritical marks), which is part of decomposable character, does not mean anything on its own, but only in the context of a complete character (also known as base character).
Character Set and Coded Character Set
A set of abstract characters is called a character set. A set by definition has no order, and thus, we must not assume any. A character set is just a concept, which is often used and is quite helpful in discussions, to refer to, a set, or a family of characters. Examples include the Latin character set, the Devanagari character set, the Japanese character set, the universal character set, and so on.
Most of these characters have names, but that is not sufficient to identify them uniquely. Moreover in the machine world, everything is represented as a number; thus, every character in the character set is assigned a number to identify it uniquely. Such a character set, where every character is assigned a unique number (an integer number, to be specific) is called a coded character set (that is Code Page, Character Repertoire, or even simply as Character Set); and the unique number assigned to a character is called its character code (that is Code Point, Code Value). A Coded Character Set is independent of any platform, operating system, or program. Some popular Coded Character Sets are Unicode, SHIFT_JIS, and ASCII.
Character Encoding and Decoding
A named algorithm to covert a character code to a sequence of code units is called character encoding (also known as Character Encoding Scheme), where, a code unit is a block of bits always represented in multiples of an octet (8-bits, or casually referred to as a byte). In other words, character encoding is an algorithm to convert a character code to octets. For example, UTF-16 is a character-encoding algorithm, which uses a code unit of 2 octets.
Note that a character, when encoded, may result into one or more octets depending on its character code and the encoding algorithm used. Such an encoding algorithm, which generates variable number of octets for different character codes, is called a variable-length encoding scheme. For example, UTF-16 is a variable-length encoding scheme, which encodes character codes in 16-bits or 32-bits. Encoding algorithms, which always generate fixed number of octets for different character codes, are called fixed-length encoding schemes. For example, US-ASCII is a fixed-length encoding scheme, which always encodes a character code in 7-bits.
A Character Code can only exist as a part of a Coded Character Set. An encoding algorithm must know what the range of valid Character Codes is, and what illegal characters are so that it can encode a character code correctly. Therefore, an encoding algorithm is also always associated with a Coded Character Set.
Mostly one Coded Character Set (or Code Page) is associated with one encoding algorithm. For example, the US-ASCII code page is associated with the US-ASCII encoding algorithm. But there is no such hard and fast rule. For example, the Unicode code page is associated with many encoding algorithms like UTF-8, UTF-16, and UTF-32.
The RFC for the Multipurpose Internet Mail Extensions (MIME) as well as many other specifications officially refer to the Character Encoding as Charset, which has caused some confusing with respect to the Character Set. But note that a “Charset” is not a “Character Set”. A charset means character encoding.
The mechanism of converting a sequence of octets back to a valid character code is called character decoding.
Character Rendering and Fonts
The process of displaying the glyph of a character on the screen is called as character rendering, and the software which does this is called as rendering software. For example, browsers, editors, and other such software are all rendering software in their core.
There are three things required to render a character – a) the rendering software b) the decoder, which is usually part of the rendering software, and, c) the required fonts.
Apart from the font, the rendering software may use other parameters like size, colour, style and effects (bold, italic, underline, strikethrough, emboss, etc.), and orientation depending on how sophisticated the rendering software is. But again, the primary thing required for rendering a character is the font.
Fonts
Things were different in earlier days when there were no concept of fonts. Rendering software used to turn bits on or off on the display screen within the allocated area of a character to render a character. Today we use fonts. Fonts are bitmap representation of characters. The rendering software draws this bitmap on the display screen to render a character. Therefore, we have more sophisticated representations of characters with fancy strokes than we used to have earlier.
There are various types of fonts including serif, sans serif, and script. But that’s a huge topic in itself, and is out of the scope of this article. For now, it’s enough to understand that a font is the bitmap representation of the glyph of a character. Typically a font file would contain the bitmaps of all the characters for a given character set, mapped to their respective character codes.
From a broader perspective, let’s take a small example to understand the complete end-to-end story of how a text file is displayed:
- User: Launches the rendering software (say, an editor or a browser).
- User: Specifies the file – directory location and filename, to render. (Most often this is the File>Open task)
- User: Specifies the encoding that was used to create the file. (Usually in the Open dialog box itself)
Note: This is a very important input for the rendering software, but, most of us ignore it, and the rendering software has to fallback to rely on the system default encoding, which might not always work. Therefore, make sure you always specify the right encoding.
- Rendering s/w: Reads the file from the user specified location using the user specified encoding.
- Decoder: While reading, the decoder converts the octets in the file to character codes as per the encoding algorithm and returns it to the rendering software where they are accumulated as a sequence of character codes.
- Rendering s/w: Then loads the user-specified or the default font map.
- Rendering s/w: Iterates over the accumulated character codes, and looks for every character code in the loaded font map, and uses the corresponding information there to render the character.
- Rendering s/w: While rendering, the rendering software uses any user-specified or default, style & effects, based on how sophisticated the rendering software is.
So we see that what gets rendered is entirely dependent on the font file – that is, to what glyph the code point is associated with. For example, below is how the string “Hello World” gets rendered in two different fonts:
This raises an important point related to data exchange. When the receiving system gets a text file from some other machine, it might not be able to display the file properly:
- If it doesn’t know what font to use for rendering, or
- If it doesn’t have the correct fonts installed, or
- If somebody has modified the font file just for kicks.
It would also be a problem if the rendering software uses an encoding algorithm to read the file that is different from the one used to create that file. Since encoding algorithms are always associated with code pages, it is possible that the same character code in the two different code pages maps to two different characters, thereby leading to garbage output. Any given computer (especially servers) needs to support many different encodings; yet whenever data is passed between different encodings or platforms, that data always runs the risk of corruption.
Therefore, make sure that:
- You always use or specify the right encoding when reading a file.
- You have the necessary fonts installed on your machine.
Directionality
But that’s not it. Rendering software also has to take care of the direction of display. Most scripts have characters that run from left to right but that’s not true for all the scripts. For example, Arabic script runs from right to left, and some Japanese script runs from top to down. The algorithm used by rendering software for display is orthogonal to the way the octets are stored and decoded to character codes. The octets are always stored from left to right and therefore it is the rendering software, which is responsible for rendering the characters with the right orientation and direction.
(Figure: Different directionality of different languages)
ASCII – 7 bits or 8 bits?
ASCII is one of the most popular code page and encoding, so it’s worth discussing it here. In the period roughly from 1963-1967, the American National Standards Institute (ANSI), released American Standard Code for Information Interchange (ASCII) code page with the intention to standardize information interchange. ASCII defined only 128 characters of which there were 33 non-printable control characters, 52 English alphabet characters (26 upper and 26 lower case characters), 10 numeric characters (0-9), and the remaining 33 were symbol and punctuation characters.
Now, 128 characters can be accommodated within 7 bits. Most computer registers (then and even now) are 8-bits, which means 1 bit was still empty, which when used could store an additional 128 characters. This mistake did not go unnoticed and computer manufacturers in various countries started using the remaining 1 bit, to accommodate characters from their native language. And thus, there was a wave of national variants of ASCII, defining their own characters using the unused bit, which defeated the entire purpose of information interchange.
Officially ASCII was, and is even now, is 7-bits. The other 8-bit variants, which emerged by extending the ASCII character set are unofficially called as Extended ASCII, and incorrectly still being referred to as ASCII. The correct name for these so called extended ASCII character sets is the ISO-8859 family (there are 10 extended ASCII character sets, from ISO-8859-1 to ISO-8859-10). This utter confusion around 7-bit vs. 8-bit could have been avoided because most characters in the ASCII character set are now obsolete, and the original ASCII specification is not available free for a common person to validate the truths and rumors about ASCII. Anyways, those interested can still purchase the original ASCII specification from ANSI for $18.
(Figure: Complete ASCII code page with 128 chars)
Because of the huge popularity of ASCII, people started using to refer to an ASCII encoded text file, simply as plain text file. This was not correct even then, and it is very wrong even now. A text file cannot exist without an encoding, and in this globalized world ASCII is more or less obsolete. The preferred MIME name for ASCII is US-ASCII.
Unicode
Now that we understand the basic concept of characters, character codes, code page, and encoding, let’s talk about the popular Unicode standard.
What is Unicode?
Unicode is a standard, a consortium, and a non-profit organization, started in the year 1988, whose objective is similar to that of the ISO/IEC 10646, which is to have a single standard universal character set that addresses all the characters in this world. From Unicode’s official site: “Unicode provides a unique number for every character, no matter what the platform, no matter what the program, no matter what the language”.
There might be some valid reasons as to why have two standard bodies doing the same thing with the same set of objectives, which is not very clear; but what is clear is that both of these bodies work in collaboration with each other, rather than competing with each other.
The primary job of Unicode is to collect all the characters from all the languages in this world and assign a unique number to every character. In short, Unicode is a Coded Character Set. But it's not as simple as it sounds. The Unicode consortium does a great deal of work. To give you an idea, following are some points, which Unicode addresses:
- Collecting all the letters, punctuations, and other details from all the languages in this world.
- Assigning each character in the character set a unique code point.
- Deciding what qualifies as an independent character and what does not. For example, should “e with an acute accent” be treated as an independent character or a composite character sequence of e and the acute accent?
- Deciding the shape of a character in the context of other characters. For example, when ‘a’ appears next to ‘e’, the shape of the character becomes ‘æ’.
- Decide the order of characters with respect to sorting when characters from different languages come together.
- And many more other things... For details see:
As mentioned earlier, there is always an encoding associated with a Code Page. Therefore, the Unicode Code Page is associated with not one, but many encoding algorithms or character encoding schemes. Some popular character encoding schemes associated with Unicode code page are – UTF-8, UTF-16 (LE/BE), and UTF-32 (LE/BE). Other less popular encoding algorithms associated with Unicode are -- UTF-7, UTF-EBCDIC, and an upcoming CESU.
Let us also see what Unicode is not:
- Unicode is not a fixed-length 16-bit encoding scheme.
- Unicode is a code page and not an encoding scheme. There are encoding schemes associated with Unicode.
- Note: Look at the “Save As” dialog box of MS Windows Notepad application. The “Encoding” drop-down there misguides you by showing the option “Unicode”. It should have been UTF-16.
- Unicode is not a font or a repository of glyphs.
- Unicode is not a rendering or any other kind of software.
- Unicode does not specify the size, shape, or style of on-screen characters.
- Unicode is not magic.
Officially, Unicode uses the U+NNNN[N]* notation to refer to the various code points in the Unicode character set, where, N is a hexadecimal number. For example, to refer to the “English Letter A”, whose code point is 65, the Unicode representation is: U+0041; and to refer to the “Ugaritic Letter Ho”, whose code point is 66437 (greater than FFFF), the Unicode representation is U+10385.
You can see the character for a given Unicode character code, at:
The latest version of Unicode while writing this article is v4.0, which defines a range of characters from U+0000 to U+10FFFF, which means one needs 21-bits to represent a Unicode code point in memory, as of now.
Combining Characters
As mentioned earlier, when a combining mark (for example diacritical marks) comes adjacent to an independent character, it has an affinity to get combined with that independent character. For example, when the acute accent comes next to the independent character ‘e’, it gets combined to become é.
For the complete list of Unicode combining diacritical characters, see:
What if such a combining mark comes in-between two independent characters, where it has affinity to get combined with either of those two adjacent independent characters? In such a case we can use a special character called Zero Width Non Joiner (ZWNJ, U+200C) to express what independent character the combining character should not join to.
For example, to resolve a situation like:
C1 CM C2
Where C1 and C2 are two independent characters and CM is a combining mark which has affinity towards both C1 and C2, we can do the following:
C1 ZWNJ CM C2
Or
C1 CM ZWNJ C2
In the former case, CM gets joined to C2, and in the latter case, CM gets joined with C1.
Now, if we want to combine two independent characters, provided they are combinable, then we can use another special character called Zero Width Joiner (ZWJ, U+200D). For example, when the character ‘a’, comes next to character ‘e’, both remain independent character and do not get joined automatically to form the ligature ‘æ’. To join such independent characters, we can do the following:
C1 ZWJ C2
On the media, everything is just bits and bytes. Therefore it is the job of the Unicode conformant rendering software to ensure that the appropriate characters are joined, and displayed properly.
Other than the ZWJ special character, many of the scripts have their own special characters to facilitate the joining of two characters. For example, in Devanagari script, the special character (U+094D) called Halant, is used to combine such independent characters. For example:
(Figure: Combining two independent characters using Halant)
Unicode Architecture
Let’s see the architecture of Unicode in more detail. There are 17 planes in Unicode and the primary plane is called Basic Multilingual Plane (BMP), and the other 16 are called supplementary planes. These planes are nothing but just a category to group a range of code points. For example, the Plane 2 (also called the Supplementary Ideographic Plane) has code points in the range from U+20000 to U+2FFFF, which are used to capture rare East Asian characters.
The idea behind having such division in so-called planes is that each plane has a special meaning and contains special characters.
One can define one's own characters and assign them to the code points in the private use area. But, to display those characters then one needs to create a new font file or update an existing font file to assign the visual representation of those characters to the appropriate character codes. These private areas are primarily used by applications to capture the new characters that are defined by, but not limited to, the CJK languages. For example, it is very common in Japan for people to have names which cannot always be written using the existing characters; and need new characters to write them. These private use areas provided by Unicode are very helpful for such applications.
Let’s move on and see the three popular Unicode encoding schemes in detail.
Unicode Character Encoding Schemes
UTF-8, UTF-16, and UTF-32 are the three popular encodings defined by Unicode which encode character codes from the Unicode code page to octets, and decode the encoded octets back to valid character codes, which exist in the Unicode code page. Other less popular encoding schemes from Unicode are CESU, UTF-EBCDIC and UTF-7.
UTF-8
UTF-8 is an 8-bit code unit, variable-length encoding algorithm, with the following properties:
- All possible characters in the Unicode code page can be encoded in UTF-8.
- UTF-8 is completely backward compatible with ASCII, which means, the first 128 characters in the Unicode are exactly the same as defined in the ASCII code page, and are encoded simply as bytes 0x00 to 0x7F, just like the way ASCII does.
- All characters beyond (see the table below). This allows easy resynchronization and makes the encoding stateless and robust against missing bytes.
- UTF-8 encoded characters may theoretically be up to six bytes long, however 16-bit BMP characters are only up to three bytes long.
- The optional initial Byte Order Mark (BOM) for UTF-8 is: EF BB BF
- The bytes 0xFE and 0xFF are never used in the UTF-8 encoding.
The algorithm (simplified)
For example, U+00E9 (é) in UTF-8 would be encoded as:
UTF-16
UTF-16 is a 16-bit code unit, variable-length encoding algorithm, with the following properties:
- It uses a 16-bit fixed-width encoding algorithm to encode characters from the BMP (U+0000 to U+FFFF)
- It uses surrogate pairs to encode characters from Supplementary planes (i.e. characters beyond U+FFFF), where each surrogate is 16-bits, thereby consuming 32-bits to encode characters from supplementary planes.
This is so, because originally Unicode was designed as a 16-bit, fixed-width encoding scheme, which could only encode characters up to U+FFFF. But, as Unicode character set grew, this had to be modified using the surrogate pair mechanism to accommodate the characters from Supplementary planes.
Surrogate Pairs
Surrogate pairs are commonly referred to as surrogates, and are pairs of two Unicode code points from the Basic Multilingual Plane, to represent characters from the Supplementary Plane. In a coded pair, the first value is a high surrogate and the second is a low surrogate. A high surrogate is a value in the range U+D800 through U+DBFF, and a low surrogate is a value in the range U+DC00 through U+DFFF. These two range of values or code points in the BMP are reserved only for Surrogate pairs and do not represent any individual character.
For example, the character Ugaritic Letter Ho, whose code point is U+10385 (greater than U+FFFF), is represented as a surrogate pair “U+D800 U+DF85” in UTF-16, whereas the character English Letter A, whose code point is U+0041 (less than U+FFFF), is represented as U+0041 in UTF-16.
Endian – Big or Little
Values which are of one octet length have a Most Significant Bit (MSb) and a Least Significant Bit (LSb); whereas values which are greater than one octet (or one byte) length have a Most Significant Byte (MSB) and a Least Significant Byte (LSB). Based on the computer architecture, at a given memory address, the MSB of the value might be stored first (called big-endian), or the LSB of the value might be stored first (called little-endian). There is no significant advantage of one over other: it is all up to the computer architecture. For example, SPARC machines use big-endian mechanism, whereas, Intel machines use little-endian mechanism to store values in memory.
In the context of UTF-16, which has a code unit of 2-bytes, the endianess makes sense, but doesn’t for UTF-8, because UTF-8 has a code unit of 1-byte. Therefore, the UTF-16 character-encoding scheme is available in two flavors – UTF-16 BE (Big-Endian) and UTF-16 LE (Little-Endian). UTF-16 without any endianess specified is assumed to be BE.
Let us take the code point for the English Letter A – U+0041, which has the MSB as 00 and the LSB as 41. This value would be stored as “00 41” in UTF-16 BE (MSB first); and as “41 00” in UTF-16 LE (LSB first). Note that the MSbits and the LSbits are never reversed.
UTF-32
Any Unicode character can be represented as a single 32-bit unit using UTF-32. This single 32-bit code unit corresponds to the Unicode scalar value, which is the code point for the abstract character in Unicode code page. The encoding and decoding of characters in UTF-32 is much faster than UTF-16, or UTF-8, however, the downside of UTF-32 is that it forces you to use 32-bits for each character, when only a maximum of 21 bits are ever needed. Also, the most common characters from BMP can be encoded in only 16-bits. Therefore, an application must choose the encoding algorithm wisely.
BOM
Unicode uses an optional signature in the beginning of the data stream (or file) when encoding code points so that when no encoding is specified to read the stream, the decoder can automatically detect from the data stream what encoding was used to generate this, and can use it to correctly read the subsequent data stream. This signature at the beginning of the data stream is called as initial Byte Order Mark (BOM). Unicode uses “FEFF” as the BOM, which gets transformed as follows when encoded using the above three encoding schemes:
(Table: initial BOM in various encoding forms)
Unicode and XML
XML supports Unicode inherently. The first edition of W3C XML 1.0 specification, which was published in early 1998, was based on Unicode 2.0. Unicode 2.0 was the then latest specification from the Unicode Consortium. The Unicode Consortium releases a new version of Unicode specification every other year (or whenever they have accumulated and studied enough new characters); therefore, specifications, which are dependent on Unicode, also need to be updated. In late 2000, second edition of W3C XML 1.0 specification was released, which was based on Unicode 3.0. Recently, W3C XML 1.0 third edition was released in early 2004, which is based on Unicode 3.2. Surprisingly, the same day W3C also released XML 1.1. Why release two different versions of XML, and that too the same day?
Updating the XML specification every time a new version of Unicode is released is a tedious and cumbersome task. Therefore, XML 1.1 was released primarily to be backward as well as forward compatible with the Unicode characters. This compatibility with Unicode is achieved at the cost of XML 1.1 being backward incompatible with XML 1.0. Therefore, a third edition of XML 1.0 was released to accommodate the new characters from Unicode 4.0 as well as remain backward compatible with XML 1.0 second edition.
Okay, here is what’s new in XML 1.1
- Fully backward and forward compatible with Unicode
- Two end-of-line characters viz. NEL (0x85) and the Unicode line separator character (0x2028) has been added to the list of characters that mark the end of a line. NEL is the end-of-line character found on mainframes, but XML 1.0 does not recognize this character.
- Control characters from 0x1 to 0x1F, which were not allowed in XML 1.0 are now allowed as character entity references. For example, is valid in XML 1.1, but invalid in XML 1.0.
- Character normalization. Those characters, which can be represented in more than one way, must be normalized so that string related operations (like comparison, etc.) work correctly. For example, a decomposable character, which also has an independent character status, must be normalized, when used in XML 1.1.
When we say XML supports Unicode, this means, the name of the elements, the name of the attributes, and the values of the attributes and the character data, all can contain Unicode characters as long as they don’t break the production rules defined in the XML specification. For example:
Encoding of XML document
XML is a text file, and therefore XML too is associated with an encoding. This encoding must be used when we want to read or write an XML document. The encoding of an XML document is specified using the xml declaration prolog, which should be the first line in any xml document.
<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
The encoding attribute however is optional. Therefore, if the encoding attribute is not specified, it is assumed to be UTF-8.
This encoding, which is specified on the xml declaration prolog, must be used to parse the xml document. But to fetch that encoding, we need to parse the xml document with the appropriate encoding (that is the encoding specified on the xml declaration prolog). No, I am not kidding, and though it may seem I am; but this is not a Catch-22 situation. Since the position and content of the xml declaration prolog is restricted, and every parser supports a finite number of encodings, the auto-detection of encoding of an xml document is a deterministic task. By analyzing the first few bytes of an XML document, the encoding can be determined in a deterministic way. Once the encoding is found, it is used to read the rest of the xml document. For more details on auto detecting the encoding of an XML document, see:
Note:
- It is an error if the encoding the xml document is stored in is different from the encoding specified in the xml declaration prolog.
- Not all xml parsers may be able to auto-detect all the possible encoding that may be specified for an XML document, correctly.
- This auto-detecting mechanism cannot be used to read non-xml documents because they do not have anything like the XML declaration prolog.
Most often people use an editor to create xml documents, but while saving it, they don’t care what encoding the document was actually saved in by their favorite editor. This could result in xml parsing errors if the encoding that the document was actually saved in, turns out to be different than the encoding specified in the xml declaration prolog of the xml document (or different than UTF-8, which is the default encoding of XML document, when no encoding is explicitly specified in the xml declaration prolog).
For example, on a Windows machine when using the character e with the acute accent in an xml document and saving it using an editor, the editor may (in most of the cases) store that document in ISO-8859-1 encoding (the Latin encoding family). Now, if no encoding were specified in the xml declaration prolog, the parser would try to parse the XML document in UTF-8, and would throw an error for the invalid character found, because the way “the letter e with an acute accent” is stored in UTF-8 is different from the way it is stored in ISO-8859-1.
Now, instead of just cribbing that “XML doesn’t recognize my character”, or “XML doesn’t supports my character”, you can go ahead and fix this problem by making sure that your XML document was saved in the encoding which is specified in the XML declaration prolog. Always specify the encoding of the document you are saving (whether it is an xml document or a non-xml document) in the “Save” dialog box (or whatever it is), and if your favorite editor doesn’t allow you to do that, just dump it, and go for another one, which allows you to specify the encoding of files you save.
If you cannot key in the character you want to use in an XML document, by directly using the keyboard, you can use a character entity reference for that character. A character entity is declared as: &#D; or &#xH; -- where D is a decimal number and H is a hexadecimal number. For example, to use the character A, whose Unicode code point is 65, one can specify a character entity reference like A or A -- where both are the same thing.
Best Practices
- When creating XML documents, it is always a good practice to explicitly specify the encoding of the xml document in the xml declaration prolog.
- Make sure the document is actually stored in the encoding as specified in the xml declaration prolog, or in UTF-8 (which is the default encoding of xml when not specified explicitly using the xml declaration prolog).
Globalization
The art of making software, which could run on different platforms and be used by people from different geographical locations, different cultural backgrounds and different languages is called Globalization. In a nutshell, it’s an art of making software for the global industry.
(Figure: Globalization = Internalization + Localization + Translation)
Internationalization
The art of making software independent of the underlying system defaults is called Internationalization (aka I18N). Every system has defaults like encoding and locale. Any piece of software that unknowingly relies on these defaults may not work correctly when ported from one system to other because system defaults vary from one system to other; and thus, is not internationalized.
A Scenario
Hattori Hanso creates a text file on a Japanese operating system using an editor and saves it to the disk. Most of the time people are not aware of, or they just don’t care about, the encoding that the editor used to save their file. That’s a bad habit. Just like the name of the file, one must always know the encoding of a text file. Anyway, let’s say the file was saved in “Shift_JIS” encoding, which also happens to be the default encoding of that Japanese operating system.
He then goes ahead and writes a program to read that text file and display its contents. When writing the program he doesn’t specify any encoding to read that text file. This is extremely dangerous, and such a program is highly inflammable. Never, ever, do this, and we’ll see why in a while. He then executes that program on the same machine and everything works perfectly fine -- just as expected.
Now, he FTP over that text file and that same program to his friend Antonio Tourino’s machine, which has an English operating system. He executes the same program again on the English operating system. The program runs, but boom – this time he sees garbage. Where did those Japanese characters go? What do you say? – “I don’t know, but it works perfectly fine on my machine!”
The Problem
The problem is that when writing the program, the programmer relied on the source operating system’s default encoding (Shift_JIS), which turned out to be different from the target operating system’s default encoding (ISO-8859-1). Note that more than 90% of the times, the default encoding of the source and target systems are different. But when executing the same program on the English OS, the default encoding used by the program was ISO-8859-1. Therefore, using ISO-8859-1 to read a Shift_JIS encoded file resulted in absolute garbage.
The Solution
The solution is that the way the program requires the name of the file to read as an input, it must also always ask the encoding of the file it was created in, as an input. After doing this fix, the program becomes internationalized, but you may still not see those Japanese characters when executing it on the English OS, because that OS might not have the required fonts for displaying the Japanese characters. But that’s a different story we will look into that in a short while.
Localization
The art of making software adapt to the underlying locale is called Localization (also called L10N). A software must rely on these defaults, to display the text messages, error messages, and other messages in the locale it is running on, so that, it makes sense for the person who is using that software.
What’s a locale?
A locale represents a language. Therefore, adapting to a locale means the software should be able to display or take inputs in a language specific manner. For example, the French language is a locale. But, French as spoken in France differs from French as spoken in Canada. So, we augment our definition of locale to say that a locale represents a specific language of a specific country. Again, a language spoken in a specific country can have variations. For example, ancient traditional Chinese spoken in China vs. simplified Chinese spoken in China. So, we augment our definition of locale again, to say that a locale represents a specific language of a specific country with variants.
When we write software that adapts to the underlying locale this actually means addressing the community, which is going to use this software. Therefore, locale-specific things like text messages, exception messages, the date and time, currency, and other messages should be displayed in a way, such that, the user of the software understands what gets displayed (that is, the output of the software). There is a community of user, which the localization tries to address, because we don’t want to re-write the entire software for every language, and every flavor of that language.
This involves writing the program once in such a way that every time it is executed, it uses the default locale of the system it is executed on to display the locale-sensitive information.
Translation
Translation is to translate all the text messages, error messages, and other messages that would be displayed to the user from the language it is written in to the various languages the software being developed wants to support.
For example, when a software is written in English, all such text messages (initially written in English) that will be displayed to the user are first identified and separated out from the code in another file. Each of these messages is assigned a unique key, which the software would use to display the message identified by that key. Then, all these messages are manually translated by language experts in various other languages, the software wants to support. Separating out such text messages from the code makes it easy to manage and translate messages. It also helps the language experts to translate these files to the various other languages independent of the software code.
Note that sentences cannot be translated from one language (or locale to be specific) to another, automatically. This is because sentences are associated with grammar. Even if we try to automate that, the translated sentences might not be grammatically correct, and at times might not make any sense at all.
Therefore, somebody has to sit down and translate all these various messages to different locales. In the IT industry this field is called as Native Language Support (NLS), which primarily comprises of Language experts.
Unicode and Java*
The Java* programming language inherently supports Unicode, and has since the beginning. This means, all the Characters and Strings used in a Java program are Unicode. The primitive data type char used to represent a character in Java is an unsigned 16-bit integer that can represent any Unicode code point in the range U+0000 to U+FFFF. When Unicode v1.0 was released it did not have those many characters, but Java had that support from the beginning. Even now, after so many years, J2SE 1.4 (code named: Merlin), which supports Unicode 3.0, can easily accommodate all the characters defined by Unicode 3.0 in 16 bits of the Java char datatype.
In Java, a character or should I say a Unicode character can be represented as:
char ch = 'A';
OR by directly using the Unicode code point as:
char ch = 65;
Both mean the same thing. A third way of representing characters in Java, is by using the “\u” escape sequence. Well, first of all, why have a third way at all? This was primarily for the ease of use to directly support Unicode characters in Java Strings, rather than all the time create a String from char[].
The “\u” escape sequence follows the form: \uNNNN, where, N is a hexadecimal number. Therefore, to represent the character ‘A’, whose Unicode code point is 65, can be represented in java using the “\u” escape sequence as:
char ch = '\u0041';
This escape sequence is very useful when creating Strings. For example:
String str = "h\u00E9llo world";
which is equivalent to:
String str = "héllo world";
Since Unicode is growing faster and theoretically puts no constraint on the number of characters it defines, Java would be in trouble when the number of characters grows beyond U+FFFF. This is because; the char datatype in Java is only 16-bits and cannot accommodate values beyond U+FFFF.
Here is the interesting part: Unicode 4.0 is now available and it defines characters in the range U+0000 and U+10FFFF. This means Java must do something if it is to support those additional characters (beyond U+FFFF) from Unicode 4.0, which are called supplementary characters. Therefore, JSR-204 was filed for supporting these supplementary characters in J2SE, and J2SE 1.5 (code named: Tiger) and supports Unicode 4.0 using the mechanism defined in JSR-204. In a nutshell, supplementary characters are supported in Java 1.5 using the surrogate pair mechanism of UTF-16. Read the article “Supplementary Characters in the Java Platform” for more details.
To represent characters from supplementary planes, or code points beyond U+FFFF, a pair of escape sequences are used – “\uXXXX \uYYYY” called surrogate pairs. Refer the Unicode UTF-16 section earlier in this article for details on surrogate pairs.
For example, to represent the character Ugaritic Letter Ho, whose code point is U+10385 (greater than U+FFFF), in Java, one should use the surrogate pair “\uD800\uDF85”. Note that using the escape sequence “\u10385” is incorrect in Java.
Java 1.5 provides APIs to get these surrogate pairs, for a given code point, without having the developers worry about how are they generated:
int unicodeCodePoint = Integer.parseInt(args[0]); char[] surrogates = Character.toChars(unicodeCodePoint); if (surrogates.length > 1) { System.out.println("High=U+"+Integer.toHexString(surrogates[0])); System.out.println("Low =U+"+Integer.toHexString(surrogates[1])); } else { System.out.println("Value="+surrogates[0]); }
I completely agree that this is not a great way to handle supplementary characters in Java. It would have been great for developers to have had the supplementary characters been supported in a way, something like: “\u{20000}”. This would have made lives much easier, but nothing much can be done about that now. Anyways, this is not too bad either, or is it?
Internationalization in Java
Bytes and Strings
Whenever we convert a String to Bytes, or create a String from Bytes, there is an encoding involved. Without an encoding this conversion is not possible at all. Yes, Java provides API which can do this conversion without a user specified encoding:
public String(byte[] bytes)
public byte[] getBytes()
Java shouldn’t have done this, because this gives an impression that no encoding is required in these conversions. But the fact is, the system default or the JVM default encoding is used to do this conversion. Most of the time, many of us use these APIs to convert String to bytes and vice-versa without specifying an encoding, and without realizing the impact of this. The impact is huge – the code is not portable, which means you might get different and incorrect results when such a program is executed on different machines, because the default encoding would vary from one machine to another.
Never do this. Instead, use the other overloaded APIs where one can specify the encoding explicitly when doing such conversions:
public String(byte[] bytes, String charsetName)
public byte[] getBytes(String charsetName)
Remember that once the conversion is done, there is no encoding information associated with the bytes or the characters. Bytes are bytes, and characters are characters. Period. If you want to do conversion, you must specify a third piece of information – encoding.
Input and Output (I/O)
Java allows you to read/write streaming data from/to external (as well as internal) data sources using the APIs in the java.io package. Broadly, the java.io package provides API to access the data as stream of Bytes or as stream of Characters. The java.io.InputStream, and the java.io.OutputStream (including all their subclasses) allows you to read/write data as bytes; whereas, the java.io.Reader and the java.io.Writer (including all their subclasses) allows you to read/write data as characters. Based on the type of data source, and the processing required, one can choose an appropriate class to do the I/O.
Byte Streams
There is no encoding involved when using byte streams to do IO. A file, for example, is stored as a sequence of bits on the file system. When we use a byte stream to read a file (e.g. java.io.FileInputStream), 8-bits (or 1-byte or 1-octet) are read at a time, and returned to the application, as it is. The IO classes supporting byte streams do not look into, or do any sort of processing with the bytes read. It is the onus of the application to process the raw bytes in whatever way it wants.
Char Streams
Character streams are byte streams plus encoding. A character stream cannot function without an encoding. IO classes supporting character streams, first read appropriate number of bytes from the underlying byte stream (depending on the encoding), and then do some processing with the content of the bytes read (depending on the encoding), and convert them to a code point. This code point, which represents a character in Unicode, is then returned to the application.
From the characters, we cannot always say what the exact sequence of bytes in the input stream was. Yes, given an encoding, we can convert the characters back to bytes, but this sequence of bytes may not be always exactly the same as the original sequence of bytes.
Even though Java allows, we must never do this:
public InputStreamReader(InputStream in)
The above uses the system default or the JVM default encoding to read the file. This means if you move the program to some other machine which has a different encoding, then this program might not work at all. Instead, one should always use:
public InputStreamReader(InputStream in, String charsetName)
Below are two flavors of a small program to read a file using the appropriate encoding (that is the encoding which was used to create the file), and then to write it back using any user specified encoding.
Listing 1:
import java.io.*; ... //create a reader to read the input file //specifying the correct encoding of the input file BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(file_in), enc_in)); //create a writer to write the output file //in the any encoding of choice BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file_out), enc_out)); //read from the input file and write to the output file char[] buffer = new char[BUFFER_SIZE]; int charsRead = -1; while ((charsRead = reader.read(buffer)) != -1) { writer.write(buffer, 0, charsRead); }
The above program doesn’t has to do anything except for creating the readers and writers correctly. The encoding conversion is done automatically by the IO classes.
Listing 2:
import java.io.*; ... //create a reader to read the input file //specifying the correct encoding of the input file BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(file_in), enc_in)); //create an output stream to write to the output file //without any encoding conversion FileOutputStream fos = new FileOutputStream(file_out); //read from the input file and write to the output file char[] in_buffer = new char[BUFFER_SIZE]; byte[] out_buffer = null; int charsRead = -1; String str = null; while ((charsRead = reader.read(in_buffer)) != -1) { str = new String(in_buffer, 0, charsRead); //do the conversion out_buffer = str.getBytes(enc_out); fos.write(out_buffer); }
The above program explicitly does the conversion using the encoding before writing the bytes to the output file.
Note: The default encoding of the JVM is same as the default encoding of the system, unless it is changed explicitly as follows:
java –Dfile.encoding=UTF-8 mypack.myapp
Java vs. IANA encoding names
For whatever reason, Java defines its own name for many of the encodings it supports in the java.lang and java.io package, rather than using the standard names for the encodings registered with Internet Assigned Numbers Authority (IANA). The list of IANA registered encoding names and their alias can be found here. Though, some of the name of the encodings supported by Java, are also registered with IANA, not all the Java supported encoding names are. For example, “UTF8” (without the hyphen), is one such encoding name supported by Java which is not registered with IANA. The complete list of the name of the encodings supported by Java can be found here.
It is always better to use standard encoding names rather than Java encoding names for interoperability reasons. For example, when a Java program is written to generate an XML file the Java program cannot use the Java encoding name in the XML declaration prolog of the output XML. This is because XML supports only standard encoding names registered with IANA in the xml declaration prolog. It would be for the good of developers if Java provides a map implementation of Java encoding names to IANA encoding names and vice-versa for such interoperability reasons.
Java modified UTF-8
Talking about UTF-8, the implementation to support Unicode standard UTF-8 in Java is a bit modified version of the standard UTF-8. The Java version is called modified UTF-8 (or UTF8). Modified UTF-8 is different from the standard UTF-8 as follows:
- The null character (U+0000) is encoded with two bytes instead of one, specifically as 11000000 10000000. This ensures that there are no embedded nulls in the encoded string.
- The way characters outside the BMP are encoded. Standard UTF-8 doesn’t differentiate, when encoding characters from BMP or Supplementary planes. In modified UTF-8 these characters are first represented as surrogate pairs (as in UTF-16), and then the surrogate pairs are encoded individually in sequence for backward compatibility reasons.
- When decoding a UTF-8 stream with an initial BOM, the Java implementation reads the BOM as yet another character. This BOM is supposed to be verified and then skipped by the decoder before it actually reads the data. A bug (#4508058) has been filed for this at, and is supposed to be fixed in Java 1.6 (code named: Mustang)
Localization in Java
Locale
As per”.
To perform a locale-sensitive operation, a locale object needs to be created first. Java provides pre-created Locales for ease of use. But, one could always explicitly create a locale by specifying either a language code, or a language code and a country code. See the Javadoc for java.util.Locale for more details.
Listing 3: This listing displays the current system date/time in a specific locale using a pre-defined date format.
import java.util.*; import java.text.*; ... //current date Date date = new Date(); print("Using DateFormat with pre-defined format to format date/time..."); DateFormat df_jp = DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.FULL, Locale.JAPAN); DateFormat df_de = DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.FULL, Locale.GERMANY); DateFormat df_en = DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.FULL, Locale.US); //format and print the localized date/time print("Date/Time in Japan = "+df_jp.format(date)); print("Date/Time in Germany = "+df_de.format(date)); print("Date/Time in US = "+df_en.format(date));
Output:
Using DateFormat with pre-defined format to format date/time...
Listing 4: This listing displays the current system date/time in a specific locale using a custom date format.
import java.util.*; import java.text.*; ... //current date Date date = new Date(); print("Using SimpleDateFormat with custom format to format date/time..."); SimpleDateFormat sdf_jp = (SimpleDateFormat)DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.FULL, Locale.JAPAN); SimpleDateFormat sdf_de = (SimpleDateFormat)DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.FULL, Locale.GERMANY); SimpleDateFormat sdf_en = (SimpleDateFormat)DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.FULL, Locale.US); //override the pre-defined pattern with a custom pattern sdf_jp.applyPattern("EEE, d MMM yyyy HH:mm:ss zzzz"); sdf_de.applyPattern("EEE, d MMM yyyy HH:mm:ss zzzz"); sdf_en.applyPattern("EEE, d MMM yyyy HH:mm:ss zzzz"); //format and print the localized date/time print("Date/Time in Japan = "+sdf_jp.format(date)); print("Date/Time in Germany = "+sdf_de.format(date)); print("Date/Time in US = "+sdf_en.format(date));
Output:
Using SimpleDateFormat with custom format to format date/time...
Listing 5: This listing parses a locale specific string representing date/time back to java Date object.
//current date Date date = new Date(); DateFormat df_jp = DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.FULL, Locale.JAPAN); String localeSpecificDateStr = df_jp.format(date); Date newDate = df_jp.parse(localeSpecificDateStr);
Listing 6: Displays a currency value in different locales.
import java.util.*; import java.text.*; ... //formatting numbers and currencies long value = 123456789; //Formatting currency using NumberFormat print("Using NumberFormat to format Currency..."); NumberFormat nf_curr_jp = NumberFormat.getCurrencyInstance(Locale.JAPAN); NumberFormat nf_curr_de = NumberFormat.getCurrencyInstance(Locale.GERMANY); NumberFormat nf_curr_en = NumberFormat.getCurrencyInstance(Locale.US); print("Currency in Japan = "+nf_curr_jp.format(value)); print("Currency in Germany = "+nf_curr_de.format(value)); print("Currency in US = "+nf_curr_en.format(value));
Output:
Note the position of comma and dots
Using NumberFormat to format Currency...
Listing 7: Displays a numeric value in different locales.
import java.util.*; import java.text.*; ... //formatting numbers and currencies long value = 123456789; //NumberFormat print("Using NumberFormat to format Numbers..."); NumberFormat nf_jp = NumberFormat.getNumberInstance(Locale.JAPAN); NumberFormat nf_de = NumberFormat.getNumberInstance(Locale.GERMANY); NumberFormat nf_en = NumberFormat.getNumberInstance(Locale.US); print("Number in Japan = "+nf_jp.format(value)); print("Number in Germany = "+nf_de.format(value)); print("Number in US = "+nf_en.format(value));
Output:
Note the position of comma and dots
Using NumberFormat to format Numbers...
Resource Bundles
Until now we have seen that date, time, currency, and numeric values can be automatically formatted to a specific locale.
But, what about the following piece of code, when it is executed on different locales?:
String str = “Hello”; Jlabel label = new Jlabel(); label.setText(str);
OR
throw new Exception(“run dude, run”);
At a first glance the code looks fine, because we never bother about what if this program is executed on a different locale. For example, what would be displayed when the above program is executed on a Japanese locale?. Shouldn’t the string “Hello” be displayed in Japanese? Yes, it should be. But the question is would it be displayed in Japanese? (Did you answer Yes?) No, the answer is no. Sentences cannot be translated automatically because as mentioned earlier, when translating a sentence to a specific locale, one needs to ensure that the grammar of the translated sentence is correct. Therefore, sentences cannot be translated from one locale to another automatically.
Resource Bundle is a collection of resource files. Each resource file contains resources (for example display messages, exception messages, and others) in the native language, and every resource in the resource file is identified by a unique key. The message may either be a static message or a parameterized message. Resource bundles are used to display static or parameterized messages into various languages.
The way a resource bundle works is simple. Here are the steps you should follow to use a resource bundles:
Design Time
First of all, identify and remove all the displayable string literals from your code, which you want to be localized, and write it in a text file, identified by a unique key. For example:
MSG_1 = “Hello.”
Parameterize the messages required. For example:
MSG_2 = “May I speak to {0}.”
The NLS group now translates this single file into various other languages. The convention used to name these resource files is:
<file name>_<lang>_<country>. This helps to easily identify what language the resource file represents, just by looking at its file name.
- The developers then refer to these constant names used in the resource files, in their code to use the locale-sensitive message.
Runtime
- The program can then load the appropriate resource file based on the locale of the JVM, and then, use the constant name to fetch the correct localized message, at runtime.
- If the message is parameterized, it must be replaced with the appropriate value before using that message.
- Now, the message is ready to be used and is returned to be displayed either in UI or in a exception message, or anywhere else.
Listing 8: Using resource bundle
import java.util.*; import java.text.*; ... //resource bundle file name String resourceBundleBaseFileName = "MyMessages"; //locale to use Locale myLocale = Locale.US; //get the correct resource bundle using the appropriate locale //See the javadoc of getBundle(), for a complete description //of the search and instantiation strategy. ResourceBundle localizedMessages = ResourceBundle.getBundle(resourceBundleBaseFileName, myLocale); //get the localized message String localizedMessage = localizedMessages.getString("MyMessage"); //create parameter values for the localized message Object[] messageArguments = { "Rahul", new Date(), "Pizza Hut", new Date() }; //substitue the parameters, if any, in the localized message //with the parameter values created above MessageFormat formatter = new MessageFormat(localizedMessage, myLocale); String finalMessage = formatter.format(messageArguments); //This final localized string now can be used wherever required. //For example as exception messages or messages in UI, etc. System.out.println(finalMessage);
MyMessages.properties
MyMessage = Mary is going out on a date with {0} on {1, date} meeting at {2} at {3, time}.
Output:
Mary is going out on a date with Rahul on 15.01.2006 meeting at Pizza Hut at 16:47:03.
For details on parameterized messages, see:
Note: When the JVM starts, its default locale is same as the default locale of the system, unless it is changed explicitly as follows:
java –Duser.language=ja -Duser.country=JP mypak.myapp
Conclusion
Basic concepts of characters and encodings are essential for every developer. Globalization is an art of writing programs. And, Unicode is the future. | https://software.intel.com/zh-cn/articles/characters-encodings-and-globalization | CC-MAIN-2019-35 | refinedweb | 10,113 | 52.8 |
4 replies on
1 page.
Most recent reply:
Apr 20, 2009 3:51 AM
by
Patrick Kua
So here's the problem: Let's say you have a database class that is unit
tested. I like doctests, but maybe you like Python unittest. Your class has
a column (exposed in your ORM class) for the date that the row was last
touched, which is initialized from today's date. How do you test this?
Your test could just ensure that some date was stuffed in the
attribute/column, but you can't really tell if it's the date you care about
because that's going to be different every day you run the test. So this
solution isn't very good.
You could change your API to allow you to pass a known date into it, and your
test could call this extended API, but that's not great for several reasons.
You'd rather not clutter your API up with extra parameters only used in
testing, and it means your ORM class now has different logic for testing
environments and production environments. So I don't like this much either.
I'm sure you've thought of your own approaches, including hacking Python's
standard datetime module to stuff in instances that allow you to override
datetime.datetime.now() and datetime.date.today(). I thought of that too!
Because these are built-in types, you can't just replace those methods, but
Python does make it fairly easy to subclass built-in types. So that would
seem like a good approach except...
I use the Storm ORM in Mailman 3 and it has very strict type checking on
its column input values. Generally this is a good thing, but in this case it
prevents the subclassing approach because the DateTime column type won't
accept subclasses of the built-in datetime type.
The approach I settled on seems the least sucky to me. It's also stupid
simple, so I kind of like it for that reason too! I wrote a simple wrapper
class that only returns now() and today() and I make sure all the testable
call sites call these methods instead of the datetime module's versions.
The now() and today() in my utility module then are really instance
methods of a class which can be told whether it's in testing mode or not.
When it's not in testing mode, it simply returns datetime.datetime.now() and
datetime.date.today() as usual. When it is in testing mode, it returns
instead a known date and time, which of course, you can test!
The class itself has two additional class methods. One resets the current
date and time (in testing mode) to the original known values. The other
allows you to fast forward the known date and time. Here's the (stripped
down) code. Note that because of the conditional expressions, Python 2.5 is
required:
from __future__ import absolute_import, unicode_literals
__metaclass__ = type
import datetime
class DateFactory:
"""A factory for today() and now() that works with testing."""
# Set to True to produce predictable dates and times.
testing_mode = False
# The predictable time.
predictable_now = None
predictable_today = None
def now(self, tz=None):
return (self.predictable_now
if self.testing_mode
else datetime.datetime.now(tz))
def today(self):
return (self.predictable_today
if self.testing_mode
else datetime.date.today())
@classmethod
def reset(cls):
cls.predictable_now = datetime.datetime(2005, 8, 1, 7, 49, 23)
cls.predictable_today = cls.predictable_now.date()
@classmethod
def fast_forward(cls, days=1):
cls.predictable_now += datetime.timedelta(days=days)
cls.predictable_today = cls.predictable_now.date()
factory = DateFactory()
factory.reset()
today = factory.today
now = factory.now
Now, at the call sites, say in your database class, instead of something
like:
import datetime
self.date_created = datetime.date.today()
You'd write:
from ... import today
self.date_created = today()
And your test would do something like this:
>>> from ... import factory
>>> factory.testing_mode = True
>>> thing1 = Thing()
>>> thing1.date_created
datetime.datetime(2005, 8, 1, 7, 49, 23)
>>> factory.fast_forward(days=3)
>>> thing2 = Thing()
>>> thing2.date_created
datetime.datetime(2005, 8, 4, 7, 49, 23)
I know there are mocking libraries out there that might help you with this,
but I also think this is a nice simple approach where you don't want a lot of
extra mocking scaffolding. The cost is that you have to be disciplined not to
use the standard datetime module at your call sites. | http://www.artima.com/forums/flat.jsp?forum=106&thread=251755&start=0 | CC-MAIN-2014-42 | refinedweb | 732 | 67.96 |
Get a handle to a condition in an entity
#include <ha/ham.h> ham_condition_t *ham_condition_handle( int nd, const char *ename, const char *cname, unsigned flags ); ham_condition_t *ham_condition_handle_node( const char *nodename, const char *ename, const char *cname, unsigned flags );
libham
The ham_condition_handle() function returns a handle to a condition (cname) in an entity (ename).
The handle obtained from this function can be passed to other functions, such as ham_action_restart() or ham_condition_handle_free().
The handle returned is opaque; its contents are internal to the library.
If a node (nd) is specified, the handle is to an entity/condition/action combination that refers to a process on that remote node. The ham_condition_handle_node() function is used when a nodename is used to specify a remote HAM instead of a node identifier (nd).
There are no flags defined at this time.
A valid ham_condition_t, or NULL if an error occurred (errno is set).
A call to ham_condition_handle() and a subsequent use of the handle returned in a call such as ham_action_restart() are completely asynchronous. Therefore, a valid action/condition/entity may no longer exist when the handle is used to attach actions at a later time.
In such an event, the ham_action*() functions will return an error (ENOENT) that the condition doesn't exist in the given entity. | https://www.qnx.com/developers/docs/7.1/com.qnx.doc.ham/topic/hamapi/ham_condition_handle.html | CC-MAIN-2022-40 | refinedweb | 212 | 52.6 |
In this article, I explain how to build a web service client from a WSDL file. I am releasing this project to help those who wish to begin to use a web service with gSOAP. I won't, however, be explaining about XML Serialization, Transient Types, Memory Management, etc.
I split the article into two parts for easier learning and better understanding. In Part One, I will explain how to get the class from the WSDL file to be used in Visual C++ 6. In Part Two, I show you how to use the classes generated with gSOAP.
To begin, you will want:
Info: I used a free web service from WebserviceX.NET. If their server is busy and you get the the error "service unavailable," see if it's working here. After downloading the file, you have to build a C++ class from the WSDL file. Go to the gSoap directory and open the bin sub-folder, something like this: D:\gsoap-win32-2.7\bin. Here, you find two executable files:
Copy the WSDL to this directory and run wsdl2h.exe like this:
wsdl2h -o WSCurrencyConv.h CurrencyConvertor.wsdl
In the shell, you'll see some warning (ignore this) and at the end "To complete the process, compile with: soapcpp2 WSCurrencyConv.h". If all works fine, you'll see a new file in the directory that will be WSCurrencyConv.h (or the name you write at the command line).
N.B. You shouldn't have problems, but if you do, check the name and path you entered and try again.
Run soapcpp2.exe like this:
soapcpp2 -ID:\gsoap-win32-2.7\Import WSCurrencyConv.h
To run this executable, you need to set the path for the gSOAP import, something like this: D:\gsoap-win32-2.7\import. This is similar to what I did before with:
-ID:\gsoap-win32-2.7\Import
The second parameter is the file *.h you entered the first time with wsdl2h. If it works, you'll see in the last line "Compilation successful". Now in the directory, you'll see a few new files.
wsdl2h
N.B. You shouldn't have problems, but if you do, check that the path for the import file exists. Otherwise, you can copy all the files in the import directory to the bin directory and try again.
The new files will be:
Now you have all you want to begin deploying your application with Visual C++.
#include "CurrencyConvertorSoap.nsmap"
The Project is ready to communicate with the WS. You have all the classes you need to begin.
N.B You could get this warning (shown below), but don't worry and go ahead. This warning is derived from the self-generated class with gSOAP; gSOAP doesn't check the maximum characters.
I read many books online. I find that there are numerous mistakes and that all the examples are unusable. These books may have all you want to know in order to pass a university test, but there is too much information to begin a project. Irritated, I did this project to let you to begin to write a WS client. 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/Articles/17958/CurrencyConvertor-How-to-Use-gSOAP-and-Webservices?msg=4272559 | CC-MAIN-2014-35 | refinedweb | 546 | 74.08 |
Schetzle
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On Windows Vista and above, Internet Explorer’s Temporary Internet Files are maintained in two isolated WinINET cache containers. One cache is used for sites loaded in Protected Mode (Internet Zone and Restricted Zone) and the other cache is used for sites loaded outside of Protected Mode (Trusted Sites, Local Intranet, and Local Machine).
Each cache container consists of two components: a memory-mapped index database (index.dat) and a nested folder structure containing the response entities that have been cached. Each index holds up to 60000 entries, and each entry maps one request URL to a set of response headers, a bit of metadata, and optionally a file path to the response entity body (if one exists). The cache is cleaned (scavenged) when either the index entry limit is reached, or the disk quota (250mb by default for IE9) is exceeded. If the user deletes their browser history (Tools > Delete Browsing History) the cache index is overwritten with zeros, and all response entities are deleted from disk. If the user closes an InPrivate Browsing session, every item in the cache which was stored during the InPrivate session is removed.
When Internet Explorer asks WinINET to make a network request on its behalf, if the request flags allow, WinINET will reuse a fresh response from the local cache, if one is available. If an expired response is available, WinINET will attempt to validate its freshness by making a conditional HTTP request in order to get back a HTTP/304 if the response entity is still valid or a new copy of the response entity if the cached version is no longer up-to-date. If WinINET only has a partial response in the cache, it will issue a HTTP request with a Range header indicating the remaining part of the file which is not yet in the cache. In order to avoid corruption, the Range request will contain an If-Range header containing the ETag of the originally cached response, and/or a pre-RFC2616 Unless-Modified-Since header containing the Last-Modified time of the originally cached response. If the server’s copy of the resource has changed, it will send the entire file again; if not, it will send a HTTP/206 partial response containing only the requested range of the file.
Prior to IE6, Internet Explorer introduced a mechanism for viewing cached files; you can access this mechanism by clicking Tools > Internet Options > General > Browsing History > Settings. In the TIF and History Settings dialog, click the View Files button. Alternatively, you can simply type shell:cache into the Internet Explorer Address Bar or the Start > Run prompt. Doing this will open a Windows Explorer window to the C:\Users\username\AppData\Local\Microsoft\Windows\Temporary Internet Files folder.
It is important to understand that what you see above is not exactly what is stored on disk—alert readers will observe that Explorer is showing columns, like Internet Address and Expires, that are not typically seen for other folders.
This is accomplished through the magic of a Shell Namespace Extension. As explained on MSDN:With a namespace extension, you can take any body of data and have Windows Explorer present it to the user as a virtual folder. When a user browses into this folder, your data is presented as a tree-structured hierarchy of folders and files, much like the rest of the Shell namespace.
This folder is mapped to the Namespace Extension using the desktop.ini file within the folder; it contains the following text:
[.ShellClassInfo] UICLSID={7BD29E00-76C1-11CF-9DD0-00A0C9034933}
[.ShellClassInfo] UICLSID={7BD29E00-76C1-11CF-9DD0-00A0C9034933}
The CLSID listed refers to a COM object implemented in IEFrame.dll. When the Namespace Extension is invoked, it generates the “friendly” view of the non-Protected Mode cache. It generates this view by making API calls into the WinINET cache code. The COM object enumerates the cache using FindFirstUrlCacheEntry / FindNextUrlCacheEntry without passing any filter; this means that files download by XDomainRequest, files temporarily cached while InPrivate, and cached HTTP/3xx redirects, are not shown in this view.
The “Name” listed isn’t actually the name of the cache file on disk, but rather a filename simplistically parsed out of the URL. The HTTP expiration information and similar columns is retrieved from the metadata stored in the index.
Most importantly, this view does not show the Protected Mode cache; it only shows files that are downloaded outside of Protected Mode. In the screenshot, you’ll see a number of Internet-Zone URLs; these are here because Internet Explorer’s Medium Integrity “Frame Process” is downloading the FavIcons; the rest of these pages are downloaded and rendered by the Low Integrity Protected Mode “Tab Process.”
This view may even show files that do not exist; if the backing response entity file was deleted from the disk without calling DeleteUrlCacheEntry to delete the index entry, the Namesspace Extension will still show the entry. However, if WinINET ever wants to reuse the entry, it will find the file missing and will need to re-download from the server.
To see the actual files on disk, open shell:cache\Content.IE5. You’ll see the following view:
You see the index.dat database file, and four randomly named subfolders each of which, if opened, contains cached response files:
The folders are randomly named to mitigate certain types of attacks that involve placing malicious content at predictable file locations and then opening it using a url that uses the file:// protocol scheme. There are four of them to similarly aid in randomness, as well as for legacy reasons (older filesystems had a limit on the number of files contained in a single folder).
The Protected Mode cache files can be viewed in a similar way, by opening shell:cache\Low\Content.IE5 instead:
Again, you’ll see the same layout, with four more randomly named subfolders.
Thanks for reading!
-Eric
Hi Eric,
Thanks for the wonderful writeup on this topic. I find it very informative. Perhaps you can enlighten me on a particular pet peeve that might be related.
Whenever I'm in InPrivate mode, I find that the favicon never shows up on any of the tabs nor for any inprivate pinned sites.
Is this normal behavior? Is it because of the low integrity temp storage doesn't keep them around? Nevertheless, the favicons shows up in my Favorites.
So its bit strange and frustrating that favicons show up in one place but not the other.
Thanks.
@zz: When you create a Favorite, the page's FavIcon is copied from the Temporary Internet Files into an NTFS Alternate Data Stream on the .URL file that represents the favorite. That way, even if the TIF is cleared, the icon is still available in your favorites.
Why is there no TIF view of the protected mode parts?
@KS: The investment simply wasn't prioritized in the Windows Vista timeframe when Protected Mode was introduced; this view is a very rarely-used feature. Showing the low-integrity cache would have required a significant investment to spin up a COM object at low-integrity and enumerate the low-integrity cache at that IL.
Thanks for this informative article. Can you please put some light over accessing Temp internet files of other user profiles created on the machine? Thanks Farhan[EricLaw: Can you explain what you mean specifically? Temporary Internet Files are stored in a per-user location, so NTFS ACLs will generally prevent one user from accessing other user's files.]
What's the limit of number of objects in the cache for IE8 and IE9 respectively?
@Peter: The scavenger will run on a cache as soon as it exceeds 60,000 objects. That number is the same between IE6-IE9.
I use IE 9. If the cache limit is 60,000 whyy is my Norton antisoftawre on scanning counts >800,000 files in C:\Users\Harimohan\AppData\Local\Temp\Low\Temporary InternetFiles\Content.IE5\LM4P6AP1\... WITH ....js. Is it Ok/possible to delete these files.
EricLaw: If there are really that many files under the Content.IE5 folder, that suggests that something has corrupted the cache index and is preventing proper cleanup. You can safely open this folder in Explorer and delete everything in it (use Shift+Delete to prevent a very slow copy to the recycle bin).
Still confused. I delete my temporary internet folder, however, when I check settings and files all these icons are still in temporary internet folder. Should I delete everything one at a time from there, also? What happens if I do? Thanks
[EricLaw] I'm not sure what "delete my temporary internet folder" means? If you use the Delete Browser History command, without the "preserve favorite website" option set, the folder will be cleared.
Hi, With IE10+ the wininet cache is started by a scheduled task when the user logs on and does not end till the user logs off. Is it possible to end close the wininet cache? Ideally via an API? If the scheduled task process is killed, when you run IE the wininet cache manager is ran from dllhost, again this process doesn't terminate till the user logs off. Any ideas?
[EricLaw] When one asks: "I'd like to surgically remove the brain from a patient and put it back in later, any tips?" the proper response isn't suggesting a saw to use, but rather to ask: "Why on earth would you want to do such a thing?"
I understand that the wininet cache scavenger will be scheduled to run when the number of files cached exceeds 60000. Is it possible to initiate the cache scavenger manually, or via an API?
[EricLaw] The file count is only one trigger for the scavenger; the size of the cache is another trigger, and there's a timer (10 minutes?) for routine scavenging as well.
In other words, there is no way for an wininet application, or from commandline, to initiate a cache scavenger run?
I ask because our application is intended to run 24/7 for weeks and it is using URLDownloadToFile with HTTP to download files, although not continuously but frequently. In a citrix environment where one or more instances of our application, from the same user account, has been running fine for 15+ hours, one of the instance would start reporting failures to open the requested files which were successfully opened just moments or minutes ago (no file changes on the webserver during the run). The only way to fix this problem is to restart the application.
I'm trying to figure out what could have cause this problem: cache scavenger, exhaustion of file handles, calling wininet API from multiple threads in our application, etc?
[EricLaw] Are we having this same conversation on StackOverflow by chance? The problem isn't likely to be the scavenger; you may want to watch a "stuck" process in Process Monitor to see if you see anything suspicious. While WinINET doesn't offer a way to invoke the scavenger, you could try clearing the cache once in a "stuck" state to see if it makes any difference. See e.g.
Thanks for the feedback. I will try to use Process Monitor to watch a "stuck" process tomorrow.
I did try to purge the cache using IE but that didn't help the "stuck" process.
Thanks to your advice, by using ProcessExplorer, I was able to see that the "stuck" process has a handle count of >9700, and a long list of opened files (same files downloaded by our application multiple times and cached at different locations in the WinINET cache). I suspect that the failure to download additional files can be attributed to the exhaustion of file handles allowed in a process.
What confuses me is that our application periodically opens these files by calling InternetOpenUrl with the INTERNET_FLAG_RESYNCHRONIZE flag, retrieves the file contents by calling InternetReadFile, and then closes them by calling InternetCloseHandle. I'd expect that calling InternetCloseHandle would take care of closing all handles relating to the file.
Furthermore, if these files have remain unchanged on the webserver, why would they be downloaded and cached again at a different location when requested repeatedly? I'd expect all subsequent open requests be satisfied by accessing the cached copy because INTERNET_FLAG_RESYNCHRONIZE stipulates that "Reloads HTTP resources if the resource has been modified since the last time it was downloaded".
What am I missing here and how can these files be closed properly?
[EricLaw] I wrote about what INTERNET_FLAG_RESYNCHRONIZE does under the covers here:. Have you watched your traffic in Fiddler to see whether you're getting a HTTP/200 each time, or a HTTP/304? (Does the server's response have a Last-Modified and/or ETAG that would allow a 304?)
You said you're using URLDownloadToFile, but then said you're using InternetReadFile-- is there some reason you're not reading the created file directly (not using WinINET)? Do you see the same behavior if using URLDownloadToCacheFile instead?
I should have been clearer: Our FileControl is a ActiveX control that is responsible to download files for its clients. It provide supports for redundency via backup webservers. The FileControl basically supports two ways to return a requested file to its application clients:
1) the path of the cached file (client is responsible to open and close the cached file);
2) the content of the file in a BSTR (FileControl is expected to open and close the requested file).
The FileControl in turn calls URLDownloadToFile to faciliate for the first option and InternetOpenUrl for the second. According to ProcessExplorer, it appears that only files that were opened for option (2) were left opened.
I've not used Fiddler before, any pointers for me to get started?
[EricLaw] Install it from. Open it. Watch. | http://blogs.msdn.com/b/ieinternals/archive/2011/03/19/wininet-temporary-internet-files-cache-and-explorer-folder-view.aspx | CC-MAIN-2015-06 | refinedweb | 2,315 | 60.14 |
Not that I have much time these days to work on tech, but still, occasionally an opportunity presents itself. And thusly, we have an excuse for a quick tech post.
If you need to integrate jQWidgets with React, jQWidgets provides this guide to make it happen. Unfortunately, this doesn’t exactly work if you’re using the
jqwidgets-framework npm and don’t want to have a local copy of the core files in your application directory structure.
Should you have need for jQWidgets in your React application (with webpack), these steps will help you get it running.
Note: Bear in mind, the ‘native’ support that jQWidgets advertises appears to be just a React wrapper for each of the widgets, so you may have difficulty with component changes that will update the render without manually manipulating them through the widget’s exposed methods, or destroying and recreating the widget with each update.
Step 1: Install jQWidgets
Easy enough:
You’ll also need
babel-preset-es2015 and
babel-preset-react if you’re not using them already.
Step 2: Configure webpack
Following on from the previous step, if you’re not using ES2015 already, your webpack configuration will need to have a section similar to the following to ensure the jQWidgets framework loads correctly:
Add this after the default JS loader test. Updating the
include path to be the
jqwidgets-react directory in your
node_modules.
You may have to muck around with the
include and
exclude directives in the default JS loader test as well. For example, if you’re using React.js Boilerplate, in the default JS loader, you’ll need to replace:
with:
Specifically, the
exclude was replaced with an
include so that the ES2015 loader for jQWidgets in
node_modules won’t be skipped later on.
Step 3: Load the jQWidgets core framework
The original guide loaded the necessary jQWidgets files in
index.html. But, if you do not have a local copy of the library as an external lib, and your
node_modules isn’t exposed, you can load them directly from
node_modules by
importing them somewhere in your app, such as your main application script:
jqx-all will load all the components, but according to the docs, you should also be able to load
jqx-core and only the components you need.
Step 4: Load the jQWidgets React component
Now that the core framework is loaded, wherever you will need a jQWidgets component,
import it, and you’re done. | http://www.hatsaplenty.com/2017/09/integrating-jqwidgets-react/ | CC-MAIN-2018-09 | refinedweb | 411 | 53.65 |
object's
__contains__ method, and also works well for checking if an item exists in a list.
2) The
String.index() Method
The String type in Python has a method called
index that can be used to find the starting index of the first occurrence of a substring in a string. If the substring is not found, a
ValueError exception is thrown, which can to be handled with a try-except-else block:
fullstring = "StackAbuse" substring = "tack" try: fullstring.index(substring) except ValueError: print "Not found!" else: print "Found!"
This method is useful if you need to know the position of the substring, as opposed to just its existence within the full string.
3) The
String.find() Method
The String type has another method called
find which is more convenient to use than
index, because we don't need to worry about handling any exceptions. If
find doesn't find a match, it returns -1, otherwise it returns the left-most index of the substring in the larger string.
fullstring = "StackAbuse" substring = "tack" if fullstring.find(substring) != -1: print "Found!" else: print "Not found!"
If you'd prefer to avoid the need to catch errors, then this method should be favored over
index.
4) Regular Expressions (REGEX)
Regular expressions provide a more flexible (albeit more complex) way to check strings for pattern matching. Python is shipped with a built-in module for regular expressions, called
re. The
re module contains a function called
search, which we can use to match a substring pattern as follows:
from re import search fullstring = "StackAbuse" substring = "tack" if search(substring, fullstring): print "Found!" else: print "Not found!"
This method is best if you are needing a more complex matching function, like case insensitive matching. Otherwise the complication and slower speed of regex should be avoided for simple substring matching use-cases.. | https://stackabuse.com/python-check-if-string-contains-substring/ | CC-MAIN-2019-43 | refinedweb | 307 | 73.58 |
You want to use the
com.oreilly.servlet classes that
O'Reilly author Jason Hunter has developed to handle
file uploads.
Of course, this isn't much of a problem, as
Jason's library takes most of the work out of
uploading and accepting files. I use Jason's library
here (with his permission, of course) because it handles file uploads
nicely, and there's no good reason to reinvent a
perfectly good wheel.
Download the distribution ZIP file from. Add
the cos.jar file, which is part of the
distribution to the WEB-INF/lib directory of
your web application. Make sure that you adhere to the software
license when using the library.
A JAR file named cos.jar includes the
com.oreilly.servlet and
com.oreilly.servlet.multipart packages. These
packages include several classes, such as all of the Java classes
that begin with "Multipart," which
can be used to handle file uploading in a servlet.
The cos.jar archive also contains many other
interesting and useful classes to use with servlets, but the
following recipes focus on file uploads.
Download the latest ZIP file containing the distribution from. The
contents of the ZIP file include
cos.jar, which you need to add to the
WEB-INF/lib directory of your web application.
In your servlet, you then import the classes that you want to use:
import com.oreilly.servlet.MultipartRequest;
import com.oreilly.servlet.multipart.FileRenamePolicy;
Before you have integrated these classes into your code, make sure
that you have read the accompanying software license for this code:.
The rest of the recipes in this chapter assume that you have
cos.jar and the classes it contains available in
your web application. If you don't take steps to
make these classes available, none of the examples in this chapter
will function properly.
Recipe 8.1 on preparing the HTML for a file
upload; Recipe 8.5 on handling a single file
upload; Recipe 8.6 on handling multiple file
uploads in a servlet; Recipe 8.5 on controlling file naming; Recipe 8.6 on using a JSP to handle file uploads; the homepage for
com.oreilly.servlet:; the
RFC 1867 document on form-based file uploads:. | http://books.gigatux.nl/mirror/javaservletjspcookbook/0596005725_jsvltjspckbk-chp-8-sect-2.html | CC-MAIN-2018-43 | refinedweb | 370 | 59.4 |
count the number of duplicate nodes in the linked list
Problem Statement Understanding
Let’s first understand the problem statement with help of examples.
Suppose the given list is:
We have to count the number of duplicate nodes in the list.
From the above given linked list, we can see that:
- Count of each 1 and 8 is 2 in the linked list.
- While the count of 7 is 1 in the linked list.
So, we can say that duplicates of 1 and 8 exists in the linked list, 1 duplicate each of 1 and 8 exists in the linked list. So, we will return the count of duplicate node in linked list as (1+1) = 2.
If the given linked list is:
For the above linked list, we can see that:
- Count of each 1, 2, 3 is 2 in the linked list.
- The count of 5 is 3.
- While the count of 4 is 1 in the linked list.
So, we can say that duplicates of 1, 2, 3, 5 exists in the linked list, 1 duplicate each of 1, 2 and 3 exists and 2 duplicates of 5 exists. So, we will return the count of duplicate node in linked list as (1+1+1+2) = 5.
Now, I think it is clear from the examples what we have to do in the problem. So let’s move to approach.
Before jumping to approach, just try to think how can you approach this problem?
It's okay if your solution is brute force, we will try to optimize it together.
We will first make use of simple nested list traversal to find the duplicates, although it will be a brute force approach, but it is necessary to build the foundation.
Let us have a glance at brute force approaches.
Approach and Algorithm (Brute Force)
The approach is going to be pretty simple.
- We will create a variable count and initialize it to 0.
- Now, we will traverse through the list and for every node, we will traverse from its next node to the end of the list and whenever we will find a match, we will increase the counter and will break out of the loop. Basically here what we are trying to find out is that is this particular node duplicate or not.
This method has a time complexity of O(n2) as it is using nested traversal.
Can we do better?
Yes. We can do better. We can do it in O(n) with the help of hashing.
Let us see the efficient approach.
Approach (Hashing)
In this approach, we will use hashing.
- Firstly, we will create an unordered set, and we will insert the data of the head in the set.
- We will also create a counter whose initial value will be 0.
- Now, we will traverse through the list, starting from the next node, and for every node, we will check if that node is already present in the set or not. If it is present, we will increment the counter. We will also keep inserting the nodes, that we are traversing, in the set.
Algorithm
- Base Case - If the head is NULL, return 0.
- Create an unordered set, say s, and a variable count with an initial value of 0.
- Insert the head → data in the set.
- Traverse from the next node of the head till the end of the list.
- In every iteration, check if the node’s data is already present in the set or not. If present, increment the count.
- Insert the current node’s data in the set.
- In the end, return the count variable.
Dry Run
Code Implementation
#include
#include using namespace std; struct Node { int data; Node* next; }; void insert(Node** head, int item) { Node* temp = new Node(); temp->data = item; temp->next = *head; *head = temp; } int countNode(Node* head) { if (head == NULL) return 0;; unordered_set s; s.insert(head->data); int count = 0; for (Node *curr=head->next; curr != NULL; curr=curr->next) { if (s.find(curr->data) != s.end()) count++; s.insert(curr->data); } return count; } int main() { Node* head = NULL; insert(&head, 8); insert(&head, 8); insert(&head, 1); insert(&head, 7); insert(&head, 1); cout << countNode(head); return 0; }
import java.util.HashSet; public class PrepBytes { static class Node { int data; Node next; }; static Node head; static void insert(Node ref_head, int item) { Node temp = new Node(); temp.data = item; temp.next = ref_head; head = temp; } static int countNode(Node head) { if (head == null) return 0;; HashSet
s = new HashSet<>(); s.add(head.data); int count = 0; for (Node curr=head.next; curr != null; curr=curr.next) { if (s.contains(curr.data)) count++; s.add(curr.data); } return count; } public static void main(String[] args) { insert(head, 8); insert(head, 8); insert(head, 1); insert(head, 7); insert(head, 1); System.out.println(countNode(head)); } }
#include
#include struct Node { int data; struct Node* next; }; // Function to insert a node at the beginning void insert(struct Node** head, int item) { struct Node* temp = (struct Node*)malloc(sizeof(struct Node)); temp->data = item; temp->next = *head; *head = temp; } // Function to count the number of // duplicate nodes in the linked list int countNode(struct Node* head) { int count = 0; while (head->next != NULL) { // Starting from the next node struct Node *ptr = head->next; while (ptr != NULL) { // If some duplicate node is found if (head->data == ptr->data) { count++; break; } ptr = ptr->next; } head = head->next; } // Return the count of duplicate nodes return count; } // Main function int main() { struct Node* head = NULL; insert(&head, 5); insert(&head, 7); insert(&head, 5); insert(&head, 4); insert(&head, 7); int ans = countNode(head); printf("%d", ans); return 0; }
class Node: def __init__(self, data = None, next = None): self.next = next self.data = data head = None def insert(ref_head, item): global head temp = Node() temp.data = item temp.next = ref_head head = temp def countNode(head): if (head == None): return 0 s = set() s.add(head.data) count = 0 curr = head.next while ( curr != None ) : if (curr.data in s): count = count + 1 s.add(curr.data) curr = curr.next return count insert(head, 8) insert(head, 8) insert(head, 1) insert(head, 7) insert(head, 1) print(countNode(head))
Output
2
Time Complexity: O(n), as list traversal is needed.
[forminator_quiz id="4008"]
So, in this article, we have tried to explain the most efficient approach to find duplicates in a given linked list. This is an important question when it comes to coding interviews. If you want to solve more questions on Linked List, which are curated by our expert mentors at PrepBytes, you can follow this link Linked List.
One thought on “Count duplicates in a Linked List”
I love your website.. very nice colors & theme. Did you create this site yourself or did you hire somebody to do it for you? Plz reply back as I’m looking to create my own website and would like to know where u got this from. thank you | https://www.prepbytes.com/blog/linked-list/count-duplicates-in-a-linked-list/ | CC-MAIN-2022-21 | refinedweb | 1,168 | 73.47 |
tiddlywebplugins.etagcache 0.10.0
Cache TiddlyWeb ETags so that a 304 can be sent without checking store
This is a plugin for TiddlyWeb that creates a cache of ETags.
It uses the memcached handling provided by tiddlywebplugins.caching.
Cache invalidation is handled via store hooks and this trick:
Note the test files are not good tests, there were used to structure development but do not adequately assert anything.
The plugins keeps a cache of ETags so we don’t need to access the store to do validation.
This operates as a two tiered piece of middleware.
On the request side it checks if the request is a GET and if it includes an If-None-Match header. If it does it looks up the current URI in the cache and compares the value with what’s in the If-Match header. If they are the same we can raise a 304 right now.
On the response side, if the current request is a GET and the outgoing response has an ETag, put the current URI and ETag into the cache.
Store HOOKs are used to invalidate the cache through the management of namespaces.
Installation is simply adding the plugin name to system_plugins and twanager_plugins in tiddlywebconfig.py
Licensed as TiddlyWeb itself. Copyright 2011, Chris Dent <cdent@peermore.com>
- Author: Chris Dent
- Platform: Posix; MacOS X; Windows
- Package Index Owner: cdent, pads, BoyCook
- DOAP record: tiddlywebplugins.etagcache-0.10.0.xml | https://pypi.python.org/pypi/tiddlywebplugins.etagcache | CC-MAIN-2017-04 | refinedweb | 241 | 63.7 |
Adding custom labels to axes in a seaborn plot in Python
This tutorial will teach you how to create your own custom labels for the axes of graphs in Python seaborn plot. To do this, we will be creating a graph using seaborn, change its axes’ labels and then use matplotlib to display the plot.
Importing the Libraries
We first import the two libraries using the following piece of code:
import seaborn as sns import matplotlib.pyplot as plt
pyplot is a simple module based on matplotlib that allows you to plot graphs very easily, similar to what is done in MATLAB (if you are interested).
We create alias using the ‘as’ keyword that allows us to write more readable code. I recommend using alias while using libraries as it makes calling functions from these libraries quite simple.
The Dataset
You may use any dataset that you wish to use for this program. However, for the sake of this example, I will be using the ‘titanic’ dataset that stores information about the people that traveled on the Titanic.
Be connected to the internet while running the code because seaborn retrieves this dataset from the internet. This means that you need not have the dataset locally.
The Code and its Explanation
#Importing the necessary libraries import seaborn as sns import matplotlib.pyplot as plt #Loading the dataset into the variable 'dataset' dataset = sns.load_dataset("titanic") #Graph is created and stored in the variable 'graph' graph = sns.barplot(x="sex",y="survived",data=dataset) #The values for labels of x and y axes are taken from the keyboard x_axis = input("Enter The x-axis label : ") y_axis = input("Enter The y-axis label : ") #The custom labels are set to the x and y axes graph.set(xlabel = x_axis, ylabel=y_axis) #The plot is shown plt.show()
We first import the libraries that we need.
Next, we use the sns.load_dataset() function to load the ‘titanic’ dataset into the variable, ‘dataset’.
Subsequently, we use the sns.barplot() function to plot the graph from the dataset between the columns, ‘sex’ and ‘survived’. This denotes the number of males and females that survived in the Titanic tragedy.
In the next part, the input() function takes the custom x and y axes’ label values from the user using the keyboard.
Next, the set() function sets the x and y axes labels to the ones you entered in the previous step.
Finally, the plt.show() function shows the graph.
I have set the x-axis label and y-axis label to ‘Example x_axis’ and ‘Example y_axis’ respectively for the sake of this example.
Below is the result we can see after we run our program:
In conclusion, I recommend you to explore more about Seaborn and graphs in Python as the combination of both these modules along with another library called ‘pandas’ is some of the most used libraries in Python. You can go to the following links to learn more:
Plotting Categorical Data with Seaborn in Python
Python Matplotlib Library
Plotting a Histogram in Python using Seaborn | https://www.codespeedy.com/adding-custom-labels-to-axes-in-a-seaborn-plot-in-python/ | CC-MAIN-2020-29 | refinedweb | 510 | 62.27 |
This is the mail archive of the cygwin mailing list for the Cygwin project.
Hey guys, after a couple more trials was able to solve the issue. I am not sure exactly what was the problem but I'll be reporting the full workaround. Neither I am certain that the libgeos shipped with cygwin has an issue; it looks like it was a matplotlib basemap issue instead. Anyways here is the full process to get matplotlib basemap on cygwin: 1) <<Do not>> git clone . Instead use their releases page: . Follow the procedure indicated in their github home page. 2) After the "> ./configure --prefix=$GEOS_DIR" but before the " > make; make install" edit the file include/geos/platform.h on line 87 from: ''' #if defined(HAVE_ISNAN) # define ISNAN(x) (isnan(x)) #else # if defined(_MSC_VER) # define ISNAN(x) _isnan(x) # elif defined(__MINGW32__) // sandro furieri: sanitizing MinGW32 # define ISNAN(x) (std::isnan(x)) # elif defined(__OSX__) || defined(__APPLE__) // Hack for OS/X <cmath> incorrectly re-defining isnan() into oblivion. // It does leave a version in std. # define ISNAN(x) (std::isnan(x)) # elif defined(__sun) || defined(__sun__) # include <math.h> # define ISNAN(x) (::isnan(x)) # endif #endif ''' to ''' # define ISNAN(x) (std::isnan(x)) # include <math.h> # include <cmath> ''' now proceed to the " > make; make install" and continue the procedure as informed. Thanks for all the help! Best regards, -- Problem reports: FAQ: Documentation: Unsubscribe info: | http://cygwin.com/ml/cygwin/2016-08/msg00418.html | CC-MAIN-2018-22 | refinedweb | 233 | 58.69 |
0
It's been a while since I bugged you guys. But I need the council of my wise advisers once more.
I am trying to write a program that reads a .txt file, breaks each line into words, strips the whitespace and punctuation from the words and returns them in lowercase.
My code is far from done, but when I try to run even this. It only returns one word.
What more puzzling the word isn't even the first one nor the last. It is one near the end.
The code looks right when I read it. What did I do wrong?
import string def read_book(): f = open("alice_in_wonderland.txt", "r") for l in f.readlines(): l.strip().translate(None, string.punctuation) for w in l.split(" "): if w != "": return w def main(): """ main function """ print read_book() return 0 if __name__ == "__main__": main()
here is the book if you guys want to run my code: | https://www.daniweb.com/programming/software-development/threads/328518/help-with-python-pogram | CC-MAIN-2018-30 | refinedweb | 157 | 86.91 |
RViz is not just a visualizer application, it is also a Python library! Much of RViz’s functionality can be accessed from Python code by importing the librviz Python bindings.
This tutorial shows a simple example of creating a visualizer (rviz::VisualizationFrame) as a child widget along with other Qt widgets, programmatically loading a config file, then connecting a slider and some Qt push buttons to change display a display property and the viewpoint.
The source code for this tutorial is in the rviz_python_tutorial package. You can check out the source directly or (if you use Ubuntu) you can just apt-get install the pre-compiled Debian package like so:
sudo apt-get install ros-groovy-visualization-tutorials
The running application looks like this:
The full text of myviz.py is here: myviz.py
First we start with the standard ros Python import line:
import roslib; roslib.load_manifest('rviz_python_tutorial')
Then load sys to get sys.argv.
import sys
Next import all the Qt bindings into the current namespace, for convenience. This uses the “python_qt_binding” package which hides differences between PyQt and PySide, and works if at least one of the two is installed. The RViz Python bindings use python_qt_binding internally, so you should use it here as well.
from python_qt_binding.QtGui import * from python_qt_binding.QtCore import *
Finally import the RViz bindings themselves.
import rviz
The MyViz class is the main container widget.
class MyViz( QWidget ):
Its constructor creates and configures all the component widgets: frame, thickness_slider, top_button, and side_button, and adds them to layouts.
def __init__(self): QWidget.__init__(self)
rviz.VisualizationFrame is the main container widget of the regular RViz application, with menus, a toolbar, a status bar, and many docked subpanels. In this example, we disable everything so that the only thing visible is the 3D render window.
self.frame = rviz.VisualizationFrame()
The “splash path” is the full path of an image file which gets shown during loading. Setting it to the empty string suppresses that behavior.
self.frame.setSplashPath( "" )
VisualizationFrame.initialize() must be called before VisualizationFrame.load(). In fact it must be called before most interactions with RViz classes because it instantiates and initializes the VisualizationManager, which is the central class of RViz.
self.frame.initialize()
The reader reads config file data into the config object. VisualizationFrame reads its data from the config object.
reader = rviz.YamlConfigReader() config = rviz.Config() reader.readFile( config, "config.myviz" ) self.frame.load( config )
You can also store any other application data you like in the config object. Here we read the window title from the map key called “Title”, which has been added by hand to the config file.
self.setWindowTitle( config.mapGetChild( "Title" ).getValue() )
Here we disable the menu bar (from the top), status bar (from the bottom), and the “hide-docks” buttons, which are the tall skinny buttons on the left and right sides of the main render window.
self.frame.setMenuBar( None ) self.frame.setStatusBar( None ) self.frame.setHideButtonVisibility( False )
frame.getManager() returns the VisualizationManager instance, which is a very central class. It has pointers to other manager objects and is generally required to make any changes in an rviz instance.
self.manager = self.frame.getManager()
Since the config file is part of the source code for this example, we know that the first display in the list is the grid we want to control. Here we just save a reference to it for later.
self.grid_display = self.manager.getRootDisplayGroup().getDisplayAt( 0 )
Here we create the layout and other widgets in the usual Qt way.
layout = QVBoxLayout() layout.addWidget( self.frame ) thickness_slider = QSlider( Qt.Horizontal ) thickness_slider.setTracking( True ) thickness_slider.setMinimum( 1 ) thickness_slider.setMaximum( 1000 ) thickness_slider.valueChanged.connect( self.onThicknessSliderChanged ) layout.addWidget( thickness_slider ) h_layout = QHBoxLayout() top_button = QPushButton( "Top View" ) top_button.clicked.connect( self.onTopButtonClick ) h_layout.addWidget( top_button ) side_button = QPushButton( "Side View" ) side_button.clicked.connect( self.onSideButtonClick ) h_layout.addWidget( side_button ) layout.addLayout( h_layout ) self.setLayout( layout )
After the constructor, for this example the class just needs to respond to GUI events. Here is the slider callback. rviz.Display is a subclass of rviz.Property. Each Property can have sub-properties, forming a tree. To change a Property of a Display, use the subProp() function to walk down the tree to find the child you need.
def onThicknessSliderChanged( self, new_value ): if self.grid_display != None: self.grid_display.subProp( "Line Style" ).subProp( "Line Width" ).setValue( new_value / 1000.0 )
The view buttons just call switchToView() with the name of a saved view.
def onTopButtonClick( self ): self.switchToView( "Top View" ); def onSideButtonClick( self ): self.switchToView( "Side View" );
switchToView() works by looping over the views saved in the ViewManager and looking for one with a matching name.
view_man.setCurrentFrom() takes the saved view instance and copies it to set the current view controller.
def switchToView( self, view_name ): view_man = self.manager.getViewManager() for i in range( view_man.getNumViews() ): if view_man.getViewAt( i ).getName() == view_name: view_man.setCurrentFrom( view_man.getViewAt( i )) return print( "Did not find view named %s." % view_name )
That is just about it. All that’s left is the standard Qt top-level application code: create a QApplication, instantiate our class, and start Qt’s main event loop (app.exec_()).
if __name__ == '__main__': app = QApplication( sys.argv ) myviz = MyViz() myviz.resize( 500, 500 ) myviz.show() app.exec_()
Just type:
roscd rviz_python_tutorial ./myviz.py
myviz.py loads its config file from the current directory, so you need to run it from the directory it comes in, or adapt the script to find the file.
There are more classes in RViz which do not yet have Python bindings. If you find important ones are missing, please request them as “enhancement” issues on the RViz project on github. | http://docs.ros.org/en/hydro/api/rviz_python_tutorial/html/index.html | CC-MAIN-2021-17 | refinedweb | 938 | 51.44 |
Hello!
I am looking for a way for a process to publish some string system wide (or, preferably, user-session wide, if possible), so another process or processes could search for this string upon launch. What is important is that this string should disappear once the publishing process dies or gets killed.
I know there exist POSIX named semaphores (sem_open() ) and POSIX named shared memory segments (shmopen()), but both allow specifying a maximum of 31 bytes in their names. I need at least 255.
I was considering something like NSUserDefaults (or just regular files), but it is impossible to reliably clean them up upon process termination, which is essential.
Are there any other options available on macOS I could try?
It would be ideal, if this approach, apart from publishing a string that is accessible to other interested processes, also allowed sending messages between these processes, but this is not critical.
My main goal is to make a process and some of its configuration parameters discoverable by other instances of this process upon launch.
Thank you for answers!
Re: Looking for a named IPC on macOSjohn daniel Aug 6, 2019 5:54 PM (in response to O.W.Grant)
It sounds like NSUserDefaults is what you want to use. It is reliable and guaranteed to work. If this architecture fails, virtually every Mac app in the world fails. That's Apple's problem to fix. If you come up with something funky based on ancient UNIX, it is quite likely to fail one day because of a change to the sandbox or some funky Apple security change. When that happens, you are the only one with a broken app. That's your problem to fix.
Your requirement to reliably clean up the resources upon process termination is impossible no matter what option you pick. If someone sends kill -9 to your app, it isn't going to clean anything up. The only guaranteed way to clean something up is to set a "running" flag somewhere, either in defaults or with a PID file, and then clean it up at the next launch of your process. You can do that regardless of how you implement your persistence.
Re: Looking for a named IPC on macOSjonprescott Aug 6, 2019 7:10 PM (in response to john daniel)
Extending John's explanation, you can delete your user defaults values during controlled exit conditions (right before you exit, as part of signal handlers, exceptions handlers if you're using C++,Swift, trap handlers, atexit handlers, etc.. Extraordinary conditions like SIGKILLs are not going to be places where you'll have to have much luck intercepting the chain, and you'll need a recovery option similar to what John outlined above.
XPC is preferred solution for inter-process communication using Apple frameworks. Unix sockets and pipes are time-tested and likely to be supported indefinitely since they are pretty low-level.
Re: Looking for a named IPC on macOSO.W.Grant Aug 7, 2019 3:50 AM (in response to john daniel)
Thanks for the reply John.
It is crucial that the string disappears once the app terminates in any way - either by getting a signal or a normal termination.
Re: Looking for a named IPC on macOSjohn daniel Aug 7, 2019 5:29 AM (in response to O.W.Grant)
You have two options:
1) Have your app function as a server over a TCP or UNIX socket. The location of said socket can be stored in preferences. Any other app that wants to access the “string” will have ro connect to the service to retrieve it. If the app isn’t running, no string.
I guess there are more than two options, but they are all architecturally identical. You need a globally known address, such as a UNIX socket path, bonjour-published TCP server/port, or maybe a PID file. To access the value, you’ll have to make some query to pull it from the running app, or return an error if the app isn’t running. But it has to be some kind of active response from the app. The system isn’t going to help much. I guess the PID file is the closest to the system, but the app has to write the file to a known location.
You could also use a launchd task to get notified of when your other task is no longer running.
Re: Looking for a named IPC on macOSeskimo Aug 7, 2019 1:12 AM (in response to O.W.Grant)
It’s hard to answer this without knowing more about the runtime environment of the publisher and its clients. Are any of them distributed via the Mac App Store? Are any of them sandboxed?
Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com"
Re: Looking for a named IPC on macOSO.W.Grant Aug 7, 2019 3:48 AM (in response to eskimo)
Hello Quinn,
No, they are neither sandboxed nor published at the AppStore.
These are the requirements:
1) upon its launch, an app must publish a string to some global namespace, so other instances of the app can detect whether they are ran with the same configuration.
2) upon termination, operating system must remove this string from the global namespace.
Thank you
Re: Looking for a named IPC on macOSeskimo Aug 8, 2019 1:25 AM (in response to O.W.Grant)
These are the requirements:
1) upon its launch, an app must publish a string to some global namespace
But, to be clear, you’re talking about a global namespace, right? Because earlier you wrote:
(or, preferably, user-session wide, if possible)
I’m presuming by “user-session wide” you’re referring to a GUI login session? That is, you’re not concerned about user programs running in a non-GUI login session, like an SSH login session.
Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
let myEmail = "eskimo" + "1" + "@apple.com" | https://forums.developer.apple.com/thread/120957 | CC-MAIN-2020-05 | refinedweb | 1,012 | 70.94 |
Taking reuse to the next level with closures.
Taking reuse to the next level with closures.
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This article is about how to take reuse to the next level by using Groovy's closure language feature to aid in reuse, intercept method calls and even replace methods at runtime. Then we discuss the true nature of closures.
A closure is an executable block of code, similar to an anonymous method, but it can be treated like an object reference. It follows a lot of the same rules as an anonymous inner class in Java. Throughout this article closures true nature will be revealed.
In the last article we used invokeMethod and idiomatic method invocation with strings to garner another level of reuse. In this article we will do the same but with Groovy closures.
Using closures is essential to understanding Groovy as the GDK uses closures extensively. With Groovy closures, it is easy to go to the next level of reuse. GDK stands for Groovy Development Kit and is Groovy's way of extending Java core classes with Groovy language features (GDK even extends final classes like String and Integer).
In the last article we showed a simple example which was a Computer class that was using the Observer/Observable design pattern to notify interested third parties that a rent event occurred.
Just in case you did not read the last article, the Computer class uses/implements the Java events as follows:
RentableEvent that extends java.util.EventObject
public class RentableEvent extends EventObject{
RentableEvent (Computer source) {
super(source)
}
}
RentListener that extends java.util.EventListenered.remove(listener)
}
}
NOTE: This Computer example is adapted from our Groovy course and the original was written by Alex Kotovich and I have heavily modified it and re-purposed it a few times.
Notice that the above fires three types of events as follows: fireRentedEvent, fireOverdueEvent, and fireReturnedEvent.
Review: closures.
In Groovy, it is easy to make the listener method that gets called a parameter by using a closure. Notice the use of a closure in the fireRentEvent as follows:
Using closures to get rid of three code blocks
public void fireRentEvent(Closure closure) {
assert closure: "Closure should not be null"
RentableEvent event = new RentableEvent(this)
rentableListeners.each {RentListener listener ->
closure(event, listener)
}
}
private void fireRentedEvent() {
Closure closure = {RentableEvent event, RentListener listener -> listener.rented(event) }
fireRentEvent(closure)
}
/* Fire overdue event. */
private void fireOverdueEvent() {
fireRentEvent({RentableEvent event, RentListener listener -> listener.overdue(event) })
}
/* Fire returned event. */
private void fireReturnedEvent() {
fireRentEvent({RentableEvent event, RentListener listener -> listener.returned(event) })
}
The fireRentedEvent calls the fireRentEvent passing it a closure.
Breaking down the closure example
Let's dissect the above example a bit. To define a closure we use the following syntax:
Closure closure = {RentableEvent event, RentListener listener -> listener.rented(event) }
The above looks like we are assigning a block of code to a object reference and this is exactly what we are doing. Just like Groovy has literal support for defining a Map, List and a Regex. Groovy has literal support for defining reusable blocks of code that can be passed around like object references a.k.a. closures.
If you think of a closure as an anonymous method then you can think of the following:
RentableEvent event, RentListener listener ->
as defining the arguments to that method. Then the body of the method is after the ->, i.e.,
-> listener.rented(event)
Combined, the above defines that closure that we can later pass to the fireRentEvent as follows:
fireRentEvent(closure)
Then this block of code gets used inside of the fireRentEvent as follows:
public void fireRentEvent(Closure closure) {
assert closure: "Closure should not be null"
RentableEvent event = new RentableEvent(this)
rentableListeners.each {RentListener listener ->
closure(event, listener)
}
}
We got rid of the three for loops by using a closure.
Making it more groovy
Since these are internal methods for firing events and not public APIs, it might make sense to reduce the code size by getting rid of the strong typing. I tend to always use strong typing unless I need dynamic typing to get more reuse. To me strong typing aids in the readability of the code. However, when using closures and such, it is often easier to use dynamic typing as the object types you are dealing with are easily discernible by context. It is a matter of taste and style so without being prescriptive let's use dynamic typing as follows:
/** Fire rented event. */
public void fireRentEvent(closure = {event, listener -> listener.rented(event) } ) {
rentableListeners.each {RentListener listener ->
closure(new RentableEvent(this), listener)
}
}
/** Fire overdue event. */
private void fireOverdueEvent() {
fireRentEvent({event, listener -> listener.overdue(event) })
}
/** Fire returned event. */
private void fireReturnedEvent() {
fireRentEvent({event, listener -> listener.returned(event) })
}
Notice that the code is much shorter and we got rid of one of the methods. Since the code is shorter, it feels more comfortable using a default closure parameter. Now by default the fireRentEvent calls listener.rented by using a Groovy default argument construct.
Note that there is still strong typing in the body of the fireRentEvent so you can still see what event and listener you are dealing with but the closure as parameter construct uses the dynamically typed approach to keep it short. It is arguably a good combination of strong vs. dynamic to make the code more readable yet still get a lot of reuse.
More closures
Another option is to get rid of of the helper methods all together, make the closures members and use them as arguments to the fireRentEvent when calling it.
/** Fire rent event. */
public void fireRentEvent(closure = fireRentedEvent) {
rentableListeners.each {RentListener listener ->
closure(new RentableEvent(this), listener)
}
}
/** Fire rented event */
def fireRentedEvent = {event, listener -> listener.rented(event) }
/** Fire overdue event. */
def fireOverdueEvent = {event, listener -> listener.overdue(event) }
/** Fire returned event. */
def fireReturnedEvent = {event, listener -> listener.returned(event) }
The definition of a closure versus a method is somewhat blurred anyway. To see what I am talking about try this in the GroovyConsole app:
/* Define a closure. */
Closure helloWorldClosure = {String message, String person -> println "Hello ${person} : ${message}"}
/* Use the closure we defined. */
helloWorldClosure("How are you?", "Rick")
/* Define a method. */
def helloWorld(String message, String person) {
println "Hi ${person} : ${message}"
}
/* Use the method we just defined. See the difference? I don't. */
helloWorld("How the hell are you?", "Rick")
/* Assign the the new method to closure variable. */
helloWorldClosure = this.&helloWorld
/* Now use the closure/method. Methods and closures are first class object. */
helloWorldClosure("Hiya howzit been?", "Rick")
/* Check this out. What is this doing? */
helloWorldClosure = System.out.&println
helloWorldClosure("Hello Rick")
In the above we define a closure called helloWorldClosure and then invoke it. Then we define a nearly equivalent method called helloWorld and invoke it in the same manner. Then we assign the closure reference the method using this.&helloWorld. In this case, this refers to the Script that the GroovyConsole created. In Groovy if a file does not define a class, the the name of the file becomes the name of the class that Groovy generates on your behalf, but in the GroovyConsole there is no file so the name of class becomes things like Script12, Script13 etc. Thus, this refers to Script12 class (or whatever number the GroovyConsole is on). Then we take the closure now referencing the method and invoke it the same way. And we do this to show the similarities of closures and methods. To replace a method at runtime, one merely could assign it a closure after all Groovy is a dynamic language (could != should).
In the last section of the article we will try to un-blur the distinction between methods and closures.
Currying
If we are going to go this far opening up to closures, we would be remiss not to tap on the curry door. Let's tap currying with this example.
/** Fire rent event. */
public void fireRentEvent(closure = fireRentedEvent) {
rentableListeners.each {RentListener listener ->
closure(listener)
}
}
/** Fire rented event */
def fireRentedEvent = ({event, listener -> listener.rented(event) }).curry(new RentableEvent(this))
/** Fire overdue event. */
def fireOverdueEvent = ({event, listener -> listener.overdue(event) }).curry(new RentableEvent(this))
/** Fire returned event. */
def fireReturnedEvent = {event, listener -> listener.returned(event) }.curry(new RentableEvent(this))
In our example, the RentableEvent only holds the source of the rentable event which does not change in the context of an instance of the Computer. It would be nice if we could store the RentableEvent as part of the closure and leave it off of calls to the closure. To curry with a closure is to have the closure remember a parameter. The curry method of the Closure object returns a new instance of a Closure that remember (from left to right) the arguments that were added to the closure. Thus the fireRentedEvent remembers its first argument is a RentableArgument because it is a the results of the call to closure.curry(new RentableEvent(this)).
Standard disclaimer
I would be remiss not to add the following disclaimer. closures (this does not preclude using a Visitor design pattern but merely gives you the choice).
Case study of method references to aid in resue
Earlier in the discussion of what is a closure we introduced the subject of method pointer. In groovy a method is a true object and you can get a reference to it using the this.&methodName syntax. Recently I wrote a code generator for a client using Groovy. I had a piece of code that used meta data from a JDBC connect. The JDBC connection metaData object has two methods to get information about keys in a table, getExportedKeys and getImportedKeys. At first I had two methods that were nearly structurally identical. Then I was able to take reuse to a new level by letting the method itself be a parameter -- note processKeys calls the overloaded processKeys twice passing the connection.metaData.&getExportedKeys on the first pass and the second connection.metaData.&getImportedKeys as follows:
/**
* Process import keys and export keys
*/
def processKeys() {
tables.each {Table table ->
processKeys(table, connection.metaData.&getExportedKeys, table.exportedKeys, false)
processKeys(table, connection.metaData.&getImportedKeys, table.importedKeys, true)
}
}
def processKeys(Table table, getKeys, List keyList, boolean imported) {
if (debug) println "processing keys for table ${table.name} imported=${imported}"
jdbcUtils.iterate getKeys(catalog, schema, table.name),
{ResultSet resultSet ->
... (more code)
}
... (more code)
if (debug) println "\n"
}
We could have achieved similar reuse with closures, or even methodName/invokeMethod approach from the last article. This is just another way to stay DRY with Groovy and its an option because methods are first class object.
Advanced: Changing methods at runtime
To show how closures and methods are similar, let's change some methods with closures at runtime.
You can change methods at runtime. For example let's say we want to redirect println methods to a Swing JTextArea. We can create a printlnClosure and then switch out the println method of each of the utility classes at runtime.
Thus, when the classes run from the command line (no swing GUI), they print to the standard console, but when we run it in our swing application, we can just switch the implementation of the println method out as follows using the metaClass from Groovy:
Closure printlnClosure = {String message ->
... code to print to a TextArea
}
JdbcUtils.metaClass.println = printlnClosure
DataBaseMetaDataReader.metaClass.println = printlnClosure
JavaModelGenerator.metaClass.println = printlnClosure
XMLPersister.metaClass.println = printlnClosure
Note: JdbcUtils, DataBaseMetaDataReader, JavaModelGenerator are all Groovy classes that I created for a utility I recently wrote.
By using metaClass.println = printlnClosure we effectively switch out the method at runtime. Note: we have to do this before instances of these classes are created. You can can also switch out methods on instances. Thus when we create a new instance of DataBaseMetaDataReader its println is effectively the printlnClosure.
Advanced: Intercepting method calls
You can provide AOP like functionality by combining the ability to switch methods at runtime with the special Groovy method invokeMethod which is a method that gets called whenever a method gets invoked on an object. Here is an example of intercepting method calls:
Closure logClosure = {String methodName, methodArgs ->
}
Side bar: Notice that logClosure looks up the method by name and then checks to see if the reference is null. I choose to use the syntax validMethod==null to highlight that we are dealing with an Object reference; however, I could have relied on Groovy truth and written !validMethod. In Groovy a null reference is false. Groovy truth in general is preferred.
Here are the three classes that we decorate as follows:
DataBaseMetaDataReader.metaClass.invokeMethod = logClosure
JavaModelGenerator.metaClass.invokeMethod = logClosure
JPACodeGenerator.metaClass.invokeMethod = logClosure
Now when new instances of DataBaseMetaDataReader, JavaModelGenerator or JPACodeGenerator get created they will be decorated with our AOP-like logClosure. For example, logClosure will print out "Running someMethod(1,2,3)" and "Completed someMethod(1,2,3)" when a method called someMethod gets called with the arguments 1,2,3.
In the logClosure you may have notice the reference to delegate. And if you were like me, you are wondering what is the delegate. Well like classes have a "this" which refers to the current instance, Closure have a "delegate" which refers to the instance of the class that is being decorated. Hopefully this little sample script should clear things up a bit:
samplescript.groovy that uses modified logClosure
Closure logClosure = {String methodName, methodArgs ->
println "Delegate class ${delegate.class.name}"
println "Class ${this.class.name}"
println "Owner ${owner.class.name}"
}
class Employee {
def changeMe(hi) {
println "Hello world $hi"
}
}
println "Delegate before assign ${logClosure.delegate.class.name}"
Employee.metaClass.invokeMethod = logClosure
println "Delegate after assign ${logClosure.delegate.class.name}"
Employee emp = new Employee()
emp.changeMe("Rick")
Notice that we now print the class name of the delegate and the this. Now compare the sample code listing to the output:
richard-hightowers-macbook-pro:~ richardhightower$ groovy samplescript.groovy
Delegate before assign samplescript
Delegate after assign samplescript
Delegate class Employee
Class samplescript
Owner samplescript
Running changeMe({"Rick"})
Delegate class Employee
Class samplescript
Owner samplescript
Hello world Rick
Completed changeMe({"Rick"})
Notice that the delegate is Employee (as expected) when the logClosure is running.
Closures Redux
I sent this out for review. It felt like it was missing more of a description of closures and that I left off with just describing closures as nothing but anonymous method, and even I know better than this. But I was not sure how to discuss more of closures nature.
Then Ken Sipe wrote me and confirmed my fear. Ken just wrote an article on modern functional programming for No Fluff Just Stuff series monthly newsletter. He writes:
I just recently finished an article on functional programming which
includes the details I wanted to communicate to you on closures.
(btw... I would appreciate any feedback you might have on it as well)
Closures somehow became synonymous with anonymous functions, which
isn't necessarily the case. You mention in the article that the
definition of closure vs. method are somewhat blurred. I have to
admit I thought that as well not that long ago. However as I've
traveled a little down the functional road along with a little
research. It has become more clear. ... Closures are a specialized method.
They provide the ability within a language to store or refer to variables
which when looked at from a scope perspective are clearly out of
scope, yet the variables live on. This is a point of closure.
This is certainly the case. By the way, Ken Sipe wrote an excellent article on modern functional programming and it reinforces my desire to learn more about the Clojure language. I would publish information about where to get it, but that information is not available yet. When it becomes available, I will add it to the comments.
If you didn't know before, closures may seem like just anonymous methods but there is more to them than this. The name closure comes from the fact that they capture the local variables of the outer scope which is best illustrated with this non-groovy example which is from Ken Sipe's article:
Function powerFunctionFactory(int power) {
int powerFunction(int base) {
return pow(base, power);
}
return powerFunction;
}
Function square = powerFunctionFactory (2);
square(3); // returns 9
Function cube = powerFunctionFactory (3);
cube(3); // returns 27
"Technically closures are dynamically allocated data structures containing a code pointer, pointing to a fixed piece of code computing a function result and an environment of bound variables. A closure is used to associate a function with a set of “private” variables." --Ken Sipe, NFJS Newletter on Modern Functional Programming Languages
The above code defines an outer function called powerFunctionFactory and an inner function powerFunction. The outer function, creates instances of the inner function. The inner function is configured with the current power which it gets from the outer function; the inner function encloses the local variables from the outer function. Thus we are able to define square and cube functions from the powerFunctionFactory. In essence, powerFunctionFactory makes powerFunction configurable. The powerFunction is a block of code that has access to the local variables of powerFunctionFactory even when powerFunctionFactory variables go out of scope.
Groovy has the same concept and it can be expressed with closures as follows:
Closure powerClosureFactory(int power) {
Closure powerClosure = { int base ->
return Math.pow(power, base)
}
return powerClosure
}
Closure square = powerClosureFactory(2)
square(2)
Closure cube = powerClosureFactory(3)
cube(3)
The above code defines a method called powerClosureFactory and a closure called powerClosure. The outer methods, creates instances of the inner closure. The inner powerClosure is configured with the current power which it gets from the outer method; the inner closure encloses the local variables from the outer method. Thus we are able to define square and cube closures like methods from the powerClosureFactory. In essence, powerClosureFactory makes the powerClosure configurable. The powerClosureFactory is a block of code that has access to the local variables of powerClosureFactory even when powerClosureFactory variables go out of scope.
Here would be a groovier way to write the above:
def powerClosureFactory(power) {
{int base -> Math.pow(power, base)}
}
def square = powerClosureFactory(2)
square(2)
def cube = powerClosureFactory(3)
cube(3)
Except of course the Groovy version is much smaller and prettier (eyes of the beholder.). Note that return is not needed. The last statement is automatically the return, thus, {int base -> Math.pow(power, base)} defines a closure and returns it in one line of code. The closure body returns the results of Math.pow (again without a return).
In Ken Sipe's article, he went on to describe how F# can map values from one list to a new list as follows:
let squares2 = List.map (fun x -> x*x) [1; 2; 3; 4]
The above takes the list (with 1, 2, 3, 4 in it) and maps it to a new list of squares with the results 1, 4, 9, 16 in it. Groovy has the same concept but like Python it calls it collect as follows:
def squares = [1,2,3,4].collect{x -> x*x}
The collect method takes a closure as an argument and it maps the one list into a new list of squares and just like the F# version shown earlier it creates a new list with the values [1, 4, 9, 16]. By the way, F# is a functional programming language that runs in the .Net environment and is based on Objective Camel. Now since we are dealing with Groovy, when you only have one argument being passed to your closure you don't have to name it. By default the name of the first argument is "it" demonstrated as follows:
def squares = [1,2,3,4].collect{it*it}
The idea of this section was to introduce that closures were more then just anonymous methods. For more details on functional programming, I recommend Ken Sipe's article on Functional Programming.
Conclusion
In this short article, we showed how you can push reuse to a new level and stay extremely DRY by using Groovy's closures. We also showed how to achieve the same by using method references and how methods and closures are similar. Then we went on to show how to replace methods at runtime using closures and perform AOP like programming using closures. And then for completeness, we showed that closure were more than just anonymous methods.
Note that this article is not prescriptive. It does not say you should use method references or closure, merely, that these are viable options and weapons in your development arsenal.
Special thanks Andres Almiray, Ken Sipe and Alex Kotovich for their help. Ken and Andres provided valuable insight.
If you liked this article and you are considering learning more about Groovy, please consider ArcMind's Groovy course: Groovy training or our Grails course: Grails Training. Also I plan on adding Groovy language support to the soon to be renamed Crank project.
You can follow Rick at and
Opinions expressed by DZone contributors are their own.
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{{ parent.linkDescription }}{{ parent.urlSource.name }} | https://dzone.com/articles/taking-reuse-next-level | CC-MAIN-2019-47 | refinedweb | 3,500 | 56.15 |
This blog post is part 5 of a series of blogs on how to create a Custom Template in SAP Web IDE with OData integration.
Prerequisites
Before reading this blog please make sure that you have read, understood and implemented part 4 of this series where I have shown how to create a feature project and add plugin template to the application.
Deploy the project to SAP Cloud Platform
This step is mandatory for using the new feature, consisting of the new plugin, included in SAP Web IDE. We need to deploy our feature to SAP Cloud Platform.
This operation will also take care of automatically activating the new plugin.
Right-click the plugin repository folder and select Deploy –> Deploy to SAP Cloud Platform
Select Deploy as a new application and click Deploy.
Our plugin repository has been successfully deployed to SAP Cloud Platform.
Click on Open the application’s page in the SAP Cloud Platform cockpit.
If you check the status of your application it should be started.
Look at the Application URL on the same page and write down or copy it to the clipboard. It will be used in the next steps.
Create a destination in the SAP Cloud Platform cockpit for the new feature
In order for the system to recognize the new feature, we need to create a new destination in the SAP Cloud Platform cockpit. This is a special destination that points to the application URL of our feature application on SAP Cloud Platform.
In the cockpit, go to Destinations and click on New Destination.
Enter the following values to create the new destination:
Also add the following properties:
Save the destination.
In a similar manner, we need to add a destination for the Northwind OData service, which we will consume later.
See below:
Activate the new feature in SAP Web IDE
Let’s activate the new feature. This is made directly from SAP Web IDE.
- Open SAP Web IDE or refresh it if you have it already open.
- Click on the Settings button on the left side toolbar.
- Select Plugins.
- Choose the Features repository and enable the feature we have created
- Click Save.
Refresh SAP Web IDE.
We have successfully activated our first SAP Web IDE feature!
Execute the new template
Now we are ready to create a new project using our custom template:
- In SAP Web IDE, select File -> New – > Project From Template
- Select the newly created template from the drop down.
After template selection, we will get our new template as below:
Now provide project name & namespace and press Next.
In the Data Connection step, select Service URL on the left, and select the Northwind destination you have created (see below):
In the Template Customization step, we have to provide below information.
- First View Name : First (you can provide any name)
- Second View Name : Second (you can provide any name)
- Category : Select Category from Dropdown
- Category Title : Select Category Name from Dropdown
- Entities : Product (you can choose any other as well)
- Object Title : ProductName (you can choose any unique name from the list as well)
- Object Numeric Attribute : Any Numeric Field that you wish to provide.
- Object collection ID : ProductID
- App Title : SAP UI5 CART APP
- App Description : SAP UI5 CART
- Data Source Name : dataModel
- Growing Threshold : 6
- Growing Trigger Text : Next
Press Next and Finish.
Open the generated project, select the Component.js and run the project.
You should get the below output, which retrieves data from the Northwind OData service with our custom Cart template.
Now if we press Next button, it would fetch next 6 data from the OData service.
If we change the tab then category wise product tile gets loaded.
You can press any CART, it would navigate to the second page as below.
If you wish to go back to the first view, press the navigation back button. | https://blogs.sap.com/2018/02/03/how-to-create-a-custom-template-in-sap-web-ide-with-odata-integration-part-5/ | CC-MAIN-2018-47 | refinedweb | 643 | 61.36 |
The characters in which the characters from String gets copied.
destBegin – The index in Array starting from where the chars will be pushed into the Array.
It throws IndexOutOfBoundsException – If any of the following conditions occurs:
(
srcBegin<0) srcBegin is less than zero. (srcBegin>srcEnd) srcBegin is greater than srcEnd.
(
srcEnd > length of string) srcEnd is greater than the length of this string.
(
destBegin<0)
destBegin is negative.
dstBegin+(srcEnd-srcBegin) is larger than
dest.length.
Example: getChars() method
public class GetCharsExample{ public static void main(String args[]){ String str = new String("This is a String Handling Tutorial"); char[] array = new char[6]; str.getChars(10, 16, array, 0); System.out.println("Array Content:" ); for(char temp: array){ System.out.print(temp); } char[] array2 = new char[]{'a','a','a','a','a','a','a','a'}; str.getChars(10, 16, array2, 2); System.out.println("Second Array Content:" ); for(char temp: array2){ System.out.print(temp); } } }
Output:
Array Content: StringSecond Array Content: aaString
Is there a typo or is Array Content not supposed to print anything?
Sorry, I see now why there is no output for Array Content! Is it because String is not an array ?
Correction: I see it’s because indices 10 and 16 give spaces!
Why does String print out in the secondarray content though? I realize there should probably be a new line in front of “Second Array Content” to avoid confusion. | http://beginnersbook.com/2013/12/java-string-getchars-method-example/ | CC-MAIN-2017-09 | refinedweb | 234 | 60.92 |
Hi,
I'm trying to make a program that translates Roman Numerals to arabic numbers, I guess everyone should start with something like that. I've read all the beginner tutorials on this site and decided I wanted to test myself and made this.
Ofcourse I started with almost as much errors as the total amount of lines of code, but by looking them all up on google I managed to get rid of all of them. But I guess that's not the best way to make your program work, because now, without any errors or warnings, it still doesn't work.
So I would really appreciate if anyone could tell me what is causing my program not to work.
the problem is that whatever Roman Numeral I put in it returns the amount of Numerals * 1000.
So:
putting in L returns 1000,
putting in MCLXX returns 5000.
my code:
Code:
#include <iostream>
using namespace std;
class RtoA { // Class for translating a Roman numeral to an Arabic number.
public:
int output;
string input;
RtoA() {}; //Constructor
~RtoA() {}; //Destructor
int read(string input) { // Reads the input and returns the output.
output = 0;
unsigned int n = 0;
output = addvalues(n);
output = check(output);
return(output);
};
private:
int addvalues(unsigned int n) { // Adding the values of the Numerals using recursion.
if ( !( n > input.length() ) ) { // Bottom of the function.
n++;
output = addvalues(n) + givevalue(n);
};
if ( output == 0 ) { return(0); }
else { return(output); };
};
int givevalue(int n) { // Function giving the numerals a value.
if ( input[n] == 'M' || 'n' ) { return(1000); }
if ( input[n] == 'D' || 'd' ) { return(500); }
if ( input[n] == 'C' || 'c' ) { return(100); }
if ( input[n] == 'L' || 'l' ) { return(50); }
if ( input[n] == 'X' || 'x' ) { return(10); }
if ( input[n] == 'V' || 'v' ) { return(5); }
if ( input[n] == 'I' || 'i' ) { return(1); }
else { return(0); };
};
int check(int output) { // Checking the order of the Roman Numerals.
for ( unsigned int j = 1; j < input.length(); j++ ) {
if ( givevalue(input[j]) > givevalue(input[j-1]) ) {
output = output - givevalue(input[j-1]);
};
};
return(output);
};
};
int main()
{
RtoA translate;
cout<< "Type a Roman Numeral please: \n";
getline(cin, translate.input, '\n');
cout<< translate.read(translate.input);
cin.get();
}
Maybe it is just a stupid mistake but as I said I'm still a beginner,
Thanks a lot in advance! | http://cboard.cprogramming.com/cplusplus-programming/142638-roman-numeral-translator-where-did-i-go-wrong-printable-thread.html | CC-MAIN-2015-18 | refinedweb | 381 | 60.04 |
Show a Preloader
Our preloader is a screenshot of the final result. Usually you'd have to wait until the end of the project to make that, but I'll just give you mine. Starting with the preloader makes sense for two reasons:
- It's nicer than looking at a blank screen while data loads
- It's a good sanity check for our environment
We're using a screenshot of the final result because the full dataset takes a few seconds to load, parse, and render. It looks better if visitors see something informative while they wait.
React Suspense is about to make building preloaders a whole lot better. Adapting to the user's network speed, built-in preload functionality, stuff like that. More on that in the chapter on React Suspense and Time Slicing.
Make sure you've installed all dependencies and that
npm start is running.
We're building our preloader in 4 steps:
- Get the image
- Make the
Preloadercomponent
- Update
App
- Load Bootstrap styles in
index.js
Step 1: Get the image
Download my screenshot from Github
and save it in
src/images/preloader-screenshot.png. It goes in the
src/images/
directory because we're going to
import it in JavaScript (which makes it part
of our source code), and I like to put non-JavaScript files in
assets. Keeps
the project organized.
Step 2: Preloader component
Our
Preloader is a small component that pretends it's the
App and renders a
static title, description, and a screenshot of the end result. It goes in
src/components/Preloader.js.
We'll put all of our components in
src/components/.
We start the component off with some imports, an export, and a functional stateless component that returns an empty div element.
// src/components/Preloader.jsimport React from "react"import PreloaderImg from "../images/preloader-screenshot.png"const Preloader = () => <div className="App container"></div>export default Preloader
We
import React (which we need to make JSX syntax work) and the
PreloaderImg for our image. We can import images because of the Webpack
configuration that comes with
create-react-app. The webpack image loader
returns a URL that we put in the
PreloaderImg constant.
At the bottom, we
export default Preloader so that we can use it in
App.js
as
import Preloader. Default exports are great when your file exports a
single object. Named exports when you want to export multiple items. You'll see
that play out in the rest of this project.
The
Preloader function takes no props (because we don't need any) and returns
an empty
div. Let's fill it in.
// src/components/Preloader.jsconst Preloader = () => (<div className="App container"><h1>The average H1B in tech pays $86,164/year</h1><p className="lead">Since 2012 the US tech industry has sponsored 176,075 H1B work visas. Mostof them paid <b>$60,660 to $111,668</b> per year (1 standard deviation).{" "}<span>The best city for an H1B is <b>Kirkland, WA</b> with an averageindividual salary <b>$39,465 above local household median</b>. Medianhousehold salary is a good proxy for cost of living in an area.</span></p><img src={PreloaderImg} style={{ width: "100%" }}<h2 className="text-center">Loading data ...</h2></div>)
A little cheating with grabbing copy from the future, but that's okay. In real life you'd use some temporary text, then fill it in later.
The code itself looks like HTML. We have the usual tags -
h1,
p,
b,
img, and
h2. That's what I like about JSX: it's familiar. Even if you don't
know React, you can guess what's going on here.
But look at the
img tag: the
src attribute is dynamic, defined by
PreloaderImg, and the
style attribute takes an object, not a string. That's
because JSX is more than HTML; it's JavaScript. Think of props as function
arguments – any valid JavaScript fits.
That will be a cornerstone of our project.
Step 3: Update App
We use our new Preloader component in App –
src/App.js. Let's remove the
create-react-app defaults and import our
Preloader component.
// src/App.jsimport React from "react"// Delete the line(s) between here...import logo from "./logo.svg"import "./App.css"// ...and here.// Insert the line(s) between here...import Preloader from "./components/Preloader"// ...and here.class App extends React.Component {// Delete the line(s) between here...render() {return (<div className="App"><div className="App-header"><img src={logo}<h2>Welcome to React</h2></div><p className="App-intro">To get started, edit <code>src/App.js</code> and save to reload.</p></div>)}// ...and here.}export default App
We removed the logo and style imports, added an import for
Preloader, and
gutted the
App class. It's great for a default app, but we don't need that
anymore.
Let's define a default
techSalaries state and render our
Preloader
component when there's no data.
// src/App.jsfunction App() {const [techSalaries, setTechSalaries] = useState([])if (techSalaries.length < 1) {return <Preloader />} else {return <div className="App"></div>}}
Nowadays we can define properties directly in the class body without a constructor method. It's not part of the official JavaScript standard yet, but most React codebases use this pattern.
Properties defined this way are bound to each instance of our components so
they have the correct
this value. Late you'll see we can use this shorthand
to neatly define event handlers.
We set
techSalaries to an empty array by default. In
render we use object
destructuring to take
techSalaries out of component state,
this.state, and
check whether it's empty. When
techSalaries is empty our component renders
the preloader, otherwise an empty div.
If your
npm start is running, the preloader should show up on your screen.
Hmm… that's not very pretty. Let's fix it.
Step 4: Load Bootstrap styles
We're going to use Bootstrap styles to avoid reinventing the wheel. We're ignoring their JavaScript widgets and the amazing integration built by the react-bootstrap team. Just the stylesheets please.
They'll make our fonts look better, help with layouting, and make buttons look like buttons. We could use styled components, but writing our own styles detracts from this tutorial.
We load stylesheets in
src/index.js.
// src/index.jsimport React from "react"import ReactDOM from "react-dom"import App from "./App"// Insert the line(s) between here...import "bootstrap/dist/css/bootstrap.css"// ...and here.ReactDOM.render(<App />, document.getElementById("root"))
Another benefit of Webpack:
import-ing stylesheets. These imports turn into
<style> tags with CSS in their body at runtime.
This is also a good opportunity to see how
index.js works to render our app
👇
- loads
Appand React
- loads styles
- Uses
ReactDOMto render
<App />into the DOM
That's it.
Your preloader screen should look better now.
If you don't, try comparing your changes to this diff on Github. | https://reactfordataviz.com/tech-salaries/preloader/ | CC-MAIN-2022-40 | refinedweb | 1,158 | 67.45 |
The assignment problem below ask me to calculate the number of months it will take to pay off the loan and the total amount of interest paid over the life of the loan. I'm having trouble trying to find the right algorithm for the monthly payments. Could you please take a look at my code and see what I'm doing wrong? I'm using TextPad, btw.
You have just purchased a stereo system that cost interest. So. (Your final program need not output the monthly amount of interest paid and remaining debt, but you may want to write a preliminary version of the program that does output these values.) Use a variable to count the number of loop iterations, and hence the number of months until the debt is zero. You may want to use other variables as well. The last payment may be less than the $50 if the debt is small, but do not forget the interest. If you owe $50, then your monthly payment of $50 will not pay off your debt, although it will come close. One month's interest on $50 is only 75 cents.
Here's my code
import java.util.Scanner; public class StereoSystem { public static void main (String [] args) { Scanner in = new Scanner (System.in); System.out.print ("Enter the amount of the loan: $"); double principal = in.nextDouble (); System.out.print ("Enter the monthly payments: "); double MonthlyPayments = in.nextDouble (); System.out.print ("Enter the interest rate: "); double interestRate = in.nextDouble () / 100.0; double sum = 0; for (int n = 1; n <= years; n++) sum += (1.0 - (n - 1.0) / years); double totalInterest = principal * interestRate * sum; double numberOfMonths = (principal + totalInterest) / ( monthly payments); System.out.printf ("The number of months it will take to pay off the loan is " + ); } } | https://www.daniweb.com/programming/software-development/threads/149199/difficulty-in-finding-the-right-algorithm | CC-MAIN-2018-30 | refinedweb | 296 | 66.03 |
Hey Everyone!
My name is Ed and I am new to programming and your community. Thanks for the warm welcome and I hope you can follow me with my coding problems.
My code is for a project that simulates a simple vending machine. When the program is run three buttons will be displayed. They are representatives of a nickle, dime, and qarter. Everytime the user clicks on one of the buttons, the amount of that button is subtracted from the cost of a sode (75 cents). Then a message will be displayed that tells the users the remaining amount ("Please enter 40 more cents." if a dime and quarter buttons were clicked.)
So far I have written two files.
One is the main driver program.
The second file is where most of my work is.
In the VendingMachine class I have my JButtons, ButtonHandler, ActionListener, actionPerformed. It is here I am running into problems. I think everything is set up correctly for my buttons. I judt don't know how to setup the click procedures for them. How do you take the click procedure and have it register with the program to perform the task and then display a message?
Well guys, thanks for staying with me. If you have any suggestions I am all ears. Take care and hope to hear from you soon. Here is my code, I hope you can follow it. I am going to post the driver file first then the second file.
VendingMachineTest
// Driver package simplevendingmachine; import javax.swing.JFrame; public class VendingMachineTest { public static void main(String[] args) { VendingMachine vendingMachine = new VendingMachine(); // Create VendingMachine Frame. vendingMachine.setDefaultCloseOperation ( JFrame.EXIT_ON_CLOSE); vendingMachine.setSize ( 700 , 500 ); // Sets frame size. vendingMachine.setVisible ( true ); // Display frame. } // End main. } // End class VendingMachine
Here is my other File (VendingMachine):
// Takes the input from the three JButton package simplevendingmachine; import java.awt FlowLayout; import java.awt.event.ActionListener; import java.awt.event.ActionEvent; import javax.swing.JFrame; import javax.swing.JButton; import javax.swing.JOptionPane; import javax.swing.JLabel; public class VendingMachine extends JFrame { private JButton nickle; // nickle button private JButton dime; // dime button private JButton quarter; // quarter button // vending machine add JButtons to JFrame public VendingMachine() { super ("Vending Machine"); setLayout ( new FlowLayout() ); // seting frame layout nickle = new JButton("Nickle"); // Button with text add ( nickle ); // Add nickle button to frame. dime = new JButton ("Dime"); // Button with text. add ( dime ); // Add dime button to frame. quarter = new JButton ("Quarter"); // Button with text. add ( quarter ); // Add quarter button to frame // Create new ButtonHandler for button handling ButtonHandler handler = new ButtonHandler(); nickle.addActionListener( handler ); dime.addActionListener ( handler ); quarter.addActionListener ( handler ); } // End of VendingMachine Constructor. // Inner class for button event handling. private class ButtonHandler implements ActionListener { // Handle button events. public void actionPerformed( ActionEvent event ) { String string = ""; // Declsre string to display. // Process nickle button. if ( e.getSource() == nickle ) // Process dime button. if ( e.getSource() == dime ) // Process quarter button. if ( e.getSource() == quarter) } // End method actionPerformed. } //end private inner class ButtonHandler. } // End class VendingMachine.
Edited 3 Years Ago by mike_2000_17: Fixed formatting | https://www.daniweb.com/programming/software-development/threads/179495/vending-machine | CC-MAIN-2016-50 | refinedweb | 505 | 53.37 |
"Andrew Dalke" <adalke at mindspring.com> writes: > Ped. Indeed. Or rather what I find *really* important is that there exist proper support for interactive development (so that changes to source code can be easily reflected in a running session). I currently sometimes find myself driven to develop procedural, rather than OO code (because changes to functions in the source code can be trivially updated in the interactive shell), and sometimes I even skip the procedural bit, too, and just throw code into the global level (because if something goes wrong I get to keep the variables I've accumulated so far). [I'd like to stress that I obviously only do this in extreme cases (when the code both takes long to run and is highly experimental -- so that its final form might also well depend on intermediate results obtained during interactive development) and I presuambly just have to think harder about how to do this properly in python. Does anyone know a way to fake restartable exceptions in python BTW?]. > > I wonder ... Alexander? What should this do? > > from Q import X > > class X: > def amethod(self): return 'ah, now THIS is better!' > > Should it refine the X in the local namespace or make a new > class? I'd say redefine X in the local namespace. Have you spotted a problem with it? > > I have wondered if > > def X.amethod(self): return "...." > > should be allowed, but no longer think it should. No I don't think so either. > > OTOH, a proper reload, which updated all instance's __class__ > to the newly reloaded class, would be nice. I've stumbled > over that many a time. Indeed. I'd summarize my opinion on python as follows: python's biggest strength it is a practical language that supports interactive development, languages which don't support interactive development are worthless (but all too common). Python's biggest weakness is that it doesn't support interactive development properly and out-of-the-box (I think its generally often difficult to have the changes you made to your source code adequately reflected in your interactive session and the debugging facilities are pretty poor (and yet already *extremely* useful if used properly; ``@pdb on`` emacs/ipython sure speeds fixing things up). Bizarrely, of all the languages I've ever come across, the only one which seems to have a vaguely sensible development model is smalltalk. 'as | https://mail.python.org/pipermail/python-list/2003-August/209552.html | CC-MAIN-2016-30 | refinedweb | 399 | 59.74 |
.
#include <Wire.h>#include <LiquidCrystal_SR.h>LiquidCrystal_SR lcd(8,7,TWO_WIRE);// | |// | \-- Clock Pin// \---- Data/Enable Pin// Creat a set of new charactersbyte armsUp[8] = {0b00100,0b01010,0b00100,0b10101,0b01110,0b00100,0b00100,0b01010};byte armsDown[8] = {0b00100,0b01010,0b00100,0b00100,0b01110,0b10101,0b00100,0b01010};void setup(){ lcd.begin(16,2); // initialize the lcd lcd.createChar (0, armsUp); // load character to the LCD lcd.createChar (1, armsDown); // load character to the LCD lcd.home (); // go home lcd.print("LiquidCrystal_SR");}void loop(){ // Do a little animation for(int i = 0; i <= 15; i++) showHappyGuy(i); for(int i = 15; i >= 0; i--) showHappyGuy(i);}void showHappyGuy(int pos){ lcd.setCursor ( pos, 1 ); // go to position lcd.print(char(random(0,2))); // show one of the two custom characters delay(150); // wait so it can be seen lcd.setCursor ( pos, 1 ); // go to position again lcd.print(" "); // delete character}
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Arduino
via Egeo 16
Torino, 10131
Italy | http://forum.arduino.cc/index.php?topic=121712.msg916624 | CC-MAIN-2016-22 | refinedweb | 180 | 60.51 |
Data Science: Exploratory Data Analysis
What is Exploratory Data Analysis?
Exploratory Data Analysis (EDA) is the process of gaining a better understanding of data sets by analyzing and visualizing their primary properties. This stage is critical, especially when it comes to classifying the data to apply Machine Learning. Histograms, Box plots, Scatter plots, and other plotting options are available in EDA. Exploring the data can take a long time. We can ask to define the problem statement or definition on our extremely significant data collection through the EDA method.
What data are we exploring today?
Here we selected data set of cars from Kaggle. The data set can be downloaded from here. To give a piece of brief information about the data set this data contains more than 10, 000 rows and more than 10 columns which contains features of the car such as Engine Fuel Type, Engine Size, HP, Transmission Type, highway MPG, city MPG, and many more.
1. Importing the required libraries
import pandas as pd
import numpy as np
import seaborn as sns
import matplotlib.pyplot as plt
%matplotlib inline
sns.set(color_codes=True)
2. Loading the data set
df = pd.read_csv("Data.csv")
df.head(5) # To display the top 5 rows
df.tail(5) # To display the bottom 5 rows
3. Checking the types of data
df.dtypes
4. Dropping irrelevant columns
df = df.drop(['Engine Fuel Type', 'Market Category', 'Vehicle Style', 'Popularity', 'Number of Doors', 'Vehicle Size'], axis=1)
df.head(5)
5. Renaming the columns
df = df.rename(columns={"Engine HP": "HP", "Engine Cylinders": "Cylinders", "Transmission Type": "Transmission", "Driven_Wheels": "Drive Mode","highway MPG": "MPG-H", "city mpg": "MPG-C", "MSRP": "Price" })
df.head(5)
6. Dropping the duplicate rows
df.shape(11914, 10)duplicate_rows_df = df[df.duplicated()]
print("number of duplicate rows: ", duplicate_rows_df.shape)number of duplicate rows: (989, 10)
Now, let us remove the duplicate data.
df.count()Make 11914
Model 11914
Year 11914
HP 11845
Cylinders 11884
Transmission 11914
Drive Mode 11914
MPG-H 11914
MPG-C 11914
Price 11914
dtype: int64
So above there are 11914 rows and we are removing 989 rows of duplicate data.
df = df.drop_duplicates()
df.head(5)
df.count()Make 10925
Model 10925
Year 10925
HP 10856
Cylinders 10895
Transmission 10925
Drive Mode 10925
MPG-H 10925
MPG-C 10925
Price 10925
dtype: int64
7. Dropping the missing or null values
print(df.isnull().sum())Make 0
Model 0
Year 0
HP 69
Cylinders 30
Transmission 0
Drive Mode 0
MPG-H 0
MPG-C 0
Price 0
dtype: int64
This is the reason in the above step while counting both Cylinders and Horsepower (HP) had 10856 and 10895 over 10925 rows.
df = df.dropna()
df.count()Make 10827
Model 10827
Year 10827
HP 10827
Cylinders 10827
Transmission 10827
Drive Mode 10827
MPG-H 10827
MPG-C 10827
Price 10827
dtype: int64
Now we have removed all the rows which contain the Null or N/A values (Cylinders and Horsepower (HP)).
print(df.isnull().sum())Make 0
Model 0
Year 0
HP 0
Cylinders 0
Transmission 0
Drive Mode 0
MPG-H 0
MPG-C 0
Price 0
dtype: int64
8. Detecting Outliers
sns.boxplot(x=df[‘Price’])
sns.boxplot(x=df['HP'])
sns.boxplot(x=df['Cylinders'])
Q1 = df.quantile(0.25)
Q3 = df.quantile(0.75)
IQR = Q3 - Q1
print(IQR)Year 9.0
HP 130.0
Cylinders 2.0
MPG-H 8.0
MPG-C 6.0
Price 21327.5
dtype: float64df = df[~((df < (Q1 - 1.5 * IQR)) |(df > (Q3 + 1.5 * IQR))).any(axis=1)]
df.shape(9191, 10)
9. Plot different features against one another (scatter), against frequency (histogram)
Histogram
Histogram refers to the frequency of occurrence of variables in an interval. In this case, there are mainly 10 different types of car manufacturing companies, but it is often important to know who has the most number of cars. To do this histogram is one of the trivial solutions which lets us know the total number of cars manufactured by a different company.
df.Make.value_counts().nlargest(40).plot(kind=’bar’, figsize=(10,5))
plt.title(“Number of cars by make”)
plt.ylabel(‘Number of cars’)
plt.xlabel(‘Make’);
Heat Maps
Heat Maps is a type of plot which is necessary when we need to find the dependent variables. One of the best ways to find the relationship between the features can be done using heat maps. In the below heat map we know that the price feature depends mainly on the Engine Size, Horsepower, and Cylinders.
plt.figure(figsize=(10,5))
c= df.corr()
sns.heatmap(c,cmap="BrBG",annot=True)
c
Scatterplot
We generally use scatter plots to find the correlation between two variables. Here the scatter plots are plotted between Horsepower and Price and we can see the plot below. With the plot given below, we can easily draw a trend line. These features provide a good scattering of points.
fig, ax = plt.subplots(figsize=(10,6))
ax.scatter(df[‘HP’], df[‘Price’])
ax.set_xlabel(‘HP’)
ax.set_ylabel(‘Price’)
plt.show()
Conclusion
Hence, the above are some of the steps involved in Exploratory data analysis, these are some general steps that you must follow to perform EDA. There are many more yet to come but for now, this is more than enough idea as to how to perform a good EDA given any data sets.
GitHub - yashptl2611/DS_Practical-12
Exploratory Data Analysis (EDA) is the process of gaining a better understanding of data sets by analyzing and…
github.com
Thank You! | https://18it107.medium.com/data-science-exploratory-data-analysis-c61afdb4f75c | CC-MAIN-2021-49 | refinedweb | 924 | 58.69 |
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environ un an ago | 0 | https://fr.mathworks.com/matlabcentral/profile/authors/3028622 | CC-MAIN-2022-21 | refinedweb | 1,080 | 53.81 |
Opened 8 months ago
Closed 6 months ago
Last modified 6 months ago
#1654 closed defect (fixed)
nginx does not honor ssl_protocols for TLSv1.3
Description
When configured with ssl_protocols TLSv1 TLSv1.1 TLSv1.2; nginx should not support TLSv1.3 but it still does
curl -v --tls-max 1.3 [...] * SSL connection using TLSv1.3 / TLS_AES_256_GCM_SHA384 * ALPN, server accepted to use http/1.1
Change History (10)
comment:1 Changed 8 months ago by zizazit@…
comment:2 Changed 8 months ago by mdounin
This can be solved by explicitly calling SSL_CTX_set_max_proto_version(TLS1_2_VERSION) if TLSv1.3 is not available, so nginx will be limited to TLSv1.2 when it was compiled with TLSv1.2 as the highest protocol version but is being run with TLSv1.3 in the library. Here is a patch:
# HG changeset patch # User Maxim Dounin <mdounin@mdounin.ru> # Date 1539615549 -10800 # Mon Oct 15 17:59:09 2018 +0300 # Node ID 5f998d26af64ae048a12d65d078ea152877c9f35 # Parent 64721be763b61bf9075e9f4851a46197df9bac51 SSL: explicitly set max version (ticket #1654). With maximum version explicitly set, TLSv1.3 will not be unexpectedly enabled if nginx compiled with OpenSSL 1.1.0 (without TLSv1.3 support) will be run with OpenSSL 1.1.1 (with TLSv1.3 support). diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c --- a/src/event/ngx_event_openssl.c +++ b/src/event/ngx_event_openssl.c @@ -345,6 +345,11 @@ ngx_ssl_create(ngx_ssl_t *ssl, ngx_uint_ } #endif +#ifdef SSL_CTX_set_min_proto_version + SSL_CTX_set_min_proto_version(ssl->ctx, 0); + SSL_CTX_set_max_proto_version(ssl->ctx, TLS1_2_VERSION); +#endif + #ifdef TLS1_3_VERSION SSL_CTX_set_min_proto_version(ssl->ctx, 0); SSL_CTX_set_max_proto_version(ssl->ctx, TLS1_3_VERSION);
It is not clear if it worth the effort though.
comment:3 Changed 8 months ago by Maxim Dounin <mdounin@…>
comment:4 Changed 8 months ago by mdounin
- Resolution set to fixed
- Status changed from new to closed
Fix committed.
comment:5 Changed 7 months ago by greenreaper@…
FWIW, this seems like more of a feature than a bug if you're running on a platform like Debian stretch which you've upgraded to OpenSSL 1.1.1. Now it seems you can't enable TLS 1.3 in nginx without recompiling it as well. Maybe a cosmic build (#1661) will work, as Ubuntu pkg tend to work on Debian.
Confusingly, adding TLSv1.3 to ssl_protocols gives no warning; it just doesn't work as expected. This compares to ssl_early_data for which there is such a warning. Maybe it should override the minimum?
comment:6 Changed 7 months ago by mdounin
FWIW, this seems like more of a feature than a bug if you're running on a platform like Debian stretch which you've upgraded to OpenSSL 1.1.1.
Certainly this is a bug, especially given that we do not enable TLS 1.3 by default now. Also note that unexpectedly enabling TLS 1.3 might result in problems, see here for an example.
Confusingly, adding TLSv1.3 to ssl_protocols gives no warning; it just doesn't work as expected.
This is mostly because we used to enable by default protocols which are not present in every OpenSSL library available out there, and issuing warnings only for explicitly specified yet unsupported protocols is really cumbersome.
comment:7 Changed 6 months ago by Maxim Dounin <mdounin@…>
comment:8 follow-up: ↓ 10 Changed 6 months ago by yura3d@…
- Resolution fixed deleted
- Status changed from closed to reopened
I think the solution suggested by @mdounin above is strange.
I have nginx-1.15.7 installed from the nginx.org repository for Debian stretch. Also I have OpenSSL 1.1.1, built with TLS 1.3 support.
nginx -V:
nginx version: nginx/1.15.7 built by gcc 6.3.0 20170516 (Debian 6.3.0-18+deb9u1) built with OpenSSL 1.1.0f 25 May 2017 (running with OpenSSL 1.1.1 11 Sep 2018) TLS SNI support enabled
The problem: TLS 1.3 is not available even if I add TLSv1.3 to ssl_protocols.
When I rollback from 1.15.7 to 1.15.5 (the last version before this solution was included to nginx), TLS 1.3 makes available again.
I think you should not rely on TLS1_3_VERSION constant in code if you declare support for external ("running") OpenSSL builts. Also I don't understand, why the packages for the mainline version are still made with OpenSSL 1.1.0f, while stable 1.1.1 was ready 3 months ago.
comment:9 Changed 6 months ago by mdounin
- Resolution set to fixed
- Status changed from reopened to closed
We cannot selectively enable or disable TLSv1.3 without relying on the appropriate constant. As such, you have to rebuilt nginx with OpenSSL 1.1.1 for TLSv1.3 to be available.
Since Debian stretch is shipped with OpenSSL 1.1.0f, this is the version our packages for Debian stretch are built with. For OpenSSL different OpenSSL versions, consider rebuilding nginx yourself.
comment:10 in reply to: ↑ 8 Changed 6 months ago by GreenReaper@…
I think the solution suggested by @mdounin above is strange.
I have nginx-1.15.7 installed from the nginx.org repository for Debian stretch. Also I have OpenSSL 1.1.1, built with TLS 1.3 support.
You could also switch to the repo for Ubuntu cosmic instead, which is built for OpenSSL 1.1.1.
This is the same thing you could do to get new TCP features on jessie.
This won't work for i386 because cosmic isn't built for that anymore.
Incidentally another way to do this without having to rebuild OpenSSL is to pin libc6 libc-dev-bin libc-bin locales libc6-dev libc-l10n libssl1.1 libssl-dev openssl to Debian sid. Obviously risky, YMMV.
Oops... I didn't notice the OpenSSL version that nginx is compiled with does not support TLSv1.3, but the version its running with does. Please close the ticket, sorry. | https://trac.nginx.org/nginx/ticket/1654 | CC-MAIN-2019-26 | refinedweb | 969 | 69.68 |
)
which we will discuss in
Section 8.9. The Gated Recurrent Unit (GRU) [Cho et al., 2014] is a slightly more streamlined variant that often offers comparable performance and is significantly faster to compute. See also [Chung et al., 2014] for more details. Due to its simplicity we start with the GRU.
8.8.2. Implementation from Scratch¶
To gain a better understanding of the model let us implement a GRU from scratch.
8.8.2.1. Reading the Data Set¶
We begin by reading The Time Machine corpus that we used in Section 8.5. The code for reading the data set is given below:
import d2l from mxnet import nd from mxnet.gluon import rnn batch_size, num_steps = 32, 35 train_iter, vocab = d2l.load_data_time_machine(batch_size, num_steps).
def get_params(vocab_size, num_hiddens, ctx): num_inputs = num_outputs = vocab_size normal = lambda shape : nd.random.normal(scale=0.01, shape=shape, ctx=ctx) three = lambda : (normal((num_inputs, num_hiddens)), normal((num_hiddens, num_hiddens)), nd.zeros(num_hiddens, ctx=ctx)) W_xz, W_hz, b_z = three() # Update gate parameter W_xr, W_hr, b_r = three() # Reset gate parameter W_xh, W_hh, b_h = three() # Candidate hidden state parameter # Output layer parameters W_hq = normal(
Section 8.5, this function returns a tuple composed
of an NDArray with a shape (batch size, number of hidden units) and with
all values set to nd.concat(*outputs, dim=0), (H,)
8.8.2.4. Training and Prediction¶
Training and prediction work in exactly the same manner as before.
vocab_size, num_hiddens, ctx = len(vocab), 256, d2l.try_gpu() num_epochs, lr = 500, 1 model = d2l.RNNModelScratch(len(vocab), num_hiddens, ctx, get_params, init_gru_state, gru) d2l.train_ch8(model, train_iter, vocab, lr, num_epochs, ctx)
Perplexity 1.1, 13446 tokens/sec on gpu(0) time traveller well thattime is only a kind of space here is a p traveller it s against reason said filby what reason said.
gru_layer = rnn.GRU(num_hiddens) model = d2l.RNNModel(gru_layer, len(vocab)) d2l.train_ch8(model, train_iter, vocab, lr, num_epochs, ctx)
Perplexity 1.1, 60693 tokens/sec on gpu(0) time traveller it s against reason said filby what reason said traveller it s against reason said filby what reason said. | http://classic.d2l.ai/chapter_recurrent-neural-networks/gru.html | CC-MAIN-2020-16 | refinedweb | 350 | 59.3 |
How to: Identify a Nullable Type (C# Programming Guide)
You can use the C# typeof operator to create a Type object that represents a Nullable type:
You can also use the classes and methods of the System.Reflection namespace to generate Type objects that represent Nullable types. However, if you try to obtain type information from Nullable variables at runtime by using the GetType method or the is operator, the result is a Type object that represents the underlying type, not the Nullable type itself.
Calling GetType on a Nullable type causes a boxing operation to be performed when the type is implicitly converted to Object. Therefore GetType always returns a Type object that represents the underlying type, not the Nullable type.
The C# is operator also operates on a Nullable's underlying type. Therefore you cannot use is to determine whether a variable is a Nullable type. The following example shows that the is operator treats a Nullable<int> variable as an int.
Use the following code to determine whether a Type object represents a Nullable type. Remember that this code always returns false if the Type object was returned from a call to GetType, as explained earlier in this topic. | https://msdn.microsoft.com/en-US/library/ms366789(v=vs.110).aspx | CC-MAIN-2015-11 | refinedweb | 202 | 51.28 |
This month we integrated our newest game The Dog Run with the Google Play Store Leaderboard service. It looks, and possibly even should have been, really easy but in this reality it wasn’t. One big problem that was really time consuming was that we used the Google key signing service and then had an issue with our key. Bit I think I’ll describe that in a separate post as it probably deserves more info that we got space for here and wasn’t really what this post is all about.
This post is a about how we integrated our game with the Google Play Store Leaderboard!
(The game has gone into Beta Testing if you would like a preview click the link here!)
First of all – do the research! Read the documentation and look at some tutorials. I found the documentation for the Plugin to be useful and this tutorial to be of the most help (thanks AppGuruz):
But this is how we did it…
1. To start with you have to be logged in to your Unity account when you open up your project in the Unity Editor. You will need it to authorise stuff.
2. Next you will need to import a copy of the Google Play Games plugin for Unity. This is an open-source project which integrates the Google Play Games API with Unity. (Disclaimer: it’s not endorsed or supervised by Unity Technologies).
This is the latest version I used and if you click on the image it will take you there.
The README.md in the repository has a pretty good summary of how to set it up and configure it and examples of how to call features and functions.
The plugin supports a heap of things:
Achievements
Leaderboards
Turn-based Multiplayer
Real-time Multiplayer
Events and Quests
Saved Games and
Nearby Connections
All we wanted was the Leaderboard so let’s start there.
3. Import the package in the Unity Editor
Assets > Import Package > Custom Package
4. Then open the Google Play Games Window in the Editor that will appear after you import the package.
Window > Google Play Games > Setup (Android Setup on my machine)
In the Android Setup you will put your Resource Definitions (we only had one for the leaderboard).
I’ll get to how we set up the Resources in the Google Play Console further down but this is what it looks like completed:
(The info in this screenshot is a dummy record so I didn’t have to redact anything for security)
5. Click On “Open Play Games Console” – it’s the blue highlighted link in the Android Configuration page above.
6. Go to the Development tools section and find the Google Play game services section.
7. Click on the Game services section link
Right down the bottom will be this section confirming your API service:
8. Find the Service in the list of Services and click on Manage this API (if you need to set up more services):
9. Right there after drilling down through all those pages you will find your resources:
See that blue link there that says “Get Resources” – that’s your baby. Once you click on that there are four tabs with a variety of formats. You want the one that’s there by default for Android. Take a copy of that xml and paste it into your Androind Setup/Configuration page in your project and your halfway there. 🙂
Now for the fun bit of configuring and scripting it for the game.
There is a bit of trial and error and unless you can connect up an Android device and actively debug through the console using that device there is a long iteration cycle for testing. From within the editor you cannot test any of the functionality such as logging in as the Google Play Games user and opening the Leaderboard. You have to have the APK loaded up to the Google Play Store and in an Alpha Release Track to start testing. The package has to be signed using a full key (ie. not the default debug one) and you need to install the package on to your test Android device from the Play Store so that it has the correct keys to work. You cannot build it locally and run it straight from your workstation. The other thing is that in the Alpha Track the Leaderboard functionality can sometimes be really slow and sometimes just doesn’t load so because of that you need to be patient when testing.
To get this working in my game I created an empty game object and attached this script to it:
using UnityEngine; using GooglePlayGames; public class GPG : MonoBehaviour { #region PUBLIC_VAR public string leaderboard; // This is where to pass the resource string in! #endregion #region DEFAULT_UNITY_CALLBACKS public long my_score; // This is where I passed in the users score public bool success; public bool GPGLoginReturned; void Start() { PlayGamesPlatform.Activate(); LogIn(); } #endregion #region BUTTON_CALLBACKS // Login to Google Account public bool LogIn() { Social.localUser.Authenticate((success) => { if (success) { string userInfo = "Username: " + Social.localUser.userName + "\nUser ID: " + Social.localUser.id + "\nIsUnderage: " + Social.localUser.underage; } else { Debug.Log("Login failed"); } }); return GPGLoginReturned = true; } // Show All Leaderboards public void OnShowLeaderBoard() { Social.ShowLeaderboardUI(); } // Adds a Score to the Leaderboard public void AddScoreToLeaderBoard(long my_score) { if (Social.localUser.authenticated) { Social.ReportScore(my_score, leaderboard, (bool success) => { if (success) { Debug.Log("Update Score Success"); } else { Debug.Log("Update Score Fail"); } }); } } // Logout the Google+ Account public void OnLogOut() { ((PlayGamesPlatform)Social.Active).SignOut(); } #endregion }
That basically handles all the interaction with the Google Play Services like user logon and off, showing the leaderboard, and updating the leaderboard. It’s about as simple as you can get.
To update an actual score during gameplay I added this code to the relevant section of the game:
if (!score_uploaded) { //AddScoreToLeaderBoard() var gpg_Script = GPGObject.GetComponent(); long longScore = System.Convert.ToInt64(score_timenow); gpg_Script.AddScoreToLeaderBoard(longScore); score_uploaded = true; }
And to show the Leaderboard I attached and exposed this method to a button call.
OnShowLeaderBoard()
That’s pretty much it. But factor in more time that you think.
It took me ten package builds and releases to get it right – hopefully you won’t have that much trouble.
One thought on “Google Play Store Leaderboard Integration”
I used this article again with a new project and got this error when importing the Play Store package: Assets/GooglePlayGames/Editor/GPGSUtil.cs(452,57): error CS0122: `UnityEditor.BuildPipeline.GetPlaybackEngineDirectory(UnityEditor.BuildTarget, UnityEditor.BuildOptions)’ is inaccessible due to its protection level.
To resolve it I deleted the manifest.json in the Packages folder from the Unity Project structure. Worked automatically after that. | https://www.zuluonezero.net/2018/08/30/google-play-store-leaderboard-integration/ | CC-MAIN-2021-31 | refinedweb | 1,107 | 63.39 |
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Write a Block Method4:42 with Jason Seifer
Writing a method that takes a block is very similar to writing any other method. In this video, you'll learn to write your own block methods.
Code Samples
Our first block:
def block_method puts "This is the first line in block_method." end block_method do puts "This statement is called from the block." end
This doesn't do anything! Why? We need to tell Ruby what to do with the block. We do that with the
yield keyword which will jump out of the method and execute the block:
def block_method puts "This is the first line in block_method." yield puts "This statement is after the yield keyword." end block_method do puts "This statement is called from the block." end
This will print out:
This is the first line in block_method. This statement is called from the block. This statement is after the yield keyword.
- 0:00
Let's talk for a moment about writing methods that can be written with blocks.
- 0:05
There's actually nothing special about methods that can be called with blocks.
- 0:09
Just like with the loop or
- 0:11
times methods, we can write our own methods that utilize blocks.
- 0:16
When we do that, the block is considered an argument to the method.
- 0:21
Let's see how that works now, using Workspaces.
- 0:25
All right.
- 0:25
So, let's go ahead and write our first method that takes a block.
- 0:30
Let's go ahead and create a new file, and we will call this block method.rb.
- 0:37
And let's go ahead and name our method, block method.
- 0:44
And we will close the method definition.
- 0:47
And now, for starters, let's just go ahead and print out,
- 0:51
this is the first line in block method.
- 0:57
Now we have to be able to call this.
- 1:00
So, we call the name of our method,
- 1:02
which in this case is block method, Now we'll send a block into this.
- 1:09
And we'll just say.
- 1:12
This statement is called from the block and we will write end there.
- 1:19
So here's our method.
- 1:22
We haven't done anything special to tell it to expect a block.
- 1:25
And then we're calling the method, sending in a block, and
- 1:30
then hopefully this code gets executed.
- 1:33
So let's go ahead and run this and see what happens.
- 1:41
And all we see is this is the first line in block method.
- 1:45
Now the reason is, even though we sent in a block,
- 1:48
we haven't told our method what happens to it, or what to do with the block.
- 1:54
The way we do that is with a special keyword in Ruby called yield.
- 1:59
When we put the yield keyword in here, Ruby is going to know
- 2:02
to come out of the block where the yield statement is, then execute the code
- 2:07
inside the block which in this case is going to be our put statement.
- 2:12
Now let's try running this again and see what happens.
- 2:17
Now when I run it, we can see that it says,
- 2:19
this is the first line in block method, and then we get the printout that
- 2:23
we expected which is, this statement is called from the block.
- 2:28
Now, if we wanted to, we could do something after the yield here, and
- 2:34
print out, this statement is after the yield keyword.
- 2:44
Now let me just clear the screen here and run this again.
- 2:48
This statement is after the yield keyword is printed out right
- 2:52
after this statement is called from the block.
- 2:56
So when Ruby executes this, it sees the block method definition,
- 3:01
and then it sees the method call, and then here is the block.
- 3:05
You can think of this as one statement or one block of code.
- 3:09
So Ruby runs this block method,
- 3:12
encounters this put statement, runs it, gets to the yield.
- 3:18
Then this entire code block is executed, and
- 3:22
we return to what comes after it, which is the put statement.
- 3:28
Now, you might wonder what would happen if we put in another yield keyword.
- 3:33
See if you can guess before we run this.
- 3:39
And when we put in that second yield keyword, you can see that,
- 3:43
this statement is called from the block, is executed twice.
- 3:48
So each time we see the yield keyword in this method,
- 3:50
the block of code is executed.
- 3:55
Let's see what would happen if we just called block method without a block.
- 4:01
Clear my screen here.
- 4:05
And let's go back and scroll through the output here.
- 4:10
We get this is the first line in the block method.
- 4:12
This statement is called from the block, and this is after the yield keyword.
- 4:17
Then, block method gets called again, and
- 4:20
we get to this is the first line in block method, but
- 4:24
it says no block was given, and we get a local jump error.
- 4:30
So we can see that this requires a block.
- 4:36
Try practicing writing some of your own methods now using blocks
- 4:39
in the yield statement using workspaces. | https://teamtreehouse.com/library/write-a-block-method | CC-MAIN-2019-43 | refinedweb | 984 | 89.58 |
Just a test of syntaxhighlighter in blogger
Friday, February 27, 2009
This is just a test of syntaxhighlighter.
from couchdb.schema import Document, View, IntegerField, TextField
from couchdb import Database
map_fun = """
function(doc){
emit(doc.name, doc.age);
}
"""
class Person(Document):
name = TextField()
age = IntegerField()
by_name = View('people', map_fun)
db = Database("")
# to make a view permanent do this
from couchdb.design import ViewDefinition
ViewDefinition.sync_many(db, [Person.by_name])
Person(name = "batok", age = 48).store(db)
Person(name = "rgalvan", age = 47).store(db)
Person(name = "robert", age = 30).store(db)
for person in Person.by_name( db, limit = 3):
print person.name, person.age
Posted by Batok at 7:08 PM Comments
Introducing blogcdb
Monday, December 22, 2008
I have created a new project at github.
It's blogcdb ( a blog engine that uses couchdb ).
The blog engine is made with turbogears 2, a very good python web framework.
Also uses dojo javascript framework for some fancy stuff. Dojo version 1.2.3 is included.
To store blog posts, comments and attachments , the erlang based couchdb document database engine is used.
Requirements:
couchdb-python module by Christopher Lenz and Jan Lenhardt.
python 2.6
turbogears 2 : trunk version which also needs a lot of modules.
dojo 1.2.3 ( included ).
couchdb ( svn truk version ) available from apache software foundation.
erlang/otp
mozilla's spidermonkey.
Get blogcdb at
Posted by Batok at 4:18 PM Comments
A wxpython GUI interface to a blog.
Wednesday, December 10, 2008
I have created a github project with the name couchdb-wxpython.
The project is a python script that uses:
wxpython ( a python module for GUI which is cross-platform. It is a wrapper for wxwidgets ).
couchdb , a document oriented database to store blogposts , comments and attachments.
The program can also take screenshots and store them as attachments into couchdb.
Posted by Batok at 2:45 PM Comments | http://batok.blogspot.com/ | CC-MAIN-2014-52 | refinedweb | 311 | 61.22 |
The SysTimer class is used to provide timing for system suspension, and the idle loop in TICKLESS mode. More...
#include <SysTimer.h>
The SysTimer class is used to provide timing for system suspension, and the idle loop in TICKLESS mode.
Template for speed for testing - only one instance will be used normally.
Definition at line 50 of file SysTimer.h.
duration type used for underlying high-res timer
Definition at line 61 of file SysTimer.h.
period of underlying high-res timer
Definition at line 65 of file SysTimer.h.
time_point type used for underlying high-res timer
Definition at line 63 of file SysTimer.h.
Default constructor uses LPTICKER if available (so the timer will continue to run in deep sleep), else USTICKER.
Acknowledge an os tick.
This will queue another os tick immediately if the os is running slow
Prevent any more scheduled ticks from triggering.
If called from OS tick context, there may be remaining unacknowledged ticks.
Cancel any pending wake.
Get the current tick count.
This count is updated by the ticker interrupt, if the ticker interrupt is running. It the ticker interrupt is not running, update_and_get_tick() should be used instead.
This indicates how many ticks have been generated by the tick interrupt. The os_timer should equal this number minus the number of unacknowledged ticks.
Get the time.
Returns the instantaneous precision time from underlying timer. This is a slow operation so should not be called from critical sections.
Returns time since last tick.
Get the interrupt number for the tick.
Schedules an interrupt to cause wake-up in time for the event. Interrupt may be arranged early to account for latency. If the time has already passed, no interrupt will be scheduled.
This is called from outside a critical section, as it is known to be a slow operation.
If the wake time is already set, this is a no-op. But that check is racy, which means wake_time_set() should be rechecked after taking a critical section.
As a side-effect, this clears the unacknowledged tick count - the caller is expected to use update_and_get_tick() after the suspend operation.
Schedule an os tick to fire.
Ticks will be rescheduled automatically every tick until cancel_tick is called.
A tick will be fired immediately if there are any unacknowledged ticks.
Check whether ticker is active.
Each time the tick interrupt fires, it is automatically rescheduled, so this will remain true once the tick is started, except during processing.
Definition at line 176 of file SysTimer.h.
Check unacknowledged ticks.
Returns the count of how many times the OS timer has been queued minus the number of times is has been acknowledged.
get_tick() - unacknowledged_ticks() should equal the OS's tick count, although such a calculation is not atomic if the ticker is currently running.
Definition at line 192 of file SysTimer.h.
Update and get the current tick count.
This is a slow operation that reads the timer and adjusts for elapsed time. Can only be used when the ticker is not running, as there is no IRQ synchronization.
This clears the unacknowledged tick counter - the caller is assumed to update their timer based on this return.
Check whether the wake time has passed.
This is a fast operation, based on checking whether the wake interrupt has run.
Definition at line 122 of file SysTimer.h.
Check whether wake timer is active.
Definition at line 132 of file SysTimer.h. | https://os.mbed.com/docs/mbed-os/v6.7/mbed-os-api-doxy/classmbed_1_1internal_1_1_sys_timer.html | CC-MAIN-2021-25 | refinedweb | 571 | 68.16 |
Tie::Redis::Attribute - Variable attribute based interface to Tie::Redis
version 0.26
use Tie::Redis::Attribute; my %hash : Redis; # %hash now magically resides in a redis instance
This is an experimental module that implements attribute based tying for Redis.
Currently tying of arrays or hashes is supported.
Options may be specified using perl list syntax within the
Redis(...) attribute.
However note that attributes cannot use lexical variables, so
my %p : Redis(host = $host)> will unfortunately not work if
$host is lexical.
The key to use, if this isn't provided a key is invented based on the package name and variable name. This means for some simple purposes you may not need to specify a key.
For example:
our @queue : Redis(key => "my-queue");
Other options are as per Tie::Redis's constructor (prefix) and AnyEvent::Redis (host, port, encoding).
You may subclass this and define a
server method that returns an instance of Tie::Redis. Due to the tricky nature of attributes it is recommended to not define an
import method in your subclass other than the one provided by this class.
Tie::Redis, Attribute::Tie, Attribute::TieClasses.. | http://search.cpan.org/~dgl/Tie-Redis/lib/Tie/Redis/Attribute.pm | CC-MAIN-2016-50 | refinedweb | 190 | 55.54 |
A lot of energy companies have given away free electricity meters. These have a clamp you put round the house supply, and a wireless link to a display. They are generally branded by the energy company, but a lot of them are Current Cost EnviR meters. If you look on the back, there is what appears to be an ethernet port, but is actually a serial connection in disguise. You can get a usb data cable that connects to the Pi, and enables you to read an XML string from the meter, with the current power and temperature. You’ll need to hunt around the interwebs for this, search “Current Cost Data Cable” to try and find one on amazon or ebay.
Once you have the cable and it’s connected up, you can use a few lines of python to read the data.
import serial serialObj = serial.Serial("/dev/ttyUSB0", 57600, timeout=6) xml = serialObj.readline() print(xml)
Running this should output something like:
<msg><src>CC128-v1.29</src><dsb>00484</dsb><time>20:16:49</time><tmpr>17.8</tmpr><sensor>0</sensor><id>00077</id><type>1</type><ch1><watts>00270</watts></ch1></msg>
You can then use a regular expression, or XML library to extract the data and do something useful with it. The example below sends it to a Graphite instance that is running on the Pi.
e.g.
import serial import re import urllib2 import time import socket serialObj = serial.Serial("/dev/ttyUSB0", 57600, timeout=30) xml = serialObj.readline() print "xml: " + xml m = re.search('(.*)',xml) power = m.group(1) print 'Power: ' + power # This conditional exists because occasionally the energy monitor returns an incorrectly low number. if (int(power) > 10): # Send the data to graphite sock = socket.socket() sock.connect( ("localhost", 2003) ) sock.send("house.power %d %d \n" % (int(power), time.time())) sock.close()
See the next blog post for details on how to configure Graphite on a Raspberry Pi
If it all works, you’ll be able to end up with graphs like this:
| https://markinbristol.wordpress.com/2015/12/01/energy-monitoring-with-a-raspberry-pi/ | CC-MAIN-2019-04 | refinedweb | 344 | 57.77 |
Get filesystem statistics
#include <sys/vfs.h> /* or <sys/statfs.h> */
int statfs(const char *path, struct statfs *buf);
int fstatfs(int fd, struct statfs *buf);
The function statfs() returns information about a mounted filesystem. path is the pathname of any file within the mounted filesystem. buf is a pointer to a statfs structure defined approximately as follows:
#if __WORDSIZE == 32 /* System word size */ # define __SWORD_TYPE int #else /* __WORDSIZE == 64 */ # define __SWORD_TYPE long int #endif struct statfs { __SWORD_TYPE f_type; /* type of filesystem (see below) */ __SWORD_TYPE f_bsize; /* optimal transfer block size */ fsblkcnt_t f_blocks; /* total data blocks in filesystem */ fsblkcnt_t f_bfree; /* free blocks in fs */ fsblkcnt_t f_bavail; /* free blocks available to unprivileged user */ fsfilcnt_t f_files; /* total file nodes in filesystem */ fsfilcnt_t f_ffree; /* free file nodes in fs */ fsid_t f_fsid; /* filesystem id */ __SWORD_TYPE f_namelen; /* maximum length of filenames */ __SWORD_TYPE f_frsize; /* fragment size (since Linux 2.6) */ __SWORD_TYPE f_spare[5]; }; some are hardcoded in kernel sources.. filesystem. filesystem does not support this call.
ENOTDIR
(statfs()) A component of the path prefix of path is not a directory.
EOVERFLOW
Some values were too large to be represented in the returned struct.
Linux-specific. The Linux statfs() was inspired by the 4.4BSD one (but they do not use the same structure). structure, but the sizes of various fields are increased, to accommodate large file sizes. The glibc statfs() and fstatfs() wrapper functions transparently deal with the kernel differences. operating systems use (a variation on) the device number, or the device number combined concern.
Under some operating systems, the fsid can be used as the second argument to the sysfs(2) system call.
This page is part of release 3.74 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at. | https://www.carta.tech/man-pages/man2/statfs64.2.html | CC-MAIN-2020-45 | refinedweb | 301 | 55.24 |
Jason asked if the API can be used to “select a bunch of families from a folder and automatically place them in an .rvt”
NOTE: For this code to run, you will need to add a reference to the SharpDevelop project as follows: Project – Add Reference – select System.Windows.Forms
public void placeMultipleFamilies() { Document doc = this.ActiveUIDocument.Document; if (!(doc.ActiveView is ViewPlan)) { TaskDialog.Show("Error","Command must be run from a plan view"); return; } // use standard Windows File Open dialog to select files System.Windows.Forms.OpenFileDialog opendialog = new System.Windows.Forms.OpenFileDialog(); // let user select multiple files opendialog.Multiselect = true; // set default directory opendialog.InitialDirectory = doc.Application.GetLibraryPaths().Values.First(); opendialog.Filter = "Revit Families|*.rfa"; System.Windows.Forms.DialogResult result = opendialog.ShowDialog(); if (result == System.Windows.Forms.DialogResult.Cancel) return; Level level = doc.ActiveView.GenLevel; using (Transaction t = new Transaction(doc, "Place families")) { t.Start(); double x = 0; double y = 0; foreach (string file in opendialog.FileNames) { // load the family Family f = null; doc.LoadFamily(file, out f); if (f == null) continue; // get a family symbol (aka family type) from the family FamilySymbol fs = f.Symbols.Cast<FamilySymbol>().FirstOrDefault(); doc.Create.NewFamilyInstance(new XYZ(x, y, 0), fs, level, StructuralType.NonStructural); // increment coordinates for placing next instance x = x + 10; if (x > 50) { x = 0; y = 10; } } t.Commit(); } }
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8 thoughts on “#RTCNA wish 9 granted! Place instances of multiple families”
[…] #RTCNA Wish 9 granted! Place instances of multiple families […]
[…] #RTCNA Wish 9 granted! Place instances of multiple families […]
Greate code, Harry! When I’m trying to build macro for Revit 2014, I’m getting this error: ‘StructuralType’ is inaccessible due to its protection level (CS0122)
I have also added the statemen at the top of my file, as you suggested:
using Autodesk.Revit.UI.Selection;
But still getting the same arror.
Aslo is it possible to load all the Family Types inserted into RFA. Would be great to load all Family Types from TXT Types catalog. Is it possible. Thank you!
Hi,
Hi Adam,
Glad you like it!
The StructuralType enum is in the Autodesk.Revit.DB.Structure namespace, so if you don’t already have a using statement for that you should try adding one.
If you want to place instances of all family types, then you iterate through all symbols instead of using FirstOrDefault on this line
f.Symbols.Cast().FirstOrDefault();
Hello Harry!
Thank you very much, adding “using Autodesk.Revit.DB.Structure” solved the problem!
Now I have tested the Macro and I’ve noticed that it place 12 single families separately from each other. But if I have more then 12 files, they are overlapping each other.
Here is an example:
Is it possible to place all families I have separately from each other?
Concerning placing instances of all family types, I have modified the code as you suggested:
FamilySymbol fs = f.Symbols.Cast().All()
But I get this error: Error CS1501: No overload for method ‘All’ takes 0 arguments
Build failed.
I’m really sorry, but I’ve started C# programming 1 week ago. I bought you course: “Learn to program the Revit API by Boost Your BIM” and it helps me very much, but still I have a lot of questions.
Ok, I have figured out how to place all the families separatly changing the code:
// increment coordinates for placing next instance
x = x + 10;
if (x > 500)
Also I have found a way to add all Family Types from TXT.
Now I’d like to create an addin, but can’t find where in Visual Studio to add the reference: Project – Add Reference – select System.Windows.Forms
How can I solve this?
Project menu – Add Reference
Thanks Harry! I’ll try and will let you know if it worked.
By the way if you are interested I can share the code to place all family types from Revit families and from TXT. | https://boostyourbim.wordpress.com/2015/07/25/rtcna-wish-9-granted-place-instances-of-multiple-families/ | CC-MAIN-2017-26 | refinedweb | 653 | 50.53 |
Python Tests Run 10x Faster By Using Continuous Integration on Heroku
- 2292
In this post, I'll show you how to deploy a very simple Python web app with very long tests. I'll also show you how to speed up those tests significantly using parallelism.
In this post, I’ll show you how to deploy a very simple Python web app with very long tests. I’ll also show you how to speed up those tests significantly using parallelism.
If you are already familiar with Heroku and just want to go straight to the point, go directly to part 3.
It’s testing time.
For my last project, (a web scraping API) we decided to have part of our infrastructure on Heroku. The reason was simple: neither my co-founder nor I were very good at the ops side of dev, so we have chosen the simplest, most time-efficient way to deploy our app: Heroku. Prior to this we’d had middling experience with AWS, in particular EBS.
Make no mistake – this simplicity comes at a price, and Heroku is crazy expensive. But their free plan is very good for side projects such as a Twitch SMS notificator 😎.
So as I said, I’ve been using Heroku for quite a bit of time. And since the beginning we used the lightweight but simple CI integration that would automatically deploy our application every time we push, if and only if all our tests pass.
Nothing new under the sun here.
In this post you will see how to easily deploy a Heroku application and set up the continuous integration. But more importantly you will see how to parallelize tests.
Again, if you are already familiar with how to deploy an Heroku application and the continuous application, go directly here to learn about parallelising the test.
First, deploy an app on Heroku:
If you don’t already, you need to create a Heroku account. You also need to download and install the Heroku client. I’ve provided a test project on Github, so do not hesitate to check it out it you need help bootstrapping this tutorial.
You can pull this repo,
cd into it and just do a
heroku create --app <app name>. Then if you go onto your app dashboard, you’ll see your new app.
OK, now comes the interesting part – just go onto your dashboard and click on the name of your newly created app, then go to the “deploy” panel.
We will now link this Heroku app with your Github repo. This is rather easy: simply click on “Github” in the “Deployment method” section, add your repo in the “App connected to Github” section, and don’t forget to click “Enable automatic deploys” in the “Automatic deploys” section.
Once everything is setup it should look a little bit like this:
If you go over “Settings -> Domains” you should see the domain where your app is live.
So now you app is live, and every-time you’ll push to Github a new deploy will take place.
Then add tests and CI:
In order to run tests on Heroku you have to do to is click on “Wait for CI to deploy” in the deploy section of your app.
You also need to add your application to a Heroku pipeline.
Doing this is really easy: just go on the Deploy tab of your application and create a new Pipeline with the name of your choice.
You have now access to the Pipeline view where you can click on your previously deployed app.
Go over to the Tests tab, link your Github repo, and click on “Enable Heroku CI”. Be aware, this option costs $10 a month.
Let’s go back to our code. The test file is already written, and now, all you have to do to trigger the magic is simply to push to master.
git commit --allow-empty -m "Trigger heroku" && git push origin master
And now, the app won’t deploy right away – Heroku will wait for tests to pass before deploying. You can check what’s going on behind the curtain on the Test tab.
The command that is run during the test is defined in the
app.json file.
As you can see, tests are now being run sequentially on Heroku. If you look at the
slow-tests.py file, you will see that I defined my tests using
pytest.mark.parametrize that allows me to trigger multiple tests in one line:
@pytest.mark.parametrize("wait_time", [5] * 20) def test_slow(wait_time): time.sleep(wait_time) assert True
This decorator means that the test will be run 20 times with
wait_time=5.
As you can see in Heroku, this test suite is (artificially) rather slow:
7 is here is just the number of the build
Parallelising test on Heroku
As stated here in the doc, Heroku easily offers the ability to parallelise tests. In order to launch your tests on multiple dynos at the same time, you just have to tweak your
app.json file a little bit.
{ "environments": { "test": { "scripts": { "test-setup": "pip install -r requirements.txt", "test": "pytest --tap-stream slow-tests.py" }, "formation": { "test": { "quantity": 12 } } } }, "buildpacks": [{ "url": "heroku/python" }] }
The
quantity key will tell Heroku on how many dynos you want to run your test. From now on, pushing on master will launch the test on 12 dynos. But stopping here won’t make your tests faster because the entire test suite will be run on 12 dynos. What we want is to run 1/12 of all tests on each of the 12 dynos.
It is actually easy to check:
Tests were run on 12 dynos, but were not that much faster. So now comes the tricky and unfortunately not very well documented part: how do we tell Heroku to run 1/12 of the test suite on each of the 12 dynos?
Splitting up tests
To do this we will use 2 environment variables set by Heroku and accessible on each dyno,
CI_NODE_TOTAL and
CI_NODE_INDEX . The first one indicates the total number of the dynos on which the tests are run, and the second one indicates the current dyno are you.
Let’s see how to use them. pytest offers you the ability to overwrite the test items that are going to be executed during the test phase. To overwrite this function, just declare this snippet of code in
conftest.py file:
import os def pytest_collection_modifyitems(items, config): ci_node_total = int(os.getenv("CI_NODE_TOTAL", 1)) ci_node_index = int(os.getenv("CI_NODE_INDEX", 0)) items[:] = [ item for index, item in enumerate(items) if index % ci_node_total == ci_node_index ]
This method is used to modify test items that are going to be tested in place. This method does not return anything, which is why you have to update the array in place. This usually an example of what not to do, but that is not the subject of this post.
You have to keep in mind that this snippet is run on every test node. On every test node,
CI_NODE_TOTAL is the same and
CI_NODE_INDEX is different, so by only keeping tests whose
index in
items modulo
CI_NODE_TOTAL equals
CI_NODE_INDEX we ensure 2 things:
- every node runs 1 /
CI_NODE_TOTALnumber of tests
- every test originally in
itemsended up being run
If it is not clear, imagine that I have 24 tests in items:
[t1, t2, ...., t24]. This snippet of code, executed on the number number 1, will update the
items variable such that, at the end of
pytest_collection_modifyitems, we have
items = [t1, t13] . Then in dyno number 2 we have
items = [t2, t14], and so on.
And here is what happens on Heroku once we push:
As you can see, we did not manage to divide the time by 12. The reason is simple: each dyno takes about 30 seconds to boot, and this time is incompressible. But we managed to divide time by 2, and more importantly, we can parallelize our tests to up to 32 dynos, so there is plenty room for time improvement.
Thank you for reading
I had trouble finding documentation about parallelising tests on Heroku in Python, and I really hope you liked this post and that it will speed up your deployment time on Heroku. All source code is freely available here on Github.
I frequently blog about Python and web scraping. Actually, I recently wrote a Python web-scraping guide that got some nice attention from Reddit 😎, so don’t hesitate to check it out.
You can follow me here on twitter so you don’t miss any of my future blog posts.
Recommended Reading
☞ Python GUI Tutorial - Python GUI with Examples - Tkinter Tutorial
☞ Visual Studio Code For Python Development
Suggest:
☞ Learn Python in 12 Hours | Python Tutorial For Beginners
☞ Complete Python Tutorial for Beginners (2019)
☞ Python Programming Tutorial | Full Python Course for Beginners 2019
☞ Python Tutorials for Beginners - Learn Python Online
☞ Complete Python 3 Programming Tutorial
☞ Python Tutorial for Beginners [Full Course] 2019 | https://school.geekwall.in/p/rZdeFEjS/python-tests-run-10x-faster-by-using-continuous-integration-on-heroku | CC-MAIN-2020-40 | refinedweb | 1,496 | 69.62 |
Hi I wrote the code below for the purpose of wrapping text to fit within a given pixel width: Args: drawer: Instance of "ImageDraw.Draw()" text: string of long text to be wrapped font: instance of ImageFont (I use .truetype) containerWidth: number of pixels text lines have to fit into. Outputs described after code below: ***code*** def IntelliDraw(drawer,text,font,containerWidth): words = text.split() lines = [] # prepare a return argument lines.append(words) finished = False line = 0 while not finished: thistext = lines[line] newline = [] innerFinished = False while not innerFinished: #print 'thistext: '+str(thistext) if drawer.textsize(' '.join(thistext),font)[0] > containerWidth: # this is the heart of the algorithm: we pop words off the current # sentence until the width is ok, then in the next outer loop # we move on to the next sentence. newline.insert(0,thistext.pop(-1)) else: innerFinished = True if len(newline) > 0: lines.append(newline) line = line + 1 else: finished = True tmp = [] for i in lines: tmp.append( ' '.join(i) ) lines = tmp (width,height) = drawer.textsize(lines[0],font) return (lines,width,height) ***endcode*** Outputs of function: lines: list of strings which corresponds to the given "text" argument, but broken up into list elements. width: pixel width of the first line (should be less than containerWidth) height: pixel height of first line (used for spacing successive lines) An example of how this is used is given below: ***code*** text = 'One very extremely long string that cannot possibly fit \ into a small number of pixels of horizontal width, and the idea \ is to break this text up into multiple lines that can be placed like \ a paragraph into our image' draw = ImageDraw.Draw(OurImagePreviouslyDefined) font = fontpath = ImageFont.truetype('/usr/local/share/fonts/ttf/times.ttf',26) pixelWidth = 500 # pixels lines,tmp,h = IntelliDraw(draw,text,font,pixelWidth) j = 0 for i in lines: draw.text( (0,0+j*h), i , font=font16, fill='black') j = j + 1 ***endcode*** Hopefully this code works for you. As you may observe, the algorithm is *extremely* simple and not optimal in any way. I would have loved to have found something like this on the net, but couldn't, so maybe someone else on this list is also looking. Thanks Caleb | https://mail.python.org/pipermail/image-sig/2004-December/003064.html | CC-MAIN-2017-30 | refinedweb | 370 | 52.7 |
New 🙂_2<<
Invoking “Add @return tag” quick fix will add the tag to PHPDoc along with expected return type:
The described inspections can be a very good reminder to keep your code documentation up-to-date. And let’s be honest, that’s something we often forget to do 🙂
9 Responses to New PHPDoc inspections and quick fixes
SebCorbin says:May 10, 2011
Nice one ! I’ll finally have my function properly documented 🙂
Chen says:May 10, 2011
The best idea ever.
This will help to get all functions documented. Thanks. 🙂
Crack says:May 10, 2011
Great feature, really helps with fixing docs in old code 🙂
Morfi says:May 12, 2011
Add please PHPDoc for static magic methods (__callStatic)
Vladimir Fishchenko says:May 15, 2011
Can you add something to a batch checking code with PHP_CodeSniffer?
Jon Whitcraft says:May 19, 2011
I’m not seeing the Generate PHPDot Block when i press control+return (on a mac). How do you get this to show up??
Tim Hawkins says:May 19, 2011’s.
Rustam Vishnyakov says:May 23, 2011
Please submit your bug reports and feature requests to. Other users may vote for your improvement suggestion and this will help us to prioritize the issues. Thank you!
Henning says:November 18, 2011. | https://blog.jetbrains.com/webide/2011/05/phpdoc-inspections/ | CC-MAIN-2021-04 | refinedweb | 212 | 70.43 |
Summary
So far I’ve written a lot of posts about Fluent NHibernate using MS SQL Server. I wanted to demonstrate how to connect to Oracle and what the differences were between SQL and Oracle. Getting the connection to work is probably the most difficult part. After that, the mappings are a bit different, but not complicated.
Installing Oracle
Oracle has a free version of it’s database for development purposes. This is an excellent strategy for a company to get it’s product into smaller companies. One of the strongest influences on which database engine is used at a company is based on what the developers are familiar with. Once a database server has been established, it will be there for a long time (it’s very difficult and expensive to change database servers once a system goes live). As a developer, I like to keep my options open, so I’ve experimented with many databases in my career. I’ve also used Oracle and SQL Server on major projects, and I converted a major project from Oracle to SQL Server.
Back to the free version of Oracle that I was talking about… If you go to Oracle’s website and create an account, you can download the windows version of Oracle XE (Express Edition). This is an easy to use version of Oracle that you can install on your PC and experiment with. I’m currently working with 11g Express:
Just download the x64 (I’m assuming you are on a 64 bit machine) and install it. Once Oracle is installed you’ll have to create your own workspace and create some tables. Go to the “Get Started” application. It should startup a browser and show an interface like this:
Next, you’ll need to click on “Application Express”. This will allow you to setup a new workspace. You’ll need to use your “SYSTEM” id and password to get to the express application (which you have to set when you install the application). You should now see this screen:
This is where you’ll setup your workspace. You can choose a name for your “Database Username” which is not used in the connection string for this sample. Your Application Express Username and password is important. You’ll need these for the NHibernate connection string. Once you have created a workspace you will have access to a lot of tools to administer your database.
The easiest way to create your tables is to go to the SQL workshop section under Object Browser. There is a “Create” button that can be used to create new tables. Click that button, and select “Table”:
Now you can create one table at a time. For this demo, you’ll need three tables: store, product and producttype. Start with producttype and use this:
Make sure you set the primary key on each of these tables to populate from new sequence. This is the same as setting an identity on a primary key in MS SQL:
Then add product:
Then add store:
If you’re feeling brave, you can add in the relational integrity constraints (foreign keys) while you create your tables. Otherwise, you can dig around for the raw queries to create such constraints.
The Oracle Database Connection
You’ll need the same 3 dlls used in any of my previous NHibernate samples: FluentNHibernate.dll, Iesi.Collections.dll and NHibernate.dll. You can get these using the NuGet package manager (or just download my sample and grab them from the 3rdPartyDLLs directory.
I created a session factory to connect to my default Oracle.Instance. Here’s the code:
public class OracleSessionFactory
{
private static ISessionFactory _sessionFactory;
private static ISessionFactory SessionFactory
{
get
{
if (_sessionFactory == null)
{
_sessionFactory = Fluently.Configure()
.Database(OracleClientConfiguration.Oracle10
.ConnectionString(“DATA SOURCE=XE;USER ID=username;PASSWORD=pass;“)
.Driver<NHibernate.Driver.OracleClientDriver>())
.Mappings(m => m.FluentMappings.Add<ProductTypeMap>())
.Mappings(m => m.FluentMappings.Add<ProductMap>())
.Mappings(m => m.FluentMappings.Add<StoreMap>())
.ExposeConfiguration(config =>
{
SchemaExport schemaExport = new SchemaExport(config);
})
.BuildSessionFactory();
}
return _sessionFactory;
}
}
public static ISession OpenSession()
{
return SessionFactory.OpenSession();
}
}
You’ll need to modify your mappings to something like this:
public class ProductType
{
public virtual int Id { get; set; }
public virtual string Description { get; set; }
}
public class ProductTypeMap : ClassMap<ProductType>
{
public ProductTypeMap()
{
Table(“ProductType“);
Id(u => u.Id).GeneratedBy.Sequence(“PRODUCTTYPE_SEQ“).Not.Nullable();
Map(u => u.Description).Length(50).Nullable();
}
}
The “Sequence” attribute is necessary to declare that the “Id” field is a sequence field. This is similar to the SQL Server identity declaration.
If you were to build this program in a console application, set your user name and password correct and run the program, you’ll get an error like this:
This is an annoying side affect that can be solved by setting the bitness of the project itself. Right-click on your project and select “Properties”. Choose “Build” and change the “Platform Target” from “Any” to “x64” (if you’re using the 64 bit version of Oracle). Now you can successfully run your application.
From this point on, everything about Fluent NHibernate is the same. I have included a select, insert, delete and update query in my sample application so you can see all the CRUD operations against an Oracle server.
Testing the Connection Outside Visual Studio
If you’re having difficulty getting your Oracle connection to work you can use the “Data Link Properties” window to test your connection parameters. Create a text file on your desktop and name it “conn.udl”, then double-click on that file and you’ll see this window:
Select “Oracle Provider for OLE DB” and click the “Next >>” button. Now fill in your connection information in this window. Oracle uses “XE” as the default for the Data Source:
Once you click the “Test Connection” button you should get confirmation of a good connection. Otherwise, you’ll get an error. If you can get your settings to work in this window, then you’re one step closer to making your Oracle session work.
Sample Application
You can download this sample application and run it on your PC (after you install Oracle XE). Be sure and set your user name and password in the SessionFactory.cs file.
FluentNHibernateOracleDemo.zip | http://blog.frankdecaire.com/2014/09/01/using-oracle-with-fluent-nhibernate/ | CC-MAIN-2018-13 | refinedweb | 1,032 | 54.42 |
I have a Cyrus-IMAP server with altnamespace:yes and unixhierarchysep: yes. I want my sent messages to be stored on server, the INBOX.Sent being the most obvious choice. Setting this in Apple Mail was easy (Mailboxes>Use this folder for...>Sent). With Outlook 2007, however, I've run into a strange problem.
The Outlook documentation suggests:
" ... In the Internet E-mail Settings dialog box, click the Folders tab.
Folders tab in Internet E-mail Settings dialog box
To choose a custom folder for saving your sent items, click Choose an existing folder or create a new folder to save your sent items for this account in."
()
OK, I choose Inbox.Sent, but the sent messages are still saved in a local Outlook folder. If I try to move them to Inbox.Sent, I get an error message: server said the mailbox does not exist. Yes, what does exist, is INBOX.Sent, and both SquirrelMail and Apple Mail store sent messages there. Now, if I create a subfolder in Inbox.Sent, like Inbox/Sent/test, it DOES exist from the server perspective (and sent mail can be stored there). But Inbox/Sent still cannot be used for that, and INBOX.Sent is not visible in any folder list.
The most bizarre is that Outlook recognizes the existence of INBOX.Sent by storing its own test messages there (those generated while creating the account).
After googling half a day I'm out of wits. Please, help.
Thanks.
Tom
OK, it looks that I understand what's the problem.
Outlook 2007 takes folder names as case-sensitive, while Cyrus and the rest of the world take them as case-insensitive. So when Outlook asks Cyrus to list the available folders, it gets INBOX.Sent and other INBOX.* folders for a reply. No "Inbox.Sent" among them? Outlook just takes it as the destination folder doesn't exist and doesn't save anything on server. At the same time, it continues to insist there IS "Inbox.Sent" on the server by showing it among IMAP folders! And if you try to tell the server to create "Inbox.Sent" folder, server responds that the folder exists, as Cyrus takes INBOX as case insensitive!
The workaround is to fit the rest of the world to the Microsoft peculiarities by forcibly creating "Inbox.Sent" folder before some other e-mail client creates INBOX.Sent. Then it works with the rest of them, except that you have to specify "Inbox.Sent" explicitly to save the sent messages. And if the client does not allow it (some phone clients), then an extra Sent folder is created.
I've tested it on Apple Mail, Outlook 2003, 2007, 2010, Thunderbird 10.0.2, TheBat! 5.
If anyone has a better idea, please share.
By posting your answer, you agree to the privacy policy and terms of service.
asked
3 years ago
viewed
654 times
active | http://serverfault.com/questions/361916/inbox-inbox-and-ms-outlook-2007 | CC-MAIN-2015-27 | refinedweb | 486 | 77.23 |
How do I access a gui element?
I've read the ui guide but I haven't found a solution to my problem.
Given my pyui in my_gui.pyui:
How can I access the ui elements in my separate my_ui.py file?
For example, I want pressing the 'Small' button to set the text of the text field to 'this is small'.
Right now I cannot make the button make changes to the text field element.
import ui import imgtagr import clipboard def small_tapped(sender): sender.title = 'cool' def medium_tapped(sender): pass def large_tapped(sender): pass def none_tapped(sender): pass def main(): ui.load_view('my_gui').present('sheet') main()
there are some good tutorials over at pythonista-tools github repo.
But basically your options are:
sender.superview['textfield1']
or, storing global references to ui elements you want, or custom view with references stored in self.()
All the above looks correct. But why not start at the begining.
ui.load_view('my_gui').present('sheet') - I don't use this pattern
I use -
v = ui.load('my_gui') # then can access the subviews as subscripts v['textfield1'].text = 'Whatever I want' v.present(style='sheet')
I hope this makes sense.
v = ui.load_view('my_gui').present('sheet')
v will not work as expected.
@ramvee , not sure you are aware of the below or not. The PYUILoader was built up by @Jonb after some questions on the forums here. Basically it allows a loaded UIFile to look and act as a custom class. Not just a wrapper. If you do a search in the forum you will come up with quite a bit about it. As far as I know, the below is the most refined version. As it handles custom properties set in the pyui file also. Honestly, its worth a look. I have gone backwards and forwards on using UIFiles. I think were i will end up falling is that for very quick and dirty things as well as examples etc, i will not bother. But once I start to make something someone might possibly use other than me, then I think I should UIFiles. Several of the guys here that really know what they are doing have expressed their views on the complexity of maintaining ui.Views that start to get a little complex, using flex etc. Anyway, each to their own.
Hope the below is helpful to someone.
import ui): ''' Just have to be mindful of a few things. 1. Set your instance vars before the super is called, otherwise they will not be accessible in the did_load. 2. Do any form element setup in the did_load call back. The ui module call this method. 3. In the in the UIFile in the 'Custom View Class' section you must put in the name of this class. In this case MyClass 4. I like the dict update in the did_load method. Nothing to do with getting this class setup. But its just a quick short cut for setting instance vars to your form elms for you can access them with dot notation. of course you could have just done self.label1 = self['lablel1']. Just a nice short cut. ''' def __init__(self, uifilename, *args, **kwargs): self.set_instance_vars_here = 'Yes you got me' super().__init__(uifilename, *args, **kwargs) def did_load(self): print(self.set_instance_vars_here) # add all instance vars for the form elements to the class. # its ok, but the late binding means the editor can not help # still better than string indexs I think. # This is not recursive. It could be though. [self.__dict__.update({sv.name: sv}) for sv in self.subviews] self['label1'].text = 'My Text' self.label1.text = 'My Text' if __name__ == '__main__': uifilename = 'test1.pyui' f = (0, 0, 300, 400) v = MyClass(uifilename, frame=f) v.present(style='sheet', animated=False)
@omz as a side note. It seems to me that this functionality should be built into Pythonista. When you are learning this stuff all seems like black magic and work around for things that's should not be done.
Something built in and done elegantly and documented, I think could position UIFiles more in the Pythonista Eco system to where they should be. I think people really struggle over whether to use them or not only because of a few issues.
Again, i know only so many hours in the day. I just think if this was considered part of the normal work flow and backed up with documentation, I don't think people would agonise over the options so much. It would start to become clearer what is best for their needs.
Anyway, my thoughts for today.
Pls remember, its been around 36hrs since I have had a real cigarette :) I feel strange
@Phuket2,
Thank you for the info, will try and understand what this is about!
Admire you for your helping nature!
Namaste! | https://forum.omz-software.com/topic/4294/how-do-i-access-a-gui-element/4 | CC-MAIN-2020-45 | refinedweb | 803 | 76.93 |
Can anyone explain where the value for ADC_MAX_CODE came from (I want to use this for another function I am doing with the ADC that has different limits and I need to understand where this came from)?
#define ADC_MAX_CODE (4095)
…
//Pot Reading is Scaled to return a value of -1.0 to 1.0
float TFC_ReadPot(uint8_t Channel)
{
if(Channel == 0)
return ((float)PotADC_Value[0]/-((float)ADC_MAX_CODE/2.0))+1.0;
else
return ((float)PotADC_Value[1]/-((float)ADC_MAX_CODE/2.0))+1.0;
}
Question2: I am unable to use TERMINAL_PRINTF for printing out floating point numbers in the Code Warrior demo code FRDM-TFC_R1.0.zip ? Has anyone had any success?
Jeff
Jeffrey, I'll try to check in an update to the FRDM-TFC library-- checking it out now. Looks like it works at least confirming with Excel-- haven't checked with Labview.
The equations and ADC_MAX_CODE value make sense if the ADC result is being read by the driver in 12-bit single-ended mode.
Ah, that makes perfect sense now. Thanks Craig.
And Oded. Yes, I found that %f works using mbed, but not in Code Warrior. I am using CW right now because I had trouble getting the demo code to work correctly for mbed.
We are using mbed, and the TERMINAL_PRINTF function prints floating points numbers correctly.
-Oded | https://community.nxp.com/t5/University-Programs/Demo-code-questions/m-p/289256/highlight/true | CC-MAIN-2020-50 | refinedweb | 222 | 65.83 |
NAME
getrlimit, setrlimit, prlimit - get/set resource limits
SYNOPSIS
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/resource.h>
int getrlimit(int resource, struct rlimit *rlim);
int setrlimit(int resource, const struct rlimit *rlim);
int setrlimit(int resource, const struct rlimit *rlim);
int prlimit(pid_t pid, int resource ", const struct rlimit *" new_limit ,
struct rlimit *old_limit);
struct rlimit *old_limit);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
prlimit(): _GNU_SOURCE
DESCRIPTION
The
On success, these system calls return 0. On error, -1 is returned, and errno is set appropriately.
ERRORS
VERSIONS
The prlimit() system call is available since Linux 2.6.36. Library support is available since glibc 2.13.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
CONFORMING TO
get
A differences
Since platforms().
EXAMPLE)
} while (0)
int main(int argc, char *argv[]) {
struct rlimit old, new;
struct rlimit *newp;
pid_t pid;
struct rlimit old, new;
struct rlimit *newp;
pid_t pid;
if (!(argc == 2 || argc == 4)) {
fprintf(stderr, "Usage: %s <pid> [<new-soft-limit> "
"<new-hard-limit>]\n", argv[0]);
exit(EXIT_FAILURE);
};
}
if (argc == 4) {
new.rlim_cur = atoi(argv[2]);
new.rlim_max = atoi(argv[3]);
newp = &new;
}
/* Set CPU time limit of target process; retrieve and display
previous limit */
previous limit */
if (prlimit(pid, RLIMIT_CPU, newp, &old) == -1)
errExit("prlimit-1");
printf("Previous limits: soft=%lld; hard=%lld\n",
(long long) old.rlim_cur, (long long) old.rlim_max););
errExit("prlimit-2");
printf("New limits: soft=%lld; hard=%lld\n",
(long long) old.rlim_cur, (long long) old.rlim_max);
exit(EXIT_SUCCESS); }
SEE ALSO
COLOPHON
This page is part of release 5.00 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at. | https://reposcope.com/man/en/3/vlimit | CC-MAIN-2019-51 | refinedweb | 293 | 50.12 |
This post was originally published on the New Bamboo blog, before New Bamboo joined thoughtbot in London.
We are currently hiring at New Bamboo. As part of the process, we send candidates a code test to complete at their own leisure. I won’t reveal any details here, but it’s nothing special.
Nevertheless, I have personally reviewed a bunch of these code tests, and
there’s something that has caught my attention. A number of applicants
misunderstand the usage of the inline
rescue construct in Ruby. Not a whole
lot of them, but enough that I felt compelled to write this piece in order to
help other people out there.
What I am seeing is code like the following:
do_something rescue SomeException
I assume applicants read that as “if
SomeException is raised, rescue it and
just carry on as if nothing had happened”. Unfortunately, this is not the case.
I’ll show with a different example. See this:
do_something rescue nil
What the above does is:
- It calls the method
do_something
- If that raised an exception, it’s rescued immediately. The line evaluates to
nil
- If no exception was raised, the line evaluates to the return value of
do_something
The following is equivalent:
begin do_something rescue nil end
Five lines with their indentation against a clever one-liner. Tempting! If you
know that
do_something may raise an exception, you use an inline
rescue to
quickly stop that and continue. Isn’t that neat?
Except that it’s a headache waiting to happen. Consider this code:
def someting_is_wrong? rand < 0.01 # Good 99% of the time end def do_something if something_is_wrong? raise MyIgnorableException else "foo" end end begin do_something rescue nil end
This code looks ok. However, when we run it, something is amiss. It always
returns
nil. We expected it to fail (return
nil) only in 1% percent of the
cases, but it’s actually failing 100% of the time. What’s going on?
Well, that we misspelled the name of the first method, that’s what. Read again:
someting_is_wrong?. An “h” is missing.
We are calling a method that doesn’t exist. This raises a
NoMethodError, which
bubbles up to the
rescue, which in turn ends up rescuing more than we wanted.
Remember that an unqualified
rescue will catch any exceptions that inherit
from
StandardError. That is dangerous, as it is likely that there will be
other problems.
Instead we should use the following invocation:
begin do_something rescue MyIgnorableException nil end
This time we get a
NoMethodError straight away. We notice the problem, fix it,
and continue on our merry way, safe in the knowledge that we’ll be notified of
any unforeseen problems.
In summary, there are two problems with inline
rescue of exceptions:
- The syntax can be misleading, making you think that it’s rescuing only a specific type of exception, when it’s not. It’s rescuing any type of exception (as long as it inherits from
StandardError), then evaluating the expression that follows it
- Rescuing exceptions without sensible filtering will make you miss other problems that you didn’t expect
Therefore, here are two pieces of advice:
- Never use the unfiltered version of
rescue
- Never use the inline
rescue, as it’s effectively an unfiltered
rescue
OK, I say “never”, but Avdi Grimm could come up with a decent use case for the
inline
rescue. Rather than outlining it here, stealing Avdi’s thunder, and
making this longer than it needs to be, I’m just going to link to the screencast
where he explains it better than I can, in just 3:17 minutes. It’s issue #22 of
his excellent Ruby Tapas, and it’s available for free at his blog: Ruby Tapas
#22 - Inline Rescue.
Happy hacking! | https://thoughtbot.com/blog/don-t-inline-rescue-in-ruby | CC-MAIN-2019-47 | refinedweb | 626 | 62.48 |
.
1) What is the status of the Spring 2.0 final launch? What’s going on there?
We have just updated our 2.0 release plan after an assessment of status in a number of key areas. The target date for Spring 2.0 final is now scheduled for September 26th, 2006. We will also announce another release candidate (RC4) this week.
Since Spring 2.0 development kicked off at last year’s Spring Experience conference in December 2005, we have received a massive amount of feedback from the community. It has truly been an unbelievable response - users have not only been actively suggesting improvements, they have been performing extensive QA testing across diverse environments. This has led to major improvements to key new features such as the asynchronous JMS capabilities, the JPA support, and the new JSP form tag library.
At present we are working hard to ensure sure Spring 2.0 plays nicely in an OSGi environment, something that is very important to us and our users. In addition, a large amount of effort is being invested in our documentation. The return is evident when you open the 2.0 reference manual and see just how comprehensive the coverage is.
Overall, we have placed extra emphasis on quality and backwards compatibility for this release. We are happy about that decision. Our user base can be assured that moving to Spring 2.0 will be as painless as possible. The release should be 100% backward compatible and serve as a drop-in replacement in existing projects, however complex they may be. That is tough to achieve, but essential for us and our users given the scope of Spring adoption in the enterprise.
2) What are some of the recent JPA changes that have occurred?
The JPA 1.0 spec did not go final until well along in the Spring 2.0 release cycle, and the implementations are only now becoming mature, so we have been working against a moving target. We underestimated the impact of that on our timescales.
However, as with Spring 2.0 overall, we have also ended up offering greater functionality than we envisaged. We have widened the scope of our JPA integration to support the notion of an "extended" persistence context and the injection annotations in the specification. We have received valuable input from a number of leaders in the JPA space including Mike Keith, the co-lead of the specification. We have also done work on value adds that make it easier for users to switch between JPA providers by providing consistent configuration for features that go beyond the spec that every provider offers and every user needs. In general, we have achieved a consistent, easy-to-use model for working with JPA across environments and are very pleased about that.
Technically the JPA support was a challenge because of the byte code instrumentation that is required by the specification. To support that in all environments--including a test environment--we had to build an abstraction layer that could allow instrumentation, then implement and test it across each environment. While the initial driver here was the JPA spec, this opens up exciting possibilities for the future. For example, it means that we can enable AspectJ load-time weaving portably and efficiently, with the ease of use you would expect of Spring.
We have done a lot of productive work with Mike Keith and other members of the TopLink team to ensure that Spring works well with TopLink Essentials. We are also excited about the OpenJPA project and are working with the OpenJPA team to have out-of-the-box integration with OpenJPA by the 2.0 final release. We also provide integration with the Hibernate EntityManager and hope that other JPA vendors will contribute integration with their products or ship it themselves.
3) What about JMS?
Spring's JMS message listener facility has been tested against all major JMS providers and has been significantly improved based on user feedback to be able to adapt to any JMS scenario out there-J2EE or non-J2EE, XA or local transactions, pooled or non-pooled. It now stands as the most flexible JMS message listener facility available, offering unique capabilities for working with native JMS providers and local JMS transactions.
4) What does is it mean to use Spring in an OSGi environment?
OSGi provides an excellent foundation for dividing an application into modules (called 'bundles' in OSGi terminology) with strict visibility rules for types that are visible to a module. It supports concurrent deployment of multiple versions of modules, with clients being bound to the most recent compatible version according to their import specification. OSGi also provides a dynamic environment enabling modules to be installed, updated, started, stopped, and uninstalled at runtime. However, OSGi lacks any means to wire together the components within a module, and only provides basic support (through the declarative services specification) for wiring together services across modules. That is where we come in.
The Spring OSGi support makes it easy to configure a bundle using Spring, with a Spring application context automatically instantiated when a bundle is activated. A new Spring namespace handler for OSGi makes it equally easy to define beans representing OSGi services (and to track the lifecycle of those services), to export beans as OSGi services, and to obtain configuration properties from the OSGi configuration administration service. Spring also transparently manages the context classloader so that enterprise libraries that are not designed for OSGi can continue to be used in an OSGi environment.
In short, Spring-OSGi aims to provide the power of the underlying OSGi framework, with the simplicity and ease-of-use characteristics that have come to be associated with Spring.
5) What are IBM, BEA, and Oracle doing with OSGI and why is it important for Spring to play a part in it?
Many organisations are recognising the value that OSGi can bring to enterprise software. IBM's WebSphere 6.1 is based on an OSGi kernel, for example. Supporting the enterprise space is a new direction for the OSGi Alliance, and a special Enterprise Workshop is being organised to bring interested parties together with a view to forming an expert group. IBM, BEA, and Oracle will all be represented at that event.
IBM, BEA, and Oracle are also collaborating with Interface21 on the Spring-OSGi support. Spring and OSGi are a very natural fit: as OSGi moves towards the enterprise, enabling users to unlock the power of OSGi through Spring is the obvious thing to do.
6) What are some of the thoughts for Spring post 2.0?
We see Spring 2.0 as a strong basis for moving forward, rather than an end in itself. A lot of work has gone into providing a stable platform for the work we will be doing in the next 6-18 months.
One example of that is in the area of AOP. The integration with AspectJ in Spring 2.0 is elegant and extremely powerful. We offer a single programming model for AOP, whether users are using Spring AOP’s proxy-based runtime or AspectJ. Beyond Spring 2.0, we are interested in exploring cases for additional out of the box aspects. We will be building on the load time weaving abstraction we developed for the JPA integration, as it opens up some exciting possibilities such as enabling Spring aspects to be built with AspectJ.
We are also planning further work in the JPA area, such as working with JPA vendors to offer a portable way of offering common functionality that goes beyond the spec, such as a criteria-style API. That is another area where Spring 2.0 is already designed to offer a base for future development.
We will be steadily releasing further ease of use features, such as more XML extension tags to simplify repeated tasks. The experience of using Spring 2.0 is already notably simpler than Spring 1.x, and we are doing ongoing work in that area, especially in the area of web applications.
One major priority for the rest of the year is delivering the full OSGi integration. We have completed the groundwork in Spring 2.0, but the full implementation will follow in 2.1 or 2.2. Once the technical integration is complete we think there will be some exciting benefits for application developers, as well as companies developing server software.
7) How do Spring’s subprojects, Acegi Security, Spring Web Flow, and Spring Web Services fit in with Spring 2.0?
We expect all three of these projects to take advantage of the latest Spring 2.0 capabilities while preserving Spring 1.2 compatibility as far as possible.
Acegi is a solid piece of software and popular with our users. Spring 2.0 particularly provides an opportunity to simplify its configuration so it can reach a wider audience.
Spring Web Flow is a next generation web application development technology people are excited about. It solves the problem of orchestrating multi-step user dialogs better than anything else out there, and the 1.0 final release will set a foundation we expect to position the product well for becoming more general purpose in the future. Version 1.0 is going final in the same timescale as Spring 2.0. The next release candidate (RC4) goes out this week and introduces a custom Spring 2.0 XML schema that simplifies configuration of the flow execution engine by building in defaults.
Spring Web Services is a young project that is really starting to emerge. It builds on Spring to provide support for implementing lightweight document-driven web services in Java. Future versions will take advantage of improvements in Spring 2.0’s web and remoting support.
In general, the Spring Framework core provides a common base of services our own sub-projects also leverage to address more specific domains. We are excited about the new doors Spring 2.0 is opening for these projects, for other emerging projects in the Spring community, and for our end users.
Additional Resources
Learn how to apply the latest Spring 2 capabilities at The Spring Experience conference this December.
Interface21, the company behind the Spring Framework, offers Spring-related training, consulting, and support services worldwide.
Download the latest Spring 2.0 release candidate.
TopLink Essentials is the open-source community edition of Oracle's TopLink product and the JPA Reference Implementation.
Open JPA aims to be a fully compliant, enterprise grade open-source JPA implementation suitable for production use.
Get started with the Java Persistence Architecture (JPA) in a Spring environment.
Learn about Message Driven POJOs, asynchronous message listeners executable in a Spring environment with a standalone JMS provider.
Read more about Aspect Oriented Programming with Spring 2.0 and AspectJ.
The OSGi Alliance is an independent non-profit corporation comprised of technology innovators focused on the interoperability of applications based on the OSGi platform.
Criteria API (nice)
by
Rick Hightower
This is very nice. Its nice to see Interface21 innovate to what should have been part of the JPA spec. in the first place.
OSGi
by
Rick Hightower
Re: OSGi
by
Andy Jefferson
Re: OSGi
by
Adrian Colyer
The most recent specification version (0.7) is the attachment named spring_and_osgi_64.html. Here's a direct link.
Wrong Link
by
Benoit Moussaud
Can you correct | http://www.infoq.com/articles/spring-2-update/ | CC-MAIN-2014-15 | refinedweb | 1,891 | 56.45 |
Joy, frustration, excitement, madness, aha's, headaches, ... codito ergo sum!!
Good to see the return of SmartPart! We found the previous version invaluable for quickly developing UI-intensive web parts. The deployment info for SmartPart was good, but I was wondering if you have thoughts for deploying the user controls that get hosted by SmartPart? There doesn't appear to be a built-in mechanism for deploying user controls, and we're finding the solution\feature framework to be surprisingly un-extensible -- there doesn't seem to be a solution event receiver class like there is for feature, for example. It may just be the lack of documentation at this point, but we also can't find if there's any way to get to the files in the solution package itself from the object model.
This control seems to be very useful. Will source code be posted or available?
Thanks.
Well I was waiting for smart part!! Its works as it promised.
Great work Jan! Keep it up!
We have created a user control with Atlas, and we successfull added it using smart part. But the problem is some part of the Atals are not working properly... It will be great full if u get some way to work it out..
In Atlas control if we remove "EnablePartialRendering='True' " its works fine, the problem after removing this is "Post back is happening"... which makes the usercontrol work slower
thanks in advance
Hello,
I have been trying to get my existing User Controls that were originally developed under Son of SmartPart and I have tried migrating them to Return of SmartPart, however, I have had no success since attempting to do this. I have been using the Microsoft Enterprise Library in the past with strong naming to call my data access methods, but none of my SmartParts seems to be working any longer. Is there a way I can trace this to find out what suddenly stopped working by migrating them to WSS 2007? I have checked the Event Logs and nothing is being reported there which should indicate that there are no security permission issues or compilation errors.
Are there any other ideas on how to resolve this?
Thank You.
I have a user control that references Microsoft.Practices.EnterpriseLibrary.Data.dll, which is installed in the GAC, on the machine that is hosting Sharepoint 2007. The user control works from asp.net, but I get an error when I try to display this control using the new SmartPart control. The error message is as follows:
Error: unable to load ~\/UserControls\WebUserControl3.ascx
Details: c:\Inetpub\wwwroot\wss\VirtualDirectories\8001\usercontrols\WebUserControl3.ascx(9): error CS0234: The type or namespace name 'Practices' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?)
Any information you can provide will be greatly appricated.
Thanks,
Dawn
Can 2 smart parts "talk" to each other on a single page?
I have some difficulties using SPS Views with User Controls and SmartPart.
View returns only all items when using User Controls. When i execute exactly same codes in custom WebPart, it works fine..
Need help for resolving that!
Is there any information on integrating SmartPart with the Office Sharepoint Desginer? We are using this to edit our pages, and SmartPart doesn't seem to work too well with it.
Thanks
Hi,
is there any demo on developing the usercontrols with code behind and integrating with other assembly(Microsoft Application Block)?
i would be appreciated if that is one because i currently dont agree of uploading my ascx.cs (source) file to UserControls folder. I might miss out something, but to my knowledge of "Return Of Smart Part" it requires my source file as well, else it cannot load the my usercontrols into the smartpart, correct me if i am wrong.
SAVE LOT OF TIME , ND GREAT
Does Return of SmartPart provide communication for the different types of interfaces provided in SharePoint, such as IWebPartField, IWebPartRow, IWebPartTable, and IWebPartParameters.
How to use <SafeControl... with ASP.NET 2.0 project, the assemblys are spread all over machine.
How to build/deploy user control in ASP.NET 2.0 for use in SmartPart.
I have a problem because of confusion made by publishig Web, assembly name, single page assemblies,...etc,etc
In ASP.NET 1.1. it was easy, one project directory, one assembly output, AssemblyInfo.vb file and easy of use <SafeControl...
Any information you can provide will be greatly appreciated
Unless your ASP.Net site uses dll's that are typically located in your site's bin directory, you dont need to modify SafeControls other than for SmartPart. Just write a user control (.ascx with code behind - either .ascs.cs or .ascx.vb).
If your user control depends on dll's, then you can deploy these in your production web sites bin folder and reference them in the _layouts/web.config.
If you trust your dll's and if they are strongly typed, you can deploy them in the GAC and reference them in the safe control section in the web.config in your web sites root directory.
Hope this helps
Smart Part Rocks,
One more question for Jan,
I used your smartpart on my Sharepoing moss2007/wss 3.0 and it works like charm.
Can I have .cs file for my .ascx to put all my code in there?
I tried doing that it gave me an error: Can not load your user control.
Does it have have inline coding, or is there way I can put my code in my code behind .cs file?
Please provide any feedback.
...Snehal
You do not need to code inline. Put your .ascx.cs file in the UserControl directory along with your .ascx.
You can also deploy and leverage separate class.cs files for web services or other custom code. Deploy these in C:\Inetpub\wwwroot\wss\VirtualDirectories\80\App_Code
Markus
I loaded usercontrol in smartpart (Return of smartpart). but my usercontrol contains some comlpex controls like calendar and retrieving data from database.
when i am loading user control first time, sharepoint page is not refreshing .
( i have take the url and paste it in new browser then refresh) then page is loading correctly its happening only first time.
any body suggest me what is the problem
Regards
Prakash Patil
I am using the latest version of smartpart(return of smartpart) with MOSS 2007. It works well Jan !! Thanks. I can connect to database only when i set the impersonate=false in the web.config of wss virtual folder. By default its true for moss 2007 and when its true, the sqlconnection.Open fails !!! I am using a custom app pool for my site and it has database access
Any idea? Please help.. I am burning my head for past several days on this guys.. please help
when i did manual installation,i am facing problems like...when i selected the SmartPart webpart from the sharepoint site..an error is displayed "The selected webpart is not safe registered "
Please suggest a solution.
Can someone let me know where to find SmartPart v3(return of SmartPart)? The GotDotNet link has been taken down.
Iam using Smart part but when im using session variable
the smart part is not working.
Im storing the check box selected in session
variable and displaying the relavent record.
Could you please help me how to use?
Thank you
Sunny
GotDotNet Workspace (in the releases section)!
not accessible where I can download it else?
Yes I am also looking for a new download location since the link to GotDotNet is no longer working . Any News about this ??? thanks
I am also looking a download location for Son of SmartPart. It would appear that the smartpart.info website is also not functional.
Thanks for helping.
buy-tramadol--online.info/.../tramadol-hcl-50mg-prescibing-information.php
Hi
I have create one smartpart (producer) on one page and the other smartpart (consumer) on second page. On click of submit on my producer form on page first, it should take me to page second and producer smart part should consume data.
It does not work for cross page. Can anyone suggest. It works perfectly fine when both producer and consumer are available on the same page.
hi,
I have created a web usercontrol and put it into the usercontrols folder in the sharepoint site. my user control has datagrid with database connection. when i tried to deploy the usercontrol using smartpart it was uploading successfully. When I select my usercontrol from the smartpart dropdown and press the apply button it is not showing any error but my usercontrol is not displaying. It showing empty.
am i missing anything? or i have to use add control?
Please anybody help me!
Regards,
Kalees
I need to develop an application using impersonation to post to a list. Can I use impersonation on the smartpart ? Thanks.
looks like a great tool where can we download it since GotDotNet is link is not working
Pingback from A new SharePoint site developed by some of my colleagues at ADA ICT at Virtual Generations
SmartPart3 v1.2 Beta
Markus wrote
"If you trust your dll's and if they are strongly typed, you can deploy them in the GAC and reference them in the safe control section in the web.config in your web sites root directory."
I have tried this but whatever I do I get an error message that says "cant find type or namespace..........." I can see that the assembly is in the GAC and the SafeControl item is added in the same config file where the SmartPart itself is added. Does anyone know what I am doing wrong?
I have managed to get SmartPart to work for individual web parts in SharePoint but cannot get two web parts connected successfully. It all appears to work okay until I try and select a record from the first web part. When I do this nothing is displayed in the second web part. I have been using an example from the book "Real World SharePoint 2007" and have copied the example to the letter. Does anyone have any suggestions for me. I desperately need to get this working in very near future.
I ran into the Error: unable to load ~\/UserControls\WebUserControl3.ascx error on a secondary server, but i removed everything started from scratch and it worked. I think it happened because I deviated from the instructions somewhat.
How can I refer other assemblies and classes. I need the System.Directoryservices.....
I`m using last version return of smartpart with my sharepoint. Everything is fine, but there is no support my language (russian).
Jan, can you set property "EnableScriptGlobalization" of ScriptManager in web part to "True"? Thank you.
Pingback from Nick’s Tech Blog » ASP.NET validation controls prevent publishing pages from saving | SharePoint 2007 Mostly | http://weblogs.asp.net/jan/archive/2006/12/02/announcing-the-return-of-the-smartpart.aspx | crawl-002 | refinedweb | 1,816 | 66.74 |
Defensive programming is so groovy
Copasetic tests verify every possible path through a method– sunny day and rainy scenarios; however, in the Age of Aquarius we’re lucky enough to have a test– consequently, one can scan a cornucopia of test suites to discover a false sense of security.
You: This method has 100% code coverage?
Them: Yes.
You: It’s bug free?
Them: Totally.
You: What happens if I pass in
null?
Them:
nullwould never be passed in.
Because it’s your bag (and not theirs), you write a hip test that passes in
null and voila! that 100% covered method isn’t 100% reliable.
Of course, handling this condition is as old as programming itself (even older than disco!)– checking for
null before doing anything. But, checking for
null is a bit verbose, not to mention fairly repetitive if it’s pervasive across a series of methods. Those dancers familiar with aspect oriented programming, or AOP, will recognize this as a crosscutting concern, meaning that defensive programming techniques span horizontally across a code base.
If AOP isn’t your bag though, you can always employ Groovy’s
? construct, which still results in repetitive code, however, it’s dramatically less verbose than typical
if/
then/
else conditionals.
For example, take this hip getter on a JavaBean-like Java class:
public String getGenre() { if(genre != null){ return genre.toUpperCase(); }else{ return null; } }
The guard conditional now effectively removes the chance of a
NullpointerException should the bean be initialized without a
genre property. With Groovy, however, I can replace the entire conditional with one operator, baby.
Groovy’s
? operator is an effective safety net that you can apply before calling a method on an object you suspect could be
null. For example, the above code is guarding against the bogue
genre variable– with Groovy then, before I attempt to invoke the
toUpperCase method, I can simply place a strategic
? and thus forego any conditionals like so:
def getGenre(){ "${genre?.toUpperCase()}" }
In essence, the two code examples are exactly the same (save for a few minor keystroke differences)– either an all capitalized
String instance is returned or
null is returned. Consequently, if you find yourself writing a lot of defensive code (and your bag isn’t AOP) then consider applying Groovy’s
? operator– it’ll save you a couple lines of code and a few
NullpointerException headaches, man!
Monday 18 Feb 2008 | Andy | Groovy
Why even putting everything inside a GString? You just need to return genre?.toUpperCase().
This trick is also more appealing when you have to go through some deep objectgraph. So instead of nested if / else, you can just return car?.make?.name?.toUpperCase() withouth having to check whether car is null, and make is null, and name is null, etc.
Good call, sir– I haven’t the slightest clue why I am working with a GString in that method. Thanks for pointing that out, man, and yeah– the deep object graph example is right on.
[…] Original post by Andy […]
What I have to write if I would like to return empty (ie. “”) gstring in place of null in your example?
Don’t you think it should make a difference to write:
“${genre?.toUpperCase()}”
and
${genre?.toUpperCase()}
The first case, in my opinion, should return empty GString.
The second should return null.
If both cases return null then the GString decalaration is a little bit misleading.
Cheers,
a.
Adam, one way of acccomplishing what you want is to use the ?: (’elvis’) operator:
genre?.toUpperCase() ?: ”
This operator (new to 1.5) returns the first expression unless it’s a false (null, 0, empty, false) value, else the second expression.
Also note that “${null}” evaluates to ‘null’, not ”.
[…] ? operator saves you from constantly having to check for null. Andrew Glover has a good example of Defensive Programming with Groovy over at The Disco Blog […]
Guillaume, Guillaume, Guillaume - *Please* don’t encourage people to write code like that. While this operator is indeed handy at times, I’d only trust about 2% of all programmers to use it appropriately. (To be clear, I’m not saying that Groovy shouldn’t offer this method. It absolutely should be there. I’m simply saying that 98% of the people that employ it will do so poorly and in a manner that compensates for generally shoddy code.)
Andy - You’re right on about the false confidence of 100% code coverage. (Jay Fields has a good post on this topic.) Bottom line: When it’s that easy to get 100% test coverage and still have buggy code, there’s simply no excuse for having anything less that 100% coverage. In fact, one could argue that 100% coverage is for underachievers.
[…] back to the getGenre method on the Song class, it turns out that Groovy also has a handy syntax for null pointer safety, consequently, I can simply that method even […]
It´s so easy to be save - but is utterly unused | http://thediscoblog.com/2008/02/18/defensive-programming-is-so-groovy/ | crawl-001 | refinedweb | 825 | 64.81 |
Numbers which are not the sum of distinct squares
You are encouraged to solve this task according to the task description, using any language you may know.
Integer squares are the set of integers multiplied by themselves: 1 x 1 = 1, 2 × 2 = 4, 3 × 3 = 9, etc. ( 1, 4, 9, 16 ... )
Most positive integers can be generated as the sum of 1 or more distinct integer squares.
1 == 1 5 == 4 + 1 25 == 16 + 9 77 == 36 + 25 + 16 103 == 49 + 25 + 16 + 9 + 4
Many can be generated in multiple ways:
90 == 36 + 25 + 16 + 9 + 4 == 64 + 16 + 9 + 1 == 49 + 25 + 16 == 64 + 25 + 1 == 81 + 9 130 == 64 + 36 + 16 + 9 + 4 + 1 == 49 + 36 + 25 + 16 + 4 == 100 + 16 + 9 + 4 + 1 == 81 + 36 + 9 + 4 == 64 + 49 + 16 + 1 == 100 + 25 + 4 + 1 == 81 + 49 == 121 + 9
The number of positive integers that cannot be generated by any combination of distinct squares is in fact finite:
2, 3, 6, 7, etc.
- Task
Find and show here, on this page, every positive integer than cannot be generated as the sum of distinct squares.
Do not use magic numbers or pre-determined limits. Justify your answer mathematically.
- See also
C#[edit]
Following in the example set by the Free Pascal entry for this task, this C# code is re-purposed from Practical_numbers#C#.
It seems that finding as many (or more) contiguous numbers-that-are-the-sum-of-distinct-squares as the highest found gap demonstrates that there is no higher gap, since there is enough overlap among the permutations of the sums of possible squares (once the numbers are large enough).
using System; using System.Collections.Generic; using System.Linq; class Program { // recursively permutates the list of squares to seek a matching sum static bool soms(int n, IEnumerable<int> f) { if (n <= 0) return false; if (f.Contains(n)) return true; switch(n.CompareTo(f.Sum())) { case 1: return false; case 0: return true; case -1: var rf = f.Reverse().Skip(1).ToList(); return soms(n - f.Last(), rf) || soms(n, rf); } return false; } static void Main() { var sw = System.Diagnostics.Stopwatch.StartNew(); int c = 0, r, i, g; var s = new List<int>(); var a = new List<int>(); var sf = "stopped checking after finding {0} sequential non-gaps after the final gap of {1}"; for (i = 1, g = 1; g >= (i >> 1); i++) { if ((r = (int)Math.Sqrt(i)) * r == i) s.Add(i); if (!soms(i, s)) a.Add(g = i); } sw.Stop(); Console.WriteLine("Numbers which are not the sum of distinct squares:"); Console.WriteLine(string.Join(", ", a)); Console.WriteLine(sf, i - g, g); Console.Write("found {0} total in {1} ms", a.Count, sw.Elapsed.TotalMilliseconds); } }
- Output @Tio.run:.7904 ms
Alternate Version[edit]
A little quicker, seeks between squares.
using System; using System.Collections.Generic; using System.Linq; class Program { static List<int> y = new List<int>(); // checks permutations of squares in a binary fashion static void soms(ref List<int> f, int d) { f.Add(f.Last() + d); int l = 1 << f.Count, max = f.Last(), min = max - d; var x = new List<int>(); for (int i = 1; i < l; i++) { int j = i, k = 0, r = 0; while (j > 0) { if ((j & 1) == 1 && (r += f[k]) >= max) break; j >>= 1; k++; } if (r > min && r < max) x.Add(r); } for ( ; ++min < max; ) if (!x.Contains(min)) y.Add(min); } static void Main() { var sw = System.Diagnostics.Stopwatch.StartNew(); var s = new List<int>{ 1 }; var sf = "stopped checking after finding {0} sequential non-gaps after the final gap of {1}"; for (int d = 1; d <= 29; ) soms(ref s, d += 2); sw.Stop(); Console.WriteLine("Numbers which are not the sum of distinct squares:"); Console.WriteLine(string.Join (", ", y)); Console.WriteLine("found {0} total in {1} ms", y.Count, sw.Elapsed.TotalMilliseconds); Console.Write(sf, s.Last()-y.Last(),y.Last()); } }
- Output @Tio.run:
Numbers which are not the sum of distinct squares: 2, 3, 6, 7, 8, 11, 12, 15, 18, 19, 22, 23, 24, 27, 28, 31, 32, 33, 43, 44, 47, 48, 60, 67, 72, 76, 92, 96, 108, 112, 128 found 31 total in 9.9693 ms stopped checking after finding 128 sequential non-gaps after the final gap of 128
Go[edit]
The quicker version and hence (indirectly) a translation of C#.
package main import ( "fmt" "math" "rcu" ) func contains(a []int, n int) bool { for _, e := range a { if e == n { return true } } return false } // recursively permutates the list of squares to seek a matching sum func soms(n int, f []int) bool { if n <= 0 { return false } if contains(f, n) { return true } sum := rcu.SumInts(f) if n > sum { return false } if n == sum { return true } rf := make([]int, len(f)) copy(rf, f) for i, j := 0, len(rf)-1; i < j; i, j = i+1, j-1 { rf[i], rf[j] = rf[j], rf[i] } rf = rf[1:] return soms(n-f[len(f)-1], rf) || soms(n, rf) } func main() { var s, a []int sf := "\nStopped checking after finding %d sequential non-gaps after the final gap of %d\n" i, g := 1, 1 for g >= (i >> 1) { r := int(math.Sqrt(float64(i))) if r*r == i { s = append(s, i) } if !soms(i, s) { g = i a = append(a, g) } i++ } fmt.Println("Numbers which are not the sum of distinct squares:") fmt.Println(a) fmt.Printf(sf, i-g, g) fmt.Printf("Found %d in total\n", len(a)) } var r int
- in total
jq[edit]
Works with gojq, the Go implementation of jq
The following program is directly based on the "Spoiler" observation at Raku. In effect, therefore, it computes the "magic number". It is nevertheless quite fast: on a 3GHz machine, u+s ~ 32ms using either the C or Go implementation of jq.
Since the implementation is based on generic concepts (such as runs), the helper functions are potentially independently useful.
#def squares: range(1; infinite) | . * .; # sums of distinct squares (sods) # Output: a stream of [$n, $sums] where $sums is the array of sods based on $n def sods: # input: [$n, $sums] def next: . as [$n, $sums] | (($n+1)*($n+1)) as $next | reduce $sums[] as $s ($sums + [$next]; if index($s + $next) then . else . + [$s + $next] end) | [$n + 1, unique]; [1, [1]] | recurse(next); # Input: an array # Output: the length of the run beginning at $n def length_of_run($n): label $out | (range($n+1; length),null) as $i | if $i == null then (length-$n) elif .[$i] == .[$i-1] + 1 then empty else $i-$n, break $out end; # Input: an array def length_of_longest_run: . as $in | first( foreach (range(0; length),null) as $i (0; if $i == null then . else ($in|length_of_run($i)) as $n | if $n > . then $n else . end end; if $i == null or (($in|length) - $i) < . then . else empty end) ); def sq: .*.; # Output: [$ix, $length] def relevant_sods: first( sods | . as [$n, $s] | ($s|length_of_longest_run) as $length | if $length > ($n+1|sq) then . else empty end ); def not_sum_of_distinct_squares: relevant_sods | . as [$ix, $sods] | [range(2; $ix+2|sq)] - $sods; not_sum_of_distinct_squares
- Output:
[2,3,6,7,8,11,12,15,18,19,22,23,24,27,28,31,32,33,43,44,47,48,60,67,72,76,92,96,108,112,128]
Julia[edit]
A true proof of the sketch below would require formal mathematical induction.
#= Here we show all the 128 < numbers < 400 can be expressed as a sum of distinct squares. Now 11 * 11 < 128 < 12 * 12. It is also true that we need no square less than 144 (12 * 12) to reduce via subtraction of squares all the numbers above 400 to a number > 128 and < 400 by subtracting discrete squares of numbers over 12, since the interval between such squares can be well below 128: for example, |14^2 - 15^2| is 29. So, we can always find a serial subtraction of discrete integer squares from any number > 400 that targets the interval between 129 and 400. Once we get to that interval, we already have shown in the program below that we can use the remaining squares under 400 to complete the remaining sum. =# using Combinatorics squares = [n * n for n in 1:20] possibles = [n for n in 1:500 if all(combo -> sum(combo) != n, combinations(squares))] println(possibles)
- Output:
[2, 3, 6, 7, 8, 11, 12, 15, 18, 19, 22, 23, 24, 27, 28, 31, 32, 33, 43, 44, 47, 48, 60, 67, 72, 76, 92, 96, 108, 112, 128]
Mathematica/Wolfram Language[edit]
ClearAll[SumOfSquareable] SumOfSquareable[n_Integer] := MemberQ[Total /@ Subsets[Range[1, Floor[Sqrt[n]]]^2, {1, \[Infinity]}], n] notsummable = {}; i = 1; Do[ If[SumOfSquareable[i], If[i > 1, If[i - Max[notsummable] > Max[notsummable], Break[] ] ] , AppendTo[notsummable, i] ]; i++ , {\[Infinity]} ] notsummable
- Output:
{2, 3, 6, 7, 8, 11, 12, 15, 18, 19, 22, 23, 24, 27, 28, 31, 32, 33, 43, 44, 47, 48, 60, 67, 72, 76, 92, 96, 108, 112, 128}
Pascal[edit]
Free Pascal[edit]
Modified Practical_numbers#Pascal.
Searching for a block of numbers that are all a possible sum of square numbers.
There is a symmetry of hasSum whether
2,3,6,..108,112,128,
are not reachably nor
SumOfSquare-2, SumOfSquare-3,SumOfSquare-6,...SumOfSquare-108,SumOfSquare-112,SumOfSquare-128
program practicalnumbers; {$IFDEF Windows} {$APPTYPE CONSOLE} {$ENDIF} var HasSum: array of byte; function FindLongestContiniuosBlock(startIdx,MaxIdx:NativeInt):NativeInt; var hs0 : pByte; l : NativeInt; begin l := 0; hs0 := @HasSum[0]; for startIdx := startIdx to MaxIdx do Begin IF hs0[startIdx]=0 then BREAK; inc(l); end; FindLongestContiniuosBlock := l; end; function SumAllSquares(Limit: Uint32):NativeInt; //mark sum and than shift by next summand == add var hs0, hs1: pByte; idx, j, maxlimit, delta,MaxContiniuos,MaxConOffset: NativeInt; begin MaxContiniuos := 0; MaxConOffset := 0; maxlimit := 0; hs0 := @HasSum[0]; hs0[0] := 1; //has sum of 0*0 idx := 1; writeln('number offset longest sum of'); writeln(' block squares'); while idx <= Limit do begin delta := idx*idx; //delta is within the continiuos range than break If (MaxContiniuos-MaxConOffset) > delta then BREAK; //mark oldsum+ delta with oldsum hs1 := @hs0[delta]; for j := maxlimit downto 0 do hs1[j] := hs1[j] or hs0[j]; maxlimit := maxlimit + delta; j := MaxConOffset; repeat delta := FindLongestContiniuosBlock(j,maxlimit); IF delta>MaxContiniuos then begin MaxContiniuos:= delta; MaxConOffset := j; end; inc(j,delta+1); until j > (maxlimit-delta); writeln(idx:4,MaxConOffset:7,MaxContiniuos:8,maxlimit:8); inc(idx); end; SumAllSquares:= idx; end; var limit, sumsquare, n: NativeInt; begin Limit := 25; sumsquare := 0; for n := 1 to Limit do sumsquare := sumsquare+n*n; writeln('sum of square [1..',limit,'] = ',sumsquare) ; writeln; setlength(HasSum,sumsquare+1); n := SumAllSquares(Limit); writeln(n); for Limit := 1 to n*n do if HasSum[Limit]=0 then write(Limit,','); setlength(HasSum,0); {$IFNDEF UNIX} readln; {$ENDIF} end.
- Output:
sum of square [1..25] = 5525 number offset longest sum of block squares 1 0 2 1 -> 0,1 2 0 2 5 3 0 2 14 4 0 2 30 5 0 2 55 6 34 9 91 ->34..42 7 49 11 140 ->49..59 8 77 15 204 ->77..91 9 129 28 285 10 129 128 385 11 129 249 506 12 129 393 650 13 2,3,6,7,8,11,12,15,18,19,22,23,24,27,28,31,32,33,43,44,47,48,60,67,72,76,92,96,108,112,128,
Phix[edit]
As per Raku (but possibly using slightly different logic, and this is using a simple flag array), if we find there will be a block of n2 summables, and we are going to mark every one of those entries plus n2 as summable, those regions will marry up or overlap and it is guaranteed to become at least twice that length in the next step, and all subsequent steps since 2*n2 is also going to be longer than (n+1)2 for all n>1, hence it will (eventually) mark everything beyond that point as summable. You can run this online here.
Strictly speaking the termination test should probably be
if r and sq>r then, not that shaving off two pointless iterations makes any difference at all.
with javascript_semantics sequence summable = {true} -- (1 can be expressed as 1*1) integer n = 2 while true do integer sq = n*n summable &= repeat(false,sq) -- (process backwards to avoid adding sq more than once) for i=length(summable)-sq to 1 by -1 do if summable[i] then summable[i+sq] = true end if end for summable[sq] = true integer r = match(repeat(true,(n+1)*(n+1)),summable) if r then summable = summable[1..r-1] exit end if n += 1 end while constant nwansods = "numbers which are not the sum of distinct squares" printf(1,"%s\n",{join(shorten(apply(find_all(false,summable),sprint),nwansods,5))})
- Output:
2 3 6 7 8 ... 92 96 108 112 128 (31 numbers which are not the sum of distinct squares)
Raku[edit]
Spoiler: (highlight to read)
Once the longest run of consecutive generated sums is longer the the next square, every number after can be generated by adding the next square to every number in the run. Find the new longest run, add the next square, etc.
my @squares = ^∞ .map: *²; # Infinite series of squares for 1..∞ -> $sq { # for every combination of all squares my @sums = @squares[^$sq].combinations».sum.unique.sort; my @run; for @sums { @run.push($_) and next unless @run.elems; if $_ == @run.tail + 1 { @run.push: $_ } else { last if @run.elems > @squares[$sq]; @run = () } } put grep * ∉ @sums, 1..@run.tail and last if @run.elems > @squares[$sq]; }
- Output:
2 3 6 7 8 11 12 15 18 19 22 23 24 27 28 31 32 33 43 44 47 48 60 67 72 76 92 96 108 112 128
Wren[edit]
Well I found a proof by induction here that there are only a finite number of numbers satisfying this task but I don't see how we can prove it programatically without using a specialist language such as Agda or Coq.
Brute force[edit]
This uses a brute force approach to generate the relevant numbers, similar to Julia, except using the same figures as the above proof. Still slow in Wren, around 20 seconds.
var squares = (1..18).map { |i| i * i }.toList var combs = [] var results = [] // generate combinations of the numbers 0 to n-1 taken m at a time var combGen = Fn.new { |n, m| var s = List.filled(m, 0) var last = m - 1 var rc // recursive closure rc = Fn.new { |i, next| var j = next while (j < n) { s[i] = j if (i == last) { combs.add(s.toList) } else { rc.call(i+1, j+1) } j = j + 1 } } rc.call(0, 0) } for (n in 1..324) { var all = true for (m in 1..18) { combGen.call(18, m) for (comb in combs) { var tot = (0...m).reduce(0) { |acc, i| acc + squares[comb[i]] } if (tot == n) { all = false break } } if (!all) break combs.clear() } if (all) results.add(n) } System.print("Numbers which are not the sum of distinct squares:") System.print(results)
- Output:
Numbers which are not the sum of distinct squares: [2, 3, 6, 7, 8, 11, 12, 15, 18, 19, 22, 23, 24, 27, 28, 31, 32, 33, 43, 44, 47, 48, 60, 67, 72, 76, 92, 96, 108, 112, 128]
Quicker[edit]
Hugely quicker in fact - only 24 ms, the same as C# itself.
import "./math" for Nums import "./fmt" for Fmt // recursively permutates the list of squares to seek a matching sum var soms soms = Fn.new { |n, f| if (n <= 0) return false if (f.contains(n)) return true var sum = Nums.sum(f) if (n > sum) return false if (n == sum) return true var rf = f[-1..0].skip(1).toList return soms.call(n - f[-1], rf) || soms.call(n, rf) } var start = System.clock var s = [] var a = [] var sf = "\nStopped checking after finding $d sequential non-gaps after the final gap of $d" var i = 1 var g = 1 var r while (g >= (i >> 1)) { if ((r = i.sqrt.floor) * r == i) s.add(i) if (!soms.call(i, s)) a.add(g = i) i = i + 1 } System.print("Numbers which are not the sum of distinct squares:") System.print(a.join(", ")) Fmt.print(sf, i - g, g) Fmt.print("Found $d total in $d ms.", a.count, ((System.clock - start)*1000).round)
- ms. | https://rosettacode.org/wiki/Numbers_which_are_not_the_sum_of_distinct_squares | CC-MAIN-2022-40 | refinedweb | 2,754 | 70.84 |
Hello Nicolas,
Thank you, I can only speak on my behalf but I think its a very nice
post. I have tried to get into haXe in the beginning and was thrilled
but I was never able to get the companies I worked in to use haXe. I
know that haXe has a lot of features that AS3 doesn't have. Particularly
"using" is just plain awesome. Others are debatable like
typedef+interfaces or the notation for properties.
However I used ActionScript a lot in the past years and found ways to
work with it that are unlike the work with haXe because when I recently
tried out haXe again I was bothered by a few language features that I
use heavily in ActionScript and have not found a good equivalent in haXe
(in other words: they are missing in haXe - aren't they?):
*) Standalone variables/constants/function files outside of a class
context. I found them very liberating and as far as I can tell: haXe
only allows class/ENum/ alike.
*) e4x: Its such a pleasure to use in AS3.
*) Default initialized properties:
class ABC {
public var x: int = 1;
}
*) Working "this" in function references: Using function references
has become such a normal thing in AS3 that I wouldn't know how to
implement a similar design with without them.
*) Namespaces: While I don't "like" namespaces particularly, porting
Flex to haXe might be difficult without it.
There are other features in the compiler that are worth talking about
that I am sure would be reasonable to continue having in Flex.
*) Compiling the "asdoc" to different locales
*) Documentation on Meta-tags
*) Binding
*) Assets (Fonts!) loaded compiled through meta-data
Have there been discussions about this points in the haXe community?
yours
Martin. | http://mail-archives.apache.org/mod_mbox/incubator-flex-dev/201202.mbox/%3C4F44D30C.7010101@leichtgewicht.at%3E | CC-MAIN-2014-10 | refinedweb | 293 | 67.89 |
Django app for connecting to Iranian payment gateways.
Project description
What’s this?
You can use this app to create payments in your django project via Iranian gateways. (Right now only Zarinpal and Saman are available but the rest are coming soon)
How does it work?
You ask the app for a new payment and it will give you a link on your own site that you can redirect users to it in order to have a payment.
Installation
- pip install django-pardakht
- Add pardakht to your INSTALLED_APPS
- python manage.py migrate
- Add pardakht urls to your project’s urls.
from pardakht import urls as pardakht_urls urlpatterns = [ ... url(r'^<SOME_URL>/', include(pardakht_urls)), ... ]
- For any gateway you use, add GATEWAY_MERCHANT_ID in your project settings. For example if you are going to use zarinpal, You need to add ZARINPAL_MERCHANT_ID in your settings with value set to your zarinpal merchant ID or if you are using saman gateway, You need to add SAMAN_MERCHANT_ID in your settings.
Usage
There is a payment model that app uses to handle payments. Every payment you create needs 5 initial parameters.
- price: Price of the payment.
- description: Short description about this payment. Necessary for some gateways such as Zarinpal.
- return_function: A callable object (function) that will get called after payment is done with the payment object as it’s input. It’s optional and can be None.
- return_url: A url for user to come back where he left off on your site. It’s optional and can be None.
- login_required: Must be True if user who is paying should be authenticated. If you’re going to use this you have to set LOGIN_URL in project settings.
To create a payment:
from pardakht import handler result = handler.create_payment( price, description, return_function, return_url, login_required )
This will create a payment and returns a dict containing payment object and a link to pay it:
result['payment'] # Created payment object result['link'] # Link for paying this payment that you should redirect your user to
Extra notes
This app handles all steps of payment including UI parts.
It uses semantic-ui so if you want to use it you need to serve app’s static files.
But of course you can override templates to use your own templates with your own UI design.
Configurations
If you are using ZarinGate to send users directly to the bank payment page, set ZARINPAL_USE_ZARINGATE to True in your project settings.
Project details
Release history Release notifications | RSS feed
Download files
Download the file for your platform. If you're not sure which to choose, learn more about installing packages. | https://pypi.org/project/django-pardakht/ | CC-MAIN-2021-39 | refinedweb | 431 | 64.91 |
table of contents
NAME¶
tgamma, tgammaf, tgammal - true gamma function
SYNOPSIS¶
#include <math.h>
double tgamma(double x);
float tgammaf(float x);
long double tgammal(long double x);
Link with -lm.
tgamma(), tgammaf(), tgammal():
DESCRIPTION¶
These
These functions first appeared in glibc in version 2.1.
ATTRIBUTES¶
For an explanation of the terms used in this section, see attributes(7).
CONFORMING TO¶
C99, POSIX.1-2001, POSIX.1-2008.
NOTES¶
This function had to be called "true gamma function" since there is already a function gamma(3) that returns something else (see gamma(3) for details).
BUGS¶.
SEE ALSO¶
COLOPHON¶
This page is part of release 5.10 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at. | https://manpages.debian.org/testing/manpages-dev/tgammaf.3.en.html | CC-MAIN-2022-05 | refinedweb | 134 | 66.44 |
I had some spare time now (not much to do at work...) so I used it to browse a little bit in the entropy code ()
If found the routine that logs the 'Repository is being updated' messages in the 'libraries/entropy.py' file
- Code: Select all
def handle_repository_lock(self, repo):
# get database lock
unlocked = self.is_repository_unlocked(repo)
if not unlocked:
mytxt = "%s: %s. %s." % (
bold(_("Attention")),
red(_("Repository is being updated")),
red(_("Try again in a few minutes")),
)
self.Entropy.updateProgress(
mytxt,
importance = 1,
type = "warning",
header = "\t"
)
return True
return False
Going further down the line, following the routines I found the following (also in 'libraries/entropy.py)
- Code: Select all
def is_repository_unlocked(self, repo):
self.__validate_repository_id(repo)
rc = self.download_item("lock", repo)
if rc: # cannot download database
self.syncErrors = True
return False
return True
and
- Code: Select all
def download_item(self, item, repo, cmethod = None, lock_status_func = None):
self.__validate_repository_id(repo)
url, filepath = self.__construct_paths(item, repo, cmethod)
#some code here, left out by me (poster of this messages...)
rc = fetchConn.download()
del fetchConn
if rc in ("-1","-2","-3"):
return False
self.Entropy.setup_default_file_perms(filepath)
return True
From what I could understand further down the line (to much code to paste
If it failes then it concludes that it is unlocked, if it succeeds it concludes that it is locked.
This is all logical to me, but for some reason it succeeds to download a file that isn't event there?
P.S. I must say I was pleasantly suprised when I saw how much code there was for entropy. It was a little hard to browse through because of the large files, but then I don't have a python ide to ease the browsing between classes (I used notepad
| http://forum.sabayon.org/viewtopic.php?f=76&t=13923&start=20 | CC-MAIN-2013-20 | refinedweb | 296 | 55.84 |
Introduction:
Python is an open source, interactive, object oriented programming language. It’s very easy to learn and an extremely powerful high level language. It runs on Windows, Linux, UNIX, Mac OSX and is free to use (even for commercial purpose) since it’s based on the open source license. It can be used to write custom tools and scripts for special purpose when performing security assessment of an application.
Why program when scanners are available?
Agreed – there are commercial vulnerability scanners available in the market which can be used for vulnerability discovery, however such vulnerability scanners have their own limitations and even the most advanced scanners sometimes are not able to provide full coverage. This makes the job of a penetration tester a little more difficult, since a lot of things are missed out – especially if the product is complex. This is where custom scripts/tools come into the picture. They help in filling the gaps created by the scanner since they’re customized to the target application rather than being general purpose.
Scanners tend to perform poorly when the target application is very complex thus leaving out many pages of the applications uncovered, and hence the false negatives – which create a far more challenging situation for the security team, and the management which completely relies on scanners for automating the vulnerability assessment, when compared to false positives – which are incorrectly reported issues. False positives are easy as the security analyst can easily eliminate them. However, false negatives are difficult since these are the issues which go unreported.
It should be noted here that custom tools written for specialized purpose using languages like python should not be a replacement for vulnerability scanners, and ideally should be used in addition to these scanners to get the best throughput.
Objective:
The aim of this article is to introduce web application penetration testers with python and explain how python can be used for making customized HTTP requests – which in turn can be further expanded for development of custom scripts/tools that can be developed for special conditions where scanners fail. Readers will be introduced on libraries that can help a penetration tester in making custom HTTP requests using python.
Intended Audience:
Anyone interested in learning the basics for developing custom tools or scripts will find this article interesting, although the article has been written keeping in mind web application penetration testers as the primary audience.
Out of Scope:
This article will focus only on some of the aspects that can be relevant for security assessment of web based applications. Python can also be used for developing tools that aid in malware analysis, network security assessments, forensics etc. However, such areas are out of scope for this article. This article instead will focus on modules that can be used for making custom HTTP requests using python. Last but not the least; this is not a Python language tutorial. If you are interested in learning the basics of Python language itself, there are many out there.
It’s strongly recommended the readers new to Python take up a crash course on Python before jumping directly into this article.
Setting up the Environment
This article will not get into the details of setting up the environment – which is straight forward. Installers are available for Python and can be downloaded from –
If you are a Linux or Macintosh user, chances are high that you don’t have to install python, since it comes pre-installed for Macintosh by Apple and by concerned vendor for most Linux distro. To check if Python is installed on your system, launch the command prompt and type “python”, if python is pre-installed, we should be able to see the interpreter getting launched as shown in the following screen shot:
Although the example here is for OSX, it should not be much different for a Linux installation either.
Windows users can download the installer from above mentioned URL and install Python. To further make the use of python easier, Windows users can add python to the system path by editing the environment variable. Once done, users can just fire up python from the command prompt – irrespective of the current working directory and still be able to invoke python interpreter.
Python Modules for crafting HTTP Requests
Python has multiple modules that can be used for generating custom HTTP Requests. We’ll cover 2 such modules that can be used for developing customized scripts, and can fire up our payloads along with performing the same actions that a penetration tester performs manually – the only difference being, this is done by a script instead of a manual attempt. The modules that we will cover are:
httplib
This module has been renamed to httplib.client in python 3, however since in this article I am using version 2.7.*, I am going to stick with httplib as far as this article is concerned. Normally this module is not directly used but instead urllib module uses it internally to make HTTP Requests. However, interested users can always use it directly.
In order for us to send custom requests, we need to follow the following steps:
Import the library
Before using a library, we need to import it. Since in this case, we are going to use httplib library to send HTTP Requests and receive the responses back, we need to import it.
Create a Connection
Once imported, we can start using it straight away. In this step, we need to create a connection object first. This can be achieved using HTTPConnection() method
Send HTTP Request
So far no HTTP Request is sent on the wire. In order to do so, use request() method. This is when the HTTP packet that we have created in previous steps is sent out over the network to the target web server using the method passed on as an argument (in our case GET, as shown in following figure).
Get HTTP Response
Now that we have sent a request, we can use getresponse() object to get server’s response. This method will return HTTP Response object back, which when read will send output generated by the server.
The following Screenshot lists these four steps executed from an interpreter:
In our case, invoking a HTTP request is resulting into a 302 redirect. It should be noted here that we can’t read “res” variable as it is, since it will only point us to the HTTP Response object. The read() method provides a raw string which is returned by the target web server as shown in above figure.
-.
urllib2
“urllib2″ is a little different from “httplib” library when it comes to creating and sending out HTTP Requests. “urllib2″. We don’t have to open up a connection and instead after importing, we can directly make a request –as shown in following figure:
This is much simpler when compared to httplib. It is suggested that users make use of urllib2 as it’s recommended even by the python community.
It’s recommended that readers go through the python documentation to understand what all functions are supported by urllib2 module to explore full potential of this library and utilize it when creating your own tools or scripts.
In the following section, we’ll see a sample SQL Injection tool that I’ve created only for demonstration purpose. It hits the login page of the website and injects single payload.
Sample SQL Injection Script:
The following is a simple script:
import urllib import urllib2 location = "" values = {"username":"'","password":"password","btnSubmit":"Login"} data = urllib.urlencode(values) req = urllib2.Request(location,data) response = urllib2.urlopen(req) page_data = response.read() print page_data
First we are importing urllib and urllib2 libraries. We are then associating the target URL to variable “location” and assigned post data to variable “values”. Once these steps are completed, we are encoding the URL data and then submitting the request to the server and reading the response received.
The above script is just to show how easily one can create custom tools. The above script is far from perfect and will need much modification before using in practice. It only fires one request, while in real life our tool should fire multiple requests by iterating over a list of payloads. It’s left as an exercise to readers to go through libraries and the functions it supports to understand how they can create their own tools. A real life tool will also have to take care of session management and hence needs to also deal with cookies and other HTTP headers like referrers, Content Type etc. We’ll also need to iterate over the a list of URL’s repeatedly until all our payloads are fired one by one for each and every parameter in order to ensure coverage.
Conclusion:
Python is an easy to learn language which can be helpful to penetration testers to create their custom tools which they can use to achieve coverage. Thus plugging in holes which are at times created by vulnerability scanners because they are unable to hit certain pages due to one or the other reason. Users can create reusable code by using python’s object orientation which can help them create classes that can be inherited and extended. Python can not only be used for quick and dirty scripting to achieve small automation tasks but also be used to create enterprise class vulnerability scanning routines.
References:
hi, I recommend using library requests (it’s not standard library, look python for humans), it’s very advanced library to write our clients for web apps
best regards
HI doomedraven – Thanks for the comments. I’ll have a look at it. | http://resources.infosecinstitute.com/python-for-web-app-security-pros/ | CC-MAIN-2014-42 | refinedweb | 1,611 | 58.11 |
(Buffers and working with rate, Working with streaming }")
Flattening a stream of sequences
Situation:], NotUsed] = someDataSource val flattened: Source[Message, NotUsed] = myData.mapConcat(identity)]].
The function limit or take should always be used in conjunction in order to guarantee stream boundedness, thus preventing the program from running out of memory.
For example, this is best avoided:
// Dangerous: might produce a collection with 2 billion elements! val f: Future[Seq[String]] = mySource.runWith(Sink.seq)
Rather, use limit or take to ensure that the resulting Seq will contain only up to max elements: contains a convenience method to parse messages from a stream of ByteString s:
import akka.stream.scaladsl.Framing val linesStream = rawData.via(Framing.delimiter( ByteString("\r\n"), maximumFrameLength = 100, allowTruncation = true)) .map(_.utf8String)
Dealing with compressed data streams
Situation: A gzipped stream of bytes is given as a stream of ByteString s, for example from a FileIO source.
The Compression helper object contains convenience methods for decompressing data streams compressed with Gzip or Deflate.
import akka.stream.scaladsl.Compression val uncompressed = compressed.via(Compression.gunzip()) .map(_.utf8String) that groups the words according to the identity function, i.e. now we have a stream of streams, where every substream will serve identical words.
To count the words, we need to process the stream of streams (the actual groups containing identical words). groupBy returns a SubFlow, which means that we transform the resulting substreams directly. In this case we use the reduce combinator to aggregate the word itself and the number of its occurrences within a tuple
By extracting the parts specific to wordcount into
- a groupKey function that defines the groups
- a map map each element to value that is used by the reduce on the substream
- a reduce function that does the actual reduction
we get a generalized version below:))
Note
Please note that the reduce-by-key version we discussed above is sequential in reading the overall input stream,] = } elements with the stream of Trigger signals. Since Zip produces pairs, we simply map the output stream selecting the first element of the pair.
val graph = RunnableGraph.fromGraph(GraphDSL.create() { implicit builder => import GraphDSL.Implicits._ val zip = builder.add(Zip[Message, Trigger]()) elements ~> zip.in0 triggerSource ~> zip.in1 zip.out ~> Flow[(Message, Trigger)].map { case (msg, trigger) => msg } ~> sink ClosedShape }) = RunnableGraph.fromGraph(GraphDSL.create() { implicit builder => import GraphDSL.Implicits._ val zip = builder.add(ZipWith((msg: Message, trigger: Trigger) => msg)) elements ~> zip.in0 triggerSource ~> zip.in1 zip.out ~> sink ClosedShape }) make the worker stages run in parallel we mark them as asynchronous with async.
def balancer[In, Out](worker: Flow[In, Out, Any], workerCount: Int): Flow[In, Out, NotUsed] = { import GraphDSL.Implicits._ Flow.fromGraph(GraphDSL.create() {.async ~> merge } FlowShape(balancer.in, merge.out) }) } val processedJobs: Source[Result, NotUsed] =.
val droppyStream: Flow[Message, Message, NotUsed] = Flow[Message].conflate((lastMessage, newMessage) => newMessage)
There is a more general version of conflate named conflateWithSeed that allows to express more complex aggregations, more similar to a fold. = flow of Int where the number represents the missed ticks. A number 0 means that we were able to consume the tick fast enough (i.e. zero means: 1 non-missed tick + 0 missed ticks)
val missedTicks: Flow[Tick, Int, NotUsed] = Flow[Tick].conflateWithSeed) } } } or if the element type is a subclass of AnyRef) } } }, NotUsed] = {ring = { if (buffer.isEmpty) completeStage() else { // There are elements left in buffer, so // we keep accepting downstream pulls and push from buffer until emptied. // // It might be though, that the upstream finished while it was pulled, in which // case we will not get an onPull from the downstream, because we already had one. // In that case we need to emit from the buffer. if (isAvailable(out)) emitChunk() } } }) private def emitChunk(): Unit = { if (buffer.isEmpty) { if (isClosed(in)) completeStage() else pull(in) } else { val (chunk, nextBuffer) = buffer.splitAt(chunkSize) buffer = nextBuffer push(out, chunk) } } } } val chunksStream = rawBytes.via(new Chunker(ChunkLimit))
Limit the number of bytes passing through a stream of ByteStrings
Situation: Given a stream of ByteString s we want to fail the stream if more than a given maximum of bytes has been consumed.
This recipe uses a Graph.
val compacted: Source[ByteString, NotUsed] = data.map(_:
import scala.concurrent.duration._ val injectKeepAlive: Flow[ByteString, ByteString, NotUsed] = Flow[ByteString].keepAlive(1.second, () => keepaliveMessage)
Contents | http://doc.akka.io/docs/akka/2.4/scala/stream/stream-cookbook.html | CC-MAIN-2017-13 | refinedweb | 719 | 58.58 |
How can I copy a Python string?
I do this:
a = 'hello'
And now I just want an independent copy of
a:
import copy b = str(a) c = a[:] d = a + '' e = copy.copy(a) map( id, [ a,b,c,d,e ] )
Out[3]:
[4365576160, 4365576160, 4365576160, 4365576160, 4365576160]
Why do they all have the same memory address and how can I get a copy of
a?
You don't need to copy a Python string. They are immutable, and the
copy module always returns the original in such cases, as do
str(), the whole string slice, and concatenating with an empty string.
Moreover, your
'hello' string is interned (certain strings are). Python deliberately tries to keep just the one copy, as that makes dictionary lookups faster.
One way you could work around this is to actually create a new string, then slice that string back to the original content:
>>>>> b = (a + '.')[:-1] >>> id(a), id(b) (4435312528, 4435312432)
But all you are doing now is waste memory. It is not as if you can mutate these string objects in any way, after all.
If all you wanted to know is how much memory a Python object requires, use
sys.getsizeof(); it gives you the memory footprint of any Python object.
For containers this does not include the contents; you'd have to recurse into each container to calculate a total memory size:
>>> import sys >>>>> sys.getsizeof(a) 42 >>> b = {'foo': 'bar'} >>> sys.getsizeof(b) 280 >>> sys.getsizeof(b) + sum(sys.getsizeof(k) + sys.getsizeof(v) for k, v in b.items()) 360
You can then choose to use
id() tracking to take an actual memory footprint or to estimate a maximum footprint if objects were not cached and reused.
From: stackoverflow.com/q/24804453 | https://python-decompiler.com/article/2014-07/how-can-i-copy-a-python-string | CC-MAIN-2019-47 | refinedweb | 295 | 72.46 |
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Raspberry Pi and Arduino: Building Reliable Systems With WatchDog Timers
Introduction: Raspberry Pi and Arduino: Building Reliable Systems With WatchDog Timers
Summary: In this Instructable we look at how to build more reliable computer systems using WatchDog timers. We show how to set up and use the Raspberry Pi and Arduino internal watchdog timers. We also explain why an external WatchDog Timer is a better choice in many, but not all, systems.
See more on WatchDog Timers in Solar Power applications on.
Step 1 - Introduction to WatchDog Timers
Step 2 - How to Set Up the Raspberry Pi Internal WatchDog Timer
Step 3 - How to Set Up the Arduino Internal WatchDog Timer
Step 4 - Internal Versus External WatchDog Timers / Issues with Internal Timers
Step 5 - Adding an External WatchDog Timer to your Project
Step 6 - Suggestions for Educators and Conclusion
Objectives
In this Instructable you will learn how:
- What are WatchDog Timers and Why they are Cool
- How To use the Raspberry Pi Internal Watchdog Timer
- How to use the Arduino Internal WatchDog Timer
- Compare and Contrast Internal Versus External WatchDog Timers
- How to use an External WatchDog Timer
- Suggestions for Student Experiments with WatchDog Timers
Step 1: Introduction to WatchDog Timers
Introduction to WatchDog Timers
Computers sometimes lose their way. A power glitch, RFI (Radio Frequency Interference), hanging peripherals, or just plain bad programming can cause your small computer to hang causing your application to fail. It happens all the time. How often do you have to reboot your PC? Not very often, but once in while your Mac or PC will freeze making you have to power cycle the computer. Raspberry Pi's will sometimes freeze because of a task not freeing up sockets or consuming other system resources and from power supply fluctuations. Arduinos sometimes freeze because of brownouts on the power line or a short power interruption or because of running out of system resources such as RAM and/or stack space, which is a very limited resource in an Arduino. Sometimes even programmers (gasp!) make mistakes.
See the WatchDog Timer and Computer Block Diagram above.
In small computers, you can give your device the chance to recover from faults by using what is called a WatchDog Timer (WDT). A WDT is an electronic timer that is used to detect and recover from computer malfunctions. If the computer fails to reset the timer (also called “patting the dog”) on the WDT before the WDT timer expires, the WDT signal is used to initiate either corrective actions or simply to reboot the computer.
Will the use of a WatchDog Timer make your computer project more reliable? The answer is yes. The proper use of a WatchDog timer can make your computer reboot when it gets lost. A known problem with some Python libraries on the Raspberry Pi is that some of those libraries don't properly release sockets and after a long period of time (days generally - not weeks) the Raspberry Pi will hang or thrash because it is out of resources. A properly designed program could detect this and reboot the computer, but a WatchDog Timer can be used to cover a whole multitude of sins with one fell swoop.
In Project Curacao, we use a WatchDog Timer to reset the Battery Power Watchdog in case of a brownout or an RFI upset event.
In our WeatherPi Instructable () we use the WatchDog Timer to make sure the Raspberry Pi power is shut off after a "shutdown -h now" halt and also to detect the computer getting lost. More reliablity!
Step 2: How to Set Up the Raspberry Pi Internal WatchDog Timer
Summary: In Step 2 of this Instructable
Whew! (see our Solar Power Instructable here).
If the Raspberry Pi takes longer to bootup than 14 seconds (or to whatever value you set Wto),.
Step 3: How to Set Up the Arduino Internal WatchDog Timer
Summary: In Step 3 of this Instructable, we look at how to set up the Arduino internal watchdog timer. We also talk about the issues with the Arduino internal WatchDog Timer and explain why an external WatchDog Timer, is a better choice in many, but not all, systems.
Setting up the Arduino Internal WatchDog Timer
The Arduino is a much simpler machine than a Raspberry Pi. However, it is actually easier to hang an Arduino than it is a Raspberry Pi because all the code is single threaded on the Arduino. Single threaded means that there is only one program running at a time on the Arudino (with the exception of Interrupts, in a manner of thinking). The point is if you only have one thread running at a time, any hang up on that thread will stop the computer. Naturally, there are other problems that can cause your code to crash and Arduino to lock up. Timeouts on peripherals, power issues, RFI, etc., etc. Bad code using the millis() function is a classic problem. You need to handle the rollover at 49.5 days if you aren't using a real time clock.
How to use the Arduino Internal WatchDog (if you can make it work)
First of all a definition. Wto is defined as the maximum amount of time the WatchDog timer can count before it needs to be reset (in other words, when it will reboot the computer if the computer goes away).
There are a lot of things that will keep the internal WatchDog from working in the Arduino, so beware.
Here is a way to work with the internal Arduino WatchDog timer. First of all, the Wto of all the Arduino models is a MAXIMUM of 8 seconds. Keep that in mind. Having a longer Wto covers a lot more sins in my opinion (Wto is 16 seconds on the internal Raspberry Pi WatchDog – which still isn't long enough for our taste), so the Arduino Wto is a bit short. We often have serial processes that run longer than 8 seconds in our designs. Yes, you can incorporate patting into the code, but when you are using external libraries, that is a pain.
To experiment with your Arduino WDT , build a new sketch in the Arudino IDE. WARNING: If you are using an ArduinoMega 2560 or similar device, you may “soft brick” your device. See comments in the problems section below. My Arduino UNO from SainSmart worked fine with this sketch. Start with
#include <avr/wdt.h> #define RESETWATCHDOG void setup() { Serial.begin(57600); Serial.println(""); Serial.println ("------->Arduino Rebooted"); Serial.println(""); wdt_enable(WDTO_8S); } void loop() { #ifdef RESETWATCHDOG wdt_reset(); #endif Serial.println("Arduino Running"); delay(1000); }
Run the sketch and let it run for 30 seconds or so. You should never see the “Arduino Rebooted” message again after reboot. Then, comment out the RESETWATCHDOG statement like this:
// #define RESETWATCHDOG
Now when you run the sketch, if your WatchDog is working, then you should see the Arduino Reboot every 8 seconds or so in the serial monitor.
Problems with the Internal Arduino WatchDog Timer
Use of the Arduino Internal WatchDogTimer is problematic at best. The Arduino WatchDog Timer has a Wto of 8 seconds so if you are downloading a new sketch and the old sketch has the WatchDog enabled, then you can get into an infinite reboot sequence. This is called “soft bricking”. The Arduino is then pretty much worthless (without a lot of work), but it is still running. WatchDog expires, bootloader starts, bootload works for a while, WatchDog expires, etc., etc. etc. Some boot loaders now disable the WatchDog appropriately, but beware there are a lot of Arduinos out there (like the Mega 2560 - of which we are big fans) that still don't work. You can update the bootloader but it is not an easy job. This is a problem we have run into several times.
- The internal Arduino WatchDog does NOT power cycle the system. It reboots the Arduino via the Reset Line. This means that it does not restart in all conditions. Especially in low power / brownout conditions often experienced with Solar Powered Systems. I have seen this in Project Curacao.
- There are problems with the bootloader (see above)
- The internal WatchDog Timer is not completely independent of the Arduino. If your code jumps to a piece of code disables the WDT, you are finished. Try overwriting your stack to see what interesting things can happen to code in a small embedded system such as the Arduino.
- The maximum Wto is 8 seconds. You can easily be in routines, such as serial communication for more than 8 seconds. Figuring out all of the possibilities and putting wdt_reset() calls in the right spot is difficult and with some serial routines, impossible.
Step 4: Internal Versus External WatchDog Timers / Issues With Internal Timers
Internal Versus External WatchDog Timers
Summary: In Step 4 of this Instructable we look at the differences between an Internal and External WatchDog Timer. We also review the issues with the Arduino and the Raspberry Pi Internal WatchDog explain why an External WatchDog Timer, such as the SwitchDoc Labs Dual WatchDog Timer is a better choice in many, but not all, systems.
The Bigger the Dog the Bigger the Bite
What is an External WatchDog Timer? It is an independent timer that is separate from the package or CPU entirely. Sometimes (such as with the SwitchDog Labs WatchDog) an entirely separate board.
What is an Internal WatchDog Timer? It is a timer that is internal to the CPU and intimately related to the CPU (such as the Arduino Internal WatchDog Timer and the Raspberry Pi Internal WatchDog Timer).
In the case of the Raspberry Pi and an Arduino, an External WatchDog Timer has a much bigger bark than an Internal one. Why do we say this? Because there is NO WAY that the internal software, however buggy, can stop an External WatchDog Timer from doing its work, where an Internal WatchDog Timer can be shut off by software. In some designs, shutting off the Internal WatchDog Timer makes sense. In others, it doesn't.
Of course, if you want to shut off an External WatchDog Timer via software, you could by using a GPIO pin to control a relay or a transistor, but generally, you don't want to do that if you don't have to.
Problems With Internal WatchDog Timers
Summarizing the problems with Internal WatchDog Timers from Step 2 and Step 3:
- The internal WatchDog does NOT power cycle the system. It reboots the computer. This means that it does not restart in all conditions. Especially in low power / brownout conditions often experienced with Solar Powered Systems. Without some clever circuitry, sometimes the Raspberry Pi or Arduino will not come back with just a reset. Solution: An External WatchDog Timer can keep hitting the device until it does come back, or better yet, can power cycle the computer which will bring it back when the power levels are less brown.
- You can stretch out your Wto to a lot more than 16 seconds to cover all the possible bootup sequences. Wto is defined as the maximum amount of time the WatchDog timer can count before it needs to be reset (in other words, when it will reboot the computer if the computer goes away. Solution: A circuit like the Dual WatchDog Timer goes all the way to a Wto of 240 seconds. That is even long enough for a Windows machine to boot. Well, most of the time.
- If you halt the computer, you are finished. The internal WatchDog will not reboot. Not so much a problem with the Arduino, but a bigger problem with the Raspberry Pi. Solution: An External WatchDog is independent of what you do with the software inside. You can't screw it up.
- On the Raspberry Pi , there are situations where the CPU is loaded up too much for your program but might still do the process patting the watchdog thus keep patting the dog. On the Arduino, since the the patting is done all on one thread, this is less of an issue. Solution: An External WatchDog is independent of what you do with the software inside. You can't screw it up.
Now, please understand, we don't hate Internal WatchDog Timers. In any system design, we always look to use the internal one first. Over the past 20 years, we find ourselves drifting away from using the Internal WatchDogs because of the issues above, and just maybe, we don't have to think so hard during the design. Fewer variables to control. More defined behavior. We can see what is going on by looking at the LEDs. Even without our glasses on.
Step 5: Adding an External WatchDog Timer to Your Project
Summary: In Step 5 of this Instructable we look at setting up an External WatchDog Timer witht he Arduino and also with the Raspberry Pi. We use the SwitchDoc Labs Dual WatchDog Timer, which is a good choice for an External WatchDog Timer in many systems. Finally, we look at a real world problem of RFI (Radio Frequency Interference), which really hits the Project Curacao Box.
External WatchDog Timers for Raspberry Pi/Arduino Systems
A solution to all of the potential problems and issues with the Internal WatchDog Timers discussed in the previous 4 steps of this Instructable is to use an External WatchDog Timer. As we were exploring this set of problems with Project Curacao, we decided to build our own External WatchDog timer. Designing our own timer gives us a fixed set of parameters not dependent on other sofware processes (in the Raspberry Pi case) and which Arduino we are using (in the other case). And then there were the significant power system issues as Project Curacao is Solar and Wind Powered and has brownout issues (hey, it gets cloudy in the tropics too!).The Code for "Patting The Dog" in Python and C.
You can download the entire specification for the SwitchDoc Labs Dual WatchDog Timer here: DualWatchDog_101914-V1.3.
Setting Wto on the SwitchDoc External WatchDog Timer
You can adjust Wto from about 220 seconds to 30 seconds.
Using an External WatchDog Timer with the Arduino
Dual WatchDog and ArduinoUsing an External WatchDog Timer with the Raspberry Pi
Dual WatchDog with Raspberry Pi B+
Dual WatchDog with Raspberry Pi B (and A)
Radio Frequency Interference - A Real World Problem
The significant problem we discovered in Project Curacao with RFI (Radio Frequency Interference) was when the Amateur Radio folks powered up their worldwide radio contest in October and November on 28MHz. Our box is connected to a radio tower in Curacao. And connected to a 15 meter line which just happens to be about 3 wavelengths of 28MHz, making a very good antenna. Things looked good up until the radio contest!
The wavelength of 28MHz radio waves is about 5 meters. We had a 15 meter line. Not a bad antenna for receiving 28MHz signals. Assuming that it is about 12 meters effective we have a nice 1/2 wavelength (2.5 wavelengths actually) staring at the input to the Arduino. And the WeatherRack (seen in the distance below) is connected directly to the tower where the 28MHz signal is being transmitted.
New Solar Panels on Top of the Project Curacao Box - WeatherRack in Background
Could be an issue, for sure. We sent questions to the Radio Gods about what kind of voltages could I expect. One God (Geoff H.) replied, saying up to 2V. That is pretty close to 2.5 Volts which will start triggering things.
The second God (Jeff M.) indicated that it could be all the way up to 3V and that the contest in the past weekend was not just on 28 MHz. It was an all-band contest, on the 160, 80, 40, 20, 15, and 10 meter bands.
SwitchDoc Dual WatchDog Board Installed in Project Curacao
During daylight hours on the contest weekend, transmitting will have been on 10m (28.3 – 29.0 MHz), 15m (21.2 – 21.4), and 20m (14.15 – 14.3 MHz). During nighttime hours on the contest weekend, transmitting will have been on 160m (~1.8 – 1.9 MHz), 80m (~3.6 – 3.9 MHz), 40m (~7.05 – 7.25 MHz) and 20m (~14.15 – 14.3 MHz).
Lots of little signals running around our box with the big new wire (antenna) connected.
This contest took the Project Curacao down for the count.
Yet another reason to use an External WatchDog Timer because the RFI was putting the Arduino in a state that required a on and off power reset.
Step 6: Suggestions for Educators and Conclusion
Conclusion
WatchDog Timers can improve the reliability of your Arduino and Raspberry Pi projects. Internal WatchDogs have limitations in both the Arduino and Raspberry Pi but can still improve your project reliability. For those issues (such as Brownouts, power loss, coding errors and RFI) that aren't handled well by the Internal WatchDog Timers, a better solution is to use an External WatchDog Timer.
Suggestions for Educator Experiments
- Hooking up an Arduino with a simple program patting the dog. Show what happens when you don't pat the dog (the LED on the Dual WatchDog Board will flash when not patted)
- Do the same with a Raspberry Pi
- Write an Arduino program that purposely goes into an infinite loop, see the WatchDog reset the Arduino | http://www.instructables.com/id/Raspberry-Pi-and-Arduino-Building-Reliable-Systems/ | CC-MAIN-2017-39 | refinedweb | 2,899 | 61.87 |
Complete roguelike tutorial using C++ and libtcod - part 1: setting up
This article is the first part of a series heavily inspired by Jotaf's excellent "Complete roguelike tutorial using python + libtcod".
It is intended for C++ beginners and people who want to learn how to use libtcod to create a simple roguelike video game. It covers both Linux and Windows operating systems.
The source code of this tutorial uses the C99 standard. That means that it won't compile out of the box on Visual Studio.
While an experienced C++ developer won't have much trouble to port the code to Visual Studio, if you're a C++ beginner, I strongly advise to use one of the suggested compilers/IDE.
Introduction
Why C++ ?
While being often criticized for being complex, for lacking features or for failing to enforce a single programming style, C++ is still one of the most used languages. Here are a few reasons that make it still relevant :
- the language itself is public domain. It's not owned by a private company like the more elegant java or C#
- there are compilers that produce high-performance native binaries for almost any existing platform
- it has a great compatibility with C, which makes it easy to use with C libraries like SDL
Pre-requisite : this tutorial does not replace a C++ manual. You're supposed to have a basic knowledge of the C++ syntax and object oriented programming.
Why libtcod ?
It's easy to use and provides out of the box a lot of tools that are frequently used in a roguelike (Field of view and path finding algorithms amongst others). While browsing this tutorial, you should always have the libtcod C++ manual open. The code in this article series works with libtcod versions 1.5.1 and 1.5.2.
libtcod functions used in this article
TCODConsole::isWindowClosed
TCODSystem::checkForEvent
Pre-requisites
Installing the compiler
First you need a C++ compiler. On Linux, it's easy :
> sudo apt-get install g++ gdb libsdl1.2debian-all
On Windows, follow this tutorial : libtcod 1.5.2 documentation.
When installing Mingw, you must absolutely choose the "Use pre-packaged repository catalogues" option. Apparently, the latest version is not working with libraries compiled with the previous one.
For OS X/macOS :
First, you need to install homebrew. Then you need to install Xcode through the App Store. Then, from the command line run the following command :
> xcode-select install
This will install gcc. Then run the following command :
> brew update && brew install gdb sdl
Installing libtcod
All you have to do is download the library corresponding to your platform from this URL and extract it to your hard drive.
Note that the Windows/Mingw precompiled library only works with a 32 bits compiler. If you want to use a 64 bits compiler, you'll have to recompile the library.
For OS X/macOS :
> git clone > cd libtcod-mac > make -f makefiles/makefile-osx release
Also for OS X/macOS, at the time of writing this, there is a small file change to make. In the file ../libtcod-mac/include/libtcod.h on line 109, you will need to change the <SDL.h> to <SDL/SDL.h>.
Setting up the project
Create an empty directory somewhere on your hardrive. Inside, create 3 empty directories :
> mkdir include src lib
Then you'll have to copy those files from the libtcod directory to your project directory :
- include/*.h
- include/*.hpp
- terminal.png
For Linux only :
- libtcod.so
- libtcodxx.so
- libtcod_debug.so
- libtcodxx_debug.so
For Windows only :
- libtcod-mingw.dll
- libtcod-mingw-debug.dll
- lib/libtcod-mingw.a
- lib/libtcod-mingw-debug.a
- SDL.dll
For OS X/macOS only :
- libtcod.dylib
- libtcodxx.dylib
- libtcod_debug.dylib
- libtcodxx_debug.dylib
First program
We'll create a very simple program, just to check that we can compile and run. Let's create a src/main.cpp file :
main.cpp
#include "libtcod.hpp" int main() { TCODConsole::initRoot(80,50,"libtcod C++ tutorial",false); while ( !TCODConsole::isWindowClosed() ) { TCOD_key_t key; TCODSystem::checkForEvent(TCOD_EVENT_KEY_PRESS,&key,NULL); TCODConsole::root->clear(); TCODConsole::root->putChar(40,25,'@'); TCODConsole::flush(); } return 0; }
You can compile this on Windows with (type a single line) :
> g++ src/*.cpp -o tuto -Iinclude -Llib -ltcod-mingw -static-libgcc -static-libstdc++ -Wall
If you want to get rid of the debug console when running the game from windows explorer, add the -mwindows flag. But since we're in the development phase, it's good to be able to get the program standard output.
and on Linux with :
> g++ src/*.cpp -o tuto -Iinclude -L. -ltcod -ltcodxx -Wl,-rpath=. -Wall
and on OS X/macOS with :
> gcc src/*.cpp -o tuto -Iinclude -L. -ltcod -ltcodxx -Wall
Line by line explanation
#include "libtcod.hpp"
Here we're importing all the libtcod classes declaration. Actually, before compiling the main.cpp file, the compiler will replace this line by the content of libtcod.hpp.
int main() {
This is the function that will be called when the program starts. It returns an error code. 0 : no error. Any other value : an error occured.
TCODConsole::initRoot(80,50,"libtcod C++ tutorial",false);
Here we're calling our first libtcod function to create the game window. It will contain a 80x50 console using the default font "./terminal.png". The false value indicates that we don't want to start in fullscreen mode.
initRoot is a static function inside the TCODConsole class. It's basically a global function inside the TCODConsole namespace.
while ( !TCODConsole::isWindowClosed() ) {
Now we're starting the main game loop and we'll keep looping until the game window is closed by the player.
TCOD_key_t key;
This line creates a key variable we can use for handling input later.
TCODSystem::checkForEvent(TCOD_EVENT_KEY_PRESS,&key,NULL);
Even though we're not using keyboard input yet, we need to call checkForEvent for libtcod to process the screen redraw events.
TCODConsole::root->clear();
This is the first non static function we use. We access the static "root" variable inside the TCODConsole namespace. It's a pointer to the console bound to the main game window. We call the clear function on this console to erase everything with default color (black).
TCODConsole::root->putChar(40,25,'@');
Now we use putChar to print an @ in the middle of the screen, using the default color (white).
TCODConsole::flush();
This line actually generates the console image and displays it on the window.
The walking @
Now we're ready to reach the first step in any roguelike : the walking @ step :
#include "libtcod.hpp" int main() { int playerx=40,playery=25; TCODConsole::initRoot(80,50,"libtcod C++ tutorial",false); while ( !TCODConsole::isWindowClosed() ) { TCOD_key_t key; TCODSystem::checkForEvent(TCOD_EVENT_KEY_PRESS,&key,NULL); switch(key.vk) { case TCODK_UP : playery--; break; case TCODK_DOWN : playery++; break; case TCODK_LEFT : playerx--; break; case TCODK_RIGHT : playerx++; break; default:break; } TCODConsole::root->clear(); TCODConsole::root->putChar(playerx,playery,'@'); TCODConsole::flush(); } return 0; }
We store the player position in two variables :
int playerx=40,playery=25;
and use them to draw the @ instead of the hardcoded values :
TCODConsole::root->putChar(playerx,playery,'@');
The key variable contains everything we need to know about the keyboard input from the user. We can use it to update the player position :
switch(key.vk) { case TCODK_UP : playery--; break; case TCODK_DOWN : playery++; break; case TCODK_LEFT : playerx--; break; case TCODK_RIGHT : playerx++; break; default:break; }
That's it. Recompile the program (you can press CTRL-R and type g++ in the terminal to recall the last compilation command). | http://www.roguebasin.com/index.php?title=Complete_roguelike_tutorial_using_C%2B%2B_and_libtcod_-_part_1:_setting_up&oldid=44616 | CC-MAIN-2019-22 | refinedweb | 1,245 | 57.27 |
Provided by: shishi-doc_1.0.0-2_all
NAME
shishi_kdc_process - API function
SYNOPSIS
#include <shishi.h> int shishi_kdc_process(Shishi * handle, Shishi_asn1 kdcreq, Shishi_asn1 kdcrep, Shishi_key * key, int keyusage, Shishi_asn1 * enckdcreppart);
ARGUMENTS
Shishi * handle shishi handle as allocated by shishi_init(). Shishi_asn1 kdcreq input variable that holds the sent KDC-REQ. Shishi_asn1 kdcrep input variable that holds the received KDC-REP. Shishi_key * key input array with key to decrypt encrypted part of KDC-REP with. int keyusage kereros key usage value. Shishi_asn1 * enckdcreppart output variable that holds new EncKDCRepPart.
DESCRIPTION
Process a KDC client exchange and output decrypted EncKDCRepPart which holds details for the new ticket received. Use shishi_kdcrep_get_ticket() to extract the ticket. This function verifies the various conditions that must hold if the response is to be considered valid, specifically it compares nonces (shishi_kdc_check_nonce()) and if the exchange was a AS exchange, it also compares cname and crealm (shishi_as_check_cname() and shishi_as_check_crealm()). Usually the shishi_as_process() and shishi_tgs_process() functions should be used instead, since they simplify the decryption key computation.
RETURN VALUE
Returns SHISHI_OK iff the KDC client exchange was. | http://manpages.ubuntu.com/manpages/precise/man3/shishi_kdc_process.3.html | CC-MAIN-2020-29 | refinedweb | 176 | 50.02 |
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C# Instantiating multiple balls and making them all follow the same path as the first.
ethancodes posted a topic in General and Gameplay ProgrammingI'm trying to make a pick up that add's 4 specials "shots" when it gets picked up. The game is a brick breaker style game and when the ball hits the paddle, if we have any of the special shots left, the original ball should bounce back like normal, but there should be 7 additional balls instantiating in quick succession and those balls should all follow the first ball directly. As the balls hit objects, either bricks, walls, or anything else, they will be destroyed. The last remaining ball will become the new mainBall and will continue the gameplay like normal. All the additional balls that spawn should spawn right from the paddle and then shoot outward. I'm not so concerned about them hitting the exact same place as the first ball, as I am with them moving the same way. So if the player very quickly moves the paddle after impact, the balls may fire in a scattered line. So far, I have come up with the idea of having a Ball class that will be attached to each Ball instance. This should have basic ball behavior or attributes attached to it such as Speed, and then I would have a BallManager class that handles any modifications, spawning, destroying of balls. But I'm not sure what exactly needs to be in the Ball class and what need to be in the BallManager class. And I'm not sure how to handle the spawning and destroying, etc. I've tried to write several different forms of pseudocode to try to come up with something that makes sense, but I keep running into problems. Any ideas?.
Unity Looking For Developers To Join My Team
Armaan Gupta posted a topic in Hobby Project ClassifiedsHey There, I am a developer and Im working on a blockchain based infinite runner type game. Right now, I am working on releasing the beta version with a couple other game developers, but would love to expand the team and have other talented and bright people contributing. The game portion of the project isnt very complicated, and wouldnt require anyone to pull thier hair out for it. If you are interested in joining a project, interested in the idea, or would like some more information, please don't hesitate to ask either by commenting, discord (username: Guppy#7625), or by email (armaangupta01@gmail.com). Thank you!
Psycho Wolf - Upcoming "Antyfarming" Game
ATM posted a blog entry in All Those Moments BlogHi, Please help us to decide if our current project is cool and interesting enough. If so we will finalise it. If not we will made demo of other comncept. So add to Wishlist if you like it and would like to play someday Video of Psycho Wolf demo: Reveal Trailer Steam Page: Thanks !
Java 2D Platforming: Java or C#
bojanzarnoski@gmx.de posted a topic in General and Gameplay ProgrammingHello, I want to get into coding again by programming a 2D platformer to get started, but i don't know if i should use Java or C# with the unity engine. I am pretty fit with Java, but with c# i have to start from scratch. What do you recommend and why?
C# Ball appears to pass through brick intermittently
ethancodes posted a topic in General and Gameplay ProgrammingI've got a bug with my brick breaker style game. The bricks move down one line at a time ever 1.5 seconds. What appears to be happening is occasionally the ball will be just about to hit the brick when the brick moves down a line, and now the ball is behind it. I'm not sure how to fix this. I have two ideas but I'm not sure of implementation. 1 solution would be to check where they were and where they are going to be before rendering the frame. Then if they crossed paths, then register the brick as hit. Solution 2 would be change how the bricks move. I could maybe slide them down line by line, instead of a jump down. I'm not sure of this will fix the issue or not. Any ideas?
C# Unity is there a way to find the edge intersect?
Scouting Ninja posted a topic in General and Gameplay ProgrammingOnce again Unity is frustrating me to the point of insanity. What I am looking for is a way to find a ray intersect with the edges of the mesh, using Unity's already made collision system. I want to point out that I know how to do a line intersect, what I want to know is if Unity supports this already. The image above shows how I sweep a ray,intersecting the mesh. The top green image shows what I want and the red shows what Unity is giving me. I want to know if there is some way, to find the edges in Unity without creating a custom line intersection tool. Most engines I know don't use rays for this but instead use a plane like this: I checked the Unity "Plane intersection" but it is just a ray cast. It will still need me to find the vertices on the collision mesh to cast the ray from; if I am doing that then making my own line intersection tool is better. I looked online and can find anything on this. Also I don't want to cut the mesh, so I don't need a way to know what side is what. Does Unity even have collisions that support edge only detection? } } }
Message Passing b/w “LAN Server Only” and “LAN Client” on Different Scenes in Unity
syedali233 posted a topic in Networking and MultiplayerHi,..
Static Analysis in Video Game Development: Top 10 Software Bugs
Sergey Vasiliev posted an article in General and Gameplay ProgrammingIf. Why you should use static analysis: on static: V3010 The return value of function 'Format' is required to be utilized. V3010 The return value of function 'Format' is required to be utilized.. Conclusion.
C# Managing a growing project
zuhane posted a topic in General and Gameplay ProgrammingHello
C# Constructors with similar arguments
Scouting Ninja posted a topic in General and Gameplay ProgrammingI.
C# Change speed of object
ethancodes posted a topic in General and Gameplay ProgrammingI've got a ball object and I want to be able to manipulate the ball's speed (both speed up and slow down) based on different pickups dropped in the game. I'm not sure how best to do this. Here is my code for the Ball class: public class Ball : MonoBehaviour { private Paddle paddle; private bool hasStarted = false; private Vector3 paddleToBallVector; // Use this for initialization void Start () { paddle = GameObject.FindObjectOfType<Paddle>(); paddleToBallVector = this.transform.position - paddle.transform.position; } // Update is called once per frame void Update () { if (!hasStarted) { //Lock the ball relative to the paddle. this.transform.position = paddle.transform.position + paddleToBallVector; //Wait for a mouse press to launch. if (Input.GetMouseButtonDown (0)) { hasStarted = true; this.GetComponent<Rigidbody2D> ().velocity = new Vector2 (2f, 10f); } } } void OnCollisionEnter2D (Collision2D collider) { //use this vector2 to adjust the velocity so the ball does not get stuck in a vertical bouncing loop Vector2 tweak = new Vector2 (Random.Range(0f, 0.2f),Random.Range(0f, 0.2f)); if (hasStarted) { AudioSource audio = this.gameObject.GetComponent<AudioSource>(); audio.Play(); this.gameObject.GetComponent<Rigidbody2D>().velocity += tweak; } } } I just need to know how to manipulate the speed for this class. I'm not sure if how I have it set up now is the best way to manage movement of the ball object or if I should modify it to accommodate for speed manipulation.
C# lost in learning programming as I just left "Beginner's zone"
April_X posted a topic in General and Gameplay ProgrammingI guess my level could be classified as "just left Beginner's zone", so, gone through a lot of beginner's programming tutorials already, still junior and the problem is I don't know what's next. I mean, I found a lot of tutorials for beginners everywhere, and the next things I found everywhere are beautiful and complicated source code on Github: tutorials for beginners -- materials for "Grade 1 students" to learn beautiful and complicated source code on Github (not the beginner type of source code) -- materials for "Phd students" to learn However, what's in between? After I learned the Grade 1 materials I can't just directly jump to Phd level, I am trying to find the Grade 2,3,4,5,6 level materials to learn, right? Didn't find a lot of those. I am still a junior programmer. When I finished the beginner's programming tutorials I feel like leaving the Beginner's zone, no guidance anymore. I'm in LA, game programming is not like web programming,etc; there are some web programming bootcamps, but not game programming bootcamps, sad. Maybe as a junior programmer it is too much for me to request the market/youtube/online learning websites to produce structured intermediate level materials for learning game programming? It is also possible that I misjudge my own levels so I don't know where I am, therefore don't know what I should aim for next. The demo of the game I made for practice, somehow showing my level: The video about programming of my game, somehow showing my level: Github: I would be grateful if you give me advice like: "you are still in beginner's zone", or "you can do xxx in your game to improve yourself", or "you may do xxx in programming to improve yourself" or anything else. I don't know, I'm just lost. I'm not sure whether this is the right place to post this type of questions; I hope my struggles can help someone in someway (don't know how this will help...)
13 RONIN - DevLog #2 - Lightning
ERASERHEAD STUDIO posted a blog entry in 13 RONINOk, It hasn't been a full month since my first post here, but I still think it's time for an update, and from now on I plan to post a major news article at the beginning of every month containing a summary of what I've been up to lately. For anyone interested in more I recommend my blog at Eraserhead Studio where you can find random news, animations, images, sound and code that hopefully can help you out in your own game project. So, what have I been up to lately? Well, due to an aching hand, the result of too much asset drawing, I've let my hand rest from the tablet and instead focused on doing some proper coding. The result is two quite flexible engines: one for rain and the other one for lightning. Rain Since a few of the levels will take place in bad weather it's important for me to be able to generate some good looking rain. I talked about my rain engine already in the last post but since then I've fixed a few bugs, added some properties and posted a higher quality demonstration video on YouTube. The engine has a lot of settings, all which will help me make a living and varied rain. Some of these are: Drop velocity Drop acceleration Density Drop creation interval Wind No of splashes at ground contact There are still some minor features to add, such as individual ground height at different z-level, but majority of the engine is now done. If you want to do something similar for you own project please check out the demonstration video at YouTube . And why not download the source code from BitBucket . Lightning For an even more dramatic effect I want thunder and lightning in the game. I started doing a lightning bolt, then a lightning branch and finally a lightning engine sending randomized bolts and branches through the sky. As with the rain engine this engine also has a lot of settings, some of these are: Lightning length Lightning angle Interval between lightning strikes Lightning duration Animation Fade This was quite fun to code and I'm quite pleased with the result. Things left to add is sound for thunder and maybe a flashing background. Check out the demonstration video on YouTube and get the source code from BitBucket . A big thank you to Michael Hoffman whose awesome article was a big inspiration for this work. Other inspirations have been google images and YouTube. Internet is just awesome! Shaders Working with the lightning I spent a few hours and reading up on HLSL and including shaders in MonoGame. It was interesting and fun, but also quite time consuming. There will be a number of shaders included in the end product,. Home page I'm using WIX for the Eraserhead Studio page but unfortunately the WIX-editor is both slow and buggy. I've spent a number of hours in the editor trying to achieve a nicer looking and easier to use site than the previous one but WIX doesn't make it easy. I've still got two active tickets at the WIX-support regarding bugs I can't find any solutions for, but hopefully the site will still be better than the last one. The short lesson being - don't use WIX. Dev forums Besides writing and publishing this post I've also drawn avatar, logo and banner and added those to my profiles on: GameDev IndieGamer TIGForums GameJolt Reddit IndieDB When I've got a finished demo I'll also get on Facebook and Twitter. Do you have recommendations on other sites where you think I belong? Please let me know. Please visit Eraserhead Studio for more. Happy coding! /jan. NOTE. As always, everything I publish here or on any other site is work in progress and subject to change.
13 RONIN - DevLog #1
ERASERHEAD STUDIO posted a blog entry in 13 RONIN13 RONIN 13 RONIN is a 2D pixel art samurai sword fighting game inspired by old Japanese samurai movies and 8-bit classics such as Barbarian and The Way Of The Exploding Fist. Your mission as a noble samurai is to defeat 13 renegade ronin and their murderous leader. Although done in low-resolution pixel art the game will have a somewhat “arty” aesthetic in black and white mixed with details in color. a spare time project so please be patient. Status The main structure of the game and basic gameplay, based on placeholder graphics, is done and I’m currently switching between drawing assets and coding graphics effects like rain and lightning. News I’m quite. Happy coding! /jan.
- Advertisement | https://www.gamedev.net/search/?tags=C%23&sortby=newest | CC-MAIN-2018-26 | refinedweb | 2,921 | 59.84 |
Opened 9 years ago
Closed 9 years ago
Last modified 9 years ago
#11415 closed (wontfix)
Django doesn't call delete() for relatively deleted objects.
Description
A simple example:
class Link(models.Model):
num = models.IntegerField('foo')
def delete(self):
super(Link, self).delete()
print('doing some cleanup after killing self')
class Something(models.Model):
link = models.ForeignField(Link)
Okay, now delete some "Links" from Admin site - delete() is called.
Try to delete some "Somethings" with relations - they are deleted and related "Links" are deleted, too, but delete() is not called for related objects.
Change History (3)
comment:1 Changed 9 years ago by
comment:2 Changed 9 years ago by
This is by design, and documented as such. If delete() is called on the cascade, you could end up with a flood of calls to delete() methods. To prevent this sort of flood, delete() is only invoked on a direct call to delete an object.
comment:3 Changed 9 years ago by
So, how a developer supposed to do clean-up routines after deleting objects? It's wrong to iterate through related objects and call delete() on each of them from the delete() function.
Sorry for code mess | https://code.djangoproject.com/ticket/11415 | CC-MAIN-2018-17 | refinedweb | 199 | 66.84 |
A Concrete Application of Topological Data Analysis
Machine LearningModelingMachine LearningTopological Data Analysisposted by Mathieu Carrière January 30, 2020 Mathieu Carrière
Today, I will present a Machine Learning application of Topological Data Analysis (TDA), a rapidly evolving field of data science that makes use of topology to improve data analysis. It is largely inspired by one of my projects.
Great! Wait… what is TDA?
I will start by briefly recalling the basics of TDA. The interested reader might also want to take a look at other stories (and all references therein) for further details.
[Related Article: Implementing a Kernel Principal Component Analysis in Python]
TDA is a mathematically grounded theory which aims at characterizing data using its topology, which is done by computing features of topological nature. The most common one is the persistence diagram, which takes the form of a set of points in the plane above the diagonal.
Each point represents a topological feature (such as a connected component, a hole or a cavity) of the data. Moreover, the distance of the point to the diagonal act as an indicator of the importance of the corresponding feature, the usual interpretation being that points close to the diagonal are likely due to noise.
The computation of such diagrams requires a filtration, that is, a sequence of growing spaces: each space in the sequence is included in the next one. For instance, given a point cloud, a possible filtration would be to compute unions of balls centered on the points with a sequence of increasing radii.
The idea is then, for each space in the sequence, to record whether a topological feature is either created or destroyed in that space. For instance, if we consider the union of balls filtration, it may happen that, for some radius, the ball union contains a hole, which persists for some time until it eventually gets filled in when the balls have a sufficiently large radius, which is exactly what happens in the filtration displayed above. These radii can then be used as coordinates to create a point in the plane which represents this hole.
Sounds good but… I want an application!
Persistence diagrams have many applications in various fields of data analysis. In this note, I will present a visual application in geometry processing, namely 3D shape segmentation.
3D shapes are usually stored as a set of points, edges, and triangles in a computer. The goal of segmentation is to provide labels for each point of each shape. For instance, if you are given a bunch of 3D shapes representing humans, the goal of segmentation is to successfully assign for each point the body part to which it belongs (“torso”, “arm”, “leg”…).
The difficulty of this problem lies in the fact that you are only given point coordinates, which are poor features. Indeed, it is hopeless to characterize a point with its coordinates since they depend on the embedding, or pose, of the 3D shape. Think for instance of two human shapes, one of them having its right hand raised and not the other; the humans are identical, only their poses differ. Then, the right hand points of the two shapes will differ a lot, even though they share the same label.
TDA to the rescue!
This is where persistence diagrams come into play. Thanks to their topological nature, persistence diagrams are intrinsic, meaning that they do not depend on the embedding, or pose, of the 3D shapes. Hence, they are good candidates for point features. To do this we thus need to define an intrinsic filtration.
This can be achieved with geodesic distances. The geodesic distance between two points on a 3D shape is the length of the shortest path on the shape between these two points. You can think of it as the length of the path that an ant would walk if it had to go from the first point to the second one. This distance is obviously intrinsic since the path that the ant would walk is independent of the pose of the 3D shape.
Geodesic distances can then be used to define geodesic balls. A geodesic ball with radius r > 0 and centered on a point x is simply the set of points of the shape whose geodesic distance to x is less or equal than r. Again, by making r increase from 0 to infinity, we make the geodesic ball grow from the singleton {x} to the whole shape itself, which gives us an intrinsic filtration. Now, to compute the corresponding persistence diagram, we record the radii for which topological events occurred in the ball and use them as coordinates. In the case of 3D shapes, the topological events are quite limited: since 3D shapes are connected surfaces, their intrinsic dimension is 2 (indeed, a 3D shape locally looks like a flat plane), and the only topological events that may occur is the appearance or filling of holes in the ball. For example, take a look at the filtration displayed below on a 3D hand shape.
The growing geodesic ball is shown in red while the remaining of the shape is in blue. For the first three radii, the geodesic ball has no interesting topology: it looks just like a disc. However, for the fourth radius, each of the five fingers created a hole in the geodesic ball: five topological events appeared. They persist through the fifth radius, and eventually get filled in for the sixth radius. The corresponding persistence diagram, that I display below, thus contains five points.
What makes things more interesting is that if I apply the same process on a point located on another part of the shape, then the diagram is going to be different. Let us for example consider a point located on the middle finger:
All fingers will again create holes in the geodesic ball, but at different radii. For instance, the hole corresponding to the middle finger appeared and got filled in much earlier than for the first filtration. In the persistence diagram, the corresponding point is thus located farther apart from the other points.
Generally speaking, the persistence diagram points have different configurations depending on the location, or part, to which the 3D shape point (which was used to compute the diagram) belongs. This illustrates the fact that persistence diagrams are accurate descriptors for segmentation. I implemented code for the computation of such diagrams: see my Github if you want to give it a try.
Time to learn!
Finally! Now that we have a good feature, or descriptor, of the points, we are ready to do Machine Learning (ML).
Or are we?
A big issue of persistence diagrams is their non-structured form: persistence diagrams are sets that may contain a different number of points. They are not as easy to handle as traditional Euclidean vectors, which are the common food for ML algorithms. This is why a huge effort is currently devoted to the TDA community to derive ways to process persistence diagrams in ML. As of today, the two main approaches are either to compute vectors out of diagrams (such as persistence images or landscapes), or to define kernels on diagrams and use kernelized ML algorithms (such as PCA or SVM). See this story for more details.
I implemented most of this approaches in a python package that is scikit-learn compatible. Again, I refer the interested reader to my Github. Thanks to this package, all methods can be compared and used in a big cross validation procedure. In my notebook, I used this to perform segmentation of a bunch of 3D surfaces representing airplanes of various size and shape (see sample of code below). Final accuracy can go up to 90%, which is quite good given the difficulty of the task!
import sklearn_tda as tda from sklearn.pipeline import Pipeline from sklearn.svm import SVC from sklearn.ensemble import RandomForestClassifier from sklearn.neighbors import KNeighborsClassifier # Definition of pipeline pipe = Pipeline([("Separator", tda.DiagramSelector(limit=np.inf, point_type="finite")), ("Rotator", tda.DiagramPreprocessor(scalers=[([0,1], tda.BirthPersistenceTransform())])), ("TDA", tda.PersistenceImage()), ("Estimator", SVC())]) # Parameters of pipeline. This is the place where you specify the methods you want to use to handle diagrams param = [{"Rotator__use": [False], "TDA": [tda.SlicedWassersteinKernel()], "TDA__bandwidth": [0.1, 1.0], "TDA__num_directions": [20], "Estimator": [SVC(kernel="precomputed")]}, {"Rotator__use": [False], "TDA": [tda.PersistenceWeightedGaussianKernel()], "TDA__bandwidth": [0.1, 1.0], "TDA__weight": [lambda x: np.arctan(x[1]-x[0])], "Estimator": [SVC(kernel="precomputed")]}, {"Rotator__use": [True], "TDA": [tda.PersistenceImage()], "TDA__resolution": [ [5,5], [6,6] ], "TDA__bandwidth": [0.01, 0.1, 1.0, 10.0], "Estimator": [SVC()]}, {"Rotator__use": [False], "TDA": [tda.Landscape()], "TDA__resolution": [100], "Estimator": [RandomForestClassifier()]}, {"Rotator__use": [False], "TDA": [tda.BottleneckDistance()], "TDA__wasserstein": [1], "TDA__delta": [0.1], "Estimator": [KNeighborsClassifier(metric="precomputed")]} ]
One final word…
[Related Article: Why You Should Be Using Sentiment Analysis for Social Media and Decision Making]
Geometry processing is only one out of many possible applications of TDA. This field is very active since it connects different areas of mathematics from algebraic topology to computer science, and more and more people are becoming TDA enthusiasts. Do not miss the train! 😉 | https://opendatascience.com/a-concrete-application-of-topological-data-analysis/ | CC-MAIN-2020-40 | refinedweb | 1,510 | 54.02 |
Chapter 6 introduced some basic object-oriented aspects of Scala. This chapter will pick up where Chapter 6 left off and dive with much greater detail into Scala's support for object-oriented programming. We'll compare two fundamental relationships between classes: composition and inheritance. Composition means one class holds a reference to another, using the referenced class to help it fulfill its mission. Inheritance is the superclass/subclass relationship. In addition to these topics, we'll discuss abstract classes, parameterless methods, extending classes, overriding methods and fields, parametric fields, invoking superclass constructors, polymorphism and dynamic binding, final members and classes, and factory objects and methods.
As a running example in this chapter, we'll create a library for building and rendering two-dimensional layout elements. Each element will represent a rectangle filled with text. For convenience, the library will provide factory methods named "elem" that construct new elements from passed data. For example, you'll be able to create a layout element containing a string using a factory method with the following signature:
elem(s: String): ElementAs you can see, elements will be modeled with a type named Element. You'll be able to call above or beside on an element, passing in a second element, to get a new element that combines the two. For example, the following expression would construct a larger element consisting of two columns, each with a height of two:
val column1 = elem("hello") above elem("***") val column2 = elem("***") above elem("world") column1 beside column2Printing the result of this expression would give:
hello *** *** worldLayout elements are a good example of a system in which objects can be constructed from simple parts with the aid of composing operators. In this chapter, we'll define classes that enable element objects to be constructed from arrays, lines, and rectangles—the simple parts. We'll also define composing operators above and beside. Such composing operators are also often called combinators because they combine elements of some domain into new elements.
Thinking in terms of combinators is generally a good way to approach library design: it pays to think about the fundamental ways to construct objects in an application domain. What are the simple objects? In what ways can more interesting objects be constructed out of simpler ones? How do combinators hang together? What are the most general combinations? Do they satisfy any interesting laws? If you have good answers to these questions, your library design is on track.
Our first task is to define type Element, which represents layout elements. Since elements are two dimensional rectangles of characters, it makes sense to include a member, contents, that refers to the contents of a layout element. The contents can be represented as an array of strings, where each string represents a line. Hence, the type of the result returned by contents will be Array[String]. Listing 10.1 shows what it will look like.
abstract class Element { def contents: Array[String] }
In this class, contents is declared as a method that has no implementation. In other words, the method is an abstract member of class Element. A class with abstract members must itself be declared abstract, which is done by writing an abstract modifier in front of the class keyword:
abstract class Element ...The abstract modifier signifies that the class may have abstract members that do not have an implementation. As a result, you cannot instantiate an abstract class. If you try to do so, you'll get a compiler error:
scala> new Element <console>:5: error: class Element is abstract; cannot be instantiated new Element ^
Later in this chapter you'll see how to create subclasses of class Element, which you'll be able to instantiate because they fill in the missing definition for contents.
Note that the contents method in class Element does not carry an abstract modifier. A method is abstract if it does not have an implementation (i.e., no equals sign or body). Unlike Java, no abstract modifier is necessary (or allowed) on method declarations. Methods that do have an implementation are called concrete.
Another bit of terminology distinguishes between declarations and definitions. Class Element declares the abstract method contents, but currently defines no concrete methods. In the next section, however, we'll enhance Element by defining some concrete methods.
As a next step, we'll add methods to Element that reveal its width and height, as shown in Listing 10.2. The height method returns the number of lines in contents. The width method returns the length of the first line, or, if there are no lines in the element, zero. (This means you cannot define an element with a height of zero and a non-zero width.)
abstract class Element { def contents: Array[String] def height: Int = contents.length def width: Int = if (height == 0) 0 else contents(0).length }
Note that none of Element's three methods has a parameter list, not even an empty one. For example, instead of:
def width(): Intthe method is defined without parentheses:
def width: IntSuch parameterless methods are quite common in Scala. By contrast, methods defined with empty parentheses, such as def height(): Int, are called empty-paren methods. The recommended convention is to use a parameterless method whenever there are no parameters and the method accesses mutable state only by reading fields of the containing object (in particular, it does not change mutable state).
This convention supports the uniform access principle,[1] which says that client code should not be affected by a decision to implement an attribute as a field or method. For instance, we could have chosen to implement width and height as fields instead of methods, simply by changing the def in each definition to a val:
abstract class Element { def contents: Array[String] val height = contents.length val width = if (height == 0) 0 else contents(0).length }The two pairs of definitions are completely equivalent from a client's point of view. The only difference is that field accesses might be slightly faster than method invocations, because the field values are pre-computed when the class is initialized, instead of being computed on each method call. On the other hand, the fields require extra memory space in each Element object. So it depends on the usage profile of a class whether an attribute is better represented as a field or method, and that usage profile might change over time. The point is that clients of the Element class should not be affected when its internal implementation changes.
In particular, a client of class Element should not need to be rewritten if a field of that class gets changed into an access function so long as the access function is pure, i.e., it does not have any side effects and does not depend on mutable state. The client should not need to care either way.
So far so good. But there's still a slight complication that has to do with the way Java handles things. The problem is that Java does not implement the uniform access principle. So it's string.length() in Java, not string.length (even though it's array.length, not array.length()). Needless to say, this is very confusing.
To bridge that gap, Scala is very liberal when it comes to mixing parameterless and empty-paren methods. In particular, you can override a parameterless method with an empty-paren method, and vice versa. You can also leave off the empty parentheses on an invocation of any function that takes no arguments. For instance, the following two lines are both legal in Scala:
Array(1, 2, 3).toString "abc".length
In principle it's possible to leave out all empty parentheses in Scala function calls. However, it is recommended to still write the empty parentheses when the invoked method represents more than a property of its receiver object. For instance, empty parentheses are appropriate if the method performs I/O, or writes reassignable variables (vars), or reads vars other than the receiver's fields, either directly or indirectly by using mutable objects. That way, the parameter list acts as a visual clue that some interesting computation is triggered by the call. For instance:
"hello".length // no () because no side-effect println() // better to not drop the ()To summarize, it is encouraged style in Scala to define methods that take no parameters and have no side effects as parameterless methods, i.e., leaving off the empty parentheses. On the other hand, you should never define a method that has side-effects without parentheses, because then invocations of that method would look like a field selection. So your clients might be surprised to see the side effects. Similarly, whenever you invoke a function that has side effects, be sure to include the empty parentheses when you write the invocation. Another way to think about this is if the function you're calling performs an operation, use the parentheses, but if it merely provides access to a property, leave the parentheses off.
We still need to be able to create new element objects. You have already seen that "new Element" cannot be used for this because class Element is abstract. To instantiate an element, therefore, we will need to create a subclass that extends Element and implements the abstract contents method. Listing 10.3 shows one possible way to do that:
class ArrayElement(conts: Array[String]) extends Element { def contents: Array[String] = conts }
Class ArrayElement is defined to extend class Element. Just like in Java, you use an extends clause after the class name to express this:
... extends Element ...Such an extends clause has two effects: it makes class ArrayElement inherit all non-private members from class Element, and it makes the type ArrayElement a subtype of the type Element. Given ArrayElement extends Element, class ArrayElement is called a subclass of class Element. Conversely, Element is a superclass of ArrayElement.
If you leave out an extends clause, the Scala compiler implicitly assumes your class extends from scala.AnyRef, which on the Java platform is the same as class java.lang.Object. Thus, class Element implicitly extends class AnyRef. You can see these inheritance relationships in Figure 10.1.
Inheritance means that all members of the superclass are also members of the subclass, with two exceptions. First, private members of the superclass are not inherited in a subclass. Second, a member of a superclass is not inherited if a member with the same name and parameters is already implemented in the subclass. In that case we say the member of the subclass overrides the member of the superclass. If the member in the subclass is concrete and the member of the superclass is abstract, we also say that the concrete member implements the abstract one.
For example, the contents method in ArrayElement overrides (or, alternatively: implements) abstract method contents in class Element.[2] By contrast, class ArrayElement inherits the width and height methods from class Element. For example, given an ArrayElement ae, you can query its width using ae.width, as if width were defined in class ArrayElement:
scala> val ae = new ArrayElement(Array("hello", "world")) ae: ArrayElement = ArrayElement@d94e60
scala> ae.width res1: Int = 5
Subtyping means that a value of the subclass can be used wherever a value of the superclass is required. For example:
val e: Element = new ArrayElement(Array("hello"))Variable e is defined to be of type Element, so its initializing value should also be an Element. In fact, the initializing value's type is ArrayElement. This is OK, because class ArrayElement extends class Element, and as a result, the type ArrayElement is compatible with the type Element.[3]
Figure 10.1 also shows the composition relationship that exists between ArrayElement and Array[String]. This relationship is called composition because class ArrayElement is "composed" out of class Array[String], in that the Scala compiler will place into the binary class it generates for ArrayElement a field that holds a reference to the passed conts array. We'll discuss some design considerations concerning composition and inheritance later in this chapter, in Section 10.11.
The uniform access principle is just one aspect where Scala treats fields and methods more uniformly than Java. Another difference is that in Scala, fields and methods belong to the same namespace. This makes it possible for a field to override a parameterless method. For instance, you could change the implementation of contents in class ArrayElement from a method to a field without having to modify the abstract method definition of contents in class Element, as shown in Listing 10.4:
class ArrayElement(conts: Array[String]) extends Element { val contents: Array[String] = conts }
Field contents (defined with a val) in this version of ArrayElement is a perfectly good implementation of the parameterless method contents (declared with a def) in class Element.
On the other hand, in Scala it is forbidden to define a field and method with the same name in the same class, whereas it is allowed in Java. For example, this Java class would compile just fine:
// This is Java class CompilesFine { private int f = 0; public int f() { return 1; } }But the corresponding Scala class would not compile:
class WontCompile { private var f = 0 // Won't compile, because a field def f = 1 // and method have the same name }Generally, Scala has just two namespaces for definitions in place of Java's four. Java's four namespaces are fields, methods, types, and packages. By contrast, Scala's two namespaces are:
Consider again the definition of class ArrayElement shown in the previous section. It has a parameter conts whose sole purpose is to be copied into the contents field. The name conts of the parameter was chosen just so that it would look similar to the field name contents without actually clashing with it. This is a "code smell," a sign that there may be some unnecessary redundancy and repetition in your code.
You can avoid the code smell by combining the parameter and the field in a single parametric field definition, as shown in Listing 10.5:
class ArrayElement( val contents: Array[String] ) extends Element
Note that now the contents parameter is prefixed by val. This is a shorthand that defines at the same time a parameter and field with the same name. Specifically, class ArrayElement now has an (unreassignable) field contents, which can be accessed from outside the class. The field is initialized with the value of the parameter. It's as if the class had been written as follows, where x123 is an arbitrary fresh name for the parameter:
class ArrayElement(x123: Array[String]) extends Element { val contents: Array[String] = x123 }You can also prefix a class parameter with var, in which case the corresponding field would be reassignable. Finally, it is possible to add modifiers such as private, protected,[5] or override to these parametric fields, just as you can do for any other class member. Consider, for instance, the following class definitions:
class Cat { val dangerous = false } class Tiger( override val dangerous: Boolean, private var age: Int ) extends CatTiger's definition is a shorthand for the following alternate class definition with an overriding member dangerous and a private member age:
class Tiger(param1: Boolean, param2: Int) extends Cat { override val dangerous = param1 private var age = param2 }Both members are initialized from the corresponding parameters. We chose the names of those parameters, param1 and param2, arbitrarily. The important thing was that they not clash with any other name in scope.
You now have a complete system consisting of two classes: an abstract class Element, which is extended by a concrete class ArrayElement. You might also envision other ways to express an element. For example, clients might want to create a layout element consisting of a single line given by a string. Object-oriented programming makes it easy to extend a system with new data-variants. You can simply add subclasses. For example, Listing 10.6 shows a LineElement class that extends ArrayElement:
class LineElement(s: String) extends ArrayElement(Array(s)) { override def width = s.length override def height = 1 }
Since LineElement extends ArrayElement, and ArrayElement's constructor takes a parameter (an Array[String]), LineElement needs to pass an argument to the primary constructor of its superclass. To invoke a superclass constructor, you simply place the argument or arguments you want to pass in parentheses following the name of the superclass. For example, class LineElement passes Array(s) to ArrayElement's primary constructor by placing it in parentheses after the superclass ArrayElement's name:
... extends ArrayElement(Array(s)) ...With the new subclass, the inheritance hierarchy for layout elements now looks as shown in Figure 10.2.
Note that the definitions of width and height in LineElement carry an override modifier. In Section 6.3, you saw this modifier in the definition of a toString method. Scala requires such a modifier for all members that override a concrete member in a parent class. The modifier is optional if a member implements an abstract member with the same name. The modifier is forbidden if a member does not override or implement some other member in a base class. Since height and width in class LineElement override concrete definitions in class Element, override is required.
This rule provides useful information for the compiler that helps avoid some hard-to-catch errors and makes system evolution safer. For instance, if you happen to misspell the method or accidentally give it a different parameter list, the compiler will respond with an error message:
$ scalac LineElement.scala .../LineElement.scala:50: error: method hight overrides nothing override def hight = 1 ^
The override convention is even more important when it comes to system evolution. Say you defined a library of 2D drawing methods. You made it publicly available, and it is widely used. In the next version of the library you want to add to your base class Shape a new method with this signature:
def hidden(): BooleanYour new method will be used by various drawing methods to determine whether a shape needs to be drawn. This could lead to a significant speedup, but you cannot do this without the risk of breaking client code. After all, a client could have defined a subclass of Shape with a different implementation of hidden. Perhaps the client's method actually makes the receiver object disappear instead of testing whether the object is hidden. Because the two versions of hidden override each other, your drawing methods would end up making objects disappear, which is certainly not what you want! These "accidental overrides" are the most common manifestation of what is called the "fragile base class" problem. The problem is that if you add new members to base classes (which we usually call superclasses) in a class hierarchy, you risk breaking client code.
Scala cannot completely solve the fragile base class problem, but it improves on the situation compared to Java.[6] If the drawing library and its clients were written in Scala, then the client's original implementation of hidden could not have had an override modifier, because at the time there was no other method with that name. Once you add the hidden method to the second version of your shape class, a recompile of the client would give an error like the following:
.../Shapes.scala:6: error: error overriding method hidden in class Shape of type ()Boolean; method hidden needs `override' modifier def hidden(): Boolean = ^
That is, instead of wrong behavior your client would get a compile-time error, which is usually much preferable.
You saw in Section 10.4 that a variable of type Element could refer to an object of type ArrayElement. The name for this phenomenon is polymorphism, which means "many shapes" or "many forms." In this case, Element objects can have many forms.[7] So far, you've seen two such forms: ArrayElement and LineElement. You can create more forms of Element by defining new Element subclasses. For example, here's how you could define a new form of Element that has a given width and height and is filled everywhere with a given character:
class UniformElement( ch: Char, override val width: Int, override val height: Int ) extends Element { private val line = ch.toString * width def contents = Array.make(height, line) }
The inheritance hierarchy for class Element now looks as shown in Figure 10.3. As a result, Scala will accept all of the following assignments, because the assigning expression's type conforms to the type of the defined variable:
val e1: Element = new ArrayElement(Array("hello", "world")) val ae: ArrayElement = new LineElement("hello") val e2: Element = ae val e3: Element = new UniformElement('x', 2, 3)If you check the inheritance hierarchy, you'll find that in each of these four val definitions, the type of the expression to the right of the equals sign is below the type of the val being initialized to the left of the equals sign.
The other half of the story, however, is that method invocations on variables and expressions are dynamically bound. This means that the actual method implementation invoked is determined at run time based on the class of the object, not the type of the variable or expression. To demonstrate this behavior, we'll temporarily remove all existing members from our Element classes and add a method named demo to Element. We'll override demo in in ArrayElement and LineElement, but not in UniformElement:
abstract class Element { def demo() { println("Element's implementation invoked") } }
class ArrayElement extends Element { override def demo() { println("ArrayElement's implementation invoked") } }
class LineElement extends ArrayElement { override def demo() { println("LineElement's implementation invoked") } }
// UniformElement inherits Element's demo class UniformElement extends Element
If you enter this code into the interpreter, you can then define this method that takes an Element and invokes demo on it:
def invokeDemo(e: Element) { e.demo() }If you pass an ArrayElement to invokeDemo, you'll see a message indicating ArrayElement's implementation of demo was invoked, even though the type of the variable, e, on which demo was invoked is Element:
scala> invokeDemo(new ArrayElement) ArrayElement's implementation invokedSimilarly, if you pass a LineElement to invokeDemo, you'll see a message that indicates LineElement's demo implementation was invoked:
scala> invokeDemo(new LineElement) LineElement's implementation invokedThe behavior when passing a UniformElement may at first glance look suspicious, but it is correct:
scala> invokeDemo(new UniformElement) Element's implementation invokedBecause UniformElement does not override demo, it inherits the implementation of demo from its superclass, Element. Thus, Element's implementation is the correct implementation of demo to invoke when the class of the object is UniformElement.
Sometimes when designing an inheritance hierarchy, you want to ensure that a member cannot be overridden by subclasses. In Scala, as in Java, you do this by adding a final modifier to the member. For example, you could place a final modifier on ArrayElement's demo method, as shown in Listing 10.7.
class ArrayElement extends Element { final override def demo() { println("ArrayElement's implementation invoked") } }
Given this version of ArrayElement, an attempt to override demo in its subclass, LineElement, would not compile:
elem.scala:18: error: error overriding method demo in class ArrayElement of type ()Unit; method demo cannot override final member override def demo() { ^
You may also at times want to ensure that an entire class not be subclassed. To do this you simply declare the entire class final by adding a final modifier to the class declaration. For example, Listing 10.8 shows how you would declare ArrayElement final:
final class ArrayElement extends Element { override def demo() { println("ArrayElement's implementation invoked") } }
With this version of ArrayElement, any attempt at defining a subclass would fail to compile:
elem.scala: 18: error: illegal inheritance from final class ArrayElement class LineElement extends ArrayElement { ^
We'll now remove the final modifiers and demo methods, and go back to the earlier implementation of the Element family. We'll focus our attention in the remainder of this chapter to completing a working version of the layout library.
Composition and inheritance are two ways to define a new class in terms of another existing class. If what you're after is primarily code reuse, you should in general prefer composition to inheritance. Only inheritance suffers from the fragile base class problem, in which you can inadvertently break subclasses by changing a superclass.
One question you can ask yourself about an inheritance relationship is whether it models an is-a relationship.[8] For example, it would be reasonable to say that ArrayElement is-an Element. Another question you can ask is whether clients will want to use the subclass type as a superclass type.[9] In the case of ArrayElement, we do indeed expect clients will want to use an ArrayElement as an Element.
If you ask these questions about the inheritance relationships shown in Figure 10.3, do any of the relationships seem suspicious? In particular, does it seem obvious to you that a LineElement is-an ArrayElement? Do you think clients would ever need to use a LineElement as an ArrayElement? In fact, we defined LineElement as a subclass of ArrayElement primarily to reuse ArrayElement's definition of contents. Perhaps it would be better, therefore, to define LineElement as a direct subclass of Element, like this:
class LineElement(s: String) extends Element { val contents = Array(s) override def width = s.length override def height = 1 }In the previous version, LineElement had an inheritance relationship with ArrayElement, from which it inherited contents. It now has a composition relationship with Array: it holds a reference to an array of strings from its own contents field.[10] Given this implementation of LineElement, the inheritance hierarchy for Element now looks as shown in Figure 10.4.
As a next step, we'll implement method above in class Element. Putting one element above another means concatenating the two contents values of the elements. So a first draft of method above could look like this:
def above(that: Element): Element = new ArrayElement(this.contents ++ that.contents)The ++ operation concatenates two arrays. Arrays in Scala are represented as Java arrays, but support many more methods. Specifically, arrays in Scala inherit from a class scala.Seq, which represents sequence-like structures and contains a number of methods for accessing and transforming sequences. Some other array methods will be explained in this chapter, and a comprehensive discussion will be given in Chapter 17.
In fact, the code shown previously is not quite sufficient, because it does not permit you to put elements of different widths on top of each other. To keep things simple in this section, however, we'll leave this as is and only pass elements of the same length to above. In Section 10.14, we'll make an enhancement to above so that clients can use it to combine elements of different widths.
The next method to implement is beside. To put two elements beside each other, we'll create a new element in which every line results from concatenating corresponding lines of the two elements. As before, to keep things simple we'll start by assuming the two elements have the same height. This leads to the following design of method beside:
def beside(that: Element): Element = { val contents = new Array[String](this.contents.length) for (i <- 0 until this.contents.length) contents(i) = this.contents(i) + that.contents(i) new ArrayElement(contents) }The beside method first allocates a new array, contents, and fills it with the concatenation of the corresponding array elements in this.contents and that.contents. It finally produces a new ArrayElement containing the new contents.
Although this implementation of beside works, it is in an imperative style, the telltale sign of which is the loop in which we index through arrays. The method could alternatively be abbreviated to one expression:
new ArrayElement( for ( (line1, line2) <- this.contents zip that.contents ) yield line1 + line2 )Here, the two arrays this.contents and that.contents are transformed into an array of pairs (as Tuple2s are called) using the zip operator. The zip method picks corresponding elements in its two arguments and forms an array of pairs. For instance, this expression:
Array(1, 2, 3) zip Array("a", "b")will evaluate to:
Array((1, "a"), (2, "b"))If one of the two operand arrays is longer than the other, zip will drop the remaining elements. In the expression above, the third element of the left operand, 3, does not form part of the result, because it does not have a corresponding element in the right operand.
The zipped array is then iterated over by a for expression. Here, the syntax "for ((line1, line2) <- ...)" allows you to name both elements of a pair in one pattern, i.e., line1 stands now for the first element of the pair, and line2 stands for the second. Scala's pattern-matching system will be described in detail in Chapter 15. For now, you can just think of this as a way to define two vals, line1 and line2, for each step of the iteration.
The for expression has a yield part and therefore yields a result. The result is of the same kind as the expression iterated over, i.e., it is an array. Each element of the array is the result of concatenating the corresponding lines, line1 and line2. So the end result of this code is the same as in the first version of beside, but because it avoids explicit array indexing, the result is obtained in a less error-prone way.
You still need a way to display elements. As usual, this is done by defining a toString method that returns an element formatted as a string. Here is its definition:
override def toString = contents mkString "\n"The implementation of toString makes use of mkString, which is defined for all sequences, including arrays. As you saw in Section 7.8, an expression like "arr mkString sep" returns a string consisting of all elements of the array arr. Each element is mapped to a string by calling its toString method. A separator string sep is inserted between consecutive element strings. So the expression "contents mkString "\n"" formats the contents array as a string, where each array element appears on a line by itself.
Note that toString does not carry an empty parameter list. This follows the recommendations for the uniform access principle, because toString is a pure method that does not take any parameters.
With the addition of these three methods, class Element now looks as shown in Listing 10.9.
abstract class Element {
def contents: Array[String]
def width: Int = if (height == 0) 0 else contents(0).length
def height: Int = contents.length
def above(that: Element): Element = new ArrayElement(this.contents ++ that.contents)
def beside(that: Element): Element = new ArrayElement( for ( (line1, line2) <- this.contents zip that.contents ) yield line1 + line2 )
override def toString = contents mkString "\n" }
You now have a hierarchy of classes for layout elements. This hierarchy could be presented to your clients "as is." But you might also choose to hide the hierarchy behind a factory object. A factory object contains methods that construct other objects. Clients would then use these factory methods for object construction rather than constructing the objects directly with new. An advantage of this approach is that object creation can be centralized and the details of how objects are represented with classes can be hidden. This hiding will both make your library simpler for clients to understand, because less detail is exposed, and provide you with more opportunities to change your library's implementation later without breaking client code.
The first task in constructing a factory for layout elements is to choose where the factory methods should be located. Should they be members of a singleton object or of a class? What should the containing object or class be called? There are many possibilities. A straightforward solution is to create a companion object of class Element and make this be the factory object for layout elements. That way, you need to expose only the class/object combo of Element to your clients, and you can hide the three implementation classes ArrayElement, LineElement, and UniformElement.
object Element {
def elem(contents: Array[String]): Element = new ArrayElement(contents)
def elem(chr: Char, width: Int, height: Int): Element = new UniformElement(chr, width, height)
def elem(line: String): Element = new LineElement(line) }
Listing 10.10 is a design of the Element object that follows this scheme. The Element companion object contains three overloaded variants of an elem method. Each variant constructs a different kind of layout object.
With the advent of these factory methods, it makes sense to change the implementation of class Element so that it goes through the elem factory methods rather than creating new ArrayElement instances explicitly. To call the factory methods without qualifying them with Element, the name of the singleton object, we will import Element.elem at the top of the source file. In other words, instead of invoking the factory methods with Element.elem inside class Element, we'll import Element.elem so we can just call the factory methods by their simple name, elem. Listing 10.11 shows what class Element will look like after these changes.
import Element.elem
abstract class Element {
def contents: Array[String]
def width: Int = if (height == 0) 0 else contents(0).length
def height: Int = contents.length
def above(that: Element): Element = elem(this.contents ++ that.contents)
def beside(that: Element): Element = elem( for ( (line1, line2) <- this.contents zip that.contents ) yield line1 + line2 )
override def toString = contents mkString "\n" }
In addition, given the factory methods, the subclasses ArrayElement, LineElement and UniformElement could now be private, because they need no longer be accessed directly by clients. In Scala, you can define classes and singleton objects inside other classes and singleton objects. One way to make the Element subclasses private, therefore, is to place them inside the Element singleton object and declare them private there. The classes will still be accessible to the three elem factory methods, where they are needed. Listing 10.12 shows how that will look.
object Element {
private class ArrayElement( val contents: Array[String] ) extends Element
private class LineElement(s: String) extends Element { val contents = Array(s) override def width = s.length override def height = 1 }
private class UniformElement( ch: Char, override val width: Int, override val height: Int ) extends Element { private val line = ch.toString * width def contents = Array.make(height, line) }
def elem(contents: Array[String]): Element = new ArrayElement(contents)
def elem(chr: Char, width: Int, height: Int): Element = new UniformElement(chr, width, height)
def elem(line: String): Element = new LineElement(line) }
We need one last enhancement. The version of Element shown in Listing 10.11 is not quite sufficient, because it does not allow clients to place elements of different widths on top of each other, or place elements of different heights beside each other. For example, evaluating the following expression would not work correctly, because the second line in the combined element is longer than the first:
new ArrayElement(Array("hello")) above new ArrayElement(Array("world!"))Similarly, evaluating the following expression would not work properly, because the first ArrayElement has a height of two, and the second a height of only one:
new ArrayElement(Array("one", "two")) beside new ArrayElement(Array("one"))
Listing 10.13 shows a private helper method, widen, which takes a width and returns an Element of that width. The result contains the contents of this Element, centered, padded to the left and right by any spaces needed to achieve the required width. Listing 10.13 also shows a similar method, heighten, which performs the same function in the vertical direction. The widen method is invoked by above to ensure that Elements placed above each other have the same width. Similarly, the heighten method is invoked by beside to ensure that elements placed beside each other have the same height. With these changes, the layout library is ready for use.
import Element.elem
abstract class Element { def contents: Array[String]
def width: Int = contents(0).length def height: Int = contents.length
def above(that: Element): Element = { val this1 = this widen that.width val that1 = that widen this.width elem(this1.contents ++ that1.contents) }
def beside(that: Element): Element = { val this1 = this heighten that.height val that1 = that heighten this.height elem( for ((line1, line2) <- this1.contents zip that1.contents) yield line1 + line2) }
def widen(w: Int): Element = if (w <= width) this else { val left = elem(' ', (w - width) / 2, height) var right = elem(' ', w - width - left.width, height) left beside this beside right }
def heighten(h: Int): Element = if (h <= height) this else { val top = elem(' ', width, (h - height) / 2) var bot = elem(' ', width, h - height - top.height) top above this above bot }
override def toString = contents mkString "\n" }
A fun way to exercise almost all elements of the layout library is to write a program that draws a spiral with a given number of edges. This Spiral program, shown in Listing 10.14, will do just that:
import Element.elem
object Spiral {
val space = elem(" ") val corner = elem("+")
def spiral(nEdges: Int, direction: Int): Element = { if (nEdges == 1) elem("+") else { val sp = spiral(nEdges - 1, (direction + 3) % 4) def verticalBar = elem('|', 1, sp.height) def horizontalBar = elem('-', sp.width, 1) if (direction == 0) (corner beside horizontalBar) above (sp beside space) else if (direction == 1) (sp above space) beside (corner above verticalBar) else if (direction == 2) (space beside sp) above (horizontalBar beside corner) else (verticalBar above corner) beside (space above sp) } }
def main(args: Array[String]) { val nSides = args(0).toInt println(spiral(nSides, 0)) } }
Because Spiral is a standalone object with a main method with the proper signature, it is a Scala application. Spiral takes one command-line argument, an integer, and draws a spiral with the specified number of edges. For example, you could draw a six-edge spiral as shown below on the left, and larger spirals as shown to the right:
$ scala Spiral 6 $ scala Spiral 11 $ scala Spiral 17 +----- +---------- +---------------- | | | | +-+ | +------+ | +------------+ | + | | | | | | | | | | | +--+ | | | +--------+ | +---+ | | | | | | | | | | | | ++ | | | | | +----+ | | | | | | | | | | | | | | +----+ | | | | | ++ | | | | | | | | | | | | | +--------+ | | | +--+ | | | | | | | | | | | +------+ | | | | | | | +----------+ | | | +--------------+
In this section, you saw more concepts related to object-oriented programming in Scala. Among others, you encountered abstract classes, inheritance and subtyping, class hierarchies, parametric fields, and method overriding. You should have developed a feel for constructing a non-trivial class hierarchy in Scala. We'll work with the layout library again in Chapter 14.
[1] Meyer, Object-Oriented Software Construction meyer:oo-soft-con
[2] One flaw with this design is that because the returned array is mutable, clients could change it. For the book we'll keep things simple, but were ArrayElement part of a real project, you might consider returning a defensive copy of the array instead. Another problem is we aren't currently ensuring that every String element of the contents array has the same length. This could be solved by checking the precondition in the primary constructor, and throwing an exception if it is violated.
[3] For more perspective on the difference between subclass and subtype, see the glossary entry for subtype.
[4] The reason that packages share the same namespace as fields and methods in Scala is to enable you to import packages in addition to just importing the names of types, and the fields and methods of singleton objects. This is also something you can't do in Java. It will be described in Section 13.2.
[5] The protected modifier, which grants access to subclasses, will be covered in detail in Chapter 13.
[6] In Java 1.5, an @Override annotation was introduced that works similarly to Scala's override modifier, but unlike Scala's override, is not required.
[7] This kind of polymorphism is called subtyping polymorphism. Another kind of polymorphism in Scala, called universal polymorphism, is discussed in Chapter 19.
[8] Meyers, Effective C++ meyers:effective-cpp
[9] Eckel, Thinking in Java eckel:thinking-in-java
[10] Class ArrayElement also has a composition relationship with Array, because its parametric contents field holds a reference to an array of strings. The code for ArrayElement is shown in Listing 10.5 here. Its composition relationship is represented in class diagrams by a diamond, as shown, for example, in Figure 10.1 here. | https://www.artima.com/pins1ed/composition-and-inheritance.html | CC-MAIN-2018-17 | refinedweb | 6,705 | 53.31 |
I'm new to EE, and trying to learn analog, digital, + vhdl. I don't have
any hardware, so I'm trying this all via open source digital toolkits.
I thought I'd try to create simple VHDL components, and then use QUCS to
test them, in circuit. I'm using myHDL to generate the VHDL
().
My issue seems to be that QUCS cannot seem to process an include file
because it doesn't know what to do with the 'work' namespace...
Short Example:
File # 1: Inc.vhd
-----------------
-- import line chokes on 'work' in QUCS/freeHDL
-- File: Inc.vhd
-- Generated by MyHDL 0.7
-- Date: Sun Feb 17 10:37:41 2013
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.numeric_std.all;
use std.textio.all;
use work.pck_myhdl_07.all;
...
<snip>
File # 2: pck_myhdl
-------------------
-- File: pck_myhdl_07.vhd
-- Generated by MyHDL 0.7
-- Date: Sun Feb 17 10:37:41 2013
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
package pck_myhdl_07 is
attribute enum_encoding: string;
...
<snip>
Error
-----
>>> work.pck_myhdl_07 is undeclared
I've tried various things to work around this...copying the include file
into the target vhdl, copying the include file next to the source vhdl
file, etc.
Questions:
1. Can someone point me at some examples using VHDL and QUCS? free
2. How can I look at the exact commands QUCS is using to process the
VHDL (presumably it's calling into freeHDL...)
3. If I have to manually copy the included file, 'work.pck_myhdl_07', in
this case, ...what does that need to look like?
4. Is QUCS the appropriate tool to use for this sort of thing (i.e.
learning about electronics, vhdl, circuits, etc?)
Project attached as tgz.
-Todd | http://sourceforge.net/p/qucs/mailman/qucs-help/thread/5121525E.7020608@gmail.com/ | CC-MAIN-2014-23 | refinedweb | 284 | 79.36 |
Maybe you all know about this feature of the just-beta Java 1.5, but I was
pleasantly surprised to learn on slide 46 of the presentation below
that the new static import feature allows you to write things like
import static Math;
x = cos(PI * theta);
instead of
x = Math.cos(Math.PI * theta);
(Note that not only does "PI" not need to be qualified by "Math.", neither does
the "cos" call.)
It'll be nice when the day comes that we can actually use this feature as the
default....
Al
__________________________________
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How can I write the Makefile for edisoncer1991 Mar 30, 2015 7:36 PM
HI,
I want to build the "hello world " driver module and lsmod helloworld driver module on the edison.But I don't know how to write the Makefile.
Can anyone help me?
The hello world driver module is like below:
#include <linux/init.h> #include <linux/module.h> #include <linux/kernel.h> MODULE_LICENSE("Dual BSD/GPL"); static int hello_init(void) { printk(KERN_ALERT "Hello,world\n"); return 0; } static void hello_exit(void) { printk(KERN_ALERT "Goodbye,world\n"); } module_init(hello_init); module_exit(hello_exit);
I think the 'make' file should be like below:
the makefile is run on ARM,but I don't know how to modify it.
- obj-m := hello_module.o
- KERNEL_DIR := /root/workspace/s3c-linux.jyx
- PWD := $(shell pwd)
- all:
- make ARCH=arm CROSS_COMPILE=arm-linux- -C /root/workspace/s3c-linux.jyx/ M=$(PWD) modules
- clean:
- rm *.o *.ko
1. Re: How can I write the Makefile for edisoncer1991 Mar 30, 2015 8:11 PM (in response to cer1991)
I have finished it.
I used the Makefile like below:
obj-m := hello.o CC = gcc KERNEL_DIR := /myedison/edison-src/build/tmp/work/edison-poky-linux/linux-yocto/3.10.17+gitAUTOINC+6ad20f049a_c03195ed6e-r0/linux-edison-standard-build PWD := $(shell pwd) all: make ARCH=x86 -C $(KERNEL_DIR) M=$(PWD) modules clean: rm *.o *.ko
But,I have a question:the Makefile in Eclipse has a line "CC = i586-poky-linux-gcc -m32 -march=core2 -mtune=core2 -msse3 -mfpmath=sse -mstackrealign -fno-omit-frame-pointer --sysroot=$SDKTARGETSYSROOT'' and my Makefile just has "CC = gcc".What is the difference between the lines
2. Re: How can I write the Makefile for edisonJPMontero_Intel Mar 31, 2015 10:02 AM (in response to cer1991)
3. Re: How can I write the Makefile for edisoncer1991 Apr 1, 2015 7:59 PM (in response to JPMontero_Intel)1 of 1 people found this helpful
Hi，JPMontero_Intel，
Thank you！
The makeflie can work.I can insmod "helloworld" module into edison.
Regards,
cer1991
4. Re: How can I write the Makefile for edisonhenry1966 Jul 2, 2015 8:07 AM (in response to cer1991)
How did you get the KERNEL_DIR folders? building the Edison linux source?
5. Re: How can I write the Makefile for edisoncer1991 Jul 3, 2015 5:44 AM (in response to henry1966)
Hi,
I downloaded the edison src from the Intel's website and then build the compiling environment according to it.
6. Re: How can I write the Makefile for edisonhenry1966 Jul 6, 2015 6:23 AM (in response to cer1991)
Thanks, what image do you have on your edison? I can't get a module to load and it seem as though the compiled module is built for 3.10.17-yocto-standard, whilst my edison is running 3.10.17-poky-edison+ and as such the module can't be loaded. Do you have any ideas on how to resolve this problem?
7. Re: How can I write the Makefile for edisoncer1991 Jul 7, 2015 4:18 AM (in response to henry1966)
I build a custom kernel.
Firstly, you should build the right environment.
Then,you should build the native SDK.
You can see more from edisonbsp_ug_331188007.pdf
8. Re: How can I write the Makefile for edisonRadhika.k Sep 9, 2016 5:08 AM (in response to cer1991)
Hi,
Can I know which source code you are using inorder to make ,because I'm not finding the above mentioned directories which you have mentioned in the kernel directory .I'm using the yocto image iot-devkit-yp-poky-edison-20160606 and meta-intel-edison image using make.
Can I know much detailed explanation on the header files ,I mean where we should add and from where we are retrieving the info regarding this file
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
Thanks and Regards,
Radhika | https://communities.intel.com/thread/62158 | CC-MAIN-2018-09 | refinedweb | 649 | 66.03 |
This is a beginner's article to show how to get up and running with the new Windows 7 feature called Jumplists. When we finish, you should be able to create jumplists on the fly and add tasks to them.
The main jumplist code is in the form. There are a few things you need to download to use the Windows 7 API and get the DLL you need in order to start using the fun stuff in Windows 7 like Jumplists. The API link is here. Once you download it, you need to compile the DLL and then add a reference to it in your current project. The final bit to getting the jumplists to work is making sure to include the proper using syntax for them. In our case with Jumplists, you want to include:
using MS.WindowsAPICodePack.Internal;
using Microsoft.WindowsAPICodePack.Shell;
using Microsoft.WindowsAPICodePack.Taskbar;
Once you get the includes figured out, you can jump in and create one. Make sure you create the jumplist in the FormShown event and then just add tasks as needed. The syntax below is how to create a simple task and pass an argument as well as set the icon.
FormShown
IEPath = String.Format("C:\\Program Files\\Internet Explorer\\iexplore.exe");
JumpListLink jll = new JumpListLink(IEPath, s);
jll.IconReference = new IconReference(IEPath, 0);
jll.Arguments = txtURL.Text;
jumpList.AddUserTasks(jll);
The included demo was created to be minimized most of the time. It will scrape the current NHL.com scores site and then add the list of the current games onto a separate jumplist with a link back to the scores page. Once the timer is started, it will update the scores every timer tick which can be set in the numeric spin dial.
Once you let it run, it will update the jumplist with the current scores of the day. When you right click to get access to the jumplist, you will see something similar to the following:
One tip that I learned when doing this is that you need to make sure that the icon reference is set, otherwise you get a very ugly non recognizable icon next to your tasks.
As you can see, jumplists are handy tools to get access to various items and provide extra functionality to your program. One caveat, since this was a demo I didn't follow the proper Microsoft best practices with Jumplists. You should make sure that the functionality of the jumplists are also included inside your application. In other words, anything you do in jumplists should be able to be done inside your program. | https://www.codeproject.com/articles/56203/updating-jumplists-on-the-fly | CC-MAIN-2017-09 | refinedweb | 435 | 72.87 |
Rust, verlan of programming languages
Designed by Mozilla to write Servo, potential successor to Firefox, it has an LLVM backend.
The Rust code is available on Github and interests some programmers who see it as a possible successor to C++ in their field.
The word "rust" means red hair in old English and can be an allusion to the fox, symbol of Mozilla. It is also the name of a fungi (think hallucinogenic).
Rust is not a new C to which would have been added dynamic arrays, objects, pattern matching with mixing of different types, automatic memory management, like Vala.
Its main advantage is the safety of memory management, otherwise it takes old principles with new reserved words and syntax, which is probably more expressive, providing we are able to read it. It seems to try to be different for the principle, not for efficiency.
How the compiler works
The steps of generating an executable program are described in the following diagram:
The scanner and the parser produce the AST (Abstract Syntax Tree) code. Optimizations are performed on this code.
Then a semantic analysis is made which performs lots of controls. The 2016 version of the compiler achieves it in two steps: creating an intermediate high level code and then a medium level IR.
The next step is the LLVM code generation, which is made from MIR and in combination with the LLVM API. There is here a choice between producing bitcode, or assembly or object code. In the latter case the LLVM linker produces a binary executable depending on the platform.
Syntax of the language
Comparing the basic elements of Rust with those of C or C++ or a modern language completed by these new elements present in all recent languages.
Rust
fn main() { println!("Hello World!"); }
C
void main() { puts("Hello World!"); }
Displaying a string.
Rust
let str = "why not make it complicated"; println!("str: {}", str);
C
char *str = "when it could be simple"; puts(str);
In Rust, all local variables are declared by let and are constants! We must add the mut specifier, to be able to reassign them...
Variable in Rust
let a = 1; a += 1; // Error!
Constant in C
const int a = 1; a += 1; // Error!
A 'mutable variable' in Rust is a variable (as the name indicates) in C!!!
Mutable variable in Rust
let mut b = 2; b += 1; // Ok
Variable in C
int b = 2; b += 1; // Ok
The type is determined by inference, but as it can be ambiguous (and therefore unsafe, it should be noted) the possibility of explicit declaration is added as an option. The coercive nature of the language would have required it the default syntax.
Explicit types in Rust
let b : int = 2; let ch : char = 'x';
Explicit types in C
int b = 2; char ch = 'x';
Tuples are mixed lists. An array has the same purpose in other languages.
Tuple in Rust
let t = (4, 5.0, false, "hello");
Mixed array in modern languages
array t = { 4, 5.0, false, "hello"};
The switch structure is renamed match to be modern. The bottom line is that it is more elaborate, as in Scala.
Match in Rust
let x : int = 1; match x { 0 => { println!("Not found"); } 1 => { println!("Found"); } _ => { println!("Default"); } // Le reste }
Switch case in C
int x = 1; switch(x) { case 0: puts("Not found"); break; case 1: puts("Found"); break; println!("Default"); // Le reste }
The for loop inspired by Python is the only case where Rust is simpler than C. Premiminary versions of the language write: for i in range(0, 10). Then it has been discovered that Scriptol's langage syntax is the best.
Rust
for i in 0..10 { ... }
C
for(i = 0; i <= 10; i++) { ... }
Rust uses a special structure for infinite loops, unnecessary in C.
Rust
let ctr = 0; loop { ctr += 1; if(ctr == 1) { break; } }
C
int ctr = 0; while(1) { ctr += 1; if(ctr == 1) { break; } }
The declaration of a function shows the slang aspect of Rust compared to C! Header more complicated with no reason, return simpler but unnecessarily less secure, where is the consistency?
Rust
fn mult(x: int, y: int) -> int { x * y }
C
int mult(int x, int y) { return (x * y); }
struct have the role of classes but methods are added separately, which is an option in C++.
Struct in Rust
struct Point { x: int, y: int, } impl Point { fn Start() -> Point { Point { x: 0, y: 0 } } }
Class in C++
class Point { int x; int y; Point Start() { x = 0; y = 0; return this; } }
In conclusion, Rust was designed as a system language to replace C++ with a safer memory management, a point we do not deny. Was it necessary to achieve this change by making the syntax so obscure? The motivations of the authors are not clear because the defects of C, such as semicolons (an error according to the C authors themselves) and curly braces are retained, but the simplicity of the declarations is not.
The possibilities of the elements of the language were also restricted to reduce the risk of errors. This is something that did not turned well in the past to Pascal or Modula.
Should we use Rust?
Should we use Rust, so choose between it and Go or C++? We will put Go aside because it rather competes with server languages like Java, Python, PHP, the garbage collector is not always desirable for system programming and online modules is even less, and also the lack of generics.
It remains to choose between the insecurity of C++ when badly used, but with total freedom to achieve what you want, or deal with the obscure syntax of Rust for a safer memory management. They are many reasons for programmer to stay on C++: tons of libraries, all the usefull developement tools, speed of execution...
Reference : Rust reference manual.
Similar projects: Cyclone (ATT), Checked C (Microsoft). | http://www.scriptol.com/programming/rust.php | CC-MAIN-2016-36 | refinedweb | 986 | 71.24 |
Gluster combines object and file storage
.
GlusterFS is an open source file system that scales to petabytes with global namespace. Version 3.3 has an object interface integrated into that file system.
“Probably 95 percent of enterprise applications haven’t been able to leverage object storage and move to the cloud,” Gluster director of product marketing Tom Trainer said. “Integrating it in one system will accelerate the integration to object storage.
Gluster customers can access data as objects from any Amazon S3 compatible interface and access files from its NFS and CIFS interfaces. Trainer said service providers can use GlusterFS to build Amazon-like storage for customers. It can also be used to migrate legacy applications to the cloud and scale NAS across the Internet to a public cloud.
There have been other approaches to integrating object and file storage, although Trainer maintains that GlusterFS has the deepest integration of object and file interfaces.
Most object storage products such as EMC Atmos, Scality, OpenStack and Amazon S3 don’t have file systems. Caringo, which began as object storage, added an NFS and CIFS interface for its object store and Nirvanix’s CloudNAS makes its object storage look like NAS to an application.
Comment on this Post | http://itknowledgeexchange.techtarget.com/storage-soup/gluster-combines-object-and-file-storage/ | CC-MAIN-2015-48 | refinedweb | 206 | 54.42 |
import "net/http"())
chunked.go client.go cookie.go doc.go filetransport.go fs.go header.go jar.go lex.go request.go response.go server.go sniff.go status.go transfer.go transport.go
const (. with time.Parse and time.Time.Format when parsing or generating times in HTTP headers. It is like time.RFC1123 but hard codes GMT as the time zone."} )")
func CanonicalHeaderKey(s string) string
CanonicalHeaderKey returns the canonical format of the header key s. The canonicalization converts the first letter and any letter following a hyphen to upper case; the rest are converted to lowercase. For example, the canonical key for "accept-encoding" is "Accept-Encoding".
func DetectContentType(data []byte)(w ResponseWriter, error string, code int)
Error replies to the request with the specified error message and HTTP code. The error message should be plain text.
func Handle(pattern string, handler Handler).
func ListenAndServe(addr string, handler Handler) error
ListenAndServe listens on the TCP network address addr and then calls Serve with handler to handle requests on incoming connections.) err := http.ListenAndServe(":12345", nil) if err != nil { log.Fatal("ListenAndServe: ", err) } }
func ListenAndServeTLS(addr string, certFile string, keyFile followed) if err != nil { log.Fatal(err) } }
One can use generate_cert.go in crypto/tls to generate cert.pem and key.pem.(w ResponseWriter, r *Request)
NotFound replies to the request with an HTTP 404 not found error.)
ProxyFromEnvironment returns the URL of the proxy to use for a given request, as indicated by the environment variables $HTTP_PROXY and $NO_PROXY (or $http_proxy and $no_proxy). An error is returned if the proxy environment is invalid. A nil URL and nil error are returned if no proxy is defined in the environment, or a proxy should not be used for the given request..
Generally Get, Post, or PostForm will be used instead of Do..
func (c *Client) Head) Post(url string, bodyType string, body io.Reader) (resp *Response, err error)
Post issues a POST to the specified URL.
Caller should close resp.Body when done reading from it.
If the provided body is also an io.Closer, it is closed after the body is successfully written to the server. Cookie struct { Name string Value string Path string Domain string Expires time.Time RawExpires string //.
func (c *Cookie) String() string
String returns the serialization of the cookie for use in a Cookie header (if only Name and Value are set) or a Set-Cookie response header (if other fields are set). string
A Dir implements http.FileSystem using the native file system restricted to a specific directory tree.
An empty Dir is treated as ".".
func (d Dir) Open(name string) (File, error)
type File interface { Close() error Stat() (os.FileInfo, error) Readdir(count int) ([]os.FileInfo, error) Read([]byte) (int, error) Seek(offset int64, whence int) (int64, error) }
A File is returned by a FileSystem's Open method and can be served by the FileServer implementation..() })
type ProtocolError struct { ErrorString string }
HTTP request parsing errors.
func (err *ProtocolError) Error() string
type Request struct { Method string // GET, POST, PUT, etc. // URL is created from the URI supplied on the Request-Line // as stored in RequestURI. // // For most requests, fields other than Path and RawQuery // will be empty. (See RFC 2616, Section 5.1.2) URL *url.URL // The protocol version for incoming requests. // Outgoing. outgoing. Close bool // The host on which the URL is sought. // Per RFC 2616, this is either the value of the Host: header // or the host name given in the URL itself. // It may be of the form "host:port". maps trailer keys to values. Like for Header, if the // response has multiple trailer lines with the same key, they will be // concatenated, delimited by commas. // For server requests, Trailer is only populated after Body has been // closed or fully consumed. // Trailer support is only partially complete. }
A Request represents an HTTP request received by a server or to be sent by a client..
func ReadRequest(b *bufio.Reader) (req *Request, err error)
ReadRequest reads and parses a
FormValue returns the first value for the named component of the query. POST and PUT body parameters take precedence over URL query string values. FormValue calls ParseMultipartForm and ParseForm if necessary. To access multiple values of the same key use ParseForm.()MultipartForm(maxMemory int64)) PostFormValue(key string) string
PostFormValue returns the first value for the named component of the POST or PUT request body. URL query parameters are ignored. PostFormValue calls ParseMultipartForm and ParseForm if necessary.
func (r *Request) ProtoAtLeast(major, minor int) bool
ProtoAtLeast reports whether the HTTP protocol used in the request is at least major.minor.
func (r *Request) Referer() string)
Write writes an HTTP/1.1 request --) WriteProxy-lengthed body. // // // Trailer maps trailer keys to values, in the same // format as the header. Trailer Header // The Request that was sent to obtain this Response. // Request's Body is nil (having already been consumed). // This is only populated for Client requests. Request *Request }
Response represents the response from an HTTP request.
func Get(url string) (resp *Response, err error).
func ReadResponse(r *bufio.Reader, req *Request) (*Response,
Writes the response (header, body and trailer) in wire format. This method consults the following fields of the response:
StatusCode ProtoMajor ProtoMinor Request.Method TransferEncoding Trailer Body ContentLength Header, values for non-canonical keys will have unpredictable behavior
type ResponseWriter interface { // Header returns the header map that will be sent by WriteHeader. // Changing the header after a call to WriteHeader (or Write) has // no effect..
type RoundTripper interface { // Body. The request's URL and // Header fields are guaranteed to..!") })
func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Request))
HandleFunc registers the handler function for the given pattern.
func (mux *ServeMux) Handler(r *Request) (h Handler, pattern string)) ServeHTTP(w ResponseWriter, r *Request)
ServeHTTP dispatches the request to the handler whose pattern most closely matches the request URL.. TLSNextProto map[string]func(*Server, *tls.Conn, Handler) }
A Server defines parameters for running an HTTP server.. specifies the dial function for creating TCP // connections. // If Dial is nil, net.Dial is used. Dial func(network, addr string) (net.Conn,, //) CloseIdleConnections()
CloseIdleConnections closes any connections which were previously connected from previous requests but are now sitting idle in a "keep-alive" state. It does not interrupt any connections currently in use.".
func (t *Transport) RoundTrip(req *Request) (resp *Response, err error)
RoundTrip implements the RoundTripper interface.
For higher-level HTTP client support (such as handling of cookies and redirects), see Get, Post, and the Client type.
Package http imports 25 packages (graph) and is imported by 4463 packages. Updated 2013-12-02. Refresh now. Tools for package owners. | http://godoc.org/net/http | CC-MAIN-2013-48 | refinedweb | 1,107 | 60.01 |
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