text stringlengths 454 608k | url stringlengths 17 896 | dump stringclasses 91
values | source stringclasses 1
value | word_count int64 101 114k | flesch_reading_ease float64 50 104 |
|---|---|---|---|---|---|
Repository: Python Repository Github
Software Requirements:
Visual Studio Code(Or any preferred code editor)
What you will learn:
In this tutorial you would learn to build a web crawler with these functionalities
- Understand What Crawling is
- Learn how to observe url pattern changes and use them to create better crawlers.
- Use the
Beautiful Souppackage in the
bs4module.
Difficulty: Beginner
Tutorial
What is crawling
In this tutorial we would be further developing the bot we started creating in the last of this series. We would add more advanced functionality so that it would be able to search through more pages by observing url patterns for the site we would want to crawl.
Before we do this, due to a comment by @portugalcoin, i would try to explain what a webcrawler is a bit better.
Lets start with the wikipedia definition.. Web crawlers copy pages for processing by a search engine which indexes the >downloaded pages so users can search more efficiently.
So that quite simplifies the definition to a well understandable form. Lets move on to improving our code.
When writing a webcrawler using beautiful soup, you would need to understand how the web url are directed and rerouted. Most times, whenever you navigate to a new page, the name is just added to the preset url like '/newpage'.
Some websites are structured differently, so you would still need to move around and understand the structure for that site before you write your crawler.
So on to the coding
From our last tutorial, this is where we are
from bs4 import BeautifulSoup import requests import re def thecrawler(maxpages,movie): page = 1 searchnetnaija(movie) while page < maxpages: searchtoxicwap() def searchtoxicwap(): url="" def searchnetnaija(movie): search = True while(search): print('This works') url1="" sourcecode = requests.get(url1) plain_text = sourcecode.text soup = BeautifulSoup(plain_text,'lxml') list = [] for link in soup.find_all('a'): lin = link.get('href') list.append(lin) search = False; for dat in list: x = re.search(r'movies',dat) if x: s = r'%s' % movie y = re.search(s,dat) if y: print(dat)
Understanding Url patterns
We can see that the problem with this is that it only searches one page in the website. To make it search other pages, we would need to see how our url changes for other websites. First head to the website here and navigate through the movie pages while noticing how it changes.
.png)
From this page all we want is the url
.png)
So if you payed attention you would see that as stated earlier the number at the end of the url for each page changes to the corresponding page number and this is the feature that we can exploit.
To loop through a certain number of pages we would use a while loop like this
def searchnetnaija(movie,max_pages):#Add a new max_pages arguement to the function page = 2#Start off from page 2 while(page < max_pages): url1=""+ str(page)#Interpolate into the url page += 1#navigate to the next page
Since we would want to use a single function to search through multiple sites, we would need to send the same max_pages parameter through all the pages. Hence, you could use this parameter to call all the functions within your main function.
def thecrawler(maxpages,movie): searchnetnaija(movie,max_pages)
So after this is done we would like the crawler to navigate to the link we've found and find the download link within it. Most sites wouldnt want bots going through their websites and downloading files, so they make on-screen buttons that must be used to download these files. You could choose to just navigate to the link your bot has provided or you could choose to use a module called
pyautogui to actually click on the button and download your file within your browser(This would be quite more complex, but would be happy to do a tutorial on it if interest is indicated).
So we would need to navigate to our new page and look for the link for the download.From the url method we learnt above, we would see that the links for movie downloads have '/download' beside them which leads to a new site for download. So we just add this to our code and we should be good to go.
for link in newSoup.find_all('a'): a = link.get('href') lis.append(a) for dat in lis: x = re.search(r'movies',y) if x: s = r'%s' % movie y = re.search(s,y) if y: new_link = url1 + '/download'#this line adds the download to the url and gets us the link requests.get(new_link)
Thanks for reading
You could head to my Github to see the code for this tutorial.
Thank you for your contribution @yalzeee.
After an analysis of your tutorial we suggest the points below:
Improve your tutorial texts, and please put punctuation. It is important that the tutorial be well written.
We suggest you add more comments to your code, so it's very important for the reader to understand what you are developing.
Put your tutorial as detailed as possible for the user to understand well the theory and practice that you are explaining in your tutorial.
We suggest that in your tutorial always have advances of your code without repeating the code of the previous tutorial.
Thanks]
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Thank you for your review, @portugalcoin! Keep up the good work!
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So, I have a UnityEvent< T > variable in my script and I want to add a listener to it, but since I am not adding any listeners through the inspector, the variable is never initialized and throws a NullReferenceException when I call "AddListener" on the Awake method of my script.
I checked and, indeed, it is null when I try to call its method, but since I'm using the generic version, which is an abstract class, I'm not able to initialize it by simply calling "new UnityEvent< T >()".
Is there any way to make this work without having to create a derived class of my own?
Answer by Brijs
·
Jun 13, 2016 at 01:26 PM
UnityEvent class is a generic abstract class. it is not a concrete class.
So we can not instantiate it directly.
I tried it which worked for me
1) Derive another class from UnityEvent class.
2) Now declare variable of that class in monobehaviour. It will be instantiated and will be shown in inspector also.
For example
[System.Serializable]
public class OnClickEvent : UnityEvent<bool>
{
}
public class NewBehaviourScript : MonoBehaviour
{
public OnClickEvent onClick = new OnClickEvent();
}
Yeah, I figured this would be the best (if not the only) way. I wanted to just use UnityEvent< T > and have it work, but since that class is abstract it only makes sense it wouldn't, my bad...ReferenceException Error how to solve?
2
Answers
Im trying to build a game.I have an enemy Ai that uses the players position to track and move.But i get a null reference exception when player dies.Can anybody help ?
0
Answers
Some help for "animation event triggers multiple times"
0
Answers
Array values not being initialised unless the object with the (Player) script is selected in the inspector whilst the game is on
1
Answer
Unity 2019.2.0f1. Game doesn't restart after back button pressed during splash screen display in android?
0
Answers
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...
CodingForums.com
>
:: Computing & Sciences
>
Computer Programming
> simple c program with gui
PDA
simple c program with gui
rock_14
08-05-2007, 02:55 AM
Hi,
If I have a simple c program that prints "hello world" and I want to make a graphical page with a button that someone can click and then it will show "hello world" somewhere on the page, how can this be done?
Any help would be greatly appreciated.
Thanks
ralph l mayo
08-06-2007, 07:08 AM
This is C++, but maybe it'll still help. NB I don't really know anything about this stuff, I just hacked it together from the official wxWidgets "Hello World" to include a button. You've got to have the wxWidgets headers installed to compile this, but it should work ok on any of the major platforms, providing I didn't do anything really stupid.
#include "wx/wx.h"
class MyApp : public wxApp
{
bool OnInit();
};
class MyFrame : public wxFrame
{
public:
MyFrame(const wxString& title, const wxPoint& pos, const wxSize& size);
void DoHello(wxCommandEvent& event);
};
IMPLEMENT_APP(MyApp)
bool MyApp::OnInit()
{
MyFrame* frame = new MyFrame(
_T("Press butan"), // Title, _T makes wxStrings out of its arg
wxPoint(50, 50), // Suggested top left corner
wxSize(400, 200) // width x height in px
);
frame->Show(TRUE);
SetTopWindow(frame);
return TRUE;
}
MyFrame::MyFrame(const wxString& title, const wxPoint& pos, const wxSize& size)
: wxFrame((wxFrame*)NULL, -1, title, pos, size)
{
wxButton* button = new wxButton(
this, // Place on this frame
-1, // This is the ID parameter, I think -1 means "assign anything convenient" but that's just a guess
_T("...") // Caption
// optional params for placement follow
);
// Hook the button to the handler
Connect(
button->GetId(), // Maybe I should have suggested a specific id instead of -1 to avoid this?
wxEVT_COMMAND_BUTTON_CLICKED, // the id of the event clicking raises
wxCommandEventHandler(MyFrame::DoHello) // wraps the event interface around a function reference
);
}
void MyFrame::DoHello(wxCommandEvent& WXUNUSED(event))
{
wxMessageBox(
_T("Hello world"), // Caption
_T("Standard nub greeting follows"), // Title
wxOK | wxICON_INFORMATION, // Display options + extras
this // I don't know, the parent window responsible for this?
);
}
I can't figure out how to attach an exit event without also including more extraneous code for a menubar, so it leaks those pointers. :/
oracleguy
08-06-2007, 05:21 PM
It doesn't leak any memory. Those wx objects that you dynamically created will automatically get cleaned up when the parent deconstructs, that is why you have to pass it the parent.
And also if you want an exit event on your application you can override the OnExit (I think that is the name) function in your MyApp class.
Also using the Connect method to link the event handling does work but you can use event tables in wxWidgets which are easier to use. And yes, you'd want to specify a specific ID number to the button. It works since you only have one control though.
ralph l mayo
08-06-2007, 05:33 PM
Thanks... I assumed I'd have to call the Close(bool) method to trigger garbage collection. I tried either OnExit() or OnQuit(), but it must have been the wrong one because I couldn't establish any evidence that it was ever called.
I started out with the event table approach from their hello world but it wasn't clicking for me, probably because I didn't understand how ids worked. That approach is a probably better for happening at compile-time, but using those #defines feels a lot more hackish than Connect.
Either way it seems infinitely preferable to what (admittedly little) I remember about the win32 native API.
oracleguy
08-06-2007, 06:25 PM
That approach is a probably better for happening at compile-time, but using those #defines feels a lot more hackish than Connect.
I know what you mean but once you get used to it, it isn't too bad compared how many ways they could of done it worse.
Either way it seems infinitely preferable to what (admittedly little) I remember about the win32 native API.
Oh yeah... I had do some stuff with the Win32 API a few months ago and have doing lots of wxWidgets before that, it was painful. :)
Oh, but if you can't use C++, you'll probably have to use the native API for whatever platform you are using. Is this going to be a Windows program?
rock_14
08-08-2007, 04:56 AM
Thanks, I will take a look at this. I really appreciate the help.
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Euler Problem 1 Definition
If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23. Find the sum of all the multiples of 3 or 5 below 1000.
Solution
There are four ways to solve this problem in R.
- Brute force loop through all numbers from 1 to 999 and test whether they are divisible by 3 or by 5 using the modulus function.
- Vector arithmetics.
- Sequences of 3 and 5, excluding duplicates (numbers divisible by 15).
- Using an arithmetic approach.
By the way, the problem definition on the Project Euler website is not consistent: the title mentions multiples of 3 AND 5, while the description asks for multiples of 3 OR 5.
# Solution 1 answer <- 0 for (i in 1:999) { if (i%%3 == 0 | i%%5 == 0) answer <- answer + i } # Solution 2 sum((1:999)[((1:999)%%3 == 0) | ((1:999)%%5 == 0)]) # Solution 3 sum(unique(c(seq(3, 999, 3), seq(5, 999, 5))))
The sum of an arithmetic progression , where n is the number of elements and a1 and an are the lowest and highest value, is:
The numbers divisible by
can be expressed as:
We can now easily calculate the sum of all divisors by combining the above progression with the formula for arithmetic progressions as expressed in the above code, where m is the divisor and n<\i> the extent of the sequence.
p is the highest number less than n divisible by m. In the case of 5, this number is 995.
Substitution gives:
# Solution 4 SumDivBy <- function(m, n) { p <- floor(n/m)*m # Round to multiple of n return (m*(p/m)*(1+(p/m))/2) } answer <- SumDivBy(3, 999) + SumDivBy(5, 999) - SumDivBy(15, 999)
The post Euler Problem 1: Multiples of 3 or 5... | https://www.r-bloggers.com/euler-problem-1-multiples-of-3-or-5/ | CC-MAIN-2018-22 | refinedweb | 315 | 55.78 |
In this blog we will learn how to display images in GridView from folder in ASP.NET programming.
We need to display images in GridView control from a folder in ASP.NET. This is really very simple task.
Gridview is very rich control and easy to use. The GridView control is a powerful data grid control that allows you to display an entire collection of data, sorting, paging, and perform inline editing.
Display images in GridView from folder - Example
In the following example we will see how to upload image to folder and display the uploaded images in GridView control. Web form
Import the following namespace using System.IO;
Output | https://www.c-sharpcorner.com/blogs/display-images-in-gridview-from-folder-in-asp-net1 | CC-MAIN-2018-51 | refinedweb | 110 | 55.95 |
/* ** (c) COPYRIGHT MIT 1995. ** Please first read the full copyright statement in the file COPYRIGH. */
This module is an easy to use interface to SQL databases. It contains both a generic interface and some specific examples of how this can be used to connect a Web client to an SQL server. This requires that you have linked against the MySQL library. See the installation instructions for details.
#ifndef WWWSQL_H #define WWWSQL interacts with the MYSQL C client library to perform SQL operations. It is not intended as a complete SQL API but handles most of the typical error situations talking to an SQL server so that the caller doesn't have to think about it.
#ifdef HT_MYSQL #include "HTSQL.h" #endif
This SQL based log class generates a SQL database and a set of tables storing the results of a request. The result is stored in different tables depending on whether it is information about the request or the resource returned.
#ifdef HT_MYSQL #include "HTSQLLog.h" #endif
#ifdef __cplusplus } /* end extern C definitions */ #endif #endif /* WWWSQL_H */ | http://www.w3.org/Library/src/WWWSQL.html | CC-MAIN-2014-49 | refinedweb | 176 | 66.44 |
3.24 Wed Oct 12 00:34:02 PDT 2016 - Fixed test suite failure when running under Perl 5.8.2 - Refactored test suite not to use isa_ok to avoid an issue found while debugging the above failure - Refactored core modules not to use `each` iterator 3.23 Mon Oct 10 19:31:34 PDT 2016 - Fixed another issue with unescaped curly bracket warning in Perl 5.23.6+ - Misc documentation fixes 3.22 Mon Aug 1 11:32:17 PDT 2016 - Fixed the issue with unescaped curly bracket warning in Perl 5.23.6+ 3.21 Thu May 14 20:38:51 PDT 2015 - Fixed a bug when exceptions could be thrown as ARRAY instead of a string in ExtDirect attribute handler 3.20 Tue Mar 31 21:37:10 PDT 2015 - Added support for call metadata available in Ext JS 5.1+ - Added support for JSON argument decoding in Form handlers - Updated the documentation - Tests, more tests - Version bumped to 3.20 in concert with gateway releases 3.03 Thu Jan 29 22:58:24 PST 2015 - Fixed outdated attribute parser check that required at least one name in params arrayref for named Methods - Named Methods with empty params will force !strict in constructor - Misc documentation fixes 3.02 Mon Oct 27 17:36:12 PDT 2014 - Added timeout and max_retries API config options - Some test fixes and improvements - Miscellaneous doc fixes 3.01 Thu Jun 19 23:01:25 PDT 2014 - Minor refactoring of the Method argument checking; it now happens in the Method itself, as opposed to be divided among other modules. It should have been this way since the beginning, but oh well. - Tests updated to accommodate for the Method changes - ExtDirect attribute parsing is more robust now, and tested - Fixed several minor but very embarrassing bugs uncovered by the new attribute parser tests - Assorted tiny fixes here and there 3.00 Thu Jun 12 17:54:23 PDT 2014 - Major refactoring of the RPC::ExtDirect module internals - Configuration is now instance-based with RPC::ExtDirect::Config - Package global variables are deprecated - API tree is now kept in an RPC::ExtDirect::API instance rather than internal data structures; Action and Method are full fledged objects with public API - API tree can now be initialized from a hashref as an alternative to sub attributes - Class-based Serialize and Deserialize packages are deprecated in favor of combined instance based Serializer - Improved authorization support for API generation and Method invocation - Tests used in all gateways are now unified and shipped with the core RPC::ExtDirect package - Tons of other changes and fixes, and no doubt more bugs 2.15 Tue May 6 17:44:10 2014 - Fixed failing tests due to changes in JSON::XS error output 2.14 Mon Nov 11 10:43:54 2013 - Fixed a memory leak in hook handling 2.13 Fri Mar 29 18:38:11 2013 - Additional round of refactoring: moved hook initialization to RPC::ExtDirect::add_method, this allows adding methods explicitly without using ExtDirect attributes. Added support for methods without parameter declaration; it is assumed that parameters are passed by-name without strict checking. 2.12 Fri Mar 8 21:20:11 2013 - Some more refactoring; no API changes. 2.11 Wed Feb 27 20:42:23 2013 - Refactored some packages internally, to provide better extensibility. No major code changes. 2.10 Sun Sep 30 22:36:48 2012 - Split UNIVERSAL::ExtDirect sub declaration into separate modules for Perls < 5.12 and 5.12+, which makes RPC::ExtDirect 2.x compatible with Perl 5.6+ again. With older Perls, ExtDirect attribute handler will be processed in CHECK phase as it was in 1.x; with 5.12+ the handler is processed in BEGIN phase to make it compatible with Apache2/mod_perl. So now we have the both of two worlds and it is no longer necessary to keep RPC::ExtDirect 1.x for older Perls. 2.02 Wed Jun 20 17:03:38 2012 - Fixed a small bug in request handling. 2.01 Tue Jun 19 10:34:11 2012 - Pod reformatted for more compatibility with HTML generators. - Minor documentation tweaks. 2.00 Mon Jun 18 12:16:32 2012 - Added new feature: Hooks. See documentation for details. - Added new feature: Environment objects. See documentation for details. - Moved ExtDirect attribute handling to BEGIN phase for better compatibility with Apache/mod_perl environment. This change breaks compatibility with Perls below 5.12. - Improved attribute error messages. - Updated documentation and test suite. - Fixed some bugs in documentation. 1.31 Thu Jun 7 11:13:32 2012 - Fixed a bug in RPC::ExtDirect::Router that allowed some misformed method output to break result serialization without catching the error, leading to route() finishing prematurely. - Added bugtracker and repository properties in Makefile.PL. 1.30 Wed Jun 6 09:43:58 2012 - Fixed a bug in RPC::ExtDirect::Router: form/file upload responses improperly escaped double quotes, which didn't play well with client side. - Fixed small misfeature: API definition no longer include Ext.app namespace declaration. That seemed like a good idea at the time, but turned out to be more trouble than it was worth. - More diagnostics for attribute handler in RPC::ExtDirect. - Fixed a couple of bugs in RPC::ExtDirect documentation and expanded it a bit. 1.21 Mon Nov 21 00:39:12 2011 - Fixed dependency on Attribute::Handlers version >= 0.87 as an attempt to fix failing tests reported by CPAN testers. Removed versions from all packages except RPC::ExtDirect. No point in versioning submodules, it only confuses me. 1.20 Tue Oct 4 21:16:00 2011 - Fixed a bug in RPC::ExtDirect::API: Methods with 0 numbered parameters (i.e. no parameters at all) were not defined properly in generated JavaScript API string. 1.10 Sat Oct 1 20:41:28 2011 - Fixed improper exception handling: RPC::ExtDirect::Exception object did not contain required 'action', 'method' and 'tid' properties which prevented client side from knowing which request raised an exception. 1.02 Fri Sep 30 11:18:13 2011 - Fixed an embarrassing error in RPC::ExtDirect Pod. 1.01 Fri Sep 30 00:00:39 2011 - Minor changes to documentation; added $VERSION to Demo modules. 1.00 Thu Sep 29 14:42:39 2011 - Original version. | https://metacpan.org/changes/distribution/RPC-ExtDirect | CC-MAIN-2017-26 | refinedweb | 1,046 | 64.91 |
Hi John, Hi the list, I almost have finished updating the
> fltkAgg, to add the new subplot formatter and the blit
> method for fast animation. Everything seems to work fine,
> but I still need to do some code clean-up, and before
> commiting the changes I have to ask what you think about
> the method I used:
Hi Gregory, Great news. Ken McIvor just emailed me this morning that
he completed the same with a _wxagg module that he will post shortly.
That means we have (or will soon have) blit methods for all GUIs
except Qt and Cocoa (gentle reminder).
> Instead of writing a special method taking account of the
> bbox for bliting, similar to the agg_to_gtk_drawable, or
> a aggcanvas->str conversion like the proposed
> aggcanvas.as_rgba_str(bbox), I just changed the method
> that I introduced for normal draw in fltkAdd, that rely
> on pytho buffer objects to transfer the agg buffer to the
> fltk library.
> The old method of the Agg backend that was used to get
> the buffer object was:
....snip...
> As fltkAgg is able to use an image source with a pixel
> stride (skipping the a of the rgba quatuor) and a line
> stride (taking a part of wide w1 from an image of wide
> w2), no copy or special method is needed with the new
> version of RendererAgg::buffer_rgba...
> Now I checked and other backends (qtagg, cocoaagg) now
> use RendererAgg::buffer_rgba. If this is ok, I will
> update all the calls to pass (0,0) instead of no
> arguments, but I wonder if the new methods could not
> simplify things for those backends too...
Yep, this all looks right. I will look into this for gtkagg as well
tomorrow. It may make rendering to a bbox even faster because gtkagg
and tkagg may both make an unnecessary copy that your method avoids.
> Another remarks is that the animation code seems quite
> fragile for the moment: if one do a resize of the output
> window, the background copy is not updated correctly and
> one have a very interresting effect
Well, at leat I
> observe that under fltkAgg (my local version supporting
> blit) and GTKAgg. tkagg does not do this..because it is
> not possible to resize the window during animation (well,
> window is resizable but the size of the inside canvas
> does not change during this resize...).
> I think some extra steps should be performed to make
> resize and anim play nicely together (like freezing the
> anim during resize, and restarting afterwards with the
> correct background...)
What I do is connect to the new 'draw_event' which is called at the
end of Figure.draw (no GUI specific event handling required). If you
set the animated property of the Artist, and then connect your
background saver to the 'draw_event', it should handle this case.
Additionally you want to make sure your draw events are processed in
an idle queue on resizes, etc.
background cacheing, the guts of which are
def __init__(self, ax, useblit=False, **lineprops):
...snip
self.canvas.mpl_connect('draw_event', self.clear)
def clear(self, event):
'clear the cursor'
if self.useblit:
self.background = self.canvas.copy_from_bbox(self.ax.bbox)
Does this work for you in GTKAGG and/or FLTK? If everything looks
good, you may want to update the canonical animation examples in the
examples directory and on the wiki.
JDH | https://discourse.matplotlib.org/t/animation-attn-backend-maintainers/3284 | CC-MAIN-2019-51 | refinedweb | 556 | 66.78 |
I read on D's documentation that it's possible to format strings with arguments as print statements, such as the following:
float x = 100 / 3.0; writefln("Number: %.*g", 2, x); Number: 33.33
However, I'm wondering how I would do this if I just wanted the string equivalent, without printing it. I've looked at the std.format library but that seems way to messy for something I only need to use once. Is there anything a little bit more clear available?
Import
std.string or
std.format and use the
format function.
import std.string; void main() { float x = 100 / 3.0; auto s = format("Number: %.*g", 4, x); assert(s == "Number: 33.33"); } | http://databasefaq.com/index.php/answer/1851/string-formatting-d-formatting-a-string-in-d | CC-MAIN-2018-39 | refinedweb | 118 | 78.85 |
Simple, Organized Queueing with Resque
After having used many different queueing systems, from the venerable BackgrounDRb, to DelayedJob, to roll-your-own solutions, I’ve settled on the excellent Resque.
The now-famous blog post from GitHub’s Chris Wanstrath says it all, and the README has everything you could ever hope for in terms of getting up and running. However, Resque leaves a lot up to the imagination for exactly how to integrate it into your app. This is, of course, one of its strengths, as it allows for a high degree of flexibility.
In this article, I am going to introduce one such integration strategy I’ve found particularly useful, clean, and most importantly, simple.
A Namespace of Its Own
In order to free up dependency on your database, which can cause all kinds of performance problems down the road, Resque uses Redis for its data store (note: if you’d like to read more about getting up and running with Redis, read my previous article here).
Assuming you have already setup Redis in your app, you probably already have a $redis global variable to represent the connection. Resque uses the redis-namespace gem by default to avoid polluting the key space of your redis server, but I personally like to have control over important details like this.
Fortunately, Resque allows this, so initializing the connection is as simple as adding the following to
config/initializers/resque.rb:
Enqueueing Jobs
Inspired by Delayed Job, in Resque all you need to run code in the background is provide a class or module that responds to the
perform method. These objects also specify the name of the queue which processes them.
The most evident solution to integrating Resque, therefore, is to have one of these objects per background task. For example, you might have one class for processing user-uploaded images, another class for sending your monthly newsletter to all users, and yet another for updating search indices.
As you might imagine, the number of these workers is going to increase over time. Furthermore, Resque prioritizes queues based solely on the order in which they are specified to a worker, so you’re going to need to remember which workers act on which queues. If you have an app where new background tasks are constantly being added, removed, or re-prioritized, this is not only going to be confusing, but will also necessitate a lot of upkeep.
A Cleaner Approach
Rather than focusing on what needs to happen in the background, let’s focus on when. That is, my approach is to let priority be the guiding factor on how to design an interface to Resque.
The first step is to note that 99% of the time, background jobs are going to fall into one of three possible priorities: high, normal, and low. While it will be easy to add more priorities later, it will only happen in very rare circumstances.
Having only three priorities also makes worker configuration much simpler. Every worker is always assigned to these three queues, so except for the count of workers, the command is always the same:
If necessary, to throw more processing power at the queue, simply spawn more workers:
Enqueue Methods Instead
The next step to this approach is to make it easier to throw any instance or class method on to one of these queues. This is where the dynamic nature of Ruby is going to help out a lot. To begin at the end, we’re going to be able to enqueue anything like this:
In addition, it’s not going to matter if
some_object is a class, module, or instance. We can change the priority of a method simply by changing between
Queue::Normal,
Queue::High,
Queue::Low.
Let’s look at how we can code this. The above interface clearly dictates that each class will need to specify an enqueue method. We also know that each class needs to specify a queue name and a perform method, so that’s a good place to start:
We can already see that these classes have the same interface, so let’s refactor it into a superclass:
The
enqueue method’s only job is to supply data to the
perform method, which will be called by Resque. The
perform method needs to find the object by ID, invoke the enqueued method, and pass the enqueued arguments to it. Since everything passed to Resque needs to be serializable to JSON, we need to pass the class name of the object, the method, and the object’s ID as a special “meta” argument:
Then, in the
perform method, we can make use of the
constantize Rails extension to get the class from its name, find the object, and send the method along with its arguments:
And with that, we are ready to enqueue any instance method. Here is an example of how the big picture might look:
That’s all there is to it. The only caveat is that all arguments passed to
background_method are going to be serialized to JSON, and then deserialized back into Ruby. Usually this will not cause any problems, but one big difference is that all hashes with symbol keys will have string keys in
background_method.
Enqueueing Class or Module Methods
Only one final step remains. We also want to enqueue class or module-level methods. That is, we don’t always need to find an instance by ID to accomplish certain background tasks. For example, we might want to send an email to every registered user. The code would look something like this:
This is going to require some slight modification to the
enqueue and
perform methods, since we need to be able to tell the difference between an enqueued class or module and an enqueued object.
To do this, we need to see if the object’s class responds to
:find_by_id or not. This works because if
object is a class or module, its class is
Class, which does not respond to
:find_by_id. If
object is not a model instance, we do not add the
'id' key to the meta information.
As such, the
perform method has only to check for the existence of this key to determine whether to invoke the method directly on the object, or to find an instance by ID first:
Note: this article assumes the ActiveRecord ORM. Depending on your application, you may need to modify the definition of
is_model? to more accurately specify what constitutes a model instance.
Robustness
We have a working queue interface, but there’s still plenty of room for programmer error. The
enqueue method should ideally raise exceptions when the programmer attempts to enqueue a non-existent method, or tries to pass too many or too few arguments to that method.
By adding a few quick checks, the number of queue-side failures can be reduced dramatically. Let’s add a method,
ensure_queueable! to
Queue::Base that raises an exception unless the method exists and the appropriate number of arguments have been passed. With these changes in place, the entire
Queue::Base class looks like this:
Note: checking method arity is somewhat complex, as methods that accept a variable number of arguments return a negative number. See the Ruby documentation of
Method for more information.
That’s All
With that, we have a simple and clean interface to Resque which allows us to enqueue any instance or class method with minimum effort. We can also add new priorities in a few lines of code by simply defining a new subclass of
Queue::Base.
Furthermore, we have provided a single entry point into the queue which uses Resque as its implementation, but should we decide to swap out Resque for another solution in the future, we should only need to make changes to
Queue::Base.
I hope this article has been useful. Have fun with Resque, and happy queueing!
- berto | http://www.sitepoint.com/simple-organized-queueing-with-resque/ | CC-MAIN-2015-27 | refinedweb | 1,323 | 56.69 |
if ($min < $x < $max) { ... }
[download]
# not this
if (($min < $x) < $max) {...}
# or this
if ($min < ($x < $max)) {...}
# but this
if ($min < $x && $x < $max) {...}
[download]
MeowChow
s aamecha.s a..a\u$&owag.print
Almost certainly won't happen for Perl 5 though.
-- Randal L. Schwartz, Perl hacker
if ( $x in [$min, $max] ) { ... } #inclusive container,
# $x==$min would be true
# OR
if ( $x in ($min, $max) ) { ... } #exclusive container,
# $x==$min would be false
# OR
if ( $x in ($min, $max] ) { ... } #mixed ends
[download]
if ($min < $x < $y <$max) { ... }
[download]
I will never understand what is wrong with writing
a simple subroutine like:
sub in_open_range {
my ($x, $min, $max) = @_;
return ($min < $x && $x < $max);
}
[download]
Why do they all want to modify the Perl parser?
Is it not complicated enough?
Christian Lemburg
Brainbench MVP for Perl
Well, I know why I'd like to see it.
One of the reasons I like Perl is its 'humanness', e.g. when I speak to
humans (well, some of them anyway) I can say 'it' or 'those' and they
usually know what I mean and in Perl, of course, we've got $_ and @_.
In short, I like my programming language to be as much like my
speaking language as possible. Us humans have no trouble understanding
what 1 < x < y <= z < 12 means without writing it as a conjunction of
independent order tests: ( 1 < x ) && ( x < y ) ...
Therefore, I wish Perl was such that perl could understand the human
form as well.
Alternately, yes you could write a subroutine but ... then you'd have
to write a subroutine!
I prefer to have the tools I use do as much of my work for me as
possible -- well, all of it actually but that hasn't ever happened yet
and I'm not optimistic. :)
Penultimately, I say it's definitely not complicated enough. When I
can talk to it in English and have it do what I want, then it'll be
complicated'.
Ultimately, since I don't have to write the parser
... :)
Scott
Penultimately, I say it's definitely not complicated enough. When I can talk to it in English and have it do what I want, then it'll be complicated enough.
Well OK then, how does the proposal generalize to things
like this:
$mystery = $a < $b < $c < $d < $f;
[download]
Quick - say: which one is the ternary operator?
Why cause such problems when a little subroutine
is'.
Perl is a language for getting your job done - right.
After writing this little subroutine, the job is done.
Why wait for other people to do jobs for you that you
can do for yourself in 30 seconds.
A < B >= C -> (A < B) && (B >= C)
A > B < C -> (A > B) && (B < C)
[download]
The other common case you
want is that $x is outside some range. So will
people try to write this:
if( $min > $x < $max ) {
which would always be false (provided $min < $max).
Or would you only allow inequalities of the same "direction"
to be clustered together like that? Personally I never use
> nor >= because I find the code
easier to understand when the values are sort left-to-right,
smallest-to-largest. (:
if ($min > $x > $max) { ... }
[download]
unless ($min < $x < $max) { ... }
[download]
See, I told you I can't understand code that uses >. (:
But you just illustrated more problems with this. For
example, your last line should have been:
unless( $min <= $x <= $max )
But I don't find those compelling reasons to not
implement it. If someone actually managed to produce a
patch for this I wouldn't be opposed | http://www.perlmonks.org/index.pl?node=Why%20not%20support%20this%20syntax%3F | CC-MAIN-2015-22 | refinedweb | 600 | 74.19 |
We.
I have a look at the submitted patch for DRLVM (GC write barrier update
patch for DRLVM -), but
seems it's only for interpreter.
If no one complains, I would like to implement the WB4J we are
discussing here in .jet.
As we currently don't have C-based GC with WB support (do we?),
for the first iteration I'm going to instrument code with WB4J in
response to OpenMethodExecutionParams:: exe_insert_write_barriers. can guess what 'src' is - this is the object being written, right ?
But could you please point me what all other args are ?
Can't we go without all the stuff and have only 2 args - an
object being written and the destination class/array/instance ? :-)
--
Thanks,
Alex
>
> Allowing the "java" write barrier to be selected on a method by method
> basis would be very useful for MMTk bring up. The concept is to
> initially run MMTK sort of like a "user mode linux". That is, startup
> the JVM w/o barriers turned on. Run "hello world". Then switch on
> MMTK collector/allocator and Java write barriers and compile/run the
> following method:
>
> public class InitialMMTkBringup {
>
> public int stressTheMMTkAllocator () {
> while(true) {
> Object obj = new Object();
> Object [] ia = new Object[100];
> //at a later stage, add code that causes a write barrier
> //at a later stage, add code that will randomly chain Object
> arrays together...
> }
> }
>
> The above would be running while the underlying JVM GC is running. If
> not careful this could cause lots of confusion. The intention is to
> run MMTk in "user mode" only to the point where MMTk alloc,
> collection, write barrier code paths are exercised. Provided we do
> not do anything to cause the underlying JVM GC to kick in, we should
> be OK.
>
> As a second step actually integrate MMTk into the JVM. Note that
> basic garden variety Java debugger should work w/o modification with a
> "user mode MMTk".
>
>
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There.
The goal of the team that works on the FCL is to provide complete
compatibility between versions of the Framework. You ought to be able to
write an application using version 1.0 of the Framework and run it on
version 1.1 with no problems and vice versa.
Related Reading
.NET Framework Essentials
By Thuan L. Thai, Hoang Lam
If you examine the .NET 1.0 and 1.1 FCLs, you'll find about 1100 API
changes: members, classes, and even entire namespaces added or
removed. The vast majority of these changes consist of adding new things
to the Framework. By definition, these are not breaking
changes. You can't reasonably expect an application that uses a new class
to run using the old FCL. For example, the 1.1 FCL contains the
System.Data.Odbc namespace, which isn't a part of the 1.0 FCL
(though it's available as an add-on). Any code that uses classes from this
namespace won't run on the base 1.0 FCL.
System.Data.Odbc
Breaking changes are more insidious. A change is considered breaking
when code looks like it ought to run on the other version of the
FCL, and is syntactically valid, but behaves differently. These behavioral
changes are further subdivided into backward breaking changes
(which affect a 1.0 application trying to run with the 1.1 Framework) and
forward breaking changes (which affect a 1.1 application trying
to run on the 1.0 Framework).
Comparatively few developers have yet moved on to the new versions
(Visual Studio .NET 2003 and the .NET Framework 1.1). Consequently, most
of us are more likely to hit backward breaking changes than forward
breaking changes. Here are my selections for the backward breaking changes
most likely to cause trouble for the average .NET developer.
1. Internet Security Changes Microsoft has waffled again on the
correct security default for code downloaded from the Internet. In 1.0,
the default security policy never gave code from the Internet permissions
to run. In 1.1 this has been liberalized a bit: code from the Internet
will now run within the constraints of the Internet permission set (which
is pretty constrained but does allow, for example, use of disk files via
the Isolated
Storage mechanism). If you want to tighten up security back to 1.0
levels, you can use the Adjust Security Wizard to move the Internet zone
back to No Trust.
2. Better handling of null defaults in DataSets. In 1.0 there
are times when the DataSet will treat a default value of "" (the empty
string) as a DBNull. In particular, if you serialize the DataSet using
WriteXml() and then deserialize it with ReadXml(), the column default will
magically change to DBNull. In 1.1, the empty string remains as an empty
string. This is obviously the correct behavior, but if you wrote code in
1.0 to catch or depend on the incorrect behavior you'll need to revise
it.
3. New exception from SqlDataReader. In the
System.Data.SqlClient namespace, you construct a SqlDataReader with code
similar to this:
Dim myCommand As New SqlCommand(mySelectQuery, myConnection)
myConnection.Open()
Dim myReader As SqlDataReader
myReader = myCommand.ExecuteReader()
In 1.0 this code would succeed, even if the command was chosen as the
deadlock victim by SQL Server (in the case where there's a locking issue
with another connection, of course). You wouldn't get a SqlException back
until you actually tried to read data from the SqlDataReader. In 1.1 the
ExecuteReader() method can now throw a SqlException. If you've got error
handling that depends on only seeing this particular exception when you're
actually reading data, you'll need to revise the code to move up.
4. HttpWebRequest.MaximumResponseHeadersLength property. This
property is new in version 1.1 of the FCL. As you might guess, it sets the
maximum size of the headers that will be processed with the HttpWebRequest
object. Any response with more than the allowed length will raise an
exception. By default, this is set to 64K. In the 1.0 FCL there was no
limit. This is the sort of change that I used to think would never bring
any grief to anyone. But these days I know that someone, somewhere, is
using HTTP headers to pass truly enormous blocks of information around. If
that someone is you, be sure you set this property in your code to avoid
maddening failures.
5. Dialogs that don't hang. I'm not sure that I can see how
anyone would depend on the 1.0 behavior here, but the potential issue is
so common that it's worth mentioning anyhow. .NET divides threads into UI
interactive (those running on a desktop with a user watching) and non-UI
interactive. In the 1.0 Framework, if you call Form.ShowDialog() or
CommonDialog.ShowDialog() from a non-UI interactive thread, you'll hang
the thread. In 1.1, the method will throw an InvalidOperationException
instead.
6. Environment.UserInteractive now works. Related to the
previous item, the FCL supplies the Environment.UserInteractive property,
which is supposed to tell you whether the current thread is UI
interactive. The problem is that in 1.0 this property returns true whether
the thread is UI interactive or not. In 1.1 this is fixed, and now returns
false if you call it from, for example, a Windows service or XML Web
service. If you're using the ShowDialog() method from arbitrary threads,
it now makes sense to use this property to avoid throwing an exception
when the thread isn't UI interactive.
7. Form Load fixes. There are a pair of changes to the Load
event of Windows forms that are worth knowing about. In 1.0 if you call
Close() from within the Load event of a modal form, nothing happens. In
1.1 the form closes, which is what you'd expect. The second is a fix to a
rather more insidious bug: in 1.0 if a form has an ActiveX control
(remember ActiveX controls?), the Load event doesn't fire. But in 1.1 it
does.
8. Change to WSDL mapping. The Web Services Description Language
Tool (wsdl.exe) is used to create proxy classes for calling web
services. In 1.0, this tool uses System.String as the native data type for
schema elements with a WSDL data type of xsd:anyType. In 1.1, the tool
uses System.Object for this purpose. If you're using the tool to generate
proxies on the fly, or refreshing a Web Reference, you might find that the
proxy class changes from what you expected even though the web service
hasn't changed.
To round out the list, here are a few changes that can make it tough
for 1.1 applications to run on the 1.0 Framework.
9. Improvements to SQL Execution. The 1.0 version of the
SqlCommand object isn't friendly to batched statements. For example, you
might want to execute this set of statements as a single operation:
SET STATISTICS PROFILE ON
SELECT * FROM MyTable
SET STATISTICS PROFILE OFF
In 1.0 an attempt to execute this through a SqlCommand (to return a
second result set with query execution statistics) will always fail. In
1.1 such a batch query will succeed, which saves you from needing to
build a stored procedure to execute it. Of course, once you depend on this
feature, your 1.1 code will no longer work on the 1.0 FCL.
10. TextBox.MaxLength changes. The MaxLength property on a
Windows Forms TextBox control sets the maximum length of text that can be
set via the keyboard or the mouse. Sometimes, though, it's useful to limit
keyboard input and still be able to set the text to longer values
programmatically. In the 1.1 FCL you can use the AppendText() method and
the SelectedText property to work with a strong longer than the specified
MaxLength. In 1.0 this won't work.
It's important to bear in mind that these breaking changes can only
break your applications if you are running with the "wrong" version of the
FCL (that is, the one that you didn't build the application with). By
default, though, 1.1 applications will try to run with the 1.0 FCL, and
vice versa, if the correct version can't be found.
There's a two-pronged strategy you can adopt to deal with this. First,
if you're not positive that your application will run with the other FCL,
simply install the version that you expect. The two versions are designed
to run
side-by-side. They can both be installed on the same computer without
conflicts. This is the best way to handle potential incompatibilities,
especially if you're not sure that your testing has been
exhaustive. Second, you can use XML
binding policy files to specify exactly which versions of which
assemblies your application needs to run. This gives you a way to
precisely specify the behavior that your application should have with the
other FCL.
And finally, don't neglect the underlying lesson here: version
compatibility is never perfect. You'll always need to deal with
issues such as these when some component further down the software stack
than your application gets upgraded. The best developers are those with a
proactive strategy for spotting such issues. If you don't already have a
solid set of unit tests and a good bug-tracking system for your
application, put them in place before the next round of breaking
changes.. | http://archive.oreilly.com/pub/a/dotnet/2003/05/20/fcl_gotchas.html?page=last&x-order=date | CC-MAIN-2015-27 | refinedweb | 1,611 | 67.04 |
pg.
This article is about versions 2.x of pgloader, which are not supported anymore. Consider using pgloader version 3.x instead.
Here’s what the pgloader documentation has to say about this reformat parameter: The value of this option is a comma separated list of columns to rewrite, which are a colon separated list of column name, reformat module name, reformat function name.
And here’s the examples/pgloader.conf section that deals with reformat:
[reformat] table = reformat format = text filename = reformat/reformat.data field_sep = | columns = id, timestamp reformat = timestamp:mysql:timestamp
The documentation says some more about it, so check it out. Also, the
reformat_path option (set either on the command line or in the configuration
file) is used to find the python module implementing the reformat function.
Please refer to the manual as to how to set it.
Now, obviously, for the reformat to happen we need to write some code. That’s the whole point of the option: you need something very specific, you are in a position to write the 5 lines of code needed to make it happen, pgloader allows you to just do that. Of course, the code needs to be written in python here, so that you can even benefit from the parallel pgloader settings.
Let’s see an reformat module exemple, as found in
reformat/mysql.py in the
pgloader sources:
# Author: Dimitri Fontaine <[email protected]> # # pgloader mysql reformating module # def timestamp(reject, input): """ Reformat str as a PostgreSQL timestamp MySQL timestamps are like: 20041002152952 We want instead this input: 2004-10-02 15:29:52 """ if len(input) != 14: e = "MySQL timestamp reformat input too short: %s" % input reject.log(e, input) year = input[0:4] month = input[4:6] day = input[6:8] hour = input[8:10] minute = input[10:12] seconds = input[12:14] return '%s-%s-%s %s:%s:%s' % (year, month, day, hour, minute, seconds)
This reformat module will
transform a
timestamp representation as issued by
certain versions of MySQL into something that PostgreSQL is able to read as
a timestamp.
If you’re in the camp that wants to write as little code as possible rather than easy to read and maintain code, I guess you could write it this way instead:
import re def timestamp(reject, input): """ 20041002152952 -> 2004-10-02 15:29:52 """ g = re.match(r"(\d{4})(\d{2})(\d{2})(\d{2})(\d{2})(\d{2})", input) return '%s-%s-%s %s:%s:%s' % tuple([g.group(x+1) for x in range(6)])
Whenever you have an input file with data that PostgreSQL chokes upon, you can solve this problem from pgloader itself: no need to resort to scripting and a pipelines of awk (which I use a lot in other cases, don’t get me wrong) or other tools. See, you finally have an excuse to Dive into Python! | https://tapoueh.org/blog/2011/08/pgloader-reformating/ | CC-MAIN-2022-27 | refinedweb | 481 | 58.92 |
>>
Number of Integral Points between Two Points the finds the number of integral points between the given two points.
The number of points between two given points will be gcd(abs(x2), abs(y1-y2)) - 1.
If the line joining is parallel to x-axis, then the number of integral points will be abs(y1 - y2) - 1.
If the line joining is parallel to y-axis, then the number of integral points will be abs(x1 - x2) - 1
If the x points of both points are equal, then they are parallel to the x-axis. If the y points of both points are equal, then they are parallel to the y-axis.
Let's see an example.
Input
pointOne = [1, 5] pointTwo = [1, 3]
Output
1
Algorithm
- Initialise two points.
- Check whether they are parallel to x-axis or not.
- If they are parallel to the x-axis, then use the formula abs(y1 - y2) - 1.
- Check whether they are parallel to y-axis or not.
- If they are parallel to the y-axis, then use the formula abs(x1 - x2) - 1.
- If they are not parallel to any of the axes, then use the formula gcd(abs(x1-x2), abs(y1- y2)) - 1.
- Compute the result and print it.
Implementation
Following is the implementation of the above algorithm in C++
#include <bits/stdc++.h> using namespace std; int gcd(int a, int b) { if (b == 0) { return a; } return gcd(b, a % b); } int getCount(int pointOne[], int pointTwo[]) { if (pointOne[0] == pointTwo[0]) { return abs(pointOne[1] - pointTwo[1]) - 1; } if (pointOne[1] == pointTwo[1]) { return abs(pointOne[0] - pointTwo[0]) - 1; } return gcd(abs(pointOne[0] - pointTwo[0]), abs(pointOne[1] - pointTwo[1])) - 1; } int main() { int pointOne[] = {1, 3}, pointTwo[] = {10, 12}; cout << getCount(pointOne, pointTwo) << endl; return 0; }
Output
If you run the above code, then you will get the following result.
8
- Related Questions & Answers
- Program to find out the number of integral coordinates on a straight line between two points in Python
- Prime points (Points that split a number into two primes) in C++
- C program to calculate distance between two points
- Find number of endless points in C++
- Shading an area between two points in a Matplotlib plot
- Program to Find the Shortest Distance Between Two Points in C++
- How do you create line segments between two points in Matplotlib?
- Finding distance between two points in a 2-D plane using JavaScript
- Minimum number of points to be removed to get remaining points on one side of axis using C++.
- Number of ordered points pair satisfying line equation in C++
- Count of obtuse angles in a circle with ‘k' equidistant points between 2 given points in C++
- Closest Pair of Points Problem
- Collect maximum points in a grid using two traversals
- Reaching Points in C++
- C++ Program to Find Number of Articulation points in a Graph | https://www.tutorialspoint.com/number-of-integral-points-between-two-points-in-cplusplus | CC-MAIN-2022-40 | refinedweb | 484 | 63.63 |
CodePlexProject Hosting for Open Source Software
Hello,
I am pretty new to Visual Studio, I have just installed VS2010 Integrated shell and decided to give it a try as an IDE for working with Python.
I had Python 2.7.2 installed on my machine, along with IPython 0.10.2 (from a Python distro), and and then installed Python Tools for Visual Studio. When I try to execute some simple code I get the following error message:
Python interactive window.
Type $help for a list of commands.
Resetting execution engine
Failed to launch REPL process
Exception AttributeError: AttributeError("'NoneType' object has no attribute 'platform'",) in <function _remove at 0x01D123B0>
Unhandled exception in thread started by <bound method BasicReplBackend._repl_loop of <__main__.BasicReplBackend object at 0x01C9DF90>> ignored
Traceback (most recent call last): File "C:\Program Files\Microsoft Visual Studio 10.0\Common7\IDE\Extensions\Microsoft\Python Tools for Visual Studio\1.1\visualstudio_py_repl.py", line 135, in _repl_loop
close failed in file object destructor:sys.excepthook is missinglost sys.stderr
In the end I get the actual output of my code (some prints to see if the code is running). Any idea why I get this error message and how do I get rid of it?
Thanks.
Have you customized site.py in anyway or done something to make IPython the default? If you start a normal interpreter in a console window and do:
import sys
sys.platform
Do you get something outputted or do you get an exception?
Also, to enable IPython in VS you'll need to go to Tools->Options->Python Tools->Interactive Windows, select Python 2.7, and make sure IPython mode is selected for the interactive mode. Also you may need to install pyzmq, but I'm guessing
we'll need to get you past this first exception either way.
thank your for your fast reply. I did not have much time available since then to go through this issue (I am not a professional programmer) but I did find out that I needed to install the Python modules in Windows Vista as a machine administrator. Apparently
the VS2010 Integrated Shell + PTVS1.1 now works ok most of the times although when I do a reset of the Python2.7 interactive window I still get error messages from time to time. I get the impression that they are related to a startup script but I do not know
if it exists nor do I know where it is located.
Regretably, I have not been able to install IPython on my machine so far so I decided to drop it for the time being. I would like very much to use it both as a standalone application and inside VS2010 Integrated Shell. Got any clues as to how I can
install it in Windows Vista? Apparently there is bug with the installer...
Are you sure you want to delete this post? You will not be able to recover it later.
Are you sure you want to delete this thread? You will not be able to recover it later. | https://pytools.codeplex.com/discussions/353609 | CC-MAIN-2016-44 | refinedweb | 512 | 74.49 |
Interface to Tektronix Scope
Project description
Overview
This package can be used to record data from a Tektronix scope.
Installation
You need first to install the PyVISA package. To install PyTektronixScope, download the package and run the command:
python setup.py install
You can also directly move the PyTektronixScope directory to a location that Python can import from (directory in which scripts using PyDAQmx are run, etc.)
Sources can also be download on the PyTektronixScope github repository.
Usage
Typical usage:
from PyTektronixScope import PyTektronixScope scope = TektronixScope(instrument_resource_name) X,Y = scope.read_data_one_channel('CH2', t0 = 0, DeltaT = 1E-6, x_axis_out=True)
Please send bug reports or feedback to Pierre Clade.
Version history
Main changes:
- 0.1 Initial relase
- 0.2 Update to new version of visa
Project details
Release history Release notifications
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/PyTektronixScope/ | CC-MAIN-2019-30 | refinedweb | 151 | 50.02 |
Details
- Type:
Bug
- Status: Closed
- Priority:
Major
- Resolution: Fixed
- Affects Version/s: 1.1.3
-
- Component/s: Injection and Lookup
- Labels:None
Description
Expected behaviour: beanManager.getBeans(Object.class, new ServiceQualifier()) finds all beans that are qualified as "Service", regardless of the beans implementation type
Effective behaviour: The BeanManager fails if a base type (Object in this example) is provided instead of a leaf type. In theses cases, the BeanManager finds the Alternative beans only and forgets about all beans that lack of an Alternative
Reason: The BeanManager's helper org.apache.webbeans.container.InjectionResolver fails in method implResolveByType method as it can not handle collections of beans of different types. It treats all beans as if they where of the same type (and therefore have the same Alternative)
Activity
- All
- Work Log
- History
- Activity
- Transitions
oki, back from talking with Pete. 5.1 defines 'available for injection' and 11.3.4 specifies that getBeans() only returns beans which are available for injection.
getBeans(TypeX) only resolves beans which are enabled for filling an InjetionPoint of TypeX!
> beanManager.getBeans(BaseBean.class, new ServiceQualifier()) should return MyBeanA and MyBeanBAlt
nope, because MyBeanBAlt is also an @Alternative for MyBeanA. (because of the extends BaseBean).
MyBeanBAlt + MyBeanA would only be returned if MyBeanBAlt would NOT extend BaseBean.
And yes, filter criterias are a region where we certainly need to take care off in the spec. I'm also not 100% sure if BeanManager#getBeans() or BeanManager#resolve() should perform this part of the filtering. I'll discuss this with the colleagues in the EG.
Our case is even simpler than the one you described:
>public class @Service MyBeanA extends BaseBean implements A ...
>public class @Service MyBeanB extends BaseBean implements B ...
>public class @Service @Alternative MyBeanBAlt extends BaseBean implements B ...
beanManager.getBeans(BaseBean.class, new ServiceQualifier()) should return MyBeanA and MyBeanBAlt
I understand that it is quite hard to define for which bean type filter criteria an alternative should be evaluated or not. For example:
>Example 1: beanManager.getBeans(Object.class)
>Example 2: beanManager.getBeans(BaseBean.class)
>Example 3: beanManager.getBeans(A.class)
>...
One solution could be to return all matching beans (inclusive alternatives) if the bean type filter criteria is not an interface (examples 1 and 2). For example 3, the alternatives for A are evaluated.
Please put some ham in it. I need either a concrete example or a unit test which shows what is wrong.
The constellation you reported initially (query for Object.class + Classifier) works now, isn't?
If so then please create a follow up issue and set this one to resolved.
The reason is that I like to start the 1.1.4 release tonight, and it is impossible to track those issues otherwise.
I tested the 1.1.4-SNAPSHOT and found the results promising but by far not "fixed". Therefore I'd like to reopen this issue.
can you please try with the latest SNAPSHOT? The behaviour is not yet final as we need to specify the correct behaviour in the EG first.
This might need some bigger change. In case of an isAlternative(), we should also store for which types! This is typically needed if a
> public class MyBean implements ServiceA, ServiceB {};
> public class @Alternative MyAlternative implements ServiceA
Thus for
> private @Inject ServiceA a;
you will get an instance of MyAlternative.
But for
> private @Inject ServiceB b;
you will get an instance of MyBean.
txs 4 the report! I'll dig into this in the next few days. In any case before our upcoming 1.1.4 release.
released with
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I'm trying to set up a looping walk cycle from Blender in Mecanim. It appears to be fine but I'm getting this alert in the console:
MuscleClip 'Prototype'conversion warning: 'metarig/Hips_Main/Hips/Leg_Upper_L' has translation animation. It is not supported.
Like I said, the animation appears to have been imported accurately but what exactly is this alert trying to tell me?
Anyone have any input? From more observation, it appears as if the up and down movement of my character's hips bone is not being carried over into Unity
Just had the same issue. Looking for solutions as well.
I'm betting you have two hip bones with no Control bone. Under this setup, the hip rotations are ignored and translate as some funky leg movement.
I'm getting this warning on the L_Leg too, I was using Maya's Human IK systeme. Did you find any solution as to stop the warning?
Answer by Rosie-Posie
·
Dec 16, 2014 at 04:53 AM
Hi guys, the solution I found for this was to force the baking of my animation in maya ( I dont know about blender or anything, but I imagine you can do that too). Basically don't rely on the baking done when you export you FBX. I was using Maya's Human IK and I found that as soon as I backed the animations from my controllers to my bones, I was fine. It kind of sucks, since this means you will constantly need to animate, bake, export, and undo once its exported in order to keep your animations on your controllers. But i'm sure there's a way to write up a script and automate this.
I hope this helps!
Answer by fredlierman1
·
Jul 19, 2018 at 04:09 PM
import the fbx, (or your original rig) and remove all "location" and "scale" keyframes from all bones except your root bone. re-import and set to humanoid with DOF enabled.
That worked for me. A bit cumbersome.
Crazy Mecanim Glitch
1
Answer
Weird issue with Blender animation running riot in Unity
2
Answers
Mecanim animation importing
2
Answers
Confused on importing animated model from Blender
0
Answers
how to import animation from blender to unity?
0
Answers | https://answers.unity.com/questions/689267/conversion-warning-has-translation-animation-it-is.html | CC-MAIN-2019-47 | refinedweb | 377 | 71.85 |
Episode 162 · December 20, 2016
We build a basic API and talk about the differences between a regular Rails controller and an API
What's up guys, this episode, we're going to build our very first API, and talk about all the little details that you will need to be concerned with when you're building out your own API's. First off, let's start by creating a new application called weather. What we'll do is we'll build a little bit of a weather service. So you might imagine that your iPhone has to hit the server to get the current temperature when it displays that, so we'll be building that server for recording and extracting the current temperature for these locations. So our application is going to require a couple things. They'll have a location model, every location will have a name. Ideally, you would also add geolocation to this, so that your location can be searched upon, so wherever you are currently at on your phone, you could search for the closest city or something like that and return the temperature for that, but for our case, we're going to keep this simple and start with just a name. Then we also need a model for the actual temperature and status of the location, so we'll just have like a recording model
rails g model Recording location:references temp:integer status
rake db:migrate
We can open this up, and maybe go into our db/seeds.rb, to set up some example data. So here we might say
l = location, and
l.recordings.create(temp: 32, status: "cloudy"). So maybe we also add some historical data in here, so maybe it was a little warmer before. Maybe it got a little colder, to 28 degrees, and went really cold to 22, and it was kind of alternating between rainy and cloudy, but then it became sunny and 22 degrees out.
db/seeds.rb
l = Location.create(name: "New York City") l.recordings.create(temp: 32, status: "cloudy") l.recordings.create(temp: 34, status: "rainy") l.recordings.create(temp: 30, status: "rainy") l.recordings.create(temp: 28, status: "cloudy") l.recordings.create(temp: 22, status: "sunny")
We can have our data like this, obviously, you would want to record the actual time stamps for each of these days, or temperatures or whatever, if this is checked hourly or in a minute basis. You can go and also set the "Created at" on this, we're just going to create all of these at once, and we'll order them by id rather than "Created at", so that we can see them in order. We need to set a location.rb to
has_many :recordings, then we can hop into our terminal, and
rake db:seed to add those to our database, and if we load up our Rails console, we should be able to see
Location.last.recordings.last, and that should give us that temperature of 22 and sunny, and it does. So that means that our database is all set up, so now we need to go into our application and start building our API. The way we're going to do this, is by going into our config/routes.rb, and we're going to add a namespace in here for the API, and the reason why we want to use a namespace here, is because we can then define our resources routes for locations, and underneath them, we can also say:
resources :recordings, so that you could grab, say historical data or whatever, and that will separate those out from
resources :locations down here, which might be for the browser to load up the html page for it instead. So our API can be designed in a separate folder, and that will serparate out the controllers, and the views for it, in case you're using jBuilder to render the JSON for the API.
This allows us to have those two separate sections of our routes that are specific to the API, and we can contain that all in the same Rails app, which can be nice. Now the other thing that I want to add here is another namespace though for version one, so that we can begin versioning our API. There are a lot of different ways that you can go about versioning. Stripe has a really interesting one where it records the current version of the API, and then it saves it to your count so that it automatically remembers that version, which is pretty neat. A more typical, simpler approach. The reason why you would want to version your API is that you may not control all of the code in one app, so when you deploy your Rails app, your mobile app might be separate, and if it hasn't been updated at the exact same second as your Rails app, then your users will probably see breaking stuff. So that might mean that logins don't work, or they can't pull the weather or any of that stuff, and that would be really bad. So you need to do it in versions, so that you can say: Ok, this version has this functionality, the mobile app can implement that, but when we want to change it, we roll out a new version, and then once that is rolled out, then our mobile app can opt in using the new version. Now this is important for your own kind of separate teams, so maybe your mobile app is a separate development team than your Rails app, you can deploy those independently, but this also becomes incredibly valuable when you have other random people building against your API. So if you have a public API that anyone can use, you don't want to go break their code, so you need to version it, so that they can choose to upgrade versions, and you can communicate to them while we rolled out version three, so we're turning off version one at this date, so make sure that you upgrade if you no longer want to support it. Versioning is going to be important, we'll talk about that more in the future. Stripe has some really really interesting approaches to that, which I want to talk about when we get around to talking about versioning more, but this is all we really need to do to create our routes. So let's go into builing our resources.
Right before we do that, let's take a look at
rake routes, this is going to show us that our URL's api/v1/locations/:location_id/recording(.:format), and the namespace actually creates folders for our controllers and our views for these in the API. So that means that our controllers are going to be a little bit different than normal, we're going to create a directory inside of app/controllers, and we'll call it app/controllers/api, and then we'll make a directory called app/controllers/api/v1/locations_controller.rb, and this will be the file that we will edit. So let me open that up, and we'll have our API v1 locations controller. This will just inherit from application controller as normal, and we will have our show action, this would request for a specific locations temperature, so we'll use that, we will have
before_action :set_location, just like you normally would expect in a regular rails controller. We'll have set_location, this is going to grab it by the id, so we'll have
@location = location.find(params[:id]), and then really all we need to do is build our view for this. So we need to make a file called
app/views/api/v1/locations/show.json.jbuilder
which is built into rails, and it gives you the ability to say
json. attribute name that you want, so you could say
json.id @location.id json.name @location.name
and then you can have anything you want, like a block, and this could be the current recording temperature, so we might say here
json.current do json.temp @location.recordings.last.temp json.status @location.recordings.last.status end
This is a way for you to kind of define your JSON output visually in a structure, which is kind of nice, and this structure allows us to actually put our JSON formatting into the views folder, which can kind of organize this a little bit nicer for us in some cases. Now you could also do this and just say
render json and create a hash in here and return the exact same format of the hash, so say:
def show render json: { id: @location.id, name: @location.name }
where you could replace the format with just a regular old ruby hash. The nice part about this is that rails knows that we are looking for the JSON type of file format when we request this, so we can just define it in our views folder, and it will figure out how to render that for us. Now let's start our rails server, and try this out in the browser. Now the reason why this works nicely in our browser is because we don't actually have any authentication yet, so we're not passing in a token, we can just load it up in our browser and see our JSON as we created it.
As you can see, jBuilder effectively just built a hash, and then it's in json format, and our browser can then parse that out into an object in JavaScript. What's really neat about this is that now that we have this URL, we can go into anything we want, we could go into Python or Swift or Android or ruby or JavaScript, and we can hit that URL, and we can grab that data. So even if we were in bash, and we wanted to run curl, we can grab the data in a curl request, and then parse that string response as JSON, and then our bash code could even have access to that. So you can build your own stuff to consume this API now, and if it ever changed, maybe the format changes, so we don't have current anymore or something. Then you could update the version, and that's really the only difference that you would need to change. And the other cool thing about this, is if you notice, this code is nothing special to API's, the only thing that we did, was we introduced a version, but the rest of this code is very very much your standard Rails controller code, the output of the show action is in JSON jBuilder format, which is fairly common, if you happen to write JavaScript, to make an AJAX request to load up some data dynamically rather than HTML. So this is almost exactly what you would normally write, and I wanted to point that out, because there's a lot of confusion between how do I write regular Rails code, I need to write an API, and it seems like it's a different thing. It's really not a different thing, it just has chosen to use a little bit different authentication, which we haven't talked about yet, it uses versioning, and it uses JSON, and this is really not a whole lot more that's specific to API's they are really pretty much the same, as building your normal Rails app.
With that said, there are important details that we do need to take into account to build an easy to work with API. For example, if we were to remove .json as the format, we're going to ge an error "unknown format". The reason for that is because, well, we didn't specify the extention in the URL. If our API is always going to return JSON, or is the default, we might as well force our controller to make sure that it uses JSON all the time.
One of the ways we can do that, is we can build our own API controller
app/controllers/api_controller.rb
class ApiController < ApplicationController before_action :set_default_format private def set_default_format request.format = :json end end
And override whatever is in the url. That way, we always have that format, and we can say that ApiController cotroller is the class that we inherit from now from all of our API controllers.
That way is is kind of acting as the parent, and enforcing all these kind of defaults upon all of your API controllers. That is nice, because now we can request this without .json, and we're going to get the expected result every time. The trouble with that is course, if you wanted to support other formats, like XML, it is not going to work, but you can just simply tweak this code to say: Well if it's XML, leave it, if it's anything other than XML, leave it, if it's anything other than XML, force it to JSON, and that will work.
That's it for this episode, we are going to be diving into authentication, formatting your JSON in a better format than just kind of arbitrary formats, we'll talk about more versioning, error handling, and a lot more in the next episode. So I will talk to you then.
Transcript written by Miguel
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Strong Name (further referred to as "SN") is a
technology introduced with the .NET platform and it brings many possibilities into
.NET applications. But many .NET developers still see Strong Names as security
enablers (which is very wrong!) and not as a technology uniquely identifying
assemblies. There is a lot of misunderstanding about SNs (as we could see
in the article "Building
Security Awareness in .NET Assemblies : Part 3 - Learn to break Strong Name .NET Assemblies
") and
this article attempts to clear those up. Now let's see what SNs are, what we
can use them for and how they work.
Strong Name is a technology based on cryptographic
principles, primary digital signatures; basic idea is presented in the figure
below:
At the heart of digital
signatures is asymmetric cryptography (RSA, EL Gamal), together with hashing
functions (MD5, SHA). So what happens when we want to sign any data? I'll try to
explain what happens in the figure above.
First we must get a public/private
key pair (from our administrator, certification authority, bank, application
etc.) that we will use for encryption/decryption. Then DATA (term DATA
represents general data we want to sign) is taken and run through some hashing algorithm
(like MD5 or SHA - however, MD5 is not recommended) and hash of DATA is
produced. The hash is encrypted by private key of user A and attached to
plaintext data. The DATA and attached signature are sent to user B who takes
public key of user A and decrypts attached signature where hash of DATA is stored
and encrypted. Finally user B runs DATA through the same hashing algorithm as
user A and if both hashes are the same then user B can be pretty sure that the DATA
has not been tampered with and also identity of user A is proven. But this is a
naive scenario because it's hard to securely deliver public keys over insecure
communication channels like Internet. That is why certificates were introduced
but I will not cover it here because certificates aren't used in SNs and
delivery of public key is a matter of publisher's policy (maybe I can cover
distribution of public keys, certificates and certification authorities in another article). Now let's assume that public key was delivered to user B
securely.
This process is used in the
creation of SN for .NET applications. You can translate term DATA as
assemblies and apply the same steps to them when SNs are used. But what is the
purpose and usage of this SN technology? Simple - there is the only one reason –
to uniquely identify each assembly. See section 24.3.3.4
of CLI ECMA specification where SNs are defined:
This header entry points to
the strong name hash for an image that can be used to deterministically
identify a module from a referencing point (Section 6.2.1.3).
SNs are not any security
enhancement; they enable unique identification and side-by-side code execution.
Now we know that SNs are not
security enablers. Where to use them then? We can see two scenarios where SNs
can be used:
Versioning solves known problem called
as "DLL hell". Signed assemblies are unique and SN solves problem with
namespace collisions (developers can distribute their assemblies even with the
same file names as shown of figure below). Assemblies signed with SNs are
uniquely identified and are protected and stored in different spaces.
In addition to collision
protection, SN should help developers to uniquely identify versions of their
.NET assemblies.
That is why when developers want
to use GAC (Global Assembly Cache) assemblies must be signed to separate
each publisher's namespace and to separate each version.
The second important feature of
Strong Names is authentication; a process where we want to ensure ourselves
about the code's origin. This can be used in many situations, such as assigning
higher permissions for chosen publishers (as will be shown later) or ensuring
that code is provided by a specific supplier.
It has been shown that signatures
and public keys can be easily removed from assemblies. Yes, that is right but
it is correct behavior even when we use digital signatures in emails or
anywhere else! Let's see how it works!
We can use some analogy from our
real life. Let's assume you are a boss of your company and you are sending an
email to your employees where new prices of your products are proposed. This
email is a plaintext and you use some non-trusted outsourcing mailing services.
Your communication can be easily monitored and your email can be easily accessed
by unauthorized persons who can change its content, for instance your prices
proposed in email.
How to solve that? The answer is cryptography,
again digital signatures that you can use to authenticate to your employees and
to verify content of your email. Simply you have to add a digital signature to
your email and then require your employees will trust just verified
emails that have your valid digital signature. Let's assume that all PKI
infrastructure is set up and working correctly. Now, when an intruder removes
the digital signature from your email, his employees will not trust them
because they can't be verified and application will alert users about this insecure
state.
The same situation is when SNs
are used. You can remove SNs from assemblies , but this makes no sense because just
as in the case of emails, assemblies without SNs can't be trusted when
environment is set up to require those digital signatures or SNs.
This is also related to another very
important point in .NET – Code Groups & Policy Levels. As in
the case of emails, when PKI is setup in a company and security policy is defined that
employees can't trust and verify emails which are not signed or where the encrypted
hash value is different from hashed plaintext content. The same can be done
with .NET Framework using the .NET Configuration tool on each machine or
by group policy for large networks.
This tool provides configuration
options for .NET Framework including Runtime Security where policy
levels and code groups can be set. Policy levels work on
intersection principle as shown in the figure below
Code groups (inside of those policy
levels) provide permission sets for applications that belong to them according
to their evidence (origin, publisher, strong name etc.). The assembly will get
those permissions based on the intersection of code groups from each policy
level applicable to it. This is a very important improvement in security
architecture and improves the traditional Windows security model that is process
centric (see figure below).
.NET introduces Code Access
Security (CAS) which is used to identify the origin of code and assign to it specific
restrictions and then make security policy more granular and protecting against
attacks such as luring attacks.
However my intention isn't to
describe CAS or Windows security internals (I can write about it in other
articles) but show SN principles. Let's move back to it!
Now we can move to the second use
for SN - administrators and developers can use SNs together with code groups to
provide assemblies with higher permissions (not the default ones that assembly
will acquire according to default .NET Framework settings). Let's see an
example! I must point out that this is just a simplified example how SN can
identify publisher, this is NOT a way to obey CLR security or how to use it
in enterprise environment. That is why please try to understand the example
as a general principle available with SNs but NOT as a design pattern!
Usage of SNs as authentication is a more complex problem and there are many
non-trivial issues when SNs are involved. But it's out of scope of this article,
so now back to the sample!
Take my sample Windows Forms
project and rebuild it and put .exe file on any share on your LAN. Then try to
start this application from this share and click on button – what happens? A security
exception is raised because application doesn't have enough privileges.
Now go to .NET Configuration tool
and add a new code group
add new code group called Test
and in the second dialog choose Strong name, click on
Import button and locate the .exe file in Debug folder of project folder and
finally assign full trust for this application
Now you have created a new code group containing just
your sample application. Now go to your network share and try to start sample
application again. And it works! Why? Because it belongs to our new code group Test
with full trust permissions.
Now remove SN from sample application (as described in his article or just
simply remove attribute [assembly: AssemblyKeyFile("KeyFile.snk")]
from AssemblyInfo.cs file), recompile and publish it on share. Try to
run it and what happens? It's not working! Why? Because assembly can't show this
strong name evidence and it belongs to the default code group (with limited
privileges) now.
It's not surprising, nothing special, no magic – just
correct usage of Strong Name technology. SNs are easy and powerful but
we have to understand how and where to use them. That is why I want to
outline some "issues" that are connected with SNs that will present all
capabilities that we can expect from SNs.
So what are the weaknesses of SNs? First we have to realize
that SNs are a lightweight version of Authenticode and they provide fast and easily
used technology to get enterprise features like versioning and authentication.
But this ease of use must be paid by something and here goes a list of
disadvantages:
Authenticode can be considered as more powerful from an enterprise
and architectural perspective. So why not use Authenticode instead of SNs?
Here are the reasons:
I hope this helps you understand the strong name technology in
the .NET Framework, and helped you see that it is very powerful, but with defined
limits. It is a technology that should be used appropriately.
With SNs we can uniquely identify an assembly and run
side-by-side our assemblies. Security scenarios are not recommended to be used
with Strong Names (even when it's supported by .NET Framework), just in case
you are advanced in security and working with certificates and key management.
There are many design patterns on how to use Strong Names and all this depends on
application architecture, client requirements and infrastructure settings
(Active Directory, PKI etc.).
There could be much more written about it (like usage of SNs
in large companies, problems with key distribution, etc.), but this was not
intended for this article, it was just a reaction to some misinterpretation of
this technology and the article is intended to put it right.
This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.
A list of licenses authors might use can be found here
Public Shared Function IsSigned(ByVal assemblyFilename As String) As Boolean
Dim asm As System.Reflection.Assembly = System.Reflection.Assembly.ReflectionOnlyLoadFrom(assemblyFilename)
For Each obj As Object In asm.Evidence
If TypeOf obj Is System.Security.Policy.StrongName Then
Return True
End If
Return False
End Function
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Odoo Help
Odoo is the world's easiest all-in-one management software. It includes hundreds of business apps:
CRM | e-Commerce | Accounting | Inventory | PoS | Project management | MRP | etc.
How to give discount on the total of a Sales order
Hello,
In sales order, we can give discount on per line basis. What about the discount on the total figure? Sometimes we give a lump sum discount on the sales order, without that, we need to adjust discount on each line.
Thanks.: Discount Sales / Invoice
Hope this can help you .... I have coded a little function (apply_discount) in a inherited class of sale.order
def apply_discount(self, cr, uid, ids, discount_rate): cur_obj = self.pool.get('res.currency') res = {} line_obj = self.pool.get('sale.order.line') for order in self.browse(cr, uid, ids, context=None): for line in order.order_line: line_obj.write(cr, uid, [line.id], {'discount': discount_rate}, context=None) return res
I have added a new column to the new inherited sublass of sale order
'discount_rate' : fields.float('Discount rate'),
Then in the sale order view (a inherited one) I have placed the new field (discount) on the sale.order.view and I have fired an event on the "on_change" of the value passing the self value of the field to the "on_change" event
<field name="discount_rate" on_change="apply_discount(discount_rate)"/>
In this way you can apply discount sequentially to the rows of the order without altering the normal process of OpenERP
Hi, great answer Alessandro, I have Open ERP online and I am new in this, where do I go to insert the code that you mentioned? Thanks!
Hello
I have developed one module which set a discount on whole sale order and customer invoice with fixed and percentage vise. when your quote will move to invoice that same discount and total will move to the invoice I think this module feature will helps you more can see on : To get the module can contact me: dsouzajoseph199@gmail.com
Good to your video in Youtube regarding discount. Can you share your module with me?
Hi Joseph, I just viewd your video on youtube, it's really great work!, I'm really interested in this feature and wonder if possible to get the module as indicated in your post. Thanks
Hi Joseph, I saw your video good work can I get those module please to work with Odoo discount feature.
Good work Joseph. I am wondering how you are dealing with accounting entries? Are you creating accounting entries based on discounted amount?
Here are some approaches:
- You can try to use module additional_discount. But when reading the comments it seems that the module is not as stable as it should be.
- You can set the same discount in every line
- You can use a separate Discount product and give it a negative unit price. This solution would give an absolute discount instead of a relative.
how do you manage the tax (VAT) issue with a global discount, specifically when your invoice is made with products having different tax percentages?
VAT is applied to the single net price discounted or not ....
In order to give discounts on the whole order, you have to use pricelists.
You can find them under: Sales -> Pricelists under the text 'Configuration' -> Pricelist
NB:
If you do not have 'Configuration', give the user the access rights 'Technical Features'
If you do not see Pricelist, give the user the access rights 'Sales Pricelists'
Now you can create a new pricelist, which you probably want to base on the default pricelist. I use in the title of the pricelist the amount of discount I give (5% discount, 10% discount, ....). Play around to find the correct value(s).
In the order it is important to change the pricelist, before adding any products, otherwise the discount is not calculated.
Important notice:
When using a discount like this, it will not show up on the discount line, but it will change the value of the product, so an article costing â¬10, and using a discount of 10% will show with a costprice of â¬9.
The problem with pricelists is that the customer doesn't see the discount. So even though he received a discount, the customer may still ask for a discount, because he can't see that he already received one. My advice is to make a custom module for this. That's what we did.
Same here, only issue we had was to find the original price, as there are different 'base' prices, depending on the currency. And for some exeptions, the base price is different than all the other base prices.... But I fixed it.
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Hello ! Is pricelist feature helpful for you ? But again its on particular line only., Discount on total for sale order and invoice too. | https://www.odoo.com/forum/help-1/question/how-to-give-discount-on-the-total-of-a-sales-order-6600 | CC-MAIN-2017-22 | refinedweb | 827 | 72.16 |
Advertisement
In this blog, we will learn the edge detection in OpenCV Python using Canny’s edge detection algorithm. Edge Detection has great importance in computer vision.
Edge Detection deals with the contours of an image that is usually denoted in an image as an outline of a particular object.
There’s a lot of edge detection algorithms like Sobel, Laplacian, and Canny.
The Canny Edge Detection algorithm is the most commonly used for ease of use as well as the degree of accuracy.
Imports for Canny Edge Detection OpenCV Algorithm
import cv2 as cv
import numpy as np
from matplotlib import pyplot as plt
Composition of Canny Edge Detection
The Canny edge detection OpenCV algorithm is composed of 5 steps:
- Noise Reduction – If noise is not removed it may cause the image to detect incorrect edges.
- Gradient Calculation
- Non-maximum Suppressions
- Double threshold
- Edge Tracking by Hysteresis
Canny Edge Detection Code
First of all, the image is loaded into a variable using the OpenCV function
cv.imread(). The image is loaded in Gray Scale as edges can be easily identified in a grayscale image.
The
canny() function takes 3 parameters from the user.
First the image, then the threshold value for the first and second.
The Edge Detection relies on the threshold values and so the values are identified by shuffling the threshold values together.
After canny edge detection is over we store the title and images in separate arrays and display them using
plt.subplot() function present in the matplotlib library.
def canny(): img = cv.imread("./img/image.jpg", 0) canny = cv.Canny(img, 150, 200) title = ["Original Image", "Canny"] images = [img, canny] for i in range(len(images)): plt.subplot(2, 2, i+1), plt.imshow(images[i], 'gray') plt.title(title[i]) plt.xticks([]), plt.yticks([]) plt.show()
Edge Detected Image
Learn More Python OpenCV topics like lane detection OpenCV python, line detection, etc.
Get the full source code of all OpenCV projects from the Github page. | https://hackthedeveloper.com/canny-edge-detection-opencv-python/ | CC-MAIN-2021-43 | refinedweb | 331 | 55.95 |
What I want to do is to insert a blank line every 6 lines in the print out, here is what I have:
// This program produces a loan amortization
#include <iostream>
#include <iomanip>
#include <cmath>
#include <fstream>
using namespace std;
int main()
{
ofstream outfile("A:Mort.txt");
char name[31];
float loan, rate, years, balance, term, payment;
cout << "Enter the name of the mort. recipant. ";
cin.getline(name, 31);
cout << "Loan amount: $";
cin >> loan;
cout << "Annual Interest Rate: ";
cin >> rate;
cout << "Years of loan: ";
cin >> years;
term = pow((1 + rate / 12.0), 12.0 * years);
payment = (loan * rate / 12.0 * term) / (term - 1.0);
outfile.precision(2);
outfile.setf(ios::fixed | ios::showpoint | ios::left);
outfile << "The loan belongs to : " << name << endl;
outfile << "Monthly payment: $" << payment << endl;
outfile << endl;
outfile << setw(10) << "Pay. No.";
outfile << setw(10) << "Interest";
outfile << setw(10) << "Principal";
outfile << setw(10) << "Balance" << endl;
outfile << "-------------------------------------\n";
balance = loan;
for (int month = 0; month < (12 * years); month++)
{
float minterest, principal;
minterest = rate / 12 * balance;
principal = payment - minterest;
outfile << setw(10) << (month + 1);
outfile << setw(10) << minterest;
outfile << setw(10) << principal;
outfile << setw(10) << balance << endl;
balance -= principal;
}
outfile.close();
return 0;
}
So I was thinking I would add :
if ((month%6)==0)
outfile << "Question how do you display a blank line?" ;
For some reason I can't remember how to display a blank line
TIA
Bill | http://cboard.cprogramming.com/cplusplus-programming/1991-how-do-you.html | CC-MAIN-2014-42 | refinedweb | 228 | 66.07 |
These are chat archives for opal/opal
module.exportsin opal? I've tried backticking it like
module.exports = MyRubyViewbut that throws an error in the compiled js: "import and export may only appear at the top level". Googling various opal/export/modules failed, so I thought I might ask here :)
$'s?
@scally Ah, I think I see what you mean. You want to be able to do something like this?
class Foo def bar end end `module.exports = #{Foo}`
And then elsewhere in JS:
import Foo from './foo'; var f = Foo.new(); foo.bar();
module.exportscommon.js/node modules -- i.e. it doesn't make sense outside of node - I'm not sure how code like that gets compiled to work on the client via browerify/webpack, etc.. I guess u want to do something like what @jgaskins posted?
@fkchang I figured he wanted to convert the compiled Ruby to a JS-like object because of this:
wanted to write something in opal that I could easily import from JS without having to wrap everything in
$'s
$method prefixes. AFAIK, the
$prefix exists purely so you can have methods and ivars with the same names (like
attr_readers). That might be the biggest obstacle to getting something like this working. | https://gitter.im/opal/opal/archives/2016/06/23 | CC-MAIN-2019-18 | refinedweb | 209 | 75.4 |
51591/run-two-functions-at-different-times
Please refer the below code for your problem:
import threading
def printit2():
threading.Timer(2.0, printit2).start()
print ("2")
def printit10():
threading.Timer(10.0, printit10).start()
print ("10")
printit2()
printit10()
Hey,@Nikitha,
Suppose you have multiple files say test_sample1.py, test_sample2.py. To ...READ MORE
You have to use the zip() function:
for ...READ MORE
Like you are using row slicing, you ...READ MORE
def add(a,b):
return a + b
#when i call ...READ MORE
You can also use the random library's ...READ MORE
Syntax :
list. count(value)
Code:
colors = ['red', 'green', ...READ MORE
can you give an example using a ...READ MORE
You can simply the built-in function in ...READ MORE
different data type is being used. that ...READ MORE
Each choice is random, so it can ...READ MORE
OR
Already have an account? Sign in. | https://www.edureka.co/community/51591/run-two-functions-at-different-times | CC-MAIN-2020-34 | refinedweb | 149 | 79.16 |
Check this:
function! ModeMsg(mode) if a:mode == 'i' hi ModeMsg ctermbg=4 ctermfg=232 elseif a:mode == 'r' hi ModeMsg ctermbg=3 ctermfg=232 else hi ModeMsg ctermbg=5 ctermfg=232 endif endfunction au InsertEnter * call ModeMsg(v:insertmode) au InsertLeave * hi ModeMsg ctermbg=11 ctermfg=232 " default col hi ModeMsg ctermbg=11 ctermfg=232
Edit: working partly, unfortunately...]]>
Hi
I tested your code, now it actually changes the text correctly. However the colour needs another keypress to change.
And yes, I have already tried powerline, but I wanted to do it on my own once
I like to do things by my own that already exist - just to learn.
But thanks anyway!]]>
Try the following Vim script. I don't know why your attempt doesn't work, but for me mode() returns also the different visual-modes.
function! DrawStatusline() let currentmode = mode() hi User1 ctermbg=black ctermfg=darkgrey hi User6 ctermbg=darkgreen ctermfg=green let mode_name='NORMAL' " Check for (any) visual mode if currentmode ==? 'v' || currentmode == '[MOVE CURSOR INSIDE THESE BRACKETS AND HIT ciSINGLEQUOTE<Ctrl-q><Ctrl-v><Esc>]' hi User1 ctermbg=darkcyan ctermfg=darkgrey hi User6 ctermbg=darkcyan ctermfg=cyan let mode_name='VISUAL' elseif currentmode == 'i' hi User1 ctermbg=darkyellow ctermfg=darkgrey hi User6 ctermbg=darkyellow ctermfg=yellow let mode_name='INSERT' endif return '%1*' . mode_name . '%6*' endfunction set statusline=%!DrawStatusline()
However I would recommend to try the plugin Powerline, which does exactly what you are trying to achieve (and much more).
HolyGuac]]>
Hope that helps.
HolyGuac
Hey, thanks for pointing out, but I actually made the typo when writing the comment, but not in the actual .vimrc (I know, a sin!)
But even with your proposition ( =~? '.*v'), it did not work.
I have found a - not too elegant - alternative way, where DrawStatusline takes a string as argument that tells what mode I am in, and map v, V and ^V like this:
noremap <silent> v :call DrawStatusline('V')<CR>v noremap <silent> V :call DrawStatusline('V')<CR>V noremap <silent> <C-v> :call DrawStatusline('V')<CR><C-v> " And then: au! InsertEnter * call DrawStatusline('I') au! InsertLeave * call DrawStatusline('N')
It isn't super elegant, but it works so far
(=> current version of my vimrc)
But yeah, I still find it weird, how mode() behaves...]]>
Hi ayekat,
You have an error in your if-conditions (= instead of ==). Therefor only the else statement is executed.
function DrawStatusline() let currentmode = mode() " Check for (any) visual mode if currentmode =~? '.*v' " do something for visual mode elseif currentmode == 'i' " do something for insert mode endif " no else needed :) " do something for normal mode (default) endfunction
Hope that helps.
HolyGuac]]>
Hi
I'm trying to configure my vim statusbar, and depending on the current mode I want to change parts of the line:
Normal:
Insert mode:
Now I would also like to configure visual, replace, etc., and I have tried mode() that should (according to the vim docs) return a string describing the current mode:
function DrawStatusline() let currentmode = mode() if currentmode = 'v' " do something for visual mode elseif currentmode = 'i' " do something for insert mode else " do something for normal mode (default) endif endfunction
However mode() only seems to return 'n'; in a forum I have read that vim always changes to normal mode for executing mode(), which means that used like this it isn't really useful.
I don't know if I'm using it wrong (maybe I mode() isn't the right choice), but could anyone give me a hint how I could achieve my goal?
Thanks in advance!]]> | https://bbs.archlinux.org/extern.php?action=feed&tid=154160&type=atom | CC-MAIN-2018-13 | refinedweb | 591 | 60.65 |
#include "page0zip.h"
#include "mtr0log.h"
#include "page0page.h"
Compressed page interface
Created June 2005 by Marko Makela
'deleted' flag
Mask of record offsets
'owned' flag
Size of an compressed page directory entry
Start offset of the area that will be compressed
Determine if enough space is available in the modification log.
Write a log record of compressing an index page without the data on the page.
Initialize a compressed page descriptor.
Determine the size of a compressed page in bytes.
Determine if the length of the page trailer.
Determine how big record can be inserted without recompressing the page.
Parses a log record of compressing an index page without the data.
Determine if a record is so big that it needs to be stored externally.
Reset the counters used for filling INFORMATION_SCHEMA.innodb_cmp_per_index.
Set the size of a compressed page in bytes.
Validate a compressed page descriptor.
Write data to the uncompressed header portion of a page. The data must already have been written to the uncompressed page. However, the data portion of the uncompressed page may differ from the compressed page when a record is being inserted in page_cur_insert_rec_zip().
Write a log record of writing to the uncompressed header portion of a page. in: mini-transaction | http://mingxinglai.com/innodb-annotation/page0zip_8ic.html | CC-MAIN-2018-51 | refinedweb | 208 | 67.86 |
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CRM | e-Commerce | Accounting | Inventory | PoS | Project management | MRP | etc.
How to extract the month from a date field?
Hello everybody!!!!
Can anyone help me please.
I have this field type date:
2016-01-01 and i want to get the month then convert it to its name.
Need help friends please.
Best Regards.
#import datetime library
from datetime import datetime
month = datetime.strptime('2016-01-01', "%Y-%m-%d").strftime('%B')#Converting a string format datetime into datetime() type.
You can use different directives as per your requirement in place of "%B". You can find them \here.
Best Regards,
Kalpana Hemnani
About This Community
Odoo Training Center
Access to our E-learning platform and experience all Odoo Apps through learning videos, exercises and Quizz.Test it now | https://www.odoo.com/forum/help-1/question/how-to-extract-the-month-from-a-date-field-97960 | CC-MAIN-2018-26 | refinedweb | 147 | 68.97 |
Q object encapsulates a SQL expression in a Python object that can be used in database-related operations. Using Q objects we can make complex queries with less and simple code.
For example, this Q object filters whether the question starts wiht 'what':
Q objects are helpfull for complex queries because they can be combined using logical operators and(&), or(|), negation(~)
For example, this statement returns if the question starts with 'who' or with 'what'.
The following code is source of Q class:
class Q(tree.Node):
AND = 'AND'
OR = 'OR'
default = AND
def __init__(self, *args, **kwargs):
super(Q, self).__init__(children=list(args) + list(six.iteritems(kwargs)))
def _combine(self, other, conn):
if not isinstance(other, Q):
raise TypeError
As you can interpret from above code, we have three operators 'or', 'and' and invert(negation) and the default operator is AND.
This is an interesting feature as we can use the operator module to create dynamic queries.
We are performing the or operation using operator.or_
To use and operations simply execute:
Q objects not only simplify complex queries, they are very handy for dynamic filtering.... | https://micropyramid.com/blog/querying-with-django-q-objects/ | CC-MAIN-2018-34 | refinedweb | 188 | 52.09 |
Hi,
I noticed the publish action for html5 canvas apps was changed rather drastically.
I am using the exported assets in a rather complex createjs application, combining multiple assets into one project.
The current exports are not compatible with my setup and I don't seem to be able to fetch the manifest from the exported libraries.
The "Symbols" namespace in "Advanced" seems to be pointless now, since that namespace is nowhere to be found in the exported file.
Can someone point me in the right direction?
Ended up finding "getLibrary()" which seems to return what I need.
Had to change my whole preloader to get it to work though...
getLibrary | https://forums.adobe.com/thread/2347448 | CC-MAIN-2018-05 | refinedweb | 111 | 64 |
Handling claims transformation in an OWIN middleware in .NET MVC part 2
October 12, 2015 2 Comments
Introduction
In the previous post we laid the foundations for this short series. We went through a refresher of claims and OWIN and started building a simple ASP.NET MVC web project to investigate what’s available about the user of the current thread in a controller. We saw that by default the only claim available about a user might be their name, unless they are anonymous of course.
In this post we’ll continue to explore claims of authenticated users.
Authenticated users and their default claims
We can easily check how the output of the code we tested in the previous part changes for authenticated users. Open the demo web app and start it in Visual Studio. Use the Register link in the top right hand corner to register a user and log in automatically. Check the Debug window when you are redirected to the home page. You’ll see something along these lines:
User authenticated: True
Claim type:, claim value type:, claim value: 46b0cbfc-74b7-4269-858b-d98972fd1a66
Claim type:, claim value type:, claim value: andras.nemes@email.com
Claim type:, claim value type:, claim value: ASP.NET Identity
Claim type: AspNet.Identity.SecurityStamp, claim value type:, claim value: 88293e8f-0399-44f0-9e3e-73ddd7206c95
I’m building the demo in Visual Studio 2013 but 2012 and 2015 may give different results. Let’s see what each claim means in turn:
- nameidentifier: this is the unique identifier of the user in the current system. Where is it coming from? The project saved the user in an SQL table. Below you’ll find a description how to find it.
- name: this is the user name. I had to provide an email address as the user name on the registration page and it was set as my name claim
- identityprovider: ASP.NET Identity is the successor of the well-know and by now outdated ASP.NET Membership provider. You can find more details about Identity here.
- SecurityStamp: this is the most difficult one to figure out. I’ve found a useful thread on StackOverflow available here. Here comes a quote from that thread: “So this is basically meant to represent the current snapshot of your user’s credentials. So if nothing changes, the stamp will stay the same. But if the user’s password is changed, or a login is removed (unlink your google/fb account), the stamp will change. This is needed for things like automatically signing users/rejecting old cookies when this occurs, which is a feature that’s coming in 2.0.“
As promised let’s see where to find the user name and user identifier claims. The default ASP.NET Identity mechanism will set up the user and membership related tables for you when the first user is registered. The tables look somewhat like the ones that the old Membership mechanism created but they are more streamlined now.
Click the Show All Files icon in the Solution Explorer and expand the App_Data folder. You’ll find the .mdf file there:
If you double-click the .mdf file the database will open in the Server Explorer window. Open the Tables folder of the DefaultConnection node, right-click the AspNetUsers table and click Show Table Data:
The Id column will hold the name identifier claim. There’s also a UserName column all the way to the right which holds the name claim.
A side note: if you’d like to know more about the new Identify framework in ASP.NET MVC5 I have an intro series on that topic starting here.
So now we know what kind of claims are available by default in an ASP.NET MVC5 project. It is possible that the above set of claims will be enough for you in your web project. However, most often than not you’ll want to dig further and find other types of claims in the database and/or suppress some of the existing ones. E.g. you might not need to know the identity provider claim.
Starting with claims transformation
We’re given an initial set of claims and we’d like to build a custom-made one, a list that only contains the claims that we’re interested in. As mentioned before the MVC5 template already includes a lot of security-related infrastructure. In fact if you add a couple of claims into the AspNetUserClaims table in the mdf database mentioned above those will be automatically retrieved for you when a user logs in, i.e. they will be visible in the…
IEnumerable<Claim> claimsCollection = claimsPrincipal.Claims;
…variable. However, for educational purposes we’ll see how to achieve something similar manually. This process helps you understand claims and OWIN better.
Add a new folder called ClaimsTransformation to the project. Insert a class called ClaimsTransformationService into it:
public class ClaimsTransformationService { public async Task<IEnumerable<Claim>> TransformInititalClaims(IEnumerable<Claim> initialClaims) { List<Claim> finalClaims = new List<Claim>(); Claim userIdClaim = (from c in initialClaims where c.Type == ClaimTypes.NameIdentifier select c).FirstOrDefault(); if (userIdClaim == null) //user not authenticated { return initialClaims; } else { //pretend that we're accessing a database await Task.Delay(1000); IList<Claim> additionalClaims = new List<Claim>(); additionalClaims.Add(new Claim("", "Monday")); additionalClaims.Add(new Claim("", "Blue")); additionalClaims.Add(new Claim("", "Developer")); finalClaims.AddRange(initialClaims); finalClaims.AddRange(additionalClaims); } return finalClaims; } }
We first check whether the user ID is available among the initial claims. That indicates that the user is authenticated. If it’s not available then we simply return the incoming list of claims. Otherwise we add a couple of custom claims that we’re pretending to get from a data store. Those could in reality come from a web service, the Amazon file storage, MongoDb, what have you. Also, this is where you can remove some unnecessary claims from the incoming list. Here we simply keep the original list and extend it with some custom-made ones.
Let’s test this service from HomeController with the following modifications:
public async Task<ActionResult> Index() { ClaimsPrincipal claimsPrincipal = User as ClaimsPrincipal; if (claimsPrincipal != null) { ClaimsIdentity claimsIdentity = claimsPrincipal.Identity as ClaimsIdentity; Debug.WriteLine("User authenticated: {0}", claimsIdentity.IsAuthenticated); IEnumerable<Claim> claimsCollection = claimsPrincipal.Claims; foreach (Claim claim in claimsCollection) { Debug.WriteLine("Claim type: {0}, claim value type: {1}, claim value: {2}", claim.Type, claim.ValueType, claim.Value); } await TestClaimsTransformationCode(claimsCollection); } return View(); } private async Task TestClaimsTransformationCode(IEnumerable<Claim> initialClaims) { ClaimsTransformationService service = new ClaimsTransformationService(); IEnumerable<Claim> finalClaims = await service.TransformInititalClaims(initialClaims); Debug.WriteLine("Claims after transformation: "); foreach (Claim claim in finalClaims) { Debug.WriteLine("Claim type: {0}, claim value type: {1}, claim value: {2}", claim.Type, claim.ValueType, claim.Value); } }
Start the application and the new service code should be invoked. Make sure you first test the home page without logging in. You’ll see that we have a single claim after the transformation which is expected:
User authenticated: False
Claim type:, claim value type:, claim value:
Claims after transformation:
Claim type:, claim value type:, claim value:
Now log in and you’ll see that the additional claims are indeed added to the original ones:
User authenticated: True
Claim type:, claim value type:, claim value: 46b0cbfc-74b7-4269-858b-d98972fd1a66
Claim type:, claim value type:, claim value: andras.nemes@nosuchemail.com
Claim type:, claim value type:, claim value: ASP.NET Identity
Claim type: AspNet.Identity.SecurityStamp, claim value type:, claim value: 88293e8f-0399-44f0-9e3e-73ddd7206c95
Claims after transformation:
Claim type:, claim value type:, claim value: 46b0cbfc-74b7-4269-858b-d98972fd1a66
Claim type:, claim value type:, claim value: andras.nemes@nosuckemail.com
Claim type:, claim value type:, claim value: ASP.NET Identity
Claim type: AspNet.Identity.SecurityStamp, claim value type:, claim value: 88293e8f-0399-44f0-9e3e-73ddd7206c95
Claim type:, claim value type:, claim value: Monday
Claim type:, claim value type:, claim value: Blue
Claim type:, claim value type:, claim value: Developer
So far so good. In the next post we’ll see how to convert this into an OWIN middleware.
You can view the list of posts on Security and Cryptography here.
Nagyon szeretem a blogját, mert tömörek és aktuálisak a bejegyzései.
Köszönöm szépen és további jó munkát kívánok Önnek.
Kedves Sándor,
Köszönöm kedves szavait, és örülök, hogy szereti olvasni a blogomat.
Üdvözlettel,
Nemes András | https://dotnetcodr.com/2015/10/12/handling-claims-transformation-in-an-owin-middleware-in-net-mvc-part-2/ | CC-MAIN-2021-17 | refinedweb | 1,376 | 57.77 |
With JPA, there finally is an ORM standard and every major IDE has support for it. Today I will show you how to map your data with IntelliJ IDEA. I also use the brand new TopLink 11g preview (a JPA implementation), but you can try this at home with every JPA-implementation.
A few weeks ago Peter showed some AMIS employees (including me) the TopLink workbench. I really was amazed how good is was. And I felt a bit bad that I didn’t knew that such a tool existed. I wanted to use the tool myself. I fiddled around with it and really love it. But I wanted to get JPA-annotations, not the TopLink XML files. Whilst searching on how to do that I discovered that every major IDE supported JPA annotation generation. Last year I mainly used iBatis and Spring-JDBC and kind of forgot about JPA, so the ‘amazing new things’ I’m about to tell might be pretty ancient by now 😉
Creating the mapping and data sources
Create a project in IntelliJ and add libraries for JUnit, Oracle JDBC (OJDBC14.jar) and the libraries for your JPA-implementation. I’m using TopLink 11g preview so I have to add persistence.jar, toplink.jar and xmlparserv2.jar
To validate your persistence classes and queries properly you have to add a data source. Go to Tools, Data Sources. Click on the plus icon in the upper left corner of the dialog.
Click on the plus icon and search for your JDBC-driver. It’s usually sufficient to hit the ‘Find Driver Classes’ button, but sometimes you have to look up the driver yourself.
The next step is the database url, user name, password and schema name. You can click the test connection to test the connection and with the refresh tables button you can test some more.
Right click your project, new, add persistence unit. My persistence unit is called Scott. IntelliJ generates the XML for you. You have to add some properties to make sure the application works outside IntelliJ. Overwrite the <persistence-unit> with
<persistence-unit <properties> <property name="toplink.jdbc.driver" value="oracle.jdbc.OracleDriver"/> <property name="toplink.jdbc.url" value="jdbc:oracle:thin:@127.0.0.1:1521:orcl"/> <property name="toplink.jdbc.user" value="scott"/> <property name="toplink.jdbc.password" value="tiger"/> <property name="com.intellij.javaee.persistence.datasource" value="Scott"/> </properties> </persistence-unit>
Note that the last property is needed for proper validation of the persistence classes and queries, otherwise you wil see red underlinings everywhere. You can remove the line when you deploy your project to a web server.
To create the mappings you just have to do some clicking. Right click your project, Generate persistence mapping and pick by database schema.
In the dialog that pops up you have to add some things:
- choose Datasource: Scott
- package: nl.amis.domain.scott
- tick add to persistence unit and pick scott
- deselect Bonus and Salgrade because we only want the Emp and Dept table.
Note that the deptno field of emp is deselected. This is because it’s a foreign key (hence the fk on the table icon) and JPA knows you probably don’t want to use that foreign key. And JPA is right, we want a department object in our employee object.
Select the Emp table and click on the plus icon to add a relation.
In the Employee object we want to select a Department, so add an attribute department and leave type on <entity>. In the department section we want to be able to select a list of employees. Change the Type to java.util.List and enter the attribute name employees.
When you’re using an ancient database without relations you can enter a source an target column, but that isn’t necessary becasue JPA is pretty smart.
Select src directory when you can choose between the resources and src directory.
Go to the package nl.amis.domain.scott and look what IntelliJ did for you. Of course there are a lot of annotations that aren’t really necessary, but they won’t hurt performance and now it’s more clear what is actually happening.
In the DeptEntity class you can see there is a one to many relation to employee:
@OneToMany(mappedBy = "department") public List<EmpEntity> getEmployees() { return employees; }
The final step is adding the used classes to persistence.xml (copy these tags just above <properties>)
<class>nl.amis.domain.scott.EmpEntity</class> <class>nl.amis.domain.scott.DeptEntity</class>
Querying your data
Now it’s finally time to query the data. Let’s have a look at this simple test case
public class TestTopLinkJPA extends TestCase { private static final Logger log = Logger.getLogger(TestTopLinkJPA.class); private EntityManagerFactory emf = null; private String s; protected void setUp() { emf = Persistence.createEntityManagerFactory("scott"); log.debug("EntityManagerFactory created"); } protected void tearDown() throws Exception { emf.close(); log.debug("EntityManagerFactory closed"); } public void testScott() throws Exception { EntityManager em = emf.createEntityManager(); Query query = em.createQuery("select e from EmpEntity e"); List<EmpEntity> list = query.getResultList(); for (int i = 0; i < list.size(); i++) { EmpEntity e = list.get(i); System.out.println(e.getEname() + ", dept location: " + e.getDepartment().getLoc()); } } }
The coolest thing about IntelliJ is that ‘they’ validate your queries! Lets add ‘where e.’ and hit ctrl-space
How cool is that!? Let’s change EmpEntity to EmpEntaty:
This will make your work so much easier, no more stupid typo’s or hours of searching because you always write Entaty and don’t know what’s wrong with that.
Conclusion
After a few hours with JPA I really love it. I’m always a bit conservative and stuck to iBatis and Spring-JDBC for too long. Not that there’s anything wrong with those two, but JPA can make you job easier (and of course it always good to check out other tools). The four major IDE’s (Eclipse, IntelliJ, NetBeans and JDeveloper) are really competing with each other and we as users get betters tools because of that competition. A few years ago it would’ve taken ages to get some proper tooling for new frameworks and now I’m suprised good tools are already out there.
Thanks for the info. It’s good to know that Alexa is starting to normalize
I have 2GB of RAM. With the Scott schema it’s pretty fast. With a large database it gets a little bit slower, but 10 minutes is too long. Did you notice the unselect all button in the toolbar above the check-boxes?
How much RAM do you have? I have 2GB, but every time I tried to check one of the deselected check-boxes in the Import Database Schema dialog, I had to wait 10-15 minutes to get my processor back. With dozens to go, this just isn’t going to work. | https://technology.amis.nl/2007/08/01/getting-started-with-jpa-mapping-how-intellij-can-map-your-data-with-a-few-clicks/ | CC-MAIN-2016-50 | refinedweb | 1,149 | 58.18 |
MKTEMP(3) BSD Programmer's Manual MKTEMP(3)
mktemp, mkstemp, mkstemps, mkdtemp - make temporary file name (unique)
#include <stdlib.h> char * mktemp(char *template); int mkstemp(char *template); int mkstemps(char *template, int suffixlen); char * mkdtemp(char *template);
The mktemp() family of functions take the given file name template and overwrite a portion of it to create a new file name. This file name is unique and suitable that can be returned depends on the number of 'X's provided; six 'X's will result in mktemp() testing roughly 26 ** 6 combinations. At least 6 'X's should be used, though 10 is much better. The mktemp() function generates a temporary file name based on a template as described above. Because mktemp() does not actually create the tem- porary file there is a window of opportunity during which another process can open the file instead. Because of this race condition the mktemp() should not be used in new code. mktemp() was marked as a legacy interface in IEEE Std 1003.1-2001 ("POSIX") and may be removed in a future release of OpenBSD.XXXXXXXXXXsuffix. mkstemps() is told the length of the suffix string, i.e., strlen("suffix"). The mkdtemp() function makes the same replacement to the template as in mktemp() and creates the template directory, mode 0700.
The mktemp() and mkdtemp() functions return a pointer to the template on success and NULL on failure. The mkstemp() and mkstemps() functions re- turn -1 if no suitable file could be created. If any call fails, an error code is placed in the global variable errno.XXXXXXXXXXXXXXXX.
The mkstemp() and mkdtemp() functions may set errno to one of the follow- ing values: [ENOTDIR] The path name portion of the template is not an existing directory..
chmod(2), getpid(2), mkdir(2), open(2), stat(2), tempnam(3), tmpfile(3), tmpnam(3)
A mktemp() function appeared in Version 7 AT&T UNIX. The mkdtemp() func- tion appeared in OpenBSD 2.2. The mkstemp() function appeared in 4.4BSD. The mkstemps() function appeared in OpenBSD 2.3.. MirOS BSD #10-current June 4, 1993. | http://mirbsd.mirsolutions.de/htman/sparc/man3/mkstemps.htm | crawl-003 | refinedweb | 349 | 63.7 |
Joe writes: > >. AFAICS, we don't need anything new in the block layer, unless someone has strong objections to the fact we are queueing write buffers during a pv_move in the first place. If you are considering 2.4 only, then you queue write requests, pass read requests through, and you don't need to set any flags anywhere. 2.4 does not have WRITEA at all. I'm not overly keen on how PE_UNLOCK flushes the queue afterwards (it keeps on getting the _pe_lock, rather than taking the whole list and flushing it in one go). I also don't like taking the _pe_lock before we even check if we are doing a WRITE, because of overhead. I re-wrote this part to check if the PE is locked without _pe_lock, and then lock, recheck, and queue only if we really need the lock. This IS the fast path for all I/O through LVM, so best to avoid getting a single global lock for ALL I/O!!! If we test pe_lock_req.lock without the lock, it is no worse than any other I/O submitted a nanosecond before the PE_LOCK_UNLOCK ioctl is called. It will not cause any problems if a write goes through at this point. Cheers, Andreas ========================================================================= diff -u -u -r1.7.2.96 lvm.c --- kernel/lvm.c 2001/04/11 19:08:58 1.7.2.96 +++ kernel/lvm.c 2001/04/23 12:47:26 @@ -599,8 +592,8 @@ lvm_lock = lvm_snapshot_lock = SPIN_LOCK_UNLOCKED; pe_lock_req.lock = UNLOCK_PE; - pe_lock_req.data.lv_dev = \ - pe_lock_req.data.pv_dev = \ + pe_lock_req.data.lv_dev = 0; + pe_lock_req.data.pv_dev = 0; pe_lock_req.data.pv_offset = 0; /* Initialize VG pointers */ @@ -1267,29 +1271,30 @@ rsector_map, stripe_length, stripe_index); } - /* handle physical extents on the move */ - down(&_pe_lock); - if((pe_lock_req.lock == LOCK_PE) && - (rdev_map == pe_lock_req.data.pv_dev) && - (rsector_map >= pe_lock_req.data.pv_offset) && - (rsector_map < (pe_lock_req.data.pv_offset + vg_this->pe_size)) && -#if LINUX_VERSION_CODE >= KERNEL_VERSION ( 2, 4, 0) - (rw == WRITE)) { -#else - ((rw == WRITE) || (rw == WRITEA))) { -#endif - _queue_io(bh, rw); - up(&_pe_lock); - up(&lv->lv_snapshot_sem); - return 0; - } - up(&_pe_lock); + /* + * Queue writes to physical extents on the move until move completes. + * Don't get _pe_lock until there is a reasonable expectation that + * we need to queue this request, because this is in the fast path. + */ + if (rw == WRITE || rw == WRITEA) { + if (pe_lock_req.lock == LOCK_PE) { + down(&_pe_lock); + if ((pe_lock_req.lock == LOCK_PE) && + (rdev_map == pe_lock_req.data.pv_dev) && + (rsector_map >= pe_lock_req.data.pv_offset) && + (rsector_map < (pe_lock_req.data.pv_offset + + vg_this->pe_size))) { + _queue_io(bh, rw); + up(&_pe_lock); + up(&lv->lv_snapshot_sem); + return 0; + } + up(&_pe_lock); + } - /* statistic */ - if (rw == WRITE || rw == WRITEA) - lv->lv_current_pe[index].writes++; - else - lv->lv_current_pe[index].reads++; + lv->lv_current_pe[index].writes++; /* statistic */ + } else + lv->lv_current_pe[index].reads++; /* statistic */ /* snapshot volume exception handling on physical device address base */ @@ -1430,7 +1435,6 @@ { pe_lock_req_t new_lock; struct buffer_head *bh; - int rw; uint p; if (vg_ptr == NULL) return -ENXIO; @@ -1439,9 +1443,6 @@ switch (new_lock.lock) { case LOCK_PE: - if(pe_lock_req.lock == LOCK_PE) - return -EBUSY; - for (p = 0; p < vg_ptr->pv_max; p++) { if (vg_ptr->pv[p] != NULL && new_lock.data.pv_dev == vg_ptr->pv[p]->pv_dev) @@ -1449,16 +1450,18 @@ } if (p == vg_ptr->pv_max) return -ENXIO; - pe_lock_req = new_lock; - - down(&_pe_lock); - pe_lock_req.lock = UNLOCK_PE; - up(&_pe_lock); - fsync_dev(pe_lock_req.data.lv_dev); down(&_pe_lock); + if (pe_lock_req.lock == LOCK_PE) { + up(&_pe_lock); + return -EBUSY; + } + /* Should we do to_kdev_t() on the pv_dev and lv_dev??? */ pe_lock_req.lock = LOCK_PE; + pe_lock_req.data.lv_dev = new_lock_req.data.lv_dev; + pe_lock_req.data.pv_dev = new_lock_req.data.pv_dev; + pe_lock_req.data.pv_offset = new_lock_req.data.pv_offset; up(&_pe_lock); break; @@ -1468,17 +1471,12 @@ pe_lock_req.data.lv_dev = 0; pe_lock_req.data.pv_dev = 0; pe_lock_req.data.pv_offset = 0; - _dequeue_io(&bh, &rw); + bh = _pe_requests; + _pe_requests = 0; up(&_pe_lock); /* handle all deferred io for this PE */ - while(bh) { - /* resubmit this buffer head */ - generic_make_request(rw, bh); - down(&_pe_lock); - _dequeue_io(&bh, &rw); - up(&_pe_lock); - } + _dequeue_io(bh); break; default: @@ -2814,12 +2836,14 @@ _pe_requests = bh; } ; } } -- Andreas Dilger \ "If a man ate a pound of pasta and a pound of antipasto, \ would they cancel out, leaving him still hungry?" -- Dogbert | http://www.redhat.com/archives/linux-lvm/2001-April/msg00213.html | CC-MAIN-2013-48 | refinedweb | 643 | 59.8 |
In this example, we will add a RKF “Activity Plan Cost” to the PCS report to be displayed after “Plan Cost”. This RKF will display plan cost for only activity resource type.
To achieve this, we will copy to existing “Plan Cost” key figure in the query and add an additional restriction of Resource Type = 0ACT queries. Queries copied to customer namespace can be changed in the same way.
To add the new RKF, Launch BEx Query Designer –> Open query /CPD/AVR_MP_Q008 –> Navigate to Rows/Columns –> Select key figure “Plan Cost” –> Right Click –> Click Copy –> Right Click “Key Figures” –> Click Paste –> Rename copied Key Figure to “Activity Plan Cost” as shown in the previous blog on renaming key figures
Double Click “Activity Plan Cost” –> Drag “Resource Type” from Plan dimension to the selection
Right Click on “Resource Type” –> Click Restrict –> Type “0ACT” in Direct Input and click Right Arrow –> Click OK
Click OK –> Save the query
Execute the PCS report. The report now shows the new RKF for “Activity Plan Cost” and displays the plan cost of only Resource Type Activity (0ACT)
| https://blogs.sap.com/2018/06/03/adding-new-key-restricted-key-figure-rkf-in-pcs-report/ | CC-MAIN-2019-35 | refinedweb | 182 | 57.95 |
The Evolution of Python 3
ScuttleMonkey posted more than 5 years ago | from the all-growd-up dept.
."
I knew it! (-1, Offtopic)
Anonymous Coward | more than 5 years ago | (#26422997)
Hah! Evolution! I knew that an Intelligent Designer couldn't have been behind Python 3.0!
I agree.... (1)
mangu (126918) | more than 5 years ago | (#26424289)-object thing.
Re:I agree.... (0)
Anonymous Coward | more than 5 years ago | (#26424395)
print(results)
Re:I agree.... (1)
spiralx (97066) | more than 5 years ago | (#26425125)
Or use
print("7.3g".format(10.0))
like every normal person would.
Combine them.... (4, Funny)
thetoadwarrior (1268702) | more than 5 years ago | (#26423003)
Re:Combine them.... (3, Funny)
morgan_greywolf (835522) | more than 5 years ago | (#26423055)
Lemme guess... you're a student of the Sun Microsystems'-sponsored Bill Joy School of Version Numbering?
Re:Combine them.... (4, Funny)
Radish03 (248960) | more than 5 years ago | (#26423259)
Either that or he's a Winamp developer.
Re:Combine them.... (2, Funny)
morgan_greywolf (835522) | more than 5 years ago | (#26423559)
Same thing.
Roland Piquepaille: a case study in madness (-1, Troll)
Anonymous Coward | more than 5 years ago | (#26423011) TERM 'BLOG')..
Roland Piquepaille's Technology Trends serves online advertisements through a service called Blogads, located at. HIT THIS FUCKER WHERE IT HURTS and talk about money. (copy-pasta faggotry)the meat of his journal entries from professional and academic journals and news magazines and submits about seven or eight of these "articles" to Slashdot each month. Is this "service" worth up to $647 a month?
Or, does each "article" represent up to $80 of work? You decide.
Re:Roland Piquepaille: a case study in madness (4, Funny)
Anonymous Coward | more than 5 years ago | (#26423027)
I don't think will be a problem any more
Re:Roland Piquepaille: a case study in madness (-1, Offtopic)
andymadigan (792996) | more than 5 years ago | (#26423475)
Re:Roland Piquepaille: a case study in madness (0)
Anonymous Coward | more than 5 years ago | (#26423887)
You mean you dropped him just because of that? Go out and live a bit.
Re:Roland Piquepaille: a case study in madness (0)
Anonymous Coward | more than 5 years ago | (#26424153)
I believe the Slashdot editors collect a good deal more than $80 per article, and they just copy and paste a summary. Roland made it easier by copying whole articles, whereas the Slashdot editors leave that to the karma whores and kind ACs.
Evolution? (2, Funny)
El_Muerte_TDS (592157) | more than 5 years ago | (#26423013)
Shouldn't that be intelligent design? Otherwise we'd have way more python flavors.
Re:Evolution? (1)
Abreu (173023) | more than 5 years ago | (#26423075)
Well, Python has a distinct, well known creator, so I guess it does qualify
Re:Evolution? (0)
Anonymous Coward | more than 5 years ago | (#26423117)
No, because there's a very limited amount of resources available so all the weaker variations quickly died off.
Re:Evolution? (1, Insightful)
Anonymous Coward | more than 5 years ago | (#26423445)
Can't evolution be controlled? I guess that is the same basic idea as in intelligent design, but it can be called evolution even though somebody steers where it's heading.
Re:Evolution? (0)
Anonymous Coward | more than 5 years ago | (#26423915)
Re:Evolution? (1)
Anthony_Cargile (1336739) | more than 5 years ago | (#26423685)
Re:Evolution? (0)
Anonymous Coward | more than 5 years ago | (#26424165)
Only apps that utilize the POSIX subsystem on Windows can call fork().
(Trivia: Even Windows 7 still comes with the OS/2 subsystem. Look for a file called os2ss.exe)
Re:Evolution? (2, Interesting)
Anthony_Cargile (1336739) | more than 5 years ago | (#26425287)
Re:Evolution? (1)
wilder_card (774631) | more than 5 years ago | (#26423691)
Re:Evolution? (2, Funny)
Shadow Wrought (586631) | more than 5 years ago | (#26425845)
I hear it bit its tail and now just slowly slithers around in a circle...
Re:Evolution? (1)
flyingfsck (986395) | more than 5 years ago | (#26424015)
"Python species"
There, fixed it for you!
;)
Probably not an issue for beginners? (2, Interesting)
NinthAgendaDotCom (1401899) | more than 5 years ago | (#26423083)
I just started learning Python a few weeks ago when I got laid off from my QA job. I imagine I'm not to the point yet where the language differences between 2.x and 3.x are going to matter?
Re:Probably not an issue for beginners? (3, Informative)
morgan_greywolf (835522) | more than 5 years ago | (#26423119)
Unless you're trying to learn how to code Django apps, which won't work on Python 3.0. Neither will a lot of other 3rd party modules.
Re:Probably not an issue for beginners? (0)
Anonymous Coward | more than 5 years ago | (#26423189)
Re:Probably not an issue for beginners? (1)
morgan_greywolf (835522) | more than 5 years ago | (#26423233).
Re:Probably not an issue for beginners? (1)
ultrabot (200914) | more than 5 years ago | (#26423697)? (-1, Troll)
Anonymous Coward | more than 5 years ago | (#26425479)
And how is that even relevant to learning Python, oh trolling furry freak? Answer? It's not, of course. Django will be updated to support Python 3.0, and in the meantime their OWN FUCKING PAGE recommends that you still use Django and learn on 2.5.x until the transition is made.
Why don't you go back to wanking in your fursuit where you aren't interacting with the real world?
Re:Probably not an issue for beginners? (3, Informative)
Random BedHead Ed (602081) | more than 5 years ago | (#26423139):Probably not an issue for beginners? (1)
TheoMurpse (729043) | more than 5 years ago | (#26425377)
Oh darnit. I've been programming amateurely (as an amateur?) for twenty years, starting with BASIC as a kindergartener or preschooler.
I've always disliked print() and preferred print as a statement. Likely because of my background in BASIC and the fact that I learned C++ and cout before I learned C and printf().
Can someone tell me why it was changed to print()? Philosophical reason or pragmatic? Just to conform with the more popular Java/JavaScript/C convention or something?
Re:Probably not an issue for beginners? (1)
hobbit (5915) | more than 5 years ago | (#26425675)
Why should print have special status as an operator? cout doesn't.
Re:Probably not an issue for beginners? (1)
Mozk (844858) | more than 5 years ago | (#26425635)
The biggest gotcha for me was that sockets now use byte arrays instead of strings.
Re:Probably not an issue for beginners? (1, Insightful)
Anonymous Coward | more than 5 years ago | (#26425819)
That link is 18 months old, in which he says "I expect it'll be two years before you'll need to learn Python 3.0", so if he followed the advice he should start learning 3.0.
Re:Probably not an issue for beginners? (2, Interesting)
joetainment (891917) | more than 5 years ago | (#26423157)
Trip over beginners? (3, Funny)
AaxelB (1034884) | more than 5 years ago | (#26423103):Trip over beginners? (1)
VirusEqualsVeryYes (981719) | more than 5 years ago | (#26423489)
Like basic grammatical structure, for instance? When did Palin become a Python dev?
Re:Trip over beginners? (0)
Anonymous Coward | more than 5 years ago | (#26423491)
First Ruby on Rails, now Python on Legs. What next?
Re:Trip over beginners? (4, Funny)
lewp (95638) | more than 5 years ago | (#26423551)
Well, Common Lisp stole my bike.
Im working on a Python clone (0, Redundant)
Daswolfen (1277224) | more than 5 years ago | (#26423125)
I call it Monty:Python
Re:Im working on a Python clone (2, Informative)
LighterShadeOfBlack (1011407) | more than 5 years ago | (#26423231)
The name Python originally came from Monty Python, so you're about 18 years late on that joke.
In all seriousness (0, Flamebait)
jgtg32a (1173373) | more than 5 years ago | (#26423323)
Maybe I'm just whiny, but the braces and everything are just easier to read.
Re:In all seriousness (2, Insightful)
bb5ch39t (786551) | more than 5 years ago | (#26423509)
Re:In all seriousness (2, Insightful)
Anonymous Coward | more than 5 years ago | (#26423531):In all seriousness (3, Insightful)
AuMatar (183847) | more than 5 years ago | (#26423957).
Re:In all seriousness (3, Insightful)
Anonymous Coward | more than 5 years ago | (#26424175):In all seriousness (0, Troll)
AuMatar (183847) | more than 5 years ago | (#26424773)
I think that it's ridiculous that a language's readability depends on the tool used to read it. It's a sign the language is broken. A proper language would use an easily distinguishable delimeter- anything other than a whitespace. It could be { [ ( or (@$^(*#*@(&#*(@&#^& for all I care. If you need a special tool to read it, its flawed. I should be able to write my code in emacs, vi, nano, pico, ed, or notepad for that matter without having to spend any time messing with the setup. And my coworkers should be able to use whatever tool they want, even if they are heretical vi users. Nor should I have to know the 1 billion features of emacs. I have better things to waste braincells on.
By the way, what would you do if you were in an environment that didn't have emacs- say editing on an embedded/mobile device? Or were working off of printouts? Or just didn't have it on the machine and couldn't install it (no network, network outage, improper permissions)?
I also love that they should behave "mostly sane" thereafter. So even with tools it isn't promised to work right? No thanks.
And I am speaking from experience here- I worked on a Python project in a team environment. It was a disaster, the whitespace thing caused daily bugs. There's no excuse for the amount of time and productivity it caused us to lose when the solution exists and is 4 or 5 decades old.
Re:In all seriousness (1)
DragonWriter (970822) | more than 5 years ago | (#26425037)
All programming languages higher level than machine code that I've encountered, except for a few esolangs, use whitespace as a delimiter.
Re:In all seriousness (4, Insightful)
horza (87255) | more than 5 years ago | (#26425137):In all seriousness (0)
Anonymous Coward | more than 5 years ago | (#26425695)
I think that it's ridiculous anyone still mods you up, it's so obvious that you're trolling it's...well...ridiculous. The more people criticize your opinion the more inflated and retarded your claims about loss of "productivity" due to fucking WHITESPACE become. If the "whitespace thing caused daily bugs" in your little band of fake Python developing friends it was because they weren't fucking writing in the language properly, or they didn't know how to make a straight, vertical line out of familiar keyboard characters. Either way the problem seems to be their stupidity rather than a problem with the language. "No excuse," blah blah blah blah. You probably just got done doing your BSD is dead cut-and-paste job on a GNAA forum you dumb fuck. No one's falling for it any more.
Re:In all seriousness (2, Insightful)
Moebius Loop (135536) | more than 5 years ago | (#26425045) are a natural part of the development process.
If developers are spending a truly inordinate amount of time on whitespace issues, it can only be due to lack of discretion and attention to detail, which I would be willing to wager is increasing the number of "real" bugs emerging as well.
Re:In all seriousness (4, Informative)
AlexMax2742 (602517) | more than 5 years ago | (#26425437)
Re:In all seriousness (4, Insightful)
SleepingWaterBear (1152169) | more than 5 years ago | (#26425451):In all seriousness (0)
Anonymous Coward | more than 5 years ago | (#26425557)
Care to provide an example of said code that looks identical but does two completely different things, perhaps? Because I couldn't do it.
i=1
while i==1:
print "test"
i = 2
output: test
i=1
while i==1:
#note the extra space for the retarded
print "test"
i = 2
output: test
As it is, I'd say you're full of shit and you're just a freak for another language trolling this thread, but hey. Everyone's entitled to their opinion. Even if it's stupid.
Re:In all seriousness (1)
hobbit (5915) | more than 5 years ago | (#26425731)
I agree. I'm a Python fan but "use a proper text editor" is passing the buck big-style. Guido should have just mandated the use of spaces rather than tabs: everything renders spaces the same.
Re:In all seriousness (0)
Anonymous Coward | more than 5 years ago | (#26426011)
This is a serious issue that seems to get dismissed regularly by the Python crowd. As you pointed out the issue is the definition of white space and like you have experienced this debugging nightmare myself.
It is especially troublesome when using code from a third party written in an unknown editor. Basically one needs to have the editor you are using set up to display the various white spaces in differing colors or in other manners so that you can visually see where your code blocks should be. Worst is the cut and paste from one source into another.
You also hinted on the solution here to the problem that would be a clear and unambiguous definition as to what is white space. Given that it wouldn't take much for a good editor programmer to come up with a really helpful Python mode.
Re:In all seriousness (0)
Anonymous Coward | more than 5 years ago | (#26423745)
You could try "from __future__ import braces", but I get the funny feeling this won't be implemented any time soon. Call it a hunch.
Re:In all seriousness (5, Funny)
ultrabot (200914) | more than 5 years ago | (#26424149)
Yes.
Example program:
class MyClass(object): #{
def myfunction(self, arg1, arg2): #{
for i in range(arg1): #{
print i
# whoops, forgot to close that bracket!
#}
#}
Re:In all seriousness (1)
KovaaK (1347019) | more than 5 years ago | (#26424191)
Sweet. Now with all that work that you've done in getting python to support braces, can you make it not depend on whitespace? I'm sure it won't take that much more effort.
Re:In all seriousness (1)
ultrabot (200914) | more than 5 years ago | (#26424321)
can you make it not depend on whitespace? I'm sure it won't take that much more effort.
It would be easy to create a preprocessor to do that, but life's too short. I'll leave the excercise to someone that cares enough.
Compatibility (-1, Flamebait)
Anonymous Coward | more than 5 years ago | (#26423221)
Mmm nothing like a fresh tranny bottom (-1, Offtopic)
Anonymous Coward | more than 5 years ago | (#26423225)
There is nothing like sticking a nice cock inside of a hot tranny's smooth bottom in the evening while you reach around and give a handjob. You slashdotters
should try it some time. They give especially good head. When you blow your load inside a tranny bitch it's like the closest slashdot experience of having a girlfriend.
I recommend the buttsex.
Re:Mmm nothing like a fresh tranny bottom (0)
Anonymous Coward | more than 5 years ago | (#26424505)
Getting into Python 3 (4, Informative)
dedazo (737510) | more than 5 years ago | (#26423237). (2, Funny)
HTH NE1 (675604) | more than 5 years ago | (#26423267):This sentence fragment. (1)
MichaelSmith (789609) | more than 5 years ago | (#26423379)
Re:This sentence fragment. (1)
HTH NE1 (675604) | more than 5 years ago | (#26423673)
Yeah, I thought about indenting it python-style (after I'd already hit Submit, natch) but it would be harder to read wrapped in <ecode></ecode> .
And I should have had another set of parentheses around "( dependencies on packages ) or ( third party software that hasn't been ported to 3.0 yet )" to associate it stronger with "like".
Re:This sentence fragment. (1)
atraintocry (1183485) | more than 5 years ago | (#26423705)
If you code in Notepad, maybe
:)
Unicode & toolkits (1)
ultrabot (200914) | more than 5 years ago | (#26423473) (1)
xant (99438) | more than 5 years ago | (#26424393) get it right. And that's VERY important. In both versions you have to think about encodings.
My prediction is about 18 months before Python 3.0 is considered the default. My team, in general a pretty early adopter of technology, won't be using it for at least 9 months, waiting for our dependency stack to fill in.
My fulltext search library, Hypy [goonmill.org] , on the other hand, should have Python 3.0 support any day now.
Oh good. (4, Insightful)
powerlord (28156) | more than 5 years ago | (#26423549)
So whitespace block delineation is finally out, in favor of braces?
:P
Re:Oh good. (5, Insightful)
SatanicPuppy (611928) | more than 5 years ago | (#26424053). (5, Insightful)
hwyhobo (1420503) | more than 5 years ago | (#26424245). (1)
salimma (115327) | more than 5 years ago | (#26424605)
Copy-and-pasting is problematic too, because the pasted code might (in fact, is likely to) end up at the wrong indentation level.
Re:Oh good. (1)
garaged (579941) | more than 5 years ago | (#26424641)
that's why python (and most programming languages) promote the DRY filosophy [slashdot.org]
Re:Oh good. (1)
hwyhobo (1420503) | more than 5 years ago | (#26424839)
While the DRY philosophy may be quite useful in large programs, in small utilities, particularly if they do not necessarily run on the same system, attempting to "librarize" or "functionize" everything may not be practical, and may in fact defeat the readability of your code (of which Python is proud), and also introduce unnecessary bloat.
Just the fact that you have to fear copy & paste is an indicator of bad design to me.
Re:Oh good. (1)
robot_love (1089921) | more than 5 years ago | (#26425721)
Methinks you have chosen a rather strange hill to die on...
Re:Oh good. (1)
hwyhobo (1420503) | more than 5 years ago | (#26425743)
Re:Oh good. (1)
hwyhobo (1420503) | more than 5 years ago | (#26425787)
Re:Oh good. (4, Insightful)
costas (38724) | more than 5 years ago | (#26424821):Oh good. (1)
hwyhobo (1420503) | more than 5 years ago | (#26425469)
Both are much less common than looking at badly-formatted code that it takes a bit to mentally parse which brace-delineated languages have.
There is nothing that prevents an organization from instituting coding standards, just like Technical Publications and Marcomm groups have their own Writing Standards (Guides). It is up to the management to punish non-adherence. However, breaking the program by design because someone missed the number of spaces or copied & pasted a few lines of code just rubs me the wrong way.
YRMV, of course.
Re:Oh good. (1)
jellomizer (103300) | more than 5 years ago | (#26425717):Oh good. (1)
Jeremi (14640) | more than 5 years ago | (#26426245) delimiting blocks of text.
Given that, everybody could use their own favorite method of code formatting...
Re:Oh good. (1)
larry bagina (561269) | more than 5 years ago | (#26424983)
indent(1) much?
The python FAQ's explanation for whitespace block levels is basically that braces/indentation might confuse you. Well, braces don't confuse me. But if you're going to pretend whitespace block indentation is good, then VB-style WHILE
... END, IF .. END IF, etc must be even better.
Re:Oh good. (1)
drauh (524358) | more than 5 years ago | (#26425671).
Re:Oh good. (1)
Kingrames (858416) | more than 5 years ago | (#26424063)
Unfortunately not (1)
mangu (126918) | more than 5 years ago | (#26424705) concise syntax is one of the best ways to make readable code. I started using C rather than Pascal because of that. I switched from Perl to Python when I rewrote some Perl programs in Python and realized that, despite the somewhat longer code, Python was clearer to read. But I still miss the =~ regular expression match operator from Perl.
An optimal programming language should be well balanced. Not like APL, where a page of code can be resumed to a single character, but it's like learning to write in Chinese. Not like Java either, where you must write several pages of declarations before anything useful comes out. C is very close to the ideal, if you take the effort to understand how a computer works before you start to program. Perl is pretty good, if you resist the temptation to show off your ability. Python was almost there, the perfect compromise between readability and conciseness. Until 3.0, when they went astray...
I love Python. I hate Py3k.
Backwards Compatibility (2, Interesting)
zwekiel (1445761) | more than 5 years ago | (#26423627).
</my two cents>
Re:Backwards Compatibility (5, Interesting)
ultrabot (200914) | more than 5 years ago | (#26423905):Backwards Compatibility (1)
MSG (12810) | more than 5 years ago | (#26424323)
A programming language deserves a "cleanup" every now and then - this is such a thing. Hey, people have survived worse things, like gcc version changes, Qt3 => Qt4, Gtk 1 => Gtk2...
Not to mention Perl4 -> Perl5.
Re:Backwards Compatibility (1)
negative3 (836451) | more than 5 years ago | (#26426193)
Correction to Title (0)
Anonymous Coward | more than 5 years ago | (#26423803)
The Intelligent Design of Python 3
Are distributions going to permit both at once? (1, Interesting)
Anonymous Coward | more than 5 years ago | (#26424029)
Are Linux distributions that include packaged python versions and apps going to permit both 2.x and 3.x python versions to co-exist so all the apps (including local additions) don't have to be ported on the same day?
Re:Are distributions going to permit both at once? (2, Informative)
joe_cot (1011355) | more than 5 years ago | (#26424277) package that "depends" on the latest version of python.
The same thing is done with different versions of Java, GTK, etc. When a toolkit or language makes a huge backward-incompatible change, it's rare that they can't just be installed alongside each other. Different 2.x versions of Python work just fine alongside each other, and I don't see how Python 3 would be any different.
Cue whitespace ranting from wannabees (0, Flamebait)
Qbertino (265505) | more than 5 years ago | (#26424221)
We've heard it all. Cut it out allready. Those ranting about Pythons whitespace are the ones that don't know what they are talking about because they have *never* even programmed in Python, and if it only were for half an hour. To all you suckers out there: Freaking write at least one simple bubblesort in Python, before you go out on a limp and talk about stuff you don't know.
Re:Cue whitespace ranting from wannabees (1)
larry bagina (561269) | more than 5 years ago | (#26424533)
Re:Cue whitespace ranting from wannabees (0)
Anonymous Coward | more than 5 years ago | (#26425861)
Actually popular literature [amazon.com] suggests that constricting, not stretching, your anus is the key to "good-bying depression".
Best scify movie, eveh! (0, Offtopic)
Gilmoure (18428) | more than 5 years ago | (#26424623)
Python vs. Mansquito III!
ie (0)
Anonymous Coward | more than 5 years ago | (#26425725)
import evolution | http://beta.slashdot.org/story/112707 | CC-MAIN-2014-41 | refinedweb | 3,830 | 71.85 |
in32(), inbe32(), inle32()
Read a 32-bit value from a port
Synopsis:
#include <hw/inout.h> uint32_t in32( uintptr_t port ); #define inbe32 ( port ) ... #define inle32 ( port ) ...
Since:
BlackBerry 10.0.0
Arguments:
- port
- The port you want to read the value from.
Library:
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
Description:
The in32() function reads a 32-bit value from the specified port.
The inbe32() and inle32() macros read a 32-bit value that's in big-endian or little-endian format, respectively, from the specified port, and returns the value as native-endian.
The inbe32() and inle32() macros access the specified port more than once if endian conversion is necessary. This could be a problem on some hardware.
Returns:
A 3232() and inle32() are implemented as macros.
Last modified: 2014-06-24
Got questions about leaving a comment? Get answers from our Disqus FAQ.comments powered by Disqus | http://developer.blackberry.com/native/reference/core/com.qnx.doc.neutrino.lib_ref/topic/i/in32.html | CC-MAIN-2014-52 | refinedweb | 161 | 61.53 |
AV Foundation is a framework for working with audio and visual media on iOS and OSX. Using AV Foundation, you can play, capture, and encode media. It is quite an extensive framework and for the purpose of this tutorial we will be focusing on the audio portion. Specifically, we will be using the
AVAudioPlayer class to play MP3 files.
Starter Project
I have provided a starter project that has all the actions and outlets already configured, and with the appropriate methods stubbed out. The classes the project uses, are already stubbed out as well so we can dive right into the code. You can download the starter project from GitHub.
1. Linking the AV Foundation Framework
Before you can use AV Foundation, you have to link the project against the framework. In the Project Navigator, make sure your project is selected. Under the General tab, go to Linked Frameworks and Libraries and from there you choose AVFoundation.framework.
2.
FileReader Class
In the starter project, you will find a file named FileReader.swift. Open this file to view its contents.
import UIKit class FileReader: NSObject { }
This is a simple stub of the class that we'll use to read files from disk. It inherits from
NSObject. We will implement a method,
readFiles, which will be a type method. Type methods allow you to call a method on the class itself, the type, as opposed to an instance of the class. Below is the implementation of the
readFiles method.
class func readFiles() -> [String] { return NSBundle.mainBundle().pathsForResourcesOfType("mp3", inDirectory: nil) as! [String] }
The main bundle contains the code and resources for your project, and it is here that we will find the MP3s. We use the method
pathsForResourcesOfType(_:inDirectory:) method, which returns an array containing the pathnames for the specified type of resource. In this case, we are searching for type
"mp3". Because we are not interested in a specific directory, we pass in
nil.
This class will be used by the
MP3Player class, which we will work on next.
3.
MP3Player Class
Next, open MP3Player.swift and view its contents.
import UIKit import AVFoundation class MP3Player: NSObject, AVAudioPlayerDelegate { }
Notice that we are adopting the
AVAudioPlayerDelegate protocol. This protocol declares a number of useful methods, one of which is
audioPlayerDidFinishPlaying(_:successfully:). By implementing the
audioPlayerDidFinishPlaying(_:successfully:) method, we will be notified when the audio has finished playing.
Step 1: Properties
Add the following to MP3Player.swift.
class MP3Player: NSObject, AVAudioPlayerDelegate { var player:AVAudioPlayer? var currentTrackIndex = 0 var tracks:[String] = [String]() }
The
player property will be an instance of the
AVAudioPlayer class, which we will use to play, pause, and stop the MP3s. The
currentTrackIndex variable keeps track of which MP3 is currently playing. Finally, the
tracks variable will be an array of the paths to the list of MP3s that are included in the application's bundle.
Step 2:
init
override init(){ tracks = FileReader.readFiles() super.init() queueTrack(); }
During initialization, we invoke the
FileReader's
readFiles method to fetch the paths of the MP3s and store this list in the
tracks array. Because this is a designated initializer, we must call the
init method of the superclass. Finally, we call
queueTrack, which we will be writing next.
Step 3:
queueTrack
Add the following implementation for the
queueTrack method to the
MP3Player class.() } }
Because we will be instantiating a new
AVAudioPlayer instance each time this method is called, we do a little housekeeping by setting
player to
nil.
We declare an optional
NSError and a constant
url. We invoke
fileURLWithPath(_:) to fetch the path to the current MP3 and store the value in
url. We are passing the
tracks array as a parameter using
currentTrackIndex as the subscript. Remember the tracks array contains the paths to the MP3s, not a reference to the MP3 files themselves.
To instantiate the
player, we pass the
url constant and
error variable into the
AVAudioPlayer's initializer. If the initialization happens to fail, the
error variable is populated with a description of the error.
If we don't encounter an error, we set the player's delegate to
self and invoke the
prepareToPlay method on the player. The
prepareToPlay method preloads the buffers and acquires the audio hardware, which minimizes any lag when calling the
play method.
Step 4:
play
The
play method first checks to see whether or not the audio is already playing by checking the aptly named
playing property. If the audio is not playing, it invokes the
play method of the
player property.
func play() { if player?.playing == false { player?.play() }
Step 5:
stop
The
stop method first checks whether the audio player is already playing. If it is, it invokes the
stop method and sets the
currentTime property to 0. When you invoke the
stop method, it just stops the audio. It does not reset the audio back to the beginning, which is why we need to do it manually.
func stop(){ if player?.playing == true { player?.stop() player?.currentTime = 0 } }
Step 6:
pause
Just like the
stop method, we first check to see if the audio player is playing. If it is, we invoke the
pause method.
func pause(){ if player?.playing == true{ player?.pause() } }
Step 7:
nextSong
The
nextSong(_:Bool) method queues up the next song and, if the player is playing, plays that song. We don't want the next song playing if the player is paused. However, this method is also called when a song finishes playing. In that case, we do want to play the next song, which is what the parameter
songFinishedPlaying is for.
func nextSong(songFinishedPlaying:Bool){ var playerWasPlaying = false if player?.playing == true { player?.stop() playerWasPlaying = true } currentTrackIndex++ if currentTrackIndex >= tracks.count { currentTrackIndex = 0 } queueTrack() if playerWasPlaying || songFinishedPlaying { player?.play() } }
The
playerWasPlaying variable is used to tell whether or not the player was playing when this method was invoked. If the song was playing, we invoke the
stop method on the
player and set
playerWasPlaying to
true.
Next, we increment the
currentTrackIndex and check to see if it is greater than or equal to
tracks.count. The
count property of an array gives us the total number of items in the array. We need to be sure that we don't try to access an element that doesn't exist in the
tracks array. To prevent this, we set
currentTrackIndex back to the first element of the array if that is the case.
Finally, we invoke
queueTrack to get the next song ready and play that song if either
playerWasPlaying or
songFinishedPlaying is
true.
Step 8:
previousSong
The
previousSong method works very similar to
nextSong. The only difference is that we decrement the
currentTrackIndex and check if it is equal to 0. If it is, we set it to the index of the last element in the array.
func previousSong(){ var playerWasPlaying = false if player?.playing == true { player?.stop() playerWasPlaying = true } currentTrackIndex-- if currentTrackIndex < 0 { currentTrackIndex = tracks.count - 1 } queueTrack() if playerWasPlaying { player?.play() } }
By utilizing both the
nextSong and
previousSong methods, we are able to cycle through all of the MP3s and start over when we reach the beginning or the end of the list.
Step 9:
getCurrentTrackName
The
getCurrentTrackName method gets the name of the MP3 without the extension.
func getCurrentTrackName() -> String { let trackName = tracks[currentTrackIndex].lastPathComponent.stringByDeletingPathExtension return trackName }
We get a reference to whatever the current MP3 is by using
tracks[currentTrackIndex]. Remember, however, that these are the paths to the MP3s and not the actual files themselves. The paths are rather long, because it is the full path to the MP3 files.
On my machine, for example, the first element of the
tracks array is equal to "/Users/jamestyner/Library/Developer/CoreSimulator/Devices/80C8CD34-22AE-4F00-862E-FD41E2D8D6BA/data/Containers/Bundle/Application/3BCF8543-BA1B-4997-9777-7EC56B1C4348/MP3Player.app/Lonesome Road Blues.mp3". This path would be different on an actual device of course.
We've got a large string that contains the path to the MP3, but we just want the name of the MP3 itself. The
NSString class defines two properties that can help us. As the name implies, the
lastPathComponent property returns the last component of a path. As you might have guessed, the
stringByDeletingPathExtension property removes the extension.
Step 10:
getCurrentTimeAsString
The
getCurrentTimeAsString method uses the
currentTime property of the
player instance and returns it as a human-readable string (e.g., 1:02).
func getCurrentTimeAsString() -> String { var seconds = 0 var minutes = 0 if let time = player?.currentTime { seconds = Int(time) % 60 minutes = (Int(time) / 60) % 60 } return String(format: "%0.2d:%0.2d",minutes,seconds) }
The
currentTime property is of type
NSTimeInterval, which is just a
typealias for a
Double. We use some math to get the
seconds and
minutes, making sure we convert
time to an
Int since we need to work with whole numbers. If you are not familiar with the remainder operator (%), it finds the remainder after division of one number by another. If the
time variable was equal to 65, then
seconds would be equal to 5 because we are using 60.
Step 11:
getProgress
The
getProgress method is used by the
UIProgressView instance to give an indication of how much of the MP3 has played. This progress is represented by a value from 0.0 to 1.0 as a
Float.
func getProgress()->Float{ var theCurrentTime = 0.0 var theCurrentDuration = 0.0 if let currentTime = player?.currentTime, duration = player?.duration { theCurrentTime = currentTime theCurrentDuration = duration } return Float(theCurrentTime / theCurrentDuration) }
To get this value, we divide the
player's
currentTime property by the
player's
duration property, we store these values in the variables
theCurrentTime and
theCurrentDuration. Like
currentTime, the
duration property is of type
NSTimeInterval and it represents the duration of the song in seconds.
Step 12:
setVolume
The
setVolume(_:Float) method invokes the
setVolume method of the
player instance.
func setVolume(volume:Float){ player?.volume = volume }
Step 13:
audioPlayerDidFinishPlaying(_:successfully:)
The
audioPlayerDidFinishPlaying(_:successfully:) method is a method of the
AVAudioPlayerDelegate protocol. This method takes as parameters the
AVAudioPlayer instance and a boolean. The boolean is set to
true if the audio player has finished playing the current song.
func audioPlayerDidFinishPlaying(player: AVAudioPlayer, successfully flag: Bool){ if flag == true { nextSong(true) } }
If the song successfully finished playing, we call the
nextSong method, passing in
true since the song finished playing on its own.
This completes the
MP3Player class. We will revisit it a bit later, after implementing the actions of the
ViewController class.
4.
ViewController Class
Open ViewController.swift and view its contents.
mport UIKit import AVFoundation class ViewController: UIViewController { var mp3Player:MP3Player? var timer:NSTimer? @IBOutlet weak var trackName: UILabel! @IBOutlet weak var trackTime: UILabel! @IBOutlet weak var progressBar: UIProgressView! override func viewDidLoad() { super.viewDidLoad() } @IBAction func playSong(sender: AnyObject) { } @IBAction func stopSong(sender: AnyObject) { } @IBAction func pauseSong(sender: AnyObject) { } @IBAction func playNextSong(sender: AnyObject) { } @IBAction func setVolume(sender: UISlider) { } @IBAction func playPreviousSong(sender: AnyObject) { } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() // Dispose of any resources that can be recreated. } }
The
mp3Player variable is an instance of the
MP3Player class we implemented earlier. The
timer variable will be used to update the
trackTime and
progressBar views every second.
In the next few steps, we will implement the actions of the
ViewController class. But first, we should instantiate the
MP3Player instance. Update the implementation of the
viewDidLoad method as shown below.
override func viewDidLoad() { super.viewDidLoad() mp3Player = MP3Player() }
Step 1:
playSong(_: AnyObject)
Enter the following in the
playSong(_: AnyObject) method.
@IBAction func playSong(sender: AnyObject) { mp3Player?.play() }
In this method, we invoke the
play method on the
mp3Player object. We are at a point where we can start testing the app now. Run the app and press the play button. The song should start playing.
Step 2:
stopSong(_: AnyObject)
The
stopSong(_: AnyObject) method invokes the stop method on the
mp3Player object.
@IBAction func stopSong(sender: AnyObject) { mp3Player?.stop() }
Run the app again and tap the play button. You should now be able to stop the song by tapping the stop button.
Step 3:
pauseSong(_: AnyObject)
As you might have guessed, the
pauseSong(_: AnyObject) method invokes the
pause method on the
mp3Player object.
@IBAction func pauseSong(sender: AnyObject) { mp3Player?.pause() }
Step 4:
playNextSong(_: AnyObject)
IBAction func playNextSong(sender: AnyObject) { mp3Player?.nextSong(false) }
In
playNextSong(_: AnyObject), we invoke the
nextSong method on the
mp3player object. Note that we pass
false as a parameter, because the song didn't finish playing on its own. We are manually starting the next song by pressing the next button.
Step 5:
previousSong(_: AnyObject)
@IBAction func playPreviousSong(sender: AnyObject) { mp3Player?.previousSong() }
As you can see, the implementation of the
previousSong(_: AnyObject) method is very similar to that of
nextSong(_: AnyObject). All the buttons of the MP3 player should be functional now. If you've not tested the app yet, now would be a good time to make sure everything is working as expected.
Step 6:
setVolume(_: UISlider)
The
setVolume(_: UISlider) method invokes the
setVolume method on the
mp3Player object. The volume property is of type
Float. The value ranges from 0.0 to 1.0. The
UISlider object is set up with 0.0 as its minimum value and 1.0 as its maximum value.
@IBAction func setVolume(sender: UISlider) { mp3Player?.setVolume(sender.value) }
Run the app one more time and play with the volume slider to test that everything is working correctly.
Step 7:
startTimer
The
startTimer method instantiates a new
NSTimer instance.
func startTimer(){ timer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: Selector("updateViewsWithTimer:"), userInfo: nil, repeats: true) }
The
scheduledTimerWithTimeInterval(_:target:selector:userInfo:repeats:) initializer takes as parameters the number of seconds between firing of the timer, the object to which to call a method on specified by
selector, the method that gets called when the timer fires, an optional
userInfo dictionary, and whether or not the timer repeats until it is invalidated.
We are using a method named
updateViewsWithTimer(_: NSTimer) as the selector, so we will create that next.
Step 8:
updateViewsWithTimer(_: NSTimer)
The
updateViewsWithTimer(_: NSTimer) method calls the
updateViews method, which we will implement in the next step.
func updateViewsWithTimer(theTimer: NSTimer){ updateViews() }
Step 9:
updateViews
The
updateViews method updates the
trackTime and
progressBar views.
func updateViews(){ trackTime.text = mp3Player?.getCurrentTimeAsString() if let progress = mp3Player?.getProgress() { progressBar.progress = progress } }
The
text property of
trackTime is updated with the
currentTime property, formatted as a string by invoking the
getCurrentTimeAsString method. We declare a constant
progress using the
mp3Player's
getProgress method, and set
progressBar.progress using that constant.
Step 10: Wiring Up the Timer
Now we need to call the
startTimer method at the appropriate places. We need to start the timer in the
playSong(_: AnyObject) method, the
playNextSong(_ :AnyObject) method, and the
playPreviousSong(_ :AnyObject) method.
@IBAction func playSong(sender: AnyObject) { mp3Player?.play() startTimer() }
@IBAction func playNextSong(sender: AnyObject) { mp3Player?.nextSong(false) startTimer() }
@IBAction func playPreviousSong(sender: AnyObject) { mp3Player?.previousSong() startTimer() }
Step 11: Stopping the Timer
We also need to stop the
timer when the pause and stop buttons are pressed. You can stop the
timer object by invoking the
invalidate method on the
NSTimer instance.
@IBAction func stopSong(sender: AnyObject) { mp3Player?.stop() updateViews() timer?.invalidate() }
@IBAction func pauseSong(sender: AnyObject) { mp3Player?.pause() timer?.invalidate() }
Step 12:
setTrackName
The
setTrackName method sets the
text property of
trackName by invoking
getCurrentTrackName on the
mp3Player object.
func setTrackName(){ trackName.text = mp3Player?.getCurrentTrackName() }
Step 13:
setupNotificationCenter
When a song finishes playing, it should automatically show the next song's name and start playing that song. Also, when the user presses the play, next, or previous buttons, the
setTrackName method should be invoked. The ideal place to do this is the
queueTrack method of the
MP3Player class.
We need a way to have the
MP3Player class tell the
ViewController class to invoke the
setTrackName method. To do that, we will use the
NSNotificationCenter class. The notification center provides a way to broadcast information throughout a program. By registering as an observer with the notification center, an object can receive these broadcasts and perform an operation. Another way to accomplish this task would be to use the delegation pattern.
Add the following method to the
ViewController class.
func setupNotificationCenter(){ NSNotificationCenter.defaultCenter().addObserver(self, selector:"setTrackName", name:"SetTrackNameText", object:nil) }
We first obtain a reference to the default notification center. We then invoke the
addObserver(_:selector:name:object:) method on the notification center. This method accepts four parameters:
- the object registering as the observer,
selfin this case
- the message that will be sent to the observer when the notification is posted
- the name of the notification for which to register the observer
- the object whose notifications the observer wants to receive
By passing in
nil as the last argument, we listen for every notification that has a name of SetTrackNameText.
Now we need to call this method in the view controller's
viewDidLoad method.
override func viewDidLoad() { super.viewDidLoad() mp3Player = MP3Player() setupNotificationCenter() }
Step 14: Posting the Notification
To post the notification, we invoke the
postNotificationName(_:object:) method on the default notification center. As I mentioned earlier, we will do this in the
queueTrack method of the
MP3Player class. Open MP3Player.swift and update the
queueTrack method as shown below.() NSNotificationCenter.defaultCenter().postNotificationName("SetTrackNameText", object: nil) } }
If you test the app now and let a song play all the way through, it should start playing the next song automatically. But you may be wondering why the song's name does not show up during the first song. The
init method of the
MP3Player class calls the
queueTrack method, but since it has not finished initializing, it has no affect.
All we need to do is manually call the
setTrackName method after we initialize the
mp3Player object. Add the following code to the
viewDidLoad method in ViewController.swift.
override func viewDidLoad() { super.viewDidLoad() mp3Player = MP3Player() setupNotificationCenter() setTrackName() updateViews() }
You'll notice that I also called the
updateViews method. This way, the player shows a time of 0:00 at the start. If you test the app now, you should have a fully functional MP3 player.
Conclusion
This was a rather long tutorial, but you now have a functional MP3 player to build and expand on. One suggestion is to allow the user to choose a song to play by implementing a
UITableView below the player. Thanks for reading and I hope you've learned something useful. | http://esolution-inc.com/blog/build-an-mp3-player-with-av-foundation--cms-24482.html | CC-MAIN-2017-51 | refinedweb | 3,083 | 58.18 |
For python I have an assignment where I have to calculate the number of words in the text file and display the average number of words per sentence. However the average number of words turns up on always becoming one.
The text file is
Hello
How are you
I am fine
Have a good day
Bye
def main():
num_words = 0
total_words = 0
total_lines = 0
in_file = open("text.txt", "r")
line = in_file.readline()
while line != "":
num_words = 0
num_lines = 0
line_list = line.split()
for word in line_list:
num_words = num_words + 1
for line in line_list:
num_lines = num_lines + 1
total_words = total_words + num_words
total_lines = total_lines + num_lines
average = total_words / total_lines
line = in_file.readline()
print "Total words: ", total_words
print "Average number of words per sentence: ", average
in_file.close()
main()
A much better way to do this would be the following:
f = open('in_file.dat') num_lines = 0 tot_words = 0 for line in f: num_lines += 1 tot_words += len(line.split()) average = tot_words / num_lines print(average) | https://codedump.io/share/sc0rfID6V3V/1/how-do-i-count-the-number-of-lines-in-a-text-file | CC-MAIN-2017-47 | refinedweb | 156 | 58.08 |
.
Posted by S.Lott at 8:00 AM 2 comments:
Labels: C, C#, java, Programming Languages,.
Posted by S.Lott at 8:00 AM 5 comments:
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Tuesday, November 30, 2010
Questions, or, How to Ask For Help
Half the fun on Stack Overflow is the endless use of closed-ended questions. "Can I do this in Python?" being so common and so hilarious.
The.
Tuesday, November 23, 2010
Open-Source, moving from "when" to "how".
Thursday, November 18, 2010
Software Patents
Here's an interesting news item: "Red Hat’s Secret Patent Deal and the Fate of JBoss Developers".
Here".
Thursday, November 11, 2010
Hadoop and SQL/Relational Hegemony
Here's a nice article on why Facebook, Yahoo and eBay use Hadoop: "Asking Any Question Of All Your Data".
The?
Posted by S.Lott at 8:00 AM No comments:
Labels: hadoop, map-reduce, RDBMS
Tuesday, November 9, 2010
Data Mapping and Conversion Tools -- Sigh
Yes, ETL is interesting and important.
But creating a home-brewed data mapping and conversion tool isn't interesting or important. Indeed, it's just an attractive nuisance. Sure, it's fun, but it isn't valuable work. The world doesn't need another ETL tool.
The core problem is talking management (and other developers) into a change of course. How do we stop development of Yet Another ETL Tool (YAETLT)?
First, there's products like Talend, CloverETL and Pentaho open source data integration. Open Source. ETL. Done.
Then, there's this list of Open Source ETL products on the Manageability blog. This list all Java, but there's nothing wrong with Java. There are a lot of jumping-off points in this list. Most importantly, the world doesn't need another ETL tool.
Here's a piece on Open Source BI, just to drive the point home.
Business Rules
The ETL tools must have rules. Either simple field alignment or more complex transformations. The rules can either be interpreted ("engine-based" ETL) or used to build a stand-alone program ("code-generating" ETL).
The engine-based ETL, when written in Java, is creepy. We have a JVM running a Java app. The Java app is an interpreter for a bunch of ETL rules. Two levels of interpreter. Why?
Code-generating ETL, OTOH, is a huge pain in the neck because you have to produce reasonably portable code. In Java, that's hard. Your rules are used to build Java code; the resulting Java code can be compiled and run. And it's often very efficient. [Commercial products often produce portable C (or COBOL) so that they can be very efficient. That's really hard to do well.]
Code-generating, BTW, has an additional complication. Bad Behavior. Folks often tweak the resulting code. Either because the tool wasn't able to generate all the proper nuances, or because the tool-generated code was inefficient in a way that's so grotesque that it couldn't be fixed by an optimizing compiler. It happens that we can have rules that run afoul of the boilerplate loops.
Old-School Architecture
First, we need to focus on the "TL" part of ETL. Our applications receive files from our customers. We don't do the extract -- they do. This means that each file we receive has a unique and distinctive "feature". We have a clear SoW and examples. That doesn't help. Each file is an experiment in novel data formatting and Semantic Heterogeneity.
A common old-school design pattern for this could be called "The ETL Two-Step". This design breaks the processing into "T" and "L" operations. There are lots of unique, simple, "T" options, one per distinctive file format. The output from "T" is a standardized file. A simple, standardized "L" loads the database from the standardized file.
Indeed, if you follow the ETL Two Step carefully, you don't need to actually write the "L" pass at all. You prepare files which your RDBMS utilities can simply load. So the ETL boils down to "simple" transformation from input file to output file.
Folks working on YAETLT have to focus on just the "T" step. Indeed, they should be writing Yet Another Transformation Tool (YATT) instead of YAETLT.
Enter the Python
If all we're doing is moving data around, what's involved?
import csv
result = {
'column1': None,
'colmnn2': None,
# etc.
}
with open("source","rb") as source:
rdr= csv.DictReader( source )
with open( "target","wb") as target:
wtr= csv.DictWriter( target, result.keys() )
for row in rdr:
result['column1']= row['some_column']
result['column2']= some_func( row['some_column'] )
# etc.
wtr.writerow( result )
That's really about it. There appear to be 6 or 7 lines of overhead. The rest is working code.
But let's not be too dismissive of the overhead. An ETL depends on the file format, summarized in the import statement. With a little care we can produce libraries similar to Python's csv that work with XLS directly, as well as XLSX and other formats. Dealing with COBOL-style fixed layout files can also be boiled down to an importable module. The import isn't overhead; it's a central part of the rules.
The file open functions could be seen as overhead. Do we really need a full line of code when we could -- more easily -- read from stdin and write to stdout? If we're willing to endure the inefficiency of processing one input file multiple times to create several standardized outputs, then we could eliminate the two with statements. If, however, we have to merge several input files to create a standardized output file, the one-in-one-out model breaks down and we need the with statements and the open functions.
The for statement could be seen as needless overhead. It goes without saying that we're processing the entire input file. Unless, of course, we're merging several files. Then, perhaps, it's not a simple loop that can be somehow implied.
It's Just Code
The point of Python-based ETL is that the problem "solved" by YATT isn't that interesting. Python is an excellent transformation engine ETL. Rather than write a fancy rule interpreter, just write Python. Done.
We don't need a higher-level data transformation engine written in Java. Emit simple Python code and use the Python engine. (We could try to emit Java code, but it's not as simple and requires a rather complex supporting library. Python's Duck Typing simplifies the supporting library.)
If we don't write a new transformation engine, but use Python, that leaves a tiny space left over for the YATT: producing the ETL rules in Python notation. Rather than waste time writing another engine, the YATT developers could create a GUI that drags and drops column names to write the assignment statements in the body of the loop.
That's right, the easiest part of the Python loop is what we can automate. Indeed, that's about all we can automate. Everything else requires complex coding that can't be built as "drag-and-drop" functionality.
Transformations
There are several standard transformations.
- Column order or name changes. Trivial assignment statements handle this.
- Mapping functions. Some simple (no hysteresis, idempotent) function is applied to one or more columns to produce one or more columns. This can be as simple as a data type conversion, or a complex calculation.
- Filter. Some simple function is used to include or exclude rows.
- Reduction. Some summary (sum, count, min, max, etc.) is applied to a collection of input rows to create output rows. This is an ideal spot for Python generator functions. But there's rarely a simple drag-n-drop for these kinds of transformations.
- Split. One file comes in, two go out. This breaks the stdin-to-stdout assumption.
- Merge. Two go in, one comes out. This breaks the stdin-to-stdout assumption, also. Further, the matching can be of several forms. There's the multi-file merge when several similarly large files are involved. There's the lookup merge when a large file is merged with smaller files. Merging also applies to doing key lookups required to match natural keys to locate database FK's.
- Normalization (or Distinct Processing). This is a more subtle form of filter because the function isn't idempotent; it depends on the state of a database or output file. We include the first of many identical items; we exclude the subsequent copies. This is also an ideal place for Python generator functions.
Of these, only the first three are candidates for drag-and-drop. And for mapping and filtering, we either need to write code or have a huge library of pre-built mapping and filtering functions.
Problems and Solutions
The YATT problem has two parts. Creating the rules and executing the rules.
Writing another engine to execute the rules is a bad idea. Just generate Python code. It's a delightfully simple language for describing data transformation. It already works.
Writing a tool to create rules is a bad idea. Just write the Python code and call it the rule set. Easy to maintain. Easy to test. Clear, complete, precise.
Posted by S.Lott at 8:00 AM 1 comment:
Thursday, November 4, 2010
Pythonic vs. "Clean"
This provokes thought: "Pythonic".
Why.
Tuesday, November 2, 2010
"Might Be Misleading" is misleading
My books (Building Skills in Programming, Building Skills in Python and Building Skills in OO Design) develop a steady stream of email. [Also, as a side note, I need to move them to the me.com server, Apple is decommissioning the homepage.mac.com domain.]...
Tuesday, October 26, 2010
Python and the "Syntactic Whitespace Problem"
About 10% of these are really just complaints about Python's syntax. Almost every Stack Overflow question on Python's use of syntactic whitespace is really just a complaint.
Here's today's example: "Python without whitespace requirements".
Here's the money quote: "I could potentially be interested in learning Python but the whitespace restrictions are an absolute no-go for me."
Here's the reality.
Everyone Indents Correctly All The Time In All Languages.
Everyone. All the time. Always.
It's amazing how well, and how carefully people indent code. Not Python code.
All Code. XML. HTML. CSS. Java. C++. SQL. All Code.
Everyone indents. And they always indent correctly. It's truly amazing how well people indent. In particular, when the syntax doesn't require any indentation, they still indent beautifully.
Consider this snippet of C code.
if( a == 0 )
printf( "a is zero" );
r = 1;
else
printf( "a is non-zero" );
r = a % 2;
Over the last few decades, I've probably spent a complete man-year reading code like that and trying to figure out why it doesn't work. It's not easy to debug.
The indentation completely and accurately reflects the programmer's intention. Everyone gets the indentation right. All the time. In every language.
And people still complain about Python, even when they indent beautifully in other languages.
Thursday, October 21, 2010
Code Base Fragmentation
Here's what I love -- an argument that can only add cost and complexity to a project.."
Tuesday, October 19, 2010
Technical Debt
Love this from Gartner. "Gartner Estimates Global 'IT Debt' to Be $500 Billion This Year, with Potential to Grow to $1 Trillion by 2015".
Network?
Wednesday, October 13, 2010
Real Security Models
Lots of folks like to wring their hands over the Big Vague Concept (BVC™) labeled "security".
There.
Posted by S.Lott at 8:00 AM 1 comment:
Monday, October 4, 2010
.xlsm and .xlsx Files -- Finally Reaching Broad Use
For years, I've been using Apache POI in Java and XLRD in Python to read spreadsheets. Finally, now that .XLSX and .XLSM files are in more widespread use, we can move away from those packages and their reliance on successful reverse engineering of undocumented features.
Spreadsheets are -- BTW -- the universal user interface. Everyone likes them, they're almost inescapable. And they work. There's no reason to attempt to replace the spreadsheet with a web page or a form or a desktop application. It's easier to cope with spreadsheet vagaries than to replace them.
The downside is, of course, that users often tweak their spreadsheets, meaning that you never have a truly "stable" interface. However, transforming each row of data into a Python dictionary (or Java mapping) often works out reasonably well to make your application mostly immune to the common spreadsheet tweaks.
Most of the .XLSX and .XLSM spreadsheets we process can be trivially converted to CSV files. It's manual, yes, but a quick audit can check the counts and totals.
Yesterday we got an .XLSM with over 80,000 plus rows. It couldn't be trivially converted to CSV by my installation of Excel.
What to do?
Python to the Rescue
Step 1. Read the standards. Start with the Wikipedia article: "Open Office XML". Move to the ECMA 376 standard.
Step 2. It's a zip archive. So, to process the file, we need to locate the various bits inside the archive. In many cases, the zip members can be processed "in memory". In the case of our 80,000+ row spreadsheet, the archive is 34M. The sheet in question expands to a 215M beast. The shared strings are 3M. This doesn't easily fit into memory.
Further, a simple DOM parser, like Python's excellent ElementTree, won't work on files this huge.
Expanding an XLSX or XLSM file
Here's step 2. Expanding the zip archive to locate the shared strings and sheets.
import zipfile
def get_worksheets(name):
arc= zipfile.ZipFile( name, "r" )
member= arc.getinfo("xl/sharedStrings.xml")
arc.extract( member )
for member in arc.infolist():
if member.filename.startswith("xl/worksheets") and member.filename.endswith('.xml'):
arc.extract(member)
yield member.filename
This does two things. First, it locates the shared strings and the various sheets within the zip archive. Second, it expands the sheets and shared strings into the local working directory.
There are many other parts to the workbook archive. The good news is that we're not interesting in complex workbooks with lots of cool Excel features. We're interested in workbooks that are basically file-transfer containers. Usually a few sheets with a consistent format.
Once we have the raw files, we have to parse the shared strings first. Then we can parse the data. Both of these files are simple XML. However, they don't fit in memory. We're forced to use SAX.
Step 3 -- Parse the Strings
Here's a SAX ContentHandler that finds the shared strings.
import xml.sax
import xml.sax.handler
class GetStrings( xml.sax.handler.ContentHandler ):
"""Locate Shared Strings."""
def __init__( self ):
xml.sax.handler.ContentHandler.__init__(self)
self.context= []
self.count= 0
self.string_dict= {}
def path( self ):
return [ n[1] for n in self.context ]
def startElement( self, name, attrs ):
print( "***Non-Namespace Element", name )
def startElementNS( self, name, qname, attrs ):
self.context.append( name )
self.buffer= ""
def endElementNS( self, name, qname ):
if self.path() == [u'sst', u'si', u't']:
self.string_dict[self.count]= self.buffer
self.buffer= ""
self.count += 1
while self.context[-1] != name:
self.context.pop(-1)
self.context.pop(-1)
def characters( self, content ):
if self.path() == [u'sst', u'si', u't']:
self.buffer += content
This handler collects the strings into a simple dictionary, keyed by their relative position in the XML file.
This handler is used as follows.
string_handler= GetStrings()
rdr= xml.sax.make_parser()
rdr.setContentHandler( string_handler )
rdr.setFeature( xml.sax.handler.feature_namespaces, True )
rdr.parse( "xl/sharedStrings.xml" )
We create the handler, create a parser, and process the shared strings portion of the workbook. When this is done, the handler has a dictionary of all strings. This is string_handler.string_dict. Note that a shelve database could be used if the string dictionary was so epic that it wouldn't fit in memory.
The Final Countdown
Once we have the shared strings, we can then parse each worksheet, using the share string data to reconstruct a simple CSV file (or JSON document or something more usable).
The Content Handler for the worksheet isn't too complex. We only want cell values, so there's little real subtlety. The biggest issue is coping with the fact that sometimes the content of a tag is reported in multiple parts.
class GetSheetData( xml.sax.handler.ContentHandler ):
"""Locate column values."""
def __init__( self, string_dict, writer ):
xml.sax.handler.ContentHandler.__init__(self)
self.id_pat = re.compile( r"(\D+)(\d+)" )
self.string_dict= string_dict
self.context= []
self.row= {}
self.writer= writer
def path( self ):
return [ n[1] for n in self.context ]
def startElement( self, name, attrs ):
print( "***Non-Namespace Element", name )
def startElementNS( self, name, qname, attrs ):
self.context.append( name )
if name[1] == "row":
self.row_num = attrs.getValueByQName(u'r')
elif name[1] == "c":
if u't' in attrs.getQNames():
self.cell_type = attrs.getValueByQName(u't')
else:
self.cell_type = None # defult, not a string
self.cell_id = attrs.getValueByQName(u'r')
id_match = self.id_pat.match( self.cell_id )
self.row_col = self.make_row_col( id_match.groups() )
elif name[1] == "v":
self.buffer= "" # Value of a cell
else:
pass # might do some debugging here.
@staticmethod
def make_row_col( col_row_pair ):
col = 0
for c in col_row_pair[0]:
col = col*26 + (ord(c)-ord("A")+1)
return int(col_row_pair[1]), col-1
def endElementNS( self, name, qname ):
if name[1] == "row":
# write the row to the CSV result file.
self.writer.writerow( [ self.row.get(i) for i in xrange(max(self.row.keys())) ] )
self.row= {}
elif name[1] == "v":
if self.cell_type is None:
try:
self.value= float( self.buffer )
except ValueError:
print( self.row_num, self.cell_id, self.cell_type, self.buffer )
self.value= None
elif self.cell_type == "s":
try:
self.value= self.string_dict[int(self.buffer)]
except ValueError:
print( self.row_num, self.cell_id, self.cell_type, self.buffer )
self.value= None
elif self.cell_type == "b":
self.value= bool(self.buffer)
else:
print( self.row_num, self.cell_id, self.cell_type, self.buffer, self.string_dict.get(int(self.buffer)) )
self.value= None
self.row[self.row_col[1]] = self.value
while self.context[-1] != name:
self.context.pop(-1)
self.context.pop(-1)
def characters( self, content ):
self.buffer += content
This class and the shared string handler could be refactored to eliminate a tiny bit of redundancy.
This class does two things. At the end of a
tag, it determines what data was found. It could be a number, a boolean value or a shared string. At the end of a
tag, it writes the row to a CSV writer.
This handler is used as follows. iterates through each sheet, transforming it into a simple .CSV file. Once we have the file in CSV format, it's smaller and simpler. It can easily be processed by follow-on applications.
The overall loop actually looks like this.
sheets= list( get_worksheets(name) )
string_handler= GetStrings()
rdr= xml.sax.make_parser()
rdr.setContentHandler( string_handler )
rdr.setFeature( xml.sax.handler.feature_namespaces, True )
rdr.parse( "xl/sharedStrings.xml" ) expands the shared strings and individual sheets. It iterates through the sheets, using the shared strings, to create a bunch of .CSV files from the .XLSM data.
The resulting .CSV -- stripped of the XML overheads -- is 80,000+ rows and only 39M. Also, it can be processed with the Python csv library.
CSV Processing
This, after all, was the goal. Read the CSV file and do some useful work.
def csv_rows(source):
rdr= csv.reader( source )
headings = []
for n, cols in enumerate( rdr ):
if n < 4:
if headings:
headings = [ (top+' '+nxt).strip() for top, nxt in zip( headings, cols ) ]
else:
headings = cols
continue
yield dict(zip(headings,cols))
We locate the four header rows and build labels from the the four rows of data. Given these big, complex headers, we can then build a dictionary from each data row. The resulting structure is exactly like the results of a csv.DictReader, and can be used to do the "real work" of the application.
Posted by S.Lott at 8:00 AM 6 comments:
Thursday, September 30, 2010
SQL Can Be Slow -- Why Do People Doubt This?
Here's a typical problem that results from "SQL Hegemony" -- all data must be in a database, and all access must be via SQL. This can also be called the "SQL Fetish" school of programming.
War.
Tuesday, September 28, 2010
Why Professional Certification Might Be Good
Sometimes I think we need professional certification in this industry. I supported the ICCP for a long time..
Thursday, September 23, 2010
See "Commenting the Code". This posting tickled my fancy because it addressed the central issue of "what requires comments outside Python docstrings". All functions, classes, modules and packages require docstrings. That's clear. But which lines of code require additional documentation?
We use Sphinx, so we make extensive use of docstrings. This posting forced me to think about non-docstring commentary. The post makes things a bit more complex than necessary. It enumerated some cases, which is helpful, but didn't see the commonality between them.
The posting lists five cases for comments in the code.
- Summarizing the code blocks. Semi-agree. However, many code blocks indicates too few functions or methods. I rarely write a function long enough to have "code blocks". And the few times I did, it became regrettable. We're unwinding a terrible mistake I made regarding an actuarial calculation. It seemed so logical to make it four steps. It's untestable as a 4-step calculation.
- Describe every "non-trivial" operation. Hmmm... Hard t0 discern what's trivial and what's non-trivial. The examples on the original post seems to be a repeat of #1. However, it seems more like this is a repeat of #5.
- TODO's. I don't use comments for these. These have to be official ".. todo::" notations that will be picked up by Sphinx. So these have to be in docstrings, not comments.
- Structures with more than a couple of elements. The example is a tuple of tuples. I'd prefer to use a namedtuple, since that includes documentation.
- Any "doubtful" code. This is -- actually -- pretty clear. When in doubt, write it out. This seems to repeat #2.
One of the other cases in the the post was really just a suggestion that comments be "clear as well as short". That's helpful, but not a separate use case for code comments.
So, of the five situations for comments described in the post, I can't distinguish two of them and don't agree with two more.
This leaves me with two use cases for Python code commentary (distinct from docstrings).
- A "summary" of the blocks in a long-ish method (or function)
- Any doubtful or "non-trivial" code. I think this is code where the semantics aren't obvious; or code that requires some kind of review of explanation of what the semantics are.
The other situations are better handled through docstrings or named tuples.
Assertions
Comments are interesting and useful, but they aren't real quality assurance.
A slightly stronger form of commentary is the assert statement. Including an assertion formalizes the code into a clear predicate that's actually executable. If the predicate fails, the program was mis-designed or mis-constructed.
Some folks argue that assertions are a lot of overhead. While they are overhead, they aren't a lot of overhead. Assertions in the body of the inner-most, inner-most loops may be expensive. But must of the really important assertions are in the edge and corner cases which (a) occur rarely and (b) are difficult to design and (c) difficult to test.
Since the obscure, oddball cases are rare, cover these with the assert statement in addition to a comment.
That's Fine, But My Colleagues are Imbeciles
There are numerous questions on Stack Overflow that amount to "comments don't work". Look at at the hundreds of question that include the keywords public, protected and private. Here's a particularly bad question with a very common answer.
Because you might not be the only developer in your project and the other developers might not know that they shouldn't change it. ...
This seems silly. "other developers might not know" sounds like "other developers won't read the comments" or "other developers will ignore the comments." In short "comments don't work."
I disagree in general. Comments can work. They work particularly well in languages like Python where the source is always available.
For languages like C++ and Java, where the source can be separated and kept secret, comments don't work. In this case, you have to resort to something even stronger.
Unit Tests
Unit tests are perhaps the best form of documentation. If someone refuses to read the comments, abuses a variable that's supposed to be private, and breaks things, then tests will fail. Done.
Further, the unit test source must be given to all the other developers so they can see how the API is supposed to work. A unit test is a living, breathing document that describes how a class, method or function behaves.
Explanatory Power
Docstrings are essential. Tools can process these.
Comments are important for describing what's supposed to happen. There seem to be two situations that call for comments outside docstrings.
Assertions can be comments which are executable. They aren't always as descriptive and English prose, but they are formal and precise.
Unit tests are important for confirming what actually happens. There's really no alternative to unit testing to supplement the documentation. | https://slott-softwarearchitect.blogspot.com/2010/ | CC-MAIN-2021-39 | refinedweb | 4,267 | 69.18 |
When I run the following code I get two error messages:
p58Exercise2.cpp(19): error C2533: 't_and_d::__ctor' : constructors not allowed a return type
p58Exercise2.cpp(19): fatal error C1903: unable to recover from previous error(s); stopping compilation
I can't figure out why? any help would be apreciated
I am working with the book "Teach Yourself C++" third edition.
The excersie I am trying to complete is as follows:
Create a class called t-and_d that is passed the current system time and date as a parameter to its constructor when it is created. Have the class include a member function that displays this time and date on the screen. (Hint: Use the standard time and date functions found in the standard library to find and display the time and date.)
I had problems with this one from the start. Finally I worked through it and out of frustraction peeeked at the answer in the back of the book.
The COde:
thanks,thanks,Code:
// Declare a class called t_and_d, that is passed the current syustem time and date
// as a parameter to it constructor when it is created,
#include <iostream>
#include <ctime>
using namespace std;
// Declare a class called t_and_d
class t_and_d {
time_t systime;
public:
t_and_d(time_t t); // constructor
void show();
}
t_and_d::t_and_d(time_t t)
{
systime = t;
}
void t_and_d::show()
{
cout << ctime(&systime);
}
int main()
{
time_t x;
x = time(NULL);
t_and_d ob(x);
ob.show();
return 0;
} | http://cboard.cprogramming.com/cplusplus-programming/62088-ctime-issue-printable-thread.html | CC-MAIN-2015-27 | refinedweb | 239 | 67.99 |
On Wed, Aug 31, 2011 at 5:41 AM, Steven D'Aprano <steve at pearwood.info>wrote: > To make it work using just ordinary assignment syntax, as you suggest, > requires more than just an "alias" function. It would need changes to the > Python internals. Possibly very large changes. Without a convincing > use-case, I don't think that will happen. > Well, once you clear up some of the ambiguities in the request, it's not quite so bad. class F(object): def m(self): alias(a, b) Which name space is a being aliased in? Function local? Instance? Class? Module? So alias needs to take a namespace of some sort. The appropriate object is easy to find, and should do the trick (though function local might be entertaining). For simplicity, we'll assume that aliases have to be in the same namespace (though doing otherwise isn't really harder, just slower). Passing in variable values doesn't work very well - especially for the new alias, which may not *have* a value yet! For the name to be aliased, you could in theory look up the value in the namespace and use the corresponding name, but there may be more than one of those. So pass that one in as a string as well. So make the call "alias(o, name1, name2)". o is a module, class, instance, or function. Name lookups are done via the __dict__ dict for all of those. It's easy to write a dict subclass that aliases it's entries. So the internal changes would be making __dict__ a writable attribute on any objects which it currently isn't, and making sure that the various objects use __setitem__ to change attribute values. I suspect the performance hit - even if you don't use this feature - would be noticeable. If you used it, it would be even worse. -1. <mike -------------- next part -------------- An HTML attachment was scrubbed... URL: <> | https://mail.python.org/pipermail/python-ideas/2011-August/011336.html | CC-MAIN-2021-39 | refinedweb | 321 | 82.24 |
At 01:35 PM 01/18/2006 -0500, Charlie Moad wrote: >Following the instruction for setuptools, I am trying to make >matplotlib and basemap (a mpl toolkit) share the namespace >"matplotlib/toolkits". I can build and install the eggs no problems. >"matplotlib/toolkits" is in both's "EGG-INFO/namespace_packages.txt" It should be matplotlib.toolkits, not matplotlib/toolkits. >files. I have added __init__.py files with >"__import__('pkg_resources').declare_namespace(__name__)" in both the >mpl and basemap matplotlib/toolkits folders. Basically I have done a >ton of playing around and "from matplotlib.toolkits import basemap" >will not work. It is always limited to the scope of the matplotlib >egg which it is hitting first. Did you run "setup.py develop" or "setup.py install" in both projects? > Are the docs not reflective of the >0.6a9 release? Any help is greatly appreciated. AFAIK, the docs are correct. If you can point me to the source code for your packages I can take a look at them. | https://mail.python.org/pipermail/distutils-sig/2006-January/005861.html | CC-MAIN-2016-44 | refinedweb | 166 | 71.71 |
WP7Contrib offers an alternative to the WP7 Silverlight Toolkit transitions, and in my humble opinion, the alternative is significantly better in this case. The Silverlight toolkit offers easy integration of transitions via a little XAML markup and a minor change to the root frame. The biggest problem with the toolkit transitions are that they’re slow and exceedingly memory intensive with complex layouts consuming copious amounts of memory. In my latest app the transitions alone could use up to 40MB. Don’t forget, there is a 90MB limit for all apps when operating on devices with 256MB RAM.
WP7Contrib offers an alternative that’s code-based rather than markup-based. This may be preferable, or it may not depending on your internal setup. Personally for something like transitions I prefer code-based so transitions are the ‘default’ rather than the exception.
The greatest thing about WP7Contrib Transitions, is that they’re a doddle to implement if you just want to have transitions between pages. In WP7 the ‘standard’ transition is the turnstile transition – this is where each screen appears and disappears as if they’re pages in a book. Here’s how to get this transition into your app:
Simple Transitions
If you want to see the transitions for yourself, click here to download the demo app. Otherwise , download WP7Contrib and compile it. Once you’ve done this, add the WP7Contrib.View.Controls and WP7Contrib.View.Transitions assemblies to your project References. These are the only two assemblies required to get transitions working, and I prefer to include as few assemblies as possible to keep load times fast.
Next you need to make some minor tweaks to every page you want to animate. Add the following namespace to the XAML file:
xmlns:animation="clr-namespace:WP7Contrib.View.Transitions.Animation;assembly=WP7Contrib.View.Transitions"
Next change the page type to ‘animation:AnimatedBasePage’. To do this the first line of your XAML file should be:
<animation:AnimatedBasePage
And the last line should be:
</animation:AnimatedBasePage>
Now go into the code-behind and change the base type of your page to ‘AnimatedBasePage’. The final change is to add the following line into the constructor:
AnimationContext = LayoutRoot;
This tells WP7Contrib that your ‘root element’ is ‘LayoutRoot’. You can set any element to be the AnimationContext, this is useful if you want to only animate a sub-area of the page between pages. Generally speaking you’ll want to target LayoutRoot, or whichever element you’ve got containing all of your UI. This is the big difference between WP7Contrib and the WP7 Toolkit which targets the page frame itself.
Compile and run your app – you should find your pages automatically use the turnstile transition. Don’t forget you can download the demo app here.
Personally, I can’t recommend WP7Contrib transitions enough. They have a few caveats, but the performance improvements and memory savings are substantial. I hope that this article has given you a taster of the transitions and how easy they are to implement.
Hungry for more? Click here to view part 2 where we cover additional transitions.
Thanks so much for this, as a complete newb (I started learning C# last week) would you be able to explain how to compile the file. I took the reference file from your sample file in the end.
Also for other beginners such as myself perhaps you should mention the fact you have to reference the namespace in the codebehind page as well.
Thanks again,
Ian
You sure are jumping into C# at the deep end! I’ll add the namespace info soon – good catch. Can you tell me what issues you had compiling the file?
Thank you so much Dan! I put these transitions into my current app: GeoFlick. Almost ready to publish the udpate, which includes very many updates, now including turnstile!
Again, thank you!
I have a simple app that used to use SilverLight toolkit transitions. I converted them to WP7Contrib transitions using this page.
App has only two pages, builds and works fine, but I see no transitions. Whats even more strange I see a transition when I click hardware back key. Just not when I click back button in my page that just does NavitionService.GoBack().
What can I do to troubleshoot?
Nice work. Your page transitions are faster than toolkit (.xaml) transitions. I will use your page transitions and I say thank you. Hopefully I can contribute in same manner in future.
Hi Dan,
Thanks for this awesome work. I’ve noticed a slight problem with the transitions though. Using your demo app, if you select an item from the list and navigate to the next page, then press the phone’s start button to leave the app. Then press the back button to go back into the app, the page does not display, we just see a blank screen. | http://dan.clarke.name/2011/07/wp7contrib-transitions-easy-page-transitions-for-windows-phone-7-part-1/?replytocom=404 | CC-MAIN-2019-39 | refinedweb | 811 | 65.42 |
Well today's been a bit of shock. After running port -v selfupdate followed by an attempt to run sudo port install py26-ipython MacPorts went around installing a whole host of stuff, including updating my Python from 2.6.4 to 2.6.5. It's nice but unexpected in a creepy way.
port -v selfupdate
sudo port install py26-ipython
So I tried to install TKInter using MacPorts with port search tkinter yielding:
port search tkinter
py-tkinter @2.4.6 (python, graphics)
Python bindings to the Tk widget set
py25-tkinter @2.5.4 (python, graphics)
This is a stub. tkinter is now built with python25
Found 2 ports.
So I tried sudo port install py25-tkinter and then it tries to install Python 2.5.5. There must be an easier way to install TkInter without being faffed around... help please?
sudo port install py25-tkinter
C extensions for python will require different shared libraries for each major version e.g. 2.x
Macports thus creates a separate set of ports for each version of python. Macports will also update its python to the latest minor version - thus in your case the upgrade from 2.5.4 to 2.5.5
To use macports python you need to choose which major version currently 2.4, 2.5, 2.6, 3.0 or 3.1 (2.7 might be there but few libraries) Then choose the libraries you need which are prefixed respecively with py-, py25-, py26-, py30- and py31-
As for TKinter it is from 2.6 onwards it is part of the base python port so you do not need to install it.
You need to choose your python version - I would suggest 2.6. This is done by installing the port python select and then running ot to choose the version e.g.
python_select python26
import Tkinter
If you don't want MacPorts to update your existing outdated software before installing a new port, use the -n switch.
-n
sudo port -n install py26-ipython
Usually it's better to upgrade first and then install new ports as it is less error-prone.
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If you are making an RPG or RTS game, chances are that you will need to use some kind of pathfinding and/or local avoidance solution for the behaviour of the mobs. They will need to get around obstacles, avoid each other, find the shortest path to their target and properly surround it. They also need to do all of this without bouncing around, getting stuck in random places and behave as any good crowd of cows would:
In this blog post I want to share my experience on how to achieve a result that is by no means perfect, but still really good, even for release. We'll talk about why I chose to use Unity's built in NavMesh system over other solutions and we will create an example scene, step by step. I will also show you a couple of tricks that I learned while doing this for my game. With all of that out of the way, let's get going.
Choosing a pathfinding library
A few words about my experiences with some of the pathfinding libraries out there.
Aron Granberg's A* Project
This is the first library that I tried to use, and it was good. When I was doing the research for which library to use, this was the go-to solution for many people. I checked it out, it seemed to have pretty much everything needed for the very reasonable price of $99. There is also a free version, but it doesn't come with Local Avoidance, so it was no good.
Purchased it, integrated it into my project and it worked reasonably well. However, it had some key problems.
- Scene loading. It adds a solid chunk of time to your scene loading time. When I decided to get rid of A* and deleted all of its files from my project (after using it for 3 months), my scene loading time dropped to 1-2 seconds, up from 5-10 seconds when I press "Play". It's a pretty dramatic difference.
- RVO Local Avoidance. Although it's one of the library's strong points, it still had issues. For example, mobs were getting randomly stuck in places where they should be able to get through, also around corners, and stuff like that. I'm sure there is a setting somewhere buried, but I just could not get it right and it drove me nuts. The good part about the local avoidance in this library is that it uses the RVO algorithm and the behaviour of the agents in a large crowd was flawless. They would never go through one another or intersect. But when you put them in an environment with walls and corners, it gets bad.
- Licensing issues. However the biggest problem of the library since a month ago is that it doesn't have any local avoidance anymore (I bet you didn't see that one coming). After checking out the Aron Granberg's forums one day, I saw that due to licensing claims by the UNC (University of North Carolina), which apparently owned the copyright for the RVO algorithm, he was asked to remove RVO from the library or pay licensing fees. Sad.
UnitySteer
Free and open source, but I just could not get this thing to work. I'm sure it's good, it looks good on the demos and videos, but I'm guessing it's for a bit more advanced users and I would stay away from it for a while. Just my two cents on this library.
Unity's built in NavMesh navigation
While looking for a replacement for A* I decided to try out Unity's built in navigation system. Note - it used to be a Unity Pro only feature, but it got added to the free version some time in late 2013, I don't know when exactly. Correct me if I'm wrong on this one. Let me explain the good and bad sides of this library, according to my experience up to this point.
The Good
It's quick. Like properly quick. I can easily support 2 to 3 times more agents in my scene, without the pathfinding starting to lag (meaning that the paths take too long to update) and without getting FPS issues due to the local avoidance I believe. I ended up limiting the number of agents to 100, just because they fill the screen and there is no point in having more.
Easy to setup. It's really easy to get this thing to work properly. You can actually make it work with one line of code only:
agent.destination = target.position;
Besides generating the navmesh itself (which is two clicks) and adding the NavMeshAgent component to the agents (default settings), that's really all you need to write to get it going. And for that, I recommend this library to people with little or no experience with this stuff.
Good pathfinding quality. What I mean by that is agents don't get stuck anywhere and don't have any problem moving in tight spaces. Put simply, it works like it should. Also, the paths that are generated are really smooth and don't need extra work like smoothing or funnelling.
The Bad
Not the best local avoidance. It's slightly worse than RVO, but nothing to be terribly worried about, at least in my opinion and for the purposes of an ARPG game. The problem comes out when you have a large crowd of agents - something like 100. They might intersect occasionally, and start jiggling around. Fortunately, I found a nice trick to fix the jiggling issue, which I will share in the example below. I don't have a solution to the intersecting yet, but it's not much of a problem anyway.
That sums up pretty much everything that I wanted to say about the different pathfinding solutions out there. Bottom line - stick with NavMesh, it's good for an RPG or RTS game, it's easy to set up and it's free.
Example project
In this section I will explain step by step how to create an example scene, which should give you everything you need for your game. I will attach the Unity project for this example at the end of the post.
Creating a test scene
Start by making a plane and set its scale to 10. Throw some boxes and cylinders around, maybe even add a second floor. As for the camera, position it anywhere you like to get a nice view of the scene. The camera will be static and we will add point and click functionality to our character to make him move around. Here is the scene that I will be using:
Next, create an empty object, position it at (0, 0, 0) and name it "player". Create a default sized cylinder, make it a child of the "player" object and set its position to (0, 1, 0). Create also a small box in front of the cylinder and make it a child of "player". This will indicate the rotation of the object. I have given the cylinder and the box a red material to stand out from the mobs. Since the cylinder is 2 units high by default, we position it at 1 on the Y axis to sit exactly on the ground plane:
We will also need an enemy, so just duplicate player object and name it "enemy".
Finally, group everything appropriately and make the "enemy" game object into a prefab by dragging it to the project window.
Generating the NavMesh
Select all obstacles and the ground and make them static by clicking the "Static" checkbox in the Inspector window.
Go to Window -> Navigation to display the Navigation window and press the "Bake" button at the bottom:
Your scene view should update with the generated NavMesh:
The default settings should work just fine, but for demo purposes let's add some more detail to the navmesh to better hug the geometry of our scene. Click the "Bake" tab in the Navigation window and lower the "Radius" value from 0.5 to 0.2:
Now the navmesh describes our scene much more accurately:
I recommend checking out the Unity Manual here to find out what each of the settings do.
However, we are not quite done yet. If we enter wireframe mode we will see a problem:
There are pieces of the navigation mesh inside each obstacle, which will be an issue later, so let's fix it.
- Create an empty game object and name it "obstacles".
- Make it a child of the "environment" object and set its coordinates to (0, 0, 0).
- Select all objects which are an obstacle and duplicate them.
- Make them children of the new "obstacles" object.
- Set the coordinates of the "obstacles" object to (0, 1, 0).
- Select the old obstacles, which are still direct children of environment and turn off the Static checkbox.
- Bake the mesh again.
- Select the "obstacles" game object and disable it by clicking the checkbox next to its name in the Inspector window. Remember to activate it again if you need to Bake again.
Looking better now:
Here is how the scene hierarchy looks like after this small hack:
Point and click
It's time to make our character move and navigate around the obstacles by adding point and click functionality to the "player" object. Before we begin, you should delete all capsule and box colliders on the "player" and "enemy" objects, as well as from the obstacles (but not the ground) since we don't need them for anything.
Start by adding a NavMeshAgent component to the "player" game object. Then create a new C# script called "playerMovement" and add it to the player as well. In this script we will need a reference to the NavMeshAgent component. Here is how the script and game object should look like:
using UnityEngine; using System.Collections; public class playerMovement : MonoBehaviour { NavMeshAgent agent; void Start () { agent = GetComponent< NavMeshAgent >(); } void Update () { } }
Now to make the character move, we need to set its destination wherever we click on the ground. To determine where on the ground the player has clicked, we need to first get the location of the mouse on the screen, cast a ray towards the ground and look for collision. The location of the collision is the destination of the character.
However, we want to only detect collisions with the ground and not with any of the obstacles or any other objects. To do that, we will create a new layer "ground" and add all ground objects to that layer. In the example scene, it's the plane and 4 of the boxes.
Here is the script so far:
using UnityEngine; using System.Collections; public class playerMovement : MonoBehaviour { NavMeshAgent agent; void Start () { agent = GetComponent< NavMeshAgent >(); } void Update () { if (Input.GetMouseButtonDown(0)) { // ScreenPointToRay() takes a location on the screen // and returns a ray perpendicular to the viewport // starting from that location Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition); RaycastHit hit; // Note that "11" represents the number of the "ground" // layer in my project. It might be different in yours! LayerMask mask = 1 < 11; // Cast the ray and look for a collision if (Physics.Raycast(ray, out hit, 200, mask)) { // If we detect a collision with the ground, // tell the agent to move to that location agent.destination = hit.point; } } } }
Now press "Play" and click somewhere on the ground. The character should go there, while avoiding the obstacles along the way.
If it's not working, try increasing the ray cast distance in the Physics.Raycast() function (it's 200 in this example) or deleting the mask argument from the same function. If you delete the mask it will detect collisions with all boxes, but you will at least know if that was the problem.
If you want to see the actual path that the character is following, select the "player" game object and open the Navigation window.
Make the agent follow the character
- Repeat the same process as we did for the "player" object - attach a NavMeshAgent and a new script called "enemyMovement".
- To get the player's position, we will also add a reference to the "player" object, so we create a public Transform variable. Remember to go back in the Editor connect the "player" object to that variable.
- In the Update() method set the agent's destination to be equal to the player's position.
Here is the script so far:
using UnityEngine; using System.Collections; public class enemyMovement : MonoBehaviour { public Transform player; NavMeshAgent agent; void Start () { agent = GetComponent< NavMeshAgent >(); } void Update () { agent.destination = player.position; } }
Press "Play" and you should see something like the following screenshot. Again, if you want to show the path of the enemy object, you need to select it and open the Navigation window.
However, there are a few things that need fixing.
- First, set the player's move speed to 6 and the enemy's speed to 4. You can do that from the NavMeshAgent component.
- Next, we want the enemy to stop at a certain distance from the player instead of trying to get to his exact location. Select the "enemy" object and on the NavMeshAgent component set the "Arrival Distance" to 2. This could also represent the mob's attack range.
- The last problem is that generally we want the enemies to body block our character so he can get surrounded. Right now, our character can push the enemy around. As a temporary solution, select the "enemy" object and on the NavMeshAgent component change the "Avoidance Priority" to 30.
Here is what the docs say about Avoidance Priority:
When the agent is performing avoidance, agents of lower priority are ignored. The valid range is from 0 to 99 where: Most important = 0. Least important = 99. Default = 50.
By setting the priority of the "enemy" to 30 we are basically saying that enemies are more important and the player can't push them around. However, this fix won't work so well if you have 50 agents for example and I will show you a better way to fix this later.
Making a crowd of agents
Now let's make this a bit more fun and add, let's say 100 agents to the scene. Instead of copying and pasting the "enemy" object, we will make a script that instantiates X number of enemies within a certain radius and make sure that they always spawn on the grid, instead of inside a wall.
Create an empty game object, name it "spawner" and position it somewhere in the scene. Create a new C# script called "enemySpawner" and add it to the object. Open enemySpawner.cs and add a few public variables - one type int for the number of enemies that we want to instantiate, one reference of type GameObject to the "enemy" prefab, and one type float for the radius in which to spawn the agents. And one more - a reference to the "player" object.
using UnityEngine; using System.Collections; public class enemySpawner : MonoBehaviour { public float spawnRadius = 10; public int numberOfAgents = 50; public GameObject enemyPrefab; public Transform player; void Start () { } }
At this point we can delete the "enemy" object from the scene (make sure you have it as a prefab) and link the prefab to the "spawner" script. Also link the "player" object to the "player" variable of the "spawner".
To make our life easier we will visualise the radius inside the Editor. Here is how:
using UnityEngine; using System.Collections; public class enemySpawner : MonoBehaviour { public float spawnRadius = 10; public int numberOfAgents = 50; public GameObject enemyPrefab; public Transform player; void Start () { } void OnDrawGizmosSelected () { Gizmos.color = Color.green; Gizmos.DrawWireSphere (transform.position, spawnRadius); } }
OnDrawGizmosSelected() is a function just like OnGUI() that gets called automatically and allows you to use the Gizmos class to draw stuff in the Editor. Very useful! Now if you go back to the Editor, select the "spawner" object and adjust the spawnRadius variable if needed. Make sure that the centre of the object sits as close to the floor as possible to avoid spawning agents on top of one of the boxes.
In the Start() function we will spawn all enemies at once. Not the best way to approach this, but will work for the purposes of this example. Here is what the code looks like:
using UnityEngine; using System.Collections; public class enemySpawner : MonoBehaviour { public float spawnRadius = 10; public int numberOfAgents = 50; public GameObject enemyPrefab; public Transform player; void Start () { for (int i=0; i < numberOfAgents; i++) { // Choose a random location within the spawnRadius Vector2 randomLoc2d = Random.insideUnitCircle * spawnRadius; Vector3 randomLoc3d = new Vector3(transform.position.x + randomLoc2d.x, transform.position.y, transform.position.z + randomLoc2d.y); // Make sure the location is on the NavMesh NavMeshHit hit; if (NavMesh.SamplePosition(randomLoc3d, out hit, 100, 1)) { randomLoc3d = hit.position; } // Instantiate and make the enemy a child of this object GameObject o = (GameObject)Instantiate(enemyPrefab, randomLoc3d, transform.rotation); o.GetComponent< enemyMovement >().player = player; } } void OnDrawGizmosSelected () { Gizmos.color = Color.green; Gizmos.DrawWireSphere (transform.position, spawnRadius); } }
The most important line in this script is the function NavMesh.SamplePosition(). It's a really cool and useful function. Basically you give it a coordinate it returns the closest point on the navmesh to that coordinate. Consider this example - if you have a treasure chest in your scene that explodes with loot and gold in all directions, you don't want some of the player's loot to go into a wall. Ever. You could use NavMesh.SamplePosition() to make sure that each randomly generated location sits on the navmesh. Here is a visual representation of what I just tried to explain:
In the video above I have an empty object which does this:
void OnDrawGizmos () { NavMeshHit hit; if (NavMesh.SamplePosition(transform.position, out hit, 100.0f, 1)) { Gizmos.DrawCube(hit.position, new Vector3 (2, 2, 2)); }
Back to our example, we just made our spawner and we can spawn any number of enemies, in a specific area. Let's see the result with 100 enemies:
Improving the agents behavior
What we have so far is nice, but there are still things that need fixing.
To recap, in an RPG or RTS game we want the enemies to get in attack range of the player and stop there. The enemies which are not in range are supposed to find a way around those who are already attacking to reach the player. However here is what happens now:
In the video above the mobs are stopping when they get into attack range, which is the NavMeshAgent's "Arrival Distance" parameter, which we set to 2. However, the enemies who are still not in range are pushing the others from behind, which leads to all mobs pushing the player as well. We tried to fix this by setting the mobs' avoidance priority to 30, but it doesn't work so well if we have a big crowd of mobs. It's an easy fix, here is what you need to do:
- Set the avoidance priority back to 30 on the "enemy" prefab.
- Add a NavMeshObstacle component to the "enemy" prefab.
- Modify the enemyMovement.cs file as follows:
using UnityEngine; using System.Collections; public class enemyMovement : MonoBehaviour { public Transform player; NavMeshAgent agent; NavMeshObstacle obstacle; void Start () { agent = GetComponent< NavMeshAgent >(); obstacle = GetComponent< NavMeshObstacle >(); } void Update () { agent.destination = player.position; // Test if the distance between the agent and the player // is less than the attack range (or the stoppingDistance parameter) if ((player.position - transform; } } }
Basically what we are doing is this - if we have an agent which is in attack range, we want him to stay in one place, so we make him an obstacle by enabling the NavMeshObstacle component and disabling the NavMeshAgent component. This prevents the other agents to push around those who are in attack range and makes sure that the player can't push them around either, so he is body blocked and can't run away. Here is what it looks like after the fix:
It's looking really good right now, but there is one last thing that we need to take care of. Let's have a closer look:
This is the "jiggling" that I was referring to earlier. I'm sure that there are multiple ways to fix this, but this is how I approached this problem and it worked quite well for my game.
- Drag the "enemy" prefab back to the scene and position it at (0, 0, 0).
- Create an empty game object, name it "pathfindingProxy", make it a child of "enemy" and position it at (0, 0, 0).
- Delete the NavMeshAgent and NavMeshObstacle components from the "enemy" object and add them to "pathfindingProxy".
- Create another empty game object, name it "model", make it a child of "enemy" and position it at (0, 0, 0).
- Make the cylinder and the cube children of the "model" object.
- Apply the changes to the prefab.
This is how the "enemy" object should look like:
What we need to do now is to use the "pathfindingProxy" object to do the pathfinding for us, and use it to move around the "model" object after it, while smoothing the motion. Modify enemyMovement.cs like this:
using UnityEngine; using System.Collections; public class enemyMovement : MonoBehaviour { public Transform player; public Transform model; public Transform proxy; NavMeshAgent agent; NavMeshObstacle obstacle;); model.rotation = proxy.rotation; } }
First, remember to connect the public variables "model" and "proxy" to the corresponding game objects, apply the changes to the prefab and delete it from the scene.
So here is what is happening in this script. We are no longer using transform.position to check for the distance between the mob and the player. We use proxy.position, because only the proxy and the model are moving, while the root object stays at (0, 0, 0). I also moved the agent.destination = player.position; line in the else statement for two reasons: Setting the destination of the agent will make it active again and we don't want that to happen if it's in attacking range. And second, we don't want the game to be calculating a path to the player if we are already in range. It's just not optimal. Finally with these two lines of code:
model.position = Vector3.Lerp(model.position, proxy.position, Time.deltaTime * 2); model.rotation = proxy.rotation;
We are setting the model.position to be equal to proxy.position, and we are using Vector3.Lerp() to smoothly transition to the new position. The "2" constant in the last parameter is completely arbitrary, set it to whatever looks good. It controls how quickly the interpolation occurs, or said otherwise, the acceleration. Finally, we just copy the rotation of the proxy and apply it to the model.
Since we introduced acceleration on the "model" object, we don't need the acceleration on the "proxy" object. Go to the NavMeshAgent component and set the acceleration to something stupid like 9999. We want the proxy to reach maximum velocity instantly, while the model slowly accelerates.
This is the result after the fix:
And here I have visualized the path of one of the agents. The path of the proxy is in red, and the smoothed path by the model is in green. You can see how the bumps and movement spikes are eliminated by the Vector3.Lerp() function:
Of course that path smoothing comes at a small cost - the agents will intersect a bit more, but I think it's totally fine and worth the tradeoff, since it will be barely noticeable with character models and so on. Also the intersecting tends to occur only if you have something like 50-100 agents or more, which is an extreme case scenario in most games.
We keep improving the behavior of the agents, but there is one last thing that I'd like to show you how to fix. It's the rotation of the agents. Right now we are modifying the proxy's path, but we are copying its exact rotation. Which means that the agent might be looking in one direction, but moving in a slightly different direction. What we need to do is rotate the "model" object according to its own velocity, rather than using the proxy's velocity. Here is the final version of enemyMovement.cs:
using UnityEngine; using System.Collections; public class enemyMovement : MonoBehaviour { public Transform player; public Transform model; public Transform proxy; NavMeshAgent agent; NavMeshObstacle obstacle; Vector3 lastPosition;); // Calculate the orientation based on the velocity of the agent Vector3 orientation = model.position - lastPosition; // Check if the agent has some minimal velocity if (orientation.sqrMagnitude > 0.1f) { // We don't want him to look up or down orientation.y = 0; // Use Quaternion.LookRotation() to set the model's new rotation and smooth the transition with Quaternion.Lerp(); model.rotation = Quaternion.Lerp(model.rotation, Quaternion.LookRotation(model.position - lastPosition), Time.deltaTime * 8); } else { // If the agent is stationary we tell him to assume the proxy's rotation model.rotation = Quaternion.Lerp(model.rotation, Quaternion.LookRotation(proxy.forward), Time.deltaTime * 8); } // This is needed to calculate the orientation in the next frame lastPosition = model.position; } }
At this point we are good to go. Check out the final result with 200 agents:
Final words
This is pretty much everything that I wanted to cover in this article, I hope you liked it and learned something new. There are also lots of improvements that could be made to this project (especially with Unity Pro), but this article should give you a solid starting point for your game.
Originally posted to
License
GDOL (Gamedev.net Open License)
Nice article indeed, but I can only imagine a bunch of zombies doing that pursuit haha, i think a bit of noise like random enemy radious while they are on pursuit mode could be an interesting tradeoff realism vs performance, did you tried?
I agree that it can be spiced up a lot with some AI to give some randomness to the agents and so on. This example just provides a good starting point.
Very good article and thanks for the sample project
Great article! The animated visuals help a ton. Thanks for taking the time to create this!
HI.
I enjoyed this article. It is well written and easy to follow.
Thanks for writing it =)
Thanks for the positive feedback, I'm glad you like the article
Very nice and informative article.
While reading it I stumbled upon some small errors:
[Point and click section]
- The figure, after you instructed the user to remove all colliders (except ground), shows the player object with a CapsuleCollider and MeshRenderer component and it doesn't contain the cylinder and cube child objects (same for the enemy prefab as it has no triangle in front of it in the Hierarchy view).
- The second script in the section also has a typo:
should be:
- You might want to add that the navigation path is only shown in the Scene view and not in the Game view.
[Improving the agents behavior section]
- The "Arrival Distance" parameters seems to be called "Stopping Distance" in Unity v4.3.2f1.
- I think the 30 in "1. Set the avoidance priority back to 30 on the "enemy" prefab." should be 50.
- In the first script in that section
should be placed in the "else" case. Otherwise Unity complains about: '"SetDestination" can only be called on an active agent that has been placed on a NavMesh.'
- When adding the pathfindingProxy object you might want to mention that the user has to set the StoppingDistance to 2 again on the new NavMeshComponent.
Good stuff, I didn't realize that Unity had made their navmesh stuff part of the standard package, and I also didn't realize Aroganberg had to pull the RVO.
Also I really liked all the animated images in the article, made it very easy to follow and kept me hooked.
@WouterV Thanks, I will fix the screens as soon as possible. Cheers!
@ferrous I'm glad you liked it!
Hi, thanks for the great post! I also didn't know about NavMesh going free. About the article, I'm not sure, but on my browser all the jpgs and gifs are not appearing. They're showing up as links, when I click on them they lead to broken links. Any idea? | http://www.gamedev.net/page/resources/_/technical/game-programming/pathfinding-and-local-avoidance-for-rpgrts-games-using-unity-r3703 | CC-MAIN-2016-22 | refinedweb | 4,731 | 62.27 |
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Hello!
I have a requirement where I need to change the fix version of stories under the epic whenever the epic fix version is changed.
How do I achieve this requirement.
This is on Jira cloud.
Appreciate your response.
You can do this with Script runner for Cloud. Here's the sample code. Basically you would need to use script listener to list for fixVersion change events and then update the same version on child stories.
Thank you for your reply but I do not understand what you are trying to pull when you say the below in the first line
customfield_10003
Ok I now get it that the epic-name is being found at the customfield_10003 but this holds good when a story is created for an epic and the fix version is set automatically.
But, my original requirement was, whenever EPIC fixVersion is changed, all the associated stories fix version should change. This does not work with the given script.
Any help on achieving it is much appreciated :)
@praneet pyati @Tarun Sapra
Were able to resolved it. I am facing the same issue. Thanks in advance.
Regards,
Deepali Bagul
Hello @Deepali Bagul
The code in the link is the exact sample of what needs to be done, can you please share what is the problem that you are facing?
try this out, this works for me..
def epicKey = issue.key
if (!epicKey) {
return false;
}
def epicFixVersions = get('/rest/api/2/issue/' + epicKey)
.header('Content-Type', 'application/json')
.asObject(Object)
def issType = epicFixVersions.body.fields.issuetype.name
println(issType)
if (issType!='Epic') {
return false;
}
def fixVersion = epicFixVersions.body.fields.fixVersions.name
def result1 = get('/rest/api/2/search?jql=cf[10003]=' + epicKey)
.header('Content-Type', 'application/json')
.asObject(Object)
def resulttotal = result1.body.total
for (def i=0;i<resulttotal;i++)
{
def isStatus = result1.body.issues.fields.status.name.value[i]
if("$isStatus" != "Done" || "$isStatus" != "Closed")
{
def result = put('/rest/api/2/issue/' + result1.body.issues.key[i])
.header('Content-Type', 'application/json')
.body([
fields:[
fixVersions: [[name:fixVersion[0]], [name:fixVersion[1]], [name:fixVersion[2]]]
]
]).as. | https://community.atlassian.com/t5/Jira-questions/Jira-cloud-changing-fix-version-of-story-whenever-epic-fix/qaq-p/703516 | CC-MAIN-2019-04 | refinedweb | 369 | 51.14 |
I have a lot (289) of 3d points with xyz coordinates which looks like:
With plotting simply 3d space with points is OK, but I have trouble with surface
There are some points:
for i in range(30):
output.write(str(X[i])+' '+str(Y[i])+' '+str(Z[i])+'\n')
-0.807237702464 0.904373229492 111.428744443
-0.802470821517 0.832159465335 98.572957317
-0.801052795982 0.744231916692 86.485869328
-0.802505546206 0.642324228721 75.279804677
-0.804158144115 0.52882485495 65.112895758
-0.806418040943 0.405733109371 56.1627277595
-0.808515314192 0.275100227689 48.508994388
-0.809879521648 0.139140394575 42.1027499025
-0.810645106092 -7.48279012695e-06 36.8668106345
-0.810676720161 -0.139773175337 32.714580273
-0.811308686707 -0.277276065449 29.5977405865
-0.812331692291 -0.40975978382 27.6210856615
-0.816075037319 -0.535615685086 27.2420699235
-0.823691366944 -0.654350489595 29.1823292975
-0.836688691603 -0.765630198427 34.2275056775
-0.854984518665 -0.86845932028 43.029581434
-0.879261949054 -0.961799684483 55.9594146815
-0.740499820944 0.901631050387 97.0261463995
-0.735011699497 0.82881933383 84.971061395
-0.733021568161 0.740454485354 73.733621269
-0.732821755233 0.638770044767 63.3815970475
-0.733876941678 0.525818698874 54.0655910105
-0.735055978521 0.403303715698 45.90859502
-0.736448900325 0.273425879041 38.935709456
-0.737556181137 0.13826504904 33.096106049
-0.738278724065 -9.73058423274e-06 28.359664343
-0.738507612286 -0.138781586244 24.627237837
-0.738539663773 -0.275090412979 21.857410904
-0.739099040189 -0.406068448513 20.1110519655
-0.741152200369 -0.529726022182 19.7019157715
Please have a look at Axes3D.plot_surface or at the other
Axes3D methods. You can find examples and inspirations here, here, or here.
Edit:
Z-Data that is not on a regular X-Y-grid (equal distances between grid points in one dimension) is not trivial to plot as a triangulated surface. For a given set of irregular (X, Y) coordinates, there are multiple possible triangulations. One triangulation can be calculated via a "nearest neighbor" Delaunay algorithm. This can be done in matplotlib. However, it still is a bit tedious:
It looks like support will be improved:
With the help of I was able to come up with a very simple solution based on mayavi:
import numpy as np from mayavi import mlab X = np.array([0, 1, 0, 1, 0.75]) Y = np.array([0, 0, 1, 1, 0.75]) Z = np.array([1, 1, 1, 1, 2]) # Define the points in 3D space # including color code based on Z coordinate. pts = mlab.points3d(X, Y, Z, Z) # Triangulate based on X, Y with Delaunay 2D algorithm. # Save resulting triangulation. mesh = mlab.pipeline.delaunay2d(pts) # Remove the point representation from the plot pts.remove() # Draw a surface based on the triangulation surf = mlab.pipeline.surface(mesh) # Simple plot. mlab.xlabel("x") mlab.ylabel("y") mlab.zlabel("z") mlab.show()
This is a very simple example based on 5 points. 4 of them are on z-level 1:
(0, 0) (0, 1) (1, 0) (1, 1)
One of them is on z-level 2:
(0.75, 0.75)
The Delaunay algorithm gets the triangulation right and the surface is drawn as expected:
I ran the above code on Windows after installing Python(x,y) with the command
ipython -wthread script.py | https://codedump.io/share/8iJkVfXmWJuI/1/python-the-simplest-way-to-plot-3d-surface | CC-MAIN-2018-22 | refinedweb | 523 | 71.34 |
I wish to have fonts resize with user resolution while having text as sharp as they can. By which I also mean they keep a scale of 1.0f in SpriteBatch.DrawString(). After thinking about several solution and trying a few, I’ve decided the simplest/best thing to do is use the MG pipeline’s spritefont generation code to generate a sprite. Only as required at game startup and after changing resolution and/or UI scale so there’s barely a speed impact - none while actually playing. What’s more, I can (most likely) use the current spritebatch code, etc… So my code should be quite brief, and updates to the pipeline should slot in quite easily.
This experiment has humbled me - at least in my knowledge of C#. I’ve learned several new things, but couldn’t find the entry point of the pipeline (the proverbial Main.cs, Pipeline.cs or Program.cs). Despite no VS solution/project I did manage to backtrack from FontDescription pretty well. Now I’m stuck on SharpFont. Never handled DLLs before (although it seems relatively easy), but I can’t find any DLL import in the pipeline source code. The SharpFont.dll and freetype6.dll aren’t included - the folder ThirdParty/Dependencies is empty. I could just muddle through and try writing my own DLL import, but that seems less than ideal.
Q1: How and/or where does the MG Pipeline code import SharpFont.dll (and perhaps freetype6.dll)?
Q2: This spritefont generation code works on Win, Linux and Mac desktops, correct? (after research various Git issues, I think Win and Linux yes, Mac not yet)
Also - and unrelated to SharpFont - why does SpriteFontContent.cs have
using Microsoft.Xna.Framework.Content.Pipeline.Serialization.Compiler;
I understand every class used in SpriteFontContent.cs has it’s own _Class_Writer.cs (e.g. SpriteFontContentWriter.cs, ListWriter.cs or Texture2DContentWriter.cs) but are those writer classes used automagically? I can’t see the link in the code.
Q3: Why or how is Microsoft.Xna.Framework.Content.Pipeline.Serialization.Compiler used in SpriteFontContent.cs?
Currently installed (for projects) MonoGame 3.5 stable. Copying code of Git source MonoGame-develop (11210 commits) downloaded 2017/02/08. SharpFont.dll and freetype6.dll are included in the MG 3.5 installation (C:/Program Files (x86)/MSBuild/MonoGame/v3.0/Tools). With a file date of 2016/03/30, these appear to be v3.0.1. | https://community.monogame.net/t/solved-appropriating-pipeline-spritefont-code-stuck-on-sharpfont/8737 | CC-MAIN-2022-40 | refinedweb | 405 | 60.92 |
I rewrote the mobile dev course sample app from W3U3. Then I created a new branch ‘xmlviews’ in the repo on Github and rebuilt the views in XML. I then took a first look at XML views in general. Now this post looks at the specific XML views that I built in the W3U3 rewrite. See the links at the bottom of the opening post of this series to get to explanations for the other areas.
We know, from the other posts in this series, that there are a number of views. Let’s just take them one by one. If you want an introduction to XML views, please refer to the previous post Mobile Dev Course W3U3 Rewrite – XML Views – An Intro. I won’t cover the basics here.
App View
The App view contains an App control (sap.m.App) which contains, in the pages aggregation, the rest of the views – the ones that are visible. This is what the App view looks like in XML.
<?xml version="1.0" encoding="UTF-8" ?> <core:View <App id="app"> <mvc:XMLView <mvc:XMLView <mvc:XMLView <mvc:XMLView </App> </core:View>
We’re aggregating four views in the App control (introduced by the <App> tag). Because the pages aggregation is the default, we don’t have to wrap the child views in a <pages> … </pages> element. Views and the MVC concept belong in the sap.ui.core library, hence the xmlns:core namespace prefix usage.
Login View
The Login view contains, within a Page control, a user and password field, and a login button in the bar at the bottom. This is what the XML view looks like.
<?xml version="1.0" encoding="UTF-8" ?> <core:View <Page title="Login" showNavButton="false"> <footer> <Bar> <contentMiddle> <Button text="Login" press="loginPress" /> </contentMiddle> </Bar> </footer> <List> <InputListItem label="Username"> <Input value="{app>/Username}" /> </InputListItem> <InputListItem label="Password"> <Input value="{app>/Password}" type="Password" /> </InputListItem> </List> </Page> </core:View>
You can see that the Page control is the ‘root’ control here, and there are a couple of properties set (title and showNavButton) along with the footer aggregation and the main content. Note that as this is not JavaScript, values that you think might appear “bare” are still specified as strings – showNavButton=”false” is a good example of this.
The Page’s footer aggregation expects a Bar control, and that’s what we have here. In turn, the Bar control has three aggregations that have different horizontal positions, currently left, middle and right. We’re using the contentMiddle aggregation to contain the Button control. Note that the Button control’s press handler “loginPress” is specified simply; by default the controller object is passed as the context for “this”. You don’t need to try and engineer something that you might have seen in JavaScript, like this:
new sap.m.Button({ text: "Login", press: [oController.loginPress, oController] }),
… it’s done automatically for you.
Note also that we can use data binding syntax in the XML element attributes just like we’d expect to be able to, for example value=”{app>/Username}”.
ProductList View
In the ProductList view, the products in the ProductCollection are displayed. There’s a couple of things that are worth highlighting in this view. First, let’s have a look at the whole thing.
<?xml version="1.0" encoding="UTF-8" ?> <core:View <Page title="Products"> <List headerText="Product Overview" items="{ path: '/ProductCollection' }"> <StandardListItem title="{Name}" description="{Description}" type="Navigation" press="handleProductListItemPress" /> </List> </Page> </core:View>
The List control is aggregating the items in the ProductCollection in the data model. Note how the aggregation is specified in the items attribute – it’s pretty much the same syntax as you’d have in JavaScript, here with the ‘path’ parameter. The only difference is that it’s specified as an object inside a string, rather than an object directly:
items="{ path: '/ProductCollection' }"
So remember get your quoting (single, double) right.
And then we have the template, the “stamp” which we use to produce a nice visible instantiation of each of the entries in the ProductCollection. This is specifiied in the default aggregation ‘items’, which, as it’s default, I’ve omitted here.
ProductDetail View
By now I’m sure you’re starting to see the pattern, and also the benefit of writing views in XML. It just makes a lot of sense, at least to me. It’s cleaner, it makes you focus purely on the controls, and also by inference causes you to properly separate your view and controller concerns. You don’t even have the option, let alone the temptation, to write event handling code in here.
So here’s the ProductDetail view.
<?xml version="1.0" encoding="UTF-8" ?> <core:View <Page title="{Name}" showNavButton="true" navButtonPress="handleNavButtonPress"> <List> <DisplayListItem label="Name" value="{Name}" /> <DisplayListItem label="Description" value="{Description}" /> <DisplayListItem label="Price" value="{Price} {CurrencyCode}" /> <DisplayListItem label="Supplier" value="{SupplierName}" type="Navigation" press="handleSupplierPress" /> </List> <VBox alignItems="Center"> <Image src="{app>/ES1Root}{ProductPicUrl}" decorative="true" densityAware="false" /> </VBox> </Page> </core:View>
We’re not aggregating any array of data from the model here, we’re just presenting four DisplayListItem controls one after the other in the List. Below that we have a centrally aligned image that shows the product picture.
SupplierDetail View
And finally we have the SupplierDetail view.
<?xml version="1.0" encoding="UTF-8" ?> <core:View <Page id="Supplier" title="{CompanyName}" showNavButton="true" navButtonPress="handleNavButtonPress"> <List> <DisplayListItem label="Company Name" value="{CompanyName}" /> <DisplayListItem label="Web Address" value="{WebAddress}" /> <DisplayListItem label="Phone Number" value="{PhoneNumber}" /> </List> </Page> </core:View>
Again, nothing really special, or specially complicated, here. Just like the other views (apart from the “root” App view), this has a Page as its outermost control. Here again we have just simple, clean declarations of what should appear, control-wise.
Conclusion
So there you have it. For me, starting to write views in XML was a revelation. The structure and the definitions seem to more easily flow, so much so, in fact, that in a last-minute addition to the DemoJam lineup at the annual SAP UK & Ireland User Group Conference in Birmingham last week, I took part, and for my DemoJam session I stood up and build an SAP Fiori-like UI live on stage. Using XML views.
This brings to an end the series that started out as an itch I wanted to scratch: To improve the quality of the SAPUI5 application code that was presented in the OpenSAP course “Introduction To Mobile Solution Development”. There are now 6 posts in the series, including this one:
Mobile Dev Course W3U3 Rewrite – Intro
Mobile Dev Course W3U3 Rewrite – Index and Structure
Mobile Dev Course W3U3 Rewrite – App and Login
Mobile Dev Course W3U3 Rewrite – ProductList, ProductDetail and SupplierDetail
Mobile Dev Course W3U3 Rewrite – XML Views – An Intro
Mobile Dev Course W3U3 Rewrite – XML Views – An Analysis
I hope you found it useful and interesting, and as always,
dj
Hi DJ,
as promised last week, here is my next question:
In the original W3U3 example, the password field is defined as followed:
In the XML view here you are defining it as
Isn’t it possible to use constants in XML views?
doesn’t work btw.
Hi Uwe
I think we answered this elsewhere, with lots of input from Oli, I think.
Right?
dj
DJ,
yes it’s answered here UI5 constants in XML views by Oliver Rogers
Thanks DJ Adams. Your blogs and posts are awesome and knowledgable. I just started doing stuff on SAPUI5 and your inputs on various topics have helped me understand the process. Last 2 – 3 weeks I was creating my views using JS and after seeing your post on SAP Fiori applications using xml views thought why not give a try and this blog helped me achieve build my small Navigation application between 2 Views 🙂 .
Your solutions are simple and to the point without having any unnecessary code.
Thanks a lot !!!
Hey thanks for the feedback … and you’re welcome! | https://blogs.sap.com/2013/12/02/mobile-dev-course-w3u3-rewrite-xml-views-an-analysis/ | CC-MAIN-2017-51 | refinedweb | 1,336 | 51.68 |
Chapter 4. The Kubernetes API Server
As mentioned in the overview of the Kubernetes components, the API server is the gateway to the Kubernetes cluster. It is the central touch point that is accessed by all users, automation, and components in the Kubernetes cluster. The API server implements a RESTful API over HTTP, performs all API operations, and is responsible for storing API objects into a persistent storage backend. This chapter covers the details of this operation.
Basic Characteristics for Manageability
For all of its complexity, from the standpoint of management, the Kubernetes API server is actually relatively simple to manage. Because all of the API server’s persistent state is stored in a database that is external to the API server, the server itself is stateless and can be replicated to handle request load and for fault tolerance. Typically, in a highly available cluster, the API server is replicated three times.
The API server can be quite chatty in terms of the logs that it outputs. It outputs at least a single line for every request that it receives. Because of this, it is critical that some form of log rolling be added to the API server so that it doesn’t consume all available disk space. However, because the API server logs are essential to understanding the operation of the API server, we highly recommend that logs be shipped from the API server to a log aggregation service for subsequent introspection and querying to debug user or component requests to the API.
Pieces of the API Server
Operating the Kubernetes API server involves three core funtions:
- API management
The process by which APIs are exposed and managed by the server
- Request processing
The largest set of functionality that processes individual API requests from a client
- Internal control loops
Internals responsible for background operations necessary to the successful operation of the API server
The following sections cover each of these broad categories.
API Management
Although the primary use for the API is servicing individual client requests, before API requests can be processed, the client must know how to make an API request. Ultimately, the API server is an HTTP server—thus, every API request is an HTTP request. But the characteristics of those HTTP requests must be described so that the client and server know how to communicate.
For the purposes of exploration, it’s great to have an API server actually up and running so that you can poke at it. You can either use an existing Kubernetes cluster that you have access to, or you can use the minikube tool for a local Kubernetes cluster. To make it easy to use the
curl tool to explore the API server, run the
kubectl tool in
proxy mode to expose an unauthenticated API server on localhost:8001 using the following command:
kubectl proxy
API Paths
Every request to the API server follows a RESTful API pattern where the request is defined by the HTTP path of the request. All Kubernetes requests begin with the prefix
/api/ (the core APIs) or
/apis/ (APIs grouped by API group). The two different sets of paths are primarily historical. API groups did not originally exist in the Kubernetes API, so the original or “core” objects, like Pods and
Services, are maintained under the '/api/' prefix without an API group. Subsequent APIs have generally been added under API groups, so they follow the '/apis/<api-group>/' path. For example, the
Job object is part of the
batch API group and is thus found under /apis/batch/v1/….
One additional wrinkle for resource paths is whether the resource is namespaced.
Namespaces in Kubernetes add
a layer of grouping to objects, namespaced resources can only be created within a namespace, and the name of that namespace is included in the HTTP path for the namespaced resource. Of course, there are resources that do not live in a namespace (the most obvious example is the
Namespace API object itself) and, in this case, they do not have a namespaces component in their HTTP path.
Here are the components of the two different paths for namespaced resource types:
/api/v1/namespaces/<namespace-name>/<resource-type-name>/<resource-name>
/apis/<api-group>/<api-version>/namespaces/<namespace-name>/<resource-type-name>/<resource-name>
Here are the components of the two different paths for non-namespaced resource types:
/api/v1/<resource-type-name>/<resource-name>
/apis/<api-group>/<api-version>/<resource-type-name>/<resource-name>
API Discovery
Of course, to be able to make requests to the API, it is necessary to understand which API objects are available to the client. This process occurs through API discovery on the part of the client. To see this process in action and to explore the API server in a more hands-on manner, we can perform this API discovery ourselves.
First off, to simplify things, we use the
kubectl command-line tool’s built-in
proxy to provide authentication to our cluster. Run:
kubectl proxy
This creates a simple server running on port 8001 on your local machine.
We can use this server to start the process of API discovery. We begin by examining the
/api prefix:
$ curl localhost:8001/api { "kind": "APIVersions", "versions": [ "v1" ], "serverAddressByClientCIDRs": [ { "clientCIDR": "0.0.0.0/0", "serverAddress": "10.0.0.1:6443" } ] }
You can see that the server returned an API object of type
APIVersions. This object provides us with a
versions field, which lists the available versions.
In this case, there is just a single one, but for the
/apis prefix, there are many. We can use this version to continue our investigation:
$ curl localhost:8001/api/v1 { "kind": "APIResourceList", "groupVersion": "v1", "resources": [ { …. { "name": "namespaces", "singularName": "", "namespaced": false, "kind": "Namespace", "verbs": [ "create", "delete", "get", "list", "patch", "update", "watch" ], "shortNames": [ "ns" ] }, … { "name": "pods", "singularName": "", "namespaced": true, "kind": "Pod", "verbs": [ "create", "delete", "deletecollection", "get", "list", "patch", "proxy", "update", "watch" ], "shortNames": [ "po" ], "categories": [ "all" ] }, { "name": "pods/attach", "singularName": "", "namespaced": true, "kind": "Pod", "verbs": [] }, { "name": "pods/binding", "singularName": "", "namespaced": true, "kind": "Binding", "verbs": [ "create" ] }, …. ] }
(This output is heavily edited for brevity.)
Now we are getting somewhere. We can see that the specific resources available on a certain path are printed out by the API server. In this case, the returned object contains the list of resources exposed under the /api/v1/ path.
The OpenAPI/Swagger JSON specification that describes the API (the meta-API object) contains a variety of interesting information in addition to the resource types. Consider the OpenAPI specification for the
Pod object:
{ "name": "pods", "singularName": "", "namespaced": true, "kind": "Pod", "verbs": [ "create", "delete", "deletecollection", "get", "list", "patch", "proxy", "update", "watch" ], "shortNames": [ "po" ], "categories": [ "all" ] }, { "name": "pods/attach", "singularName": "", "namespaced": true, "kind": "Pod", "verbs": [] }
Looking at this object, the
name field provides the name of this resource. It also indicates the subpath for these resources. Because inferring the pluralization of an English word is challenging, the API resource also contains a
singularName field, which indicates the name that should be used for a singular instance of this resource. We previously discussed namespaces. The
namespaced field in the object description indicates whether the object is namespaced. The
kind field provides the string that is present in the API object’s JSON representation to indicate what kind of object it is. The
verbs field is one of the most important in the API object, because it indicates what kinds of actions can be taken on that object. The
pods object contains all of the possible verbs. Most of the effects of the verbs are obvious from their names. The two that require a little more explanation are
watch and
proxy.
watch indicates that you can establish a watch for the resource. A watch is a long-running operation that provides notifications about changes to the object. The watch is covered in detail in later sections.
proxy is a specialized action that establishes a proxy network connection through the API server to network ports. There are only two resources (Pods and
Services) that currently support
proxy.
In addition to the actions (described as verbs) that you can take on an object, there are other actions that are modeled as subresources on a resource type. For example, the
attach command is modeled as a subresource:
{ "name": "pods/attach", "singularName": "", "namespaced": true, "kind": "Pod", "verbs": [] }
attach provides you with the ability to attach a terminal to a running container within a Pod. The
exec functionality that allows you to execute a command within a Pod is modeled similarly.
OpenAPI Spec Serving
Of course, knowing the resources and paths you can use to access the API server is only part of the information that you need in order to access the Kubernetes API. In addition to the HTTP path, you need to know the JSON payload to send and receive. The API server also provides paths to supply you with information about the schemas for Kubernetes resources. These schemas are represented using the OpenAPI (formerly Swagger) syntax. You can pull down the OpenAPI specification at the following path:
- /swaggerapi
Before Kubernetes 1.10, serves Swagger 1.2
- /openapi/v2
Kubernetes 1.10 and beyond, serves OpenAPI (Swagger 2.0)
The OpenAPI specification is a complete subject unto itself and is beyond the scope of this book. In any event, it is unlikely that you will need to access it in your day-to-day operations of Kubernetes. However, the various client programming language libraries are generated using these OpenAPI specifications (the notable exception to this is the Go client library, which is currently hand-coded). Thus, if you or a user are having trouble accessing parts of the Kubernetes API via a client library, the first stop should be the OpenAPI specification to understand how the API objects are modeled.
API Translation
In Kubernetes, an API starts out as an alpha API (e.g.,
v1alpha1). The alpha designation indicates that the API is unstable and unsuitable for production use cases. Users who adopt alpha APIs should expect both that the API surface area may change between Kubernetes releases and that the implementation of the API itself may be unstable and may even destabilize the entire Kubernetes cluster. Alpha APIs are therefore disabled in production Kubernetes clusters.
Once an API has matured, it becomes a beta API (e.g.,
v1beta1). The beta designation indicates that the API is generally stable but may have bugs or final API surface refinements. In general, beta APIs are assumed to be stable between Kubernetes releases, and backward compatability is a goal. However, in special cases, beta APIs may still be incompatible between Kubernetes releases. Likewise, beta APIs are intended to be stable, but bugs may still exist. Beta APIs are generally enabled in production Kubernetes clusters but should be used carefully.
Finally an API becomes generally available (e.g.,
v1). General availability (GA) indicates that the API is stable. These APIs come with both a guarantee of backward compatability and a deprecation guarantee. After an API is marked as scheduled for removal, Kubernetes retains the API for at least three releases or one year, whichever comes first. Deprecation is also fairly unlikely. APIs are deprecated only after a superior alternative has been developed. Likewise, GA APIs are stable and suitable for all production usage.
A particular release of Kubernetes can support multiple versions (alpha, beta, and GA). In order to accomplish this, the API server has three different representations of the API at all times: the external representation, which is the representation that comes in via an API request; the internal representation, which is the in-memory representation of the object used within the API server for processing; and the storage representation, which is recorded into the storage layer to persist the API objects. The API server has code within it that knows how to perform the various translations between all of these representations. An API object may be submitted as a
v1alpha1 version, stored as a
v1 object, and subsequently retrieved as a
v1beta1 object or any other arbitrary supported version. These transformations are achieved with reasonable performance using machine-generated deep-copy libraries, which perform the appropriate translations.
Request Management
The main purpose of the API server in Kubernetes is to receive and process API calls in the form of HTTP requests. These requests are either from other components in the Kubernetes system or they are end-user requests. In either event, they are all processed by the Kubernetes API server in the same manner.
Types of Requests
There are several broad categories of requests performed by the Kubernetes API server.
GET
The simplest requests are
GETrequests for specific resources. These requests retrieve the data associated with a particular resource. For example, an HTTP
GETrequest to the path /api/v1/namespaces/default/pods/foo retrieves the data for a Pod named foo.
LIST
A slightly more complicated but still fairly straightforward request is a
collection GET, or
LIST. These are requests to list a number of different requests. For example, an HTTP
GETrequest to the path /api/v1/namespaces/default/pods retrieves a collection of all Pods in the
defaultnamespace.
LISTrequests can also optionally specify a label query, in which case, only resources matching that label query are returned.
To create a resource, a
POSTrequest is used. The body of the request is the new resource that should be created. In the case of a
POSTrequest, the path is the resource type (e.g., /api/v1/namespaces/default/pods). To update an existing resource, a
PUTrequest is made to the specific resource path (e.g., /api/v1/namespaces/default/pods/foo).
DELETE
When the time comes to delete a request, an HTTP
DELETErequest to the path of the resource (e.g., /api/v1/namespaces/default/pods/foo) is used. It’s important to note that this change is permanent—after the HTTP request is made, the resource is deleted.
The content type for all of these requests is usually text-based JSON (
application/json) but recent releases of Kubernetes also support Protocol Buffers binary encoding. Generally speaking, JSON is better for human-readable and debuggable traffic on the network between client and server, but it is significantly more verbose and expensive to parse. Protocol Buffers are harder to introspect using common tools, like
curl, but enable greater performance and throughput of API requests.
In addition to these standard requests, many requests use the WebSocket protocol to enable streaming sessions between client and server. Examples of such protocols are the
exec and
attach commands.
These requests are described in the following sections.
Life of a Request
To better understand what the API server is doing for each of these different requests, we’ll take apart and describe the processing of a single request to the API server.
Authentication
The first stage of request processing is authentication, which establishes the identity associated with the request. The API server supports several different modes of establishing identity, including client certificates, bearer tokens, and HTTP Basic Authentication. In general, client certificates or bearer tokens, should be used for authentication; the use of HTTP Basic Authentication is discouraged.
In addition to these local methods of establishing identity, authentication is pluggable, and there are several plug-in implementations that use remote identity providers. These include support for the OpenID Connect (OIDC) protocol, as well as Azure Active Directory. These authentication plug-ins are compiled into both the API server and the client libraries. This means that you may need to ensure that both the command-line tools and API server are roughly the same version or support the same authentication methods.
The API server also supports remote webhook-based authentication configurations, where the authentication decision is delegated to an outside server via bearer token forwarding. The external server validates the bearer token from the end user and returns the authentication information to the API server.
Given the importance of this in securing a server, it is covered in depth in a later chapter.
RBAC/Authorization
After the API server has determined the identity for a request, it moves on to authorization for it. Every request to Kubernetes follows a traditional RBAC model. To access a request, the identity must have the appropriate role associated with the request. Kubernetes RBAC is a rich and complicated topic, and as such, we have devoted an entire chapter to the details of how it operates. For the purposes of this API server summary, when processing a request, the API server determines whether the identity associated with the request can access the combination of the verb and the HTTP path in the request. If the identity of the request has the appropriate role, it is allowed to proceed. Otherwise, an HTTP 403 response is returned.
This is covered in much more detail in a later chapter.
Admission control
After a request has been authenticated and authorized, it moves on to admission control. Authentication and RBAC determine whether the request is allowed to occur, and this is based on the HTTP properties of the request (headers, method, and path). Admission control determines whether the request is well formed and potentially applies modifications to the request before it is processed. Admission control defines a pluggable interface:
apply(request): (transformedRequest, error)
If any admission controller finds an error, the request is rejected. If the request is accepted, the transformed request is used instead of the initial request. Admission controllers are called serially, each receiving the output of the previous one.
Because admission control is such a general, pluggable mechanism, it is used for a wide variety of different functionality in the API server. For example, it is used to add default values to objects. It can also be used to enforce policy (e.g., requiring that all objects have a certain label). Additionally, it can be used to do things like inject an additional container into every Pod. The service mesh Istio uses this approach to inject its sidecar container transparently.
Admission controllers are quite generic and can be added dynamically to the API server via webhook-based admission control.
Validation
Request validation occurs after admission control, although it can also be implemented as part of admission control, especially for external webhook-based validation. Additionally, validation is only performed on a single object. If it requires broader knowledge of the cluster state, it must be implemented as an admission controller.
Request validation ensures that a specific resource included in a request is valid. For example, it ensures that the name of a
Service object conforms to the rules around DNS names, since eventually the name of a
Service will be programmed into the Kubernetes
Service discovery DNS server. In general, validation is implemented as custom code that is defined per resource type.
Specialized requests
In addition to the standard RESTful requests, the API server has a number of speciallized request patterns that provide expanded functionality to clients:
/proxy, /exec, /attach, /logs
The first important class of operations is open, long-running connections to the API server. These requests provide streaming data rather than immediate responses.
The
logs operation is the first streaming request we describe, because it is the easiest to understand. Indeed, by default,
logs isn’t a streaming request at all. A client makes a request to get the logs for a Pod by appending
/logs to the end of the path for a particular Pod (e.g.,
/api/v1/namespaces/default/pods/some-pod/logs) and then specifying the container name as an HTTP query parameter and an HTTP
GET request. Given a default request, the API server returns all of the logs up to the current time, as plain text, and then closes the HTTP request. However, if the client requests that the logs be tailed (by specifying the
follow query parameter), the HTTP response is kept open by the API server and new logs are written to the HTTP response as they are received from the kubelet via the API server. This connection is shown in Figure 4-1.
Figure 4-1. The basic flow of an HTTP request for container logs
logs is the easiest streaming request to understand because it simply leaves the request open and streams in more data. The rest of the operations take advantage of the WebSocket protocol for bidirectional streaming data. They also actually multiplex data within those streams to enable an arbitrary number of bidirectional streams over HTTP. If this all sounds a little complicated, it is, but it is also a valuable part of the API server’s surface area.
Note
The API server actually supports two different streaming protocols. It supports the SPDY protocol, as well as HTTP2/WebSocket. SPDY is being replaced by HTTP2/WebSocket and thus we focus our attention on the WebSocket protocol.
The full WebSocket protocol is beyond the scope of this book, but it is documented in a number of other places. For the purposes of understanding the API server, you can simply think of WebSocket as a protocol that transforms HTTP into a bidirectional byte-streaming protocol.
However, on top of those streams, the Kubernetes API server actually introduces an additional multiplexed streaming protocol. The reason for this is that, for many use cases, it is quite useful for the API server to be able to service multiple independent byte streams. Consider, for example, executing a command within a container. In this case, there are actually three streams that need to be maintained (
stdin,
stderr, and
stdout).
The basic protocol for this streaming is as follows: every stream is assigned a number from 0 to 255. This stream number is used for both input and output, and it conceptually models a single bidirectional byte stream.
For every frame that is sent via the WebSocket protocol, the first byte is the stream number (e.g., 0) and the remainder of the frame is the data that is traveling on that stream (Figure 4-2).
Figure 4-2. An example of the Kubernetes WebSocket multichannel framing
Using this protocol and WebSockets, the API server can simultaneously multiplex 256-byte streams in a single WebSocket session.
This basic protocol is used for
exec and
attach sessions, with the following channels:
- 0
The
stdinstream for writing to the process. Data is not read from this stream.
- 1
The
stdoutoutput stream for reading
stdoutfrom the process. Data should not be written to this stream.
- 2
The
stderroutput stream for reading
stderrfrom the process. Data should not be written to this stream.
The
/proxy endpoint is used to port-forward network traffic between the client and containers and services running inside the cluster, without those endpoints being externally exposed. To stream these TCP sessions, the protocol is slightly more complicated. In addition to multiplexing the various streams, the first two bytes of the stream (after the stream number, so actually the second and third bytes in the WebSockets frame) are the port number that is being forwarded, so that a single WebSockets frame for
/proxy looks like Figure 4-3.
Figure 4-3. An example of the data frame for WebSockets-based port forwarding
Watch operations
In addition to streaming data, the API server supports a watch API. A watch monitors a path for changes. Thus,
instead of polling at some interval for possible updates, which introduces
either extra load (due to fast polling) or extra latency (because of slow polling), using a watch enables a user to get low-latency updates with
a single connection. When a user establishes a watch connection to the API
server by adding the query parameter
?watch=true to some API server
request, the API server switches into watch mode, and it leaves the
connection between client and server open. Likewise, the data returned
by the API server is no longer just the API object—it is a
Watch object
that contains both the type of the change (created, updated, deleted) and the API object itself. In this way, a client can watch and observe
all changes to that object or set of objects.
Optimistically concurrent updates
An additional advanced operation supported by the API server is the ability to perform optimistically concurrent updates of the Kubernetes API. The idea behind optimistic concurrency is the ability to perform most operations without using locks (pessimistic concurrency) and instead detect when a concurrent write has occurred, rejecting the later of the two concurrent writes. A write that is rejected is not retried (it is up to the client to detect the conflict and retry the write themselves).
To understand why this optimistic concurrency and conflict detection is required, it’s important to know about the structure of a read/update/write race condition. The operation of many API server clients involves three operations:
Read some data from the API server.
Update that data in memory.
Write it back to the API server.
Now imagine what happens when two of these read/update/write patterns happen simultaneously.
Server A reads object O.
Server B reads object O.
Server A updates object O in memory on the client.
Server B updates object O in memory on the client.
Server A writes object O.
Server B writes object O.
At the end of this, the changes that Server A made are lost because they were overwritten by the update from Server B.
There are two options for solving this race. The first is a pessimistic lock, which would prevent other reads from occurring while Server A is operating on the object. The trouble with this is that it serializes all of the operations, which leads to performance and throughput problems.
The other option implemented by the Kubernetes API server is optimistic concurrency, which assumes that everything will just work out and only detects a problem when a conflicting write is attempted. To achieve this, every instance of an object returns both its data and a resource version. This resource version indicates the current iteration of the object. When a write occurs, if the resource version of the object is set, the write is only successful if the current version matches the version of the object. If it does not, an HTTP error 409 (conflict) is returned and the client musty retry. To see how this fixes the read/update/write race just described, let’s take a look at the operations again:
Server A reads object O at version v1.
Server B reads object O at version v1.
Server A updates object O at version v1 in memory in the client.
Server B updates object O at version v1 in memory in the client.
Server A writes object O at version v1; this is successful.
Server B writes object O at version v1, but the object is at v2; a 409 conflict is returned.
Alternate encodings
In addition to supporting JSON encoding of objects for requests, the API server supports two other formats for requests. The encoding of the requests is indicated by the Content-Type HTTP header on the request. If this header is missing, the content is assumed to be
application/json, which indicates JSON encoding. The first alternate encoding is YAML, which is indicated by the
application/yaml Content Type. YAML is a text-based format that is generally considered to be more human readable than JSON. There is little reason to use YAML for encoding for communicating with the server, but it can be convenient in a few circumstances (e.g., manually sending files to the server via
curl).
The other alternate encoding for requests and responses is the Protocol Buffers encoding format. Protocol Buffers are a fairly efficient binary object protocol. Using Protocol Buffers can result in more efficient and higher throughput requests to the API servers. Indeed, many of the Kubernetes internal tools use Protocol Buffers as their transport. The main issue with Protocol Buffers is that, because of their binary nature, they are significantly harder to visualize/debug in their wire format. Additionally, not all client libraries currently support Protocol Buffers requests or responses. The Protocol Buffers format is indicated by the
application/vnd.kubernetes.protobuf Content-Type header.
Common response codes
Because the API server is implemented as a RESTful server, all of the responses from the server are aligned with HTTP response codes. Beyond the typical 200 for OK responses and 500s for internal server errors, here are some of the common response codes and their meanings:
- 202
Accepted. An asyncronous request to create or delete an object has been received. The result responds with a status object until the asynchronous request has completed, at which point the actual object will be returned.
- 400
Bad Request. The server could not parse or understand the request.
- 401
Unauthorized. A request was received without a known authentication scheme.
- 403
Forbidden. The request was received and understood, but access is forbidden.
- 409
Conflict. The request was received, but it was a request to update an older version of the object.
- 422
Unprocessable entity. The request was parsed correctly but failed some sort of validation.
API Server Internals
In addition to the basics of operating the HTTP RESTful service, the API server has a few internal services that implement parts of the Kubernetes API. Generally, these sorts of control loops are run in a separate binary known as the controller manager. But there are a few control loops that have to be run inside the API server. In each case, we describe the functionality as well as the reason for its presence in the API server.
CRD Control Loop
Custom resource definitions (CRDs) are dynamic API objects that can be added to a running API server. Because the act of creating a CRD inherently creates new HTTP paths the API server must know how to serve, the controller that is responsible for adding these paths is colocated inside the API server. With the addition of delegated API servers (described in a later chapter), this controller has actually been mostly abstracted out of the API server. It currently still runs in process by default, but it can also be run out of process.
The CRD control loop operates as follows:
for crd in AllCustomResourceDefinitions: if !RegisteredPath(crd): registerPath for path in AllRegisteredPaths: if !CustomResourceExists(path): markPathInvalid(path) delete custom resource data delete path
The creation of the custom resource path is fairly straightforward, but the deletion of a custom resource is a little more complicated. This is because the deletion of a custom resource implies the deletion of all data associated with resources of that type. This is so that, if a CRD is deleted and then at some later date readded, the old data does not somehow get resurrected.
Thus, before the HTTP serving path can be removed, the path is first marked as invalid so that new resources cannot be created. Then, all data associated with the CRD is deleted, and finally, the path is removed.
Debugging the API Server
Of course, understanding the implementation of the API server is great, but more often than not, what you really need is to be able to debug what is actually going on with the API server (as well as clients that are calling in to the API server). The primary way that this is achieved is via the logs that the API server writes. There are two log streams that the API server exports—the standard or basic logs, as well as the more targeted audit logs that try to capture why and how requests were made and the changed API server state. In addition, more verbose logging can be turned on for debugging specific problems.
Basic Logs
By default, the API server logs every request that is sent to the API server. This log includes the client’s IP address, the path of the request, and the code that the server returned. If an unexpected error results in a server panic, the server also catches this panic, returns a 500, and logs that error.
I0803 19:59:19.929302 1 trace.go:76] Trace[1449222206]: "Create /api/v1/namespaces/default/events" (started: 2018-08-03 19:59:19.001777279 +0000 UTC m=+25.386403121) (total time: 927.484579ms): Trace[1449222206]: [927.401927ms] [927.279642ms] Object stored in database I0803 19:59:20.402215 1 controller.go:537] quota admission added evaluator for: { namespaces}
In this log, you can see that it starts with the timestamp
I0803 19:59:… when the
log line was emitted, followed by the line number that emitted it,
trace.go:76, and
finally the log message itself.
Audit Logs
The audit log is intended to enable a server administrator to forensically recover the state of the server and the series of client interactions that resulted in the current state of the data in the Kubernetes API. For example, it enables a user to answer questions like, “Why was that
ReplicaSet scaled up to 100?”, “Who deleted that Pod?”, among others.
Audit logs have a pluggable backend for where they are written. Generally, audit logs are written to file, but it is also possible for them to be written to a webhook. In either case, the data logged is a structured JSON object of type
event in the
audit.k8s.io API group.
Auditing itself can be configured via a policy object in the same API group. This policy allows you to specify the rules by which audit events are emitted into the audit log.
Activating Additional Logs
Kubernetes uses the
github.com/golang/glog leveled logging package for its logging. Using the
--v flag on the API server you can adjust the level of logging verbosity. In general, the Kubernetes project has set log verbosity level 2 (
--v=2) as a sane default for logging relevant, but not too spammy messages. If you are looking into specific problems, you can raise the logging level to see more (possibly spammy) messages. Because of the performance impact of excessive logging, we recommend not running with a verbose log level in production. If you are looking for more targeted logging, the
--vmodule flag enables increasing the log level for individual source files. This can be useful for very targeted verbose logging restricted to a small set of files.
Debugging kubectl Requests
In addition to debugging the API server via logs, it is also possible to debug interactions with the API server, via the
kubectl command-line tool. Like the API server, the
kubectl command-line tool logs via the
github.com/golang/glog package and supports the
--v verbosity flag. Setting the verbosity to level 10 (
--v=10) turns on maximally verbose logging. In this mode,
kubectl logs all of the requests that it makes to the server, as well as attempts to print
curl commands that you can use to replicate these requests. Note that these
curl commands are sometimes incomplete.
Additionally, if you want to poke at the API server directly, the approach that we used earlier to explore API discovery works well. Running
kubectl proxy creates a proxy server on localhost that automatically supplies your authentication and authorization credentials, based on a local $HOME/.kube/config file. After you run the proxy, it’s fairly straightforward to poke at various API requests using the
curl command.
Summary
As an operator, the core service that you are providing to your users is the Kubernetes API. To effectively provide this service, understanding the core components that make up Kubernetes and how your users will put these APIs together to build applications is critical to implementing a useful and reliable Kubernetes cluster. Having finished reading this chapter, you should have a basic knowledge of the Kubernetes API and how it is used.
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I come from the scientific computing community where, historically, most of my coding was in languages like Fortran or C due to the ease by which one can create fast code. Simulations can run for a long time, so languages that emit high performance code are important. Even languages like Python and Matlab call out to routines written in these other compiled languages for computationally intensive routines where speed matters. Unfortunately, while Fortran and C are fast, they lack in comparison to their high level cousins in that they put you fairly close to the metal and abstractions are hard to capture in the code. The problem being solved ends up being convoluted and obfuscated in the translation from the domain formulation into code. Fortran is tolerable in some cases, especially when dealing with highly array-oriented code due to the presence of a rich array type that has existed in the language since the Fortran 90 standard (which, really, was borrowed from APL). This post examines a simulation that doesn’t have this nice array-oriented structure, and instead relies on tree-based data structures for rapidly querying a particle set based on spatial properties.
The language of choice for this post is Haskell. Why? A few reasons. The code described here actually started life as a C program, which I then translated to F#. The translation to F# was due to an interest I had in that emerging language, and the fact that I’m a native ML programmer. The move to Haskell from F# was undertaken since I was eager to learn Haskell, and I was curious to see how hard it is for a non-expert in the language (like myself) to generate code that performs well. In a followup post, I’ll discuss how it was possible to achieve performance only a couple times slower than C – close enough for it to be useful.
The model in question here is known as Diffusion-Limited Aggregation (DLA), and has existed in the physics literature for about three decades. A perusal of Physical Review E for that period of time shows articles on the model consistently popping up. Here is a picture of some output from the code for 40,000 particles that I describe in this post. The data produced by the code is a list of points as coordinates (x,y,z) and the order in which they were added to the growing structure. The visualization was performed using a rather nice tool for scientific visualization from Lawrence Livermore National Laboratory called VisIt. The color of each particle corresponds with the order in which it joined the aggregate (so the core is blue near 0, and the fringe is orange near 40,000).
I’ve also made a movie of a smaller aggregate that is on YouTube where you can see a full rotation of the structure. That visualization was generated using POVRay. I admit, I think I did something wrong in the process of taking the set of nice, crisp frames and making a movie to upload to YouTube. The video that is linked to here is a bit fuzzy and ugly, but the general point seems to be conveyed.
The basic algorithm for the DLA simulation described in this post is described below. It should be noted that this deviates a bit from some of the simpler versions of the model in the literature. A more common version of the algorithm assumes that the space is discretized as a grid in two or three dimensions, and the particle walk is confined to the grid itself. The model I describe doesn’t assume that the particles are confined to a grid, which leads to the slightly more difficult task of collision detection. Confinement to a grid makes collision detection really easy – just an array look up. Modeling space continuously instead of confining motion to a rectilinear grid seemed more appealing, although algorithmically more challenging.
We start with a single seed particle that resides at the origin. A new particle is created on the surface of a sphere of radius r centered on the origin. This particle then takes a random walk with a step size that is small relative to the radius of the sphere. As the particle walks around, we check to see if it comes within a predefined epsilon of the seed particle. This epsilon can be thought of as a function of the radius of the particle treated as a sphere instead of a point. If it does come within epsilon of some particle already in the structure that is growing, we perform a test to see if it sticks to the aggregate. This decision is governed by a “stickiness” parameter. If it passes, the particle becomes fixed and we repeat the process with a new particle, testing whether or not it wanders in and sticks to the set of particles that have joined the aggregate so far.
During this process, we need to make sure particles don’t wander too far away since they may never come back. This is accomplished by creating a second, larger sphere that surrounds the sphere where particles originate, and if a particle crosses it, we destroy it and start over with a new particle somewhere on the starting sphere. Similarly, as the aggregate grows outward, we can imagine that it will approach the sphere on which the particles originate. Therefore, as the aggregate grows, we make sure that these two spheres grow along with it to ensure a safe starting distance for all new particles.
The implementation of the algorithm requires a few basic pieces:
- A space partitioning data structure for efficient collision detection. We will use a kd-tree.
- Fast random number generation. Next to collision detection, generation of random numbers is a critical computation performed in the code due to the random walk that is performed.
- A simple set of routines for manipulating vectors in 3-space.
- The algorithm that walks a single particle inwards.
- Code for detecting particles that wander too far away.
- Code for updating the sphere of origin for new particles.
I won’t bother with the implementation of the vector library, as many people have written them or downloaded one that someone else wrote at one point or another. All that is required are basic vector arithmetic operations, like addition, subtraction, scaling by a scalar value, dot product, norm, and normalization.
The only routine of interest for our purposes is one for generating random points that lie on a sphere of radius r. The code for this is below:
randVec :: Double -> DLAMonad Vec3 randVec r = do phi <- nextF (2.0 * pi) -- phi ranges from 0.0 to 2.0*pi z' <- nextF (2.0 * r) let z = z' - r -- z ranges from -r to r theta <- return $ asin (z / r) return $ Vec3 (r*(cos theta)*(cos phi)) (r*(cos theta)*(sin phi)) z
This function returns a vector in 3-space that is of length r originating from the origin (0,0,0). The return type is a consequence of how we deal with random numbers in the code. We use an instance of the State monad that is called the DLAMonad to weave our random number generator state through the code behind the scenes. This could be avoided if the random number state was threaded explicitly through the code as a parameter and return value, but that would make things messy to read and write. We also avoid using a global random number generator state since that would limit potential parallelization (a topic for another post – parallelizing DLA is somewhat subtle in order to maintain a physically meaningful model.)
The function nextF is provided by the DLAMonad, and returns a random Double that lies between 0.0 and the upper bound specified by the argument. This function is responsible for reading the current value maintained by the state monad, generating a new random value, and storing the modified random number generator state back in the state monad. This could be accomplished with explicit state passing, but I think the state monad used this way makes the code easier to follow.
The code for this monad is shown below.
import System.Random.Mersenne.Pure64 import Control.Monad.State.Strict newtype Rmonad s a = S (State s a) deriving (Monad) -- | The DLAMonad is just a specific instance of the State monad where the -- state is just the PureMT PRNG state. type DLAMonad a = Rmonad PureMT a -- | Generate a random number as a Double between 0.0 and the given upper -- bound. nextF :: Double -- ^ Upper bound. -> Rmonad PureMT Double nextF up = S $ do st <- get let (x,st') = randomDouble st put st' return (x*up) -- | Run function for the Rmonad. runRmonad :: Rmonad PureMT a -> PureMT -> (a, PureMT) runRmonad (S m) s = runState m s
As we can see, the code for nextF is fairly straightforward – get the state, sample the PRNG, put the new state back, and return the sampled random value scaled from [0,1] to [0,up]. The only other function that we provide is runRmonad, which is used to bootstrap a function that runs within the DLAMonad with an initial value for the PRNG state. We’ll see this invoked later when we describe the driver code for the simulation. Note that in a later post when showing how to tune the code to make it perform closer to the original C version that this Haskell code started from, the use of the state monad will be avoided and a specialized state monad will be used.
Another interesting property of this code is the use of Control.Monad.State.Strict. This was not something that I used in my original version of the code, and instead I used the non-strict state monad. The problem with this was that, under some circumstances I would experience crashes due to running out of memory. Why would this occur you might wonder? The cause was that laziness would result in a buildup of thunks as the particle took its random walk. An unlucky walk that took a long time to either hit the aggregate or wander into the death zone where the particle was purged would cause too many thunks to be generated, and the code would explode and crash. The strict version of the monad prevents these thunks from being stored, and instead forces each random number selected to be computed without laziness.
The next critical part of the code is the KD-Tree data structure. This allows the code to store all particles that have been added to the aggregate so far and search them based on their location. In the original code in C, I had written this using an octree. Geoff Hulette, a student that I worked with on the project last year, chose instead to use a KD-Tree. This ended up performing far better than my octree code, so we ended up using it. The octree version did not get ported through the F# and Haskell versions, so no code for it is discussed here.
The data type that represents the tree is as follows.
data KDTreeNode a = Empty | Node (KDTreeNode a) Vec3 a (KDTreeNode a) | Leaf Vec3 a deriving Show
A KDTreeNode can be either empty, a leaf containing a single particle at a single coordinate, or an inner node with a particle at a coordinate and two children. Note that the KDTreeNode data type is parameterized with a generic type that resides with the coordinates. This is used to store data related to each particle along with their coordinates. This could be something simple like the particle number so we can track the accumulation of particles over time, or something more complex related to whatever it is one could be modeling with the program. In the example code I wrote to generate the visualizations above, it was just an Int representing the order in which particles joined the structure.
The functions for working with KDTrees are below.
kdtAddWithDepth :: (KDTreeNode a) -> Vec3 -> a -> Int -> (KDTreeNode a) kdtAddWithDepth Empty pos dat _ = Leaf pos dat kdtAddWithDepth (Leaf lpos ldat) pos dat d = if (vecDimSelect pos d) < (vecDimSelect lpos d) then Node (Leaf pos dat) lpos ldat Empty else Node Empty lpos ldat (Leaf pos dat) kdtAddWithDepth (Node left npos ndata right) pos dat d = if (vecDimSelect pos d) < (vecDimSelect npos d) then Node (kdtAddWithDepth left pos dat (d+1)) npos ndata right else Node left npos ndata (kdtAddWithDepth right pos dat (d+1)) kdtAddPoint :: (KDTreeNode a) -> Vec3 -> a -> (KDTreeNode a) kdtAddPoint t p d = kdtAddWithDepth t p d 0
What is going on here? Adding a point is actually achieved with a function called kdtAddWithDepth, and kdtAddPoint calls that with an initial depth of zero. kdtAddPoint is a convenience function provided to avoid exposing this depth parameter to users of the code. The depth is used to select which component of the vector is partitioning the tree at each level. If we label the vector components as (x,y,z), then the 0th layer looks at x, 1st layer looks at y, 2nd layer looks at z, 3rd at x, and so on. The vecDimSelect function is provided by the Vec3 module to extract these components. The logic of the add function is pretty close to what we expect from any binary tree. There are three cases to worry about : adding to an empty tree, adding to a tree composed of just a leaf, and adding to a tree that has more than one element in it. In each case, the choice of which side to traverse is driven by the comparison of the depth-selected vector component.
Next, there are the functions for searching.
kdtInBounds p bMin bMax = (vecLessThan p bMax) && (vecGreaterThan p bMin) kdtRangeSearchRec :: (KDTreeNode a) -> Vec3 -> Vec3 -> Int -> [(Vec3,a)] kdtRangeSearchRec Empty _ _ _ = [] kdtRangeSearchRec (Leaf lpos ldat) bMin bMax d = if (vecDimSelect lpos d) > (vecDimSelect bMin d) && (vecDimSelect lpos d) < (vecDimSelect bMax d) && (kdtInBounds lpos bMin bMax) then [(lpos,ldat)] else [] kdtRangeSearchRec (Node left npos ndata right) bMin bMax d = if (vecDimSelect npos d) < (vecDimSelect bMin d) then kdtRangeSearchRec right bMin bMax (d+1) else if (vecDimSelect npos d) > (vecDimSelect bMax d) then kdtRangeSearchRec left bMin bMax (d+1) else if (kdtInBounds npos bMin bMax) then (npos,ndata) : ((kdtRangeSearchRec right bMin bMax (d+1))++ (kdtRangeSearchRec left bMin bMax (d+1))) else (kdtRangeSearchRec right bMin bMax (d+1))++ (kdtRangeSearchRec left bMin bMax (d+1)) kdtRangeSearch :: (KDTreeNode a) -> Vec3 -> Vec3 -> [(Vec3,a)] kdtRangeSearch t bMin bMax = kdtRangeSearchRec t bMin bMax 0
The KDTree is intended to provide a space-oriented search capability. Given a region of three dimensional space, the data structure should be able to return all points that are in the tree that fall within that region. The kdtRangeSearch function provides this. Like the function to add a point, the traversal requires knowledge of the depth at each level to decide which components of the range vectors are used for comparison. So, the kdtRangeSearch function hands control off to the actual search function with an initial depth of 0. As the kdtRangeSearchRec function traverses the tree, each point that is in the tree that falls within the bounding box defined by bMin and bMax are added to a list and returned. The result will be a list of points and their associated data. The order is meaningless within this list.
The final function of interest is that which, given a point not in the tree, determines if a collision will occur with any point already in the tree. This is the critical function called as particles take their random walk to potentially join the aggregate. Needless to say, it gets called quite frequently.
singleCollision :: Vec3 -> Vec3 -> Vec3 -> Double -> a -> Maybe (Vec3,a) singleCollision pt start a eps dat = if (sqrd_dist < eps*eps) then Just (vecAdd start p, dat) else Nothing where b = vecSub pt start xhat = (vecDot a b) / (vecDot a a) p = vecScale a xhat e = vecSub p b sqrd_dist = vecDot e e kdtCollisionDetect :: (KDTreeNode a) -> Vec3 -> Vec3 -> Double -> [(Vec3,a)] kdtCollisionDetect root start end eps = map fromJust $ filter (\i -> isJust i) colls where Vec3 sx sy sz = start Vec3 ex ey ez = end rmin = Vec3 ((min sx ex)-eps) ((min sy ey)-eps) ((min sz ez)-eps) rmax = Vec3 ((max sx ex)+eps) ((max sy ey)+eps) ((max sz ez)+eps) pts = kdtRangeSearch root rmin rmax a = vecSub end start colls = map (\(pt,dat) -> (singleCollision pt start a eps dat)) pts
The function kdtCollisionDetect takes four arguments. First is the KDTree holding the particles to check a collision against. The second parameter is the starting position of the particle that is possibly colliding with the aggregate, and the third parameter is the position that particle would be at if it took a step and did NOT collide. The final parameter is the distance between particles that we consider to be sufficient for a collision to occur. As mentioned earlier, the particles in this model are considered not to be point particles, but tiny spheres. The coordinates simply indicate the center of the sphere. Epsilon should be considered to be twice the radius of the spheres – if two spheres have centers separated by epsilon or less distance units, then they have collided. Note that for this example we are not concerned with particles getting closer than epsilon — we allow them to overlap.
The first step in collision detection is to determine the region of space where we want to see if a particle already exists in the tree. The rmin and rmax computations determine these bounds by defining the corners of the cube based on the start and end position of the moving particle. The range search function is then invoked to check this space. The variable a is computed to represent the position of the particle within this range where we move the origin to the starting position of the particle – it just helps establish a relative coordinate system for the computation. We then map the function singleCollision over all potential collision candidates in the range to find all particles that we may have collided with. The contents of the singleCollision routine are basically a small bit of linear algebra to check each of these candidates to see if they are within epsilon of the particle being checked. The return value is the list of checked candidates that did actually fall within epsilon of the particle.
Up to this point, we have all of the machinery to implement the core of the simulation. We can walk particles around along their random walk, we can store them as they join the aggregate, and we can perform collision detection to decide whether or not a new particle gets added. This core is implemented in the function to walk a single particle around to either collide or wander outside the sphere in which we are working.
-- -- walk a single particle -- walk_particle :: DLAParams -> Vec3 -> DLANode -> Int -> DLAMonad (Maybe (DLAParams, DLANode)) walk_particle params pos kdt n = do -- 1. generate a random vector of length step_size step <- randVec (step_size params) -- 2. walk current position to new position using step pos' <- return $ vecAdd pos step -- 3. compute norm of new position (used to see if it wandered too far) distance <- return $ vecNorm pos' -- 4. check if the move from pos to pos' will collide with any known -- particles already part of the aggregate collide <- return $ kdtCollisionDetect kdt pos pos' (epsilon params) -- 5. sample to see if it sticks doesStick <- sticks params -- 6. termination test : did we collide with one or more members of the -- aggregate, and if so, did we stick? termTest <- return $ (length collide) > 0 && doesStick -- 7. have we walked into the death zone? deathTest <- return (distance > (death_rad params)) -- check termination test case termTest of -- yes! so return the updated parameters and the kdtree with the -- new particle added. True -> return $ Just (update_params params pos', kdtAddPoints [(pos',n)] kdt) -- no termination... check death test False -> case deathTest of -- wandered into the zone of no return. toss the particle, -- return nothing and let the caller restart a new one. True -> return Nothing -- still good, keep walking False -> walk_particle params pos' kdt n
A single step of this algorithm first samples the random number generator to take a step in some direction by step_size units. We compute where this particle would end up by adding the step vector to the position vector where the particle currently resides. The distance of this new position from the origin is computed so that it can be checked if it has wandered too far and must be destroyed. Next, the collision detection routine is called to determine if the particle collided with the existing aggregate. In the event that it does, the stickiness parameter is used to see whether or not it sticks or continues walking. Two tests are performed to check if it did collide and did stick, or if it walked too far away and needed to be purged. The case at the end of the function checks these tests, first to see if the particle stuck (in which case it is added to the aggregate), and if it did not stick, whether or not it was too far away. If it was, Nothing is returned. Otherwise, the function is recursively called with the new position that the particle walked to and the process repeats.
Overall, the structure of the code is satisfying in that the logic of the DLA model is fairly accurately captured without much obfuscation. The use of the Maybe type is employed to allow the caller to easily determine the outcome of the walk – if a particle did stick, then the return value is the new set of parameters and the KDTree with the new particle added. If it did not stick and walked too far away, the function returns Nothing. Notice that when a particle does stick, we return two items. As the aggregate grows, we may find that it is approaching the size of the sphere on which particles originate. We must keep this sphere sufficiently far from the aggregate to allow particles to walk inwards as if they originated far away. As such, when a particle joins the aggregate, we update the simulation parameters to allow the sphere of origin (and, correspondingly, the sphere where particles die) to grow.
Much of the remaining code, such as the main function or code to load parameter files off of disk, isn’t of much interest for the post. I do provide it all for download from my publicstuff GitHub repository, so feel free to check the code out if you’re interested in messing with the code.
What now? In a post in the not so distant future, I’m going to post the results of sitting down with some Haskell experts to tune the code to achieve performance comparable to the C version. One of the results of this tuning activity was the monad-mersenne-random package added to Hackage, which resulted from noticing that the pattern of using a state monad to thread PRNG state through the code is likely to be common in codes like this. What will be interesting will be looking at what lengths are required for different performance gains. It should be noted that the C code (also posted online in the publicstuff repo for the curious) was not highly tuned. So, to be fair, the Haskell code tuning will include discussion of “low hanging fruit” that can be learned by regular Haskell programmers, and some finer tuning that is beyond the likely scope of knowledge for a regular Haskell programmer. I personally don’t think it’s fair to present highly tuned code as representative of a language — the best representative of a language is the code that someone who has read the educational materials on the language would write. If those materials lead to poorly performing code, then it obviates the need for better educational materials.
What are my thoughts on the code presented in this post? First, I like it. One thing that I do find highly attractive about Haskell is the brevity of the code. Even the DLAMonad, which admittedly took a little while to figure out how to build, eliminates annoying explicit threading of state through parameters, making function signatures a bit cleaner. The use of the Maybe types in strategic places also is appealing, and reflects a similar pattern that I commonly employ in ML code based on the option type. I have to admit, I found laziness to be a significant burden here. There is no advantage to laziness that I can see in this particular program. If anything, it got in the way and caused bugs that required me to consult some local Haskell experts to find a solution to — which ultimately boiled down to purging laziness in critical parts of the program.
Stick around if you’re curious about how we tuned this code to go fast! Or, wait a little bit and I’ll talk about another interesting little code that I’ve been working with.
13 thoughts on “3D Diffusion limited aggregation in Haskell”
I’m trying to learn Haskell, and I think this was a very interesting post. I will try to understand all the decisions for the implementation when I get the time.
However, I think the calculation of theta, in randVec, is wrong (if my brain works correctly this early in the morning…). As I understand it, you create a uniformly distributed random variable, z, and use that to calculate theta. Since asin is a nonlinear function, the distribution of theta will not be uniformly distributed. I think it should be something like
theta’ <- NextF (2.0 * pi)
theta <- return $ theta' – pi
return $ Vec3 (r*(cos theta)*(cos phi)) (r*(cos theta)*(sin phi)) (sin theta)
instead. Create a uniform random variable with bounds [0,2pi], and subtract pi to get theta with bounds [-pi,pi]. The syntax may be wrong, since I'm not sure how to work all those monad things.
Actually, I got the method for generating points uniformly distributed on a sphere from here. There is an additional page that also gives a good discussion of the problem on MathWorld.
Ok, it apparently *is* too early in the morning.
I somehow forgot the third dimension. Sorry to bother you.
Hi,
just wanted to mention that you could speed up the code by omitting the computation of theta. This can be achieved by substituting
r*(cos theta)
with
r*(cos (asin (z/r)))
=r*(sqrt (1-(z/r)^2))
=sqrt (r^2 – z^2)
which should compute faster than the trigonometric functions.
Good suggestion! I have encountered similar instances in the past where applying analytic techniques such as trig identities can lead to code that is faster by eliminating slow calls to numerical primitives. In this case, the benefit is a function of the input parameters to the code. If the step size taken by the particles is small during their walk, the code will spend most of its time there instead of on generation of particles on the sphere where they originate. But, in other cases, randVec can consume a noticeable amount of time. I’ll try your suggestion in the tuned code to see what impact it has.
Here are some mirco-comments about your haskell code. Most are simply my opinion and a matter of taste. Feel free to ignore any of my comments.
KDTree.hs
I’d be inclined to split printVec into a showVec and printVect. Also this function logically belongs in Vec3.hs
dumpKDTree should use withFile
For most of the uses of if statements, I’d be inclined to use guards instead. Again, this is a matter of taste.
In Rmonad.hs, I’m not sure why you bother newtyping Rmonad. Instead I would be inclined to write
newtype DLAmonad a = DLAMonad (State PureMT a)
Actually wrapping it in a continuation monad (actually codensity monad) may give you a performance boost (or may do nothing)
newtype DLAmonad a = DLAMonad (forall r. (ContT r (State PureMT) a))
In Driver.hs, for update_params, if you use Haskell’s record updating, you wouldn’t have to write entries for those fields that don’t change.
In general, wherever you write
x <- return expr
it would be better to write
let x = expr
In walk_particle I would be inclined to use an if statement instead of a case statement.
In singleStep you can remove the do for one line monad sequences. (i.e. remove the do in the case statement).
In main write
let [configFile, outputFile] = args
Actually I would have validateArgs return a pair as in
validateArgs [configFile, outputFile] = return $ (configFile, outputFile)
validateArgs _ = do putStrLn "Must specify config file and output file names."
exitFalure
I'm a little surprised that you had laziness troubles. I'm running your code using the lazy state monad and I haven't had any troubles yet. If you did have problems, I expect that you could also fix your problems by making your code more lazy rather than more strict. However, if you want to get C performance, you will probably have to eventually unbox your data in GHC in your inner loop which will force things to become strict (but I don't know much about getting performance out of Haskell).
There are probably a few more comments I could make, but maybe I'll end it now.
Thanks for the detailed comments! I think my wires got crossed when I wrote this since I have another code that uses the same Rmonad module that suffered from sawtoothing in the heap usage with the lazy state monad, but flat usage with strict. I will be posting the writeup on that other code in the next few weeks, but if you’re curious, it is the hsgep code on hackage. I too tried to reproduce the sawtoothing behavior with the DLA code, but was unable to. I can surely reproduce it for the hsgep library though. I will be sure to mention my mistake in the followup post on performance tuning. Sorry about that!
I’d also be curious to hear of your experience with F# in relation to Haskell along with the expected tuning post. Thanks!
Sure – I can dig that F# code up and include it.
Or maybe not even all the code, but just your experiences in developing and testing it would suffice IMHO. | https://mjsottile.wordpress.com/2010/08/22/3d-diffusion-limited-aggregation-in-haskell/?shared=email&msg=fail | CC-MAIN-2018-30 | refinedweb | 5,089 | 58.52 |
I'm trying to do something I know has to be simple but I keep getting incomplete, outdated, or just plain wrong information. I've been researching this all day, including reading every post on this site with the words "XDocument" and still can't find a complete answer.
I'm trying to load a local, static XML file into a Silverlight app so that I can iterate through the nodes. I've tried XDocument xd = XDocument.Parse("something"); but I don't know what that "something" should be for a local file. I've also read "How To: Manipulate XML Data in Silverlight" () but it's both out of date and pulling data from a remote location. I've also seen reference to XmlReader but don't know what to do with that information. I've also been playing with XElement but am obviously doing something wrong.
Here's what I have so far. It doesn't work but at least it doesn't crash either.
var xe = new XElement("localFile.xml"); var query = from item in xe.Elements() select new { firstNode = xe.Element("firstNode").Value, secondNode = xe.Element("secondNode").Value, thirdNode = xe.Element("thirdNode").Value, fourthNode = xe.Element("fourthNode").Value }; HtmlPage.Window.Alert(query.Count().ToString());
This returns a "0" every time. I noticed that if I change the xml file name to gibberish, it still returns 0. Any suggestions? Different approaches?
You can do this by using OpenFileDialog.
OpenFileDialog openFileDialog1 = new OpenFileDialog(); if (openFileDialog1.ShowDialog() == DialogResult.OK) { // Open the selected file to read. System.IO.Stream fileStream = openFileDialog1.SelectedFile.OpenRead();
using (StreamReader reader = new StreamReader(fileStream)) { // Read the first line from the file and write it // to the text box. txt.Text = reader.ReadLine(); } fileStream.Close(); }
Thierry BouquainUcaya
Did you ever solve this issue? I was just trying to do something very similar and was having issues as well. Post if you find an answer! Thanks.
Thierry's solution doesn't work for you??
(If this has answered your question, please click on "Mark as Answer" on this post. Thank you!)Best Regards,Michael SyncBlog : :
I suppose it could, though it seems like there would be a more graceful method to parse a local xml file (which I think was the original question). Maybe I misunderstood it though. Anyway, just wondering how one would go about this in silverlight.
Thanks.
Actually, this may be a valid answer:
knorsen:I suppose it could, though it seems like there would be a more graceful method to parse a local xml file (which I think was the original question).
I suppose it could, though it seems like there would be a more graceful method to parse a local xml file (which I think was the original question).
He's exactly right. The original question was about using a local project resource - a static xml file that's included in the project. The ultimate goal will be to post this on Silverlight Streaming. It'd be nice to be able to pull in an RSS feed but the source I want doesn't have the proper security certificate and there are just too many hassles and workarounds getting anything else to work correctly.
It seems to me that with all the XML classes (XmlDocument - which isn't included in the micro framework, XDocument, XElements, etc) that there should be a simple, elegant way to specify the source of an xml document, like XmlThing xt = new XmlThing("localfile.xml"), and then have all of the expected properties and methods available. It doesn't make sense to me that this is so complicated in SL 2.
Silverlight 2 Beta 1 doesn't allow direct access to local files since it is a security issue (remember it is running in the context of a browser). Your best bet is to use the OpenFileDialog as per the example given by Thierry.
Once you get the stream as string from the openfiledialog, you can pass that as input to XElement/XDocument, like this -
Yep, a slightly roundabout way of doing things, but you could probably encapsulate the above code in a method which will simplify usage. There is no way to get past the user confirmation though (openfiledialog)
Hope this helps!
Wilfred Pinto
As an experiment, here's what I cobbled together from info found in other posts on this forum and a page on Scott Gu's blog. (My rendition could be cleaner, I know). Anyway, it works and it allows me to access the XML that is part of my test project by looking at the same location as where the silverlight is running (using a HttpWebRequest instead of just trying to open the file as a local resource). I still have a feeling there is an easier way to make this work, but I haven't run accross it yet. Code/Notes below:
//will need to add System.Net.dll to Project References
//inside my Page.xaml.cspublic Page() { // get the xml file System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(new Uri(GetAppPath() + "myXmlDoc.xml")); request.BeginGetResponse(new AsyncCallback(ResponseCallback), request);} private void ResponseCallback(IAsyncResult asyncResult) { System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)asyncResult.AsyncState; System.Net.HttpWebResponse response = (System.Net.HttpWebResponse)request.EndGetResponse(asyncResult); Stream content = response.GetResponseStream(); XDocument doc = XDocument.Load(new StreamReader(response.GetResponseStream())); var test = from xml_test in doc.Descendants("xml_test") select new { my_info = xml_test.Element("my_info").Value, }; foreach (var xml_test in test) { //do something with your results } }//use to get a uri for HttpWebRequest public string GetAppPath() { string path = HtmlPage.Document.DocumentUri.AbsolutePath; path = path.Substring(0, path.LastIndexOf("/") + 1); return string.Concat("http://", HtmlPage.Document.DocumentUri.Host, ":", HtmlPage.Document.DocumentUri.Port, path); }
Knorsen- that worked well for me. Thanks!
To any n00bs (like myself) that may be following this you will need these to run knorsen's code:
using System.Net;using System.IO;using System.Windows.Browser;
J CipInteractive Developer | http://silverlight.net/forums/t/14517.aspx | crawl-001 | refinedweb | 988 | 58.28 |
Speeding up Spring, coupled to JBossTejas Mehta Jul 11, 2013 7:09 PM
Hello all,
We, the Snowdrop Dev team, have been trying to speed up Spring's Component Scanning.
Typically, Spring Applications make use of the context namespace to add beans to the Spring Container, example: <context:component-scan. In order to identify the beans it needs to initialize, Spring looks through the package and scans for @Component and its extensions. For packages with large number of Components, this process is fairly slow.
The specific steps are as follows:
After bootstrapping, the set of application components and service that need to be created are identified. AbstractbeanDefinitionReader will read resource definitions. DefaultListableBeanFactorywill be used as default bean factory based on bean definition objects.XmlBeanDefinitionReader.loadBeanDefinitions() load bean definitions from the specified XML file in which the BeanDefinitionParser will identify the context namespaces and parses the applicationContext xml. The resources are identified by the implementation of ResourcePatternResolver:, ie PathMatchingResourcePatternResolver in which the location patterns are found like an ant-style. Internally it uses ClassLoader.getResources(String name) method which returns an Enumeration containing URLs representing classpath resources. Then the ComponentScanBeanDefinitionParser will parse through the context definition nodes.
It is this last step that we want to speed up and to do so we are attempting to leverage JBoss' Jandex module.
At the start of deployment in JBoss, the Jandex module scans the classes and creates an Annotation Index. We would like to be able to utilize this Index to skip the scanning step and just initialize the pre-identified components.
Potential Solution:
Component-Scan within snowdrop's jboss namespace -:
One option is to add our custom component scanner to snowdrop's namespace. So instead of <context:component-scan, the user would use: <jboss:component-scan.
While this has the downside that the user has to change their application to make use of the feature, it forces the user to make a conscious decision.
What do you think of this feature and of how it couples a Spring app with JBoss? Is the intentional coupling worth the speed increase?
Thanks in advance for the feedback,
Tejas M. on behalf of the Snowdrop Team
1. Re: Speeding up Spring, coupled to JBossAles Justin Jul 12, 2013 4:33 AM (in response to Tejas Mehta)1 of 1 people found this helpful
Don't we already have to setup some custom hook in web.xml, to handle our VFS?
Or is that not needed anymore in AS7 / Wildfly.
Is there a way to identify deployment with Spring in it -- w/o any custom JBoss files?
(I used to do it via -spring.xml, afair :-))
As I would rather have generic transparent usage for the users, then custom hook for every feature we need to plugin to.
e.g. scanning is one thing, VFS is another, bytecode weaving, cross injection from MSC, ...
2. Re: Speeding up Spring, coupled to JBossTejas Mehta Jul 12, 2013 9:03 AM (in response to Ales Justin)
As far as I know, there are almost no custom hooks required to handle our VFS with AS7/Wildfly, based on my experience with this example:.
So users are not required to use -spring.xml to deploy spring apps.
Besides the custom hook, some of the options we looked into are AOP (too much configuration required on user's part) and javassist (not possible). We are now looking at Byteman, thanks to Vineet's suggestion. If we go this route then there would be no need for custom hooks, but would happen without users knowing, which may be a problem for some. What do you think? | https://developer.jboss.org/thread/230359 | CC-MAIN-2018-51 | refinedweb | 603 | 55.34 |
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index
XMl
XMl Hi.
please tell me about that
What characters are allowed in a qualified name?
Thanks
What is XML?
and create well formatted XML
document.
What is XML Document?
Some facts about XML...What is XML?
In the first section of XML tutorials we will learn the basics of XML and
then write our first xml document. After completing this section
XML - XML
XML What is specific definatio of XML?
Tell us about marits and demarits of XML?
use of XML?
How we can use of XML? Hi,
XML... language much like HTML used to describe data. In XML, tags are not predefined
XML Tutorial
displaying information, while XML is about describing information
W3... you understand what XML is all about. (You'll learn about XML in later sections... will learn what XML is about. You'll understand the basic XML syntax. An you
xml - XML
:// define parser and xml,in jaxp api how to up load parsers... then the program
contains syntax errors.
XML is defined as an extensible
About RoseIndia.net
About RoseIndia.Net
RoseIndia.Net is global services ...,
Perl, J2ME, XML, relational databases (MySQL, Oracle, DB2, Access). We...:
Java2EE - JMS, JSP, Servlets, EJB, JNDI, JDBC, Hibernate, Struts, Spring,
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including index in java regular expression
including index in java regular expression Hi,
I am using java regular expression to merge using underscore consecutive capatalized words e.g.... in the sentence so that i dont need to worry about first word starting with capital
Shopping Cart Index Page
the search results about the product to the
customer. In administration part part
read XML file and display it using java servlets
read XML file and display it using java servlets sir,
i can't access Xml which is present in my d drive plz can u should go through my code n tell... ServletException, IOException
{
response.setContentType("text/xml");
FileRead fr
Servlets - JDBC
(); } catch (Exception e) { e.printStackTrace(); } }}web.xml<?xml...;" xmlns:xsi="" xsi:schemaLocation="
PHP PDO Index
execute the following piece of
code and you will get to know about that, if you want...
sqlite2
This is the index page of PDO, following pages will illustrate
servlet - XML
servlet How to run xml programs.&in servlets how to implements them
servlets - Servlet Interview Questions
servlets is there anybody to send me the pdf of servlets tutorial?
Thanks in advance for who cares about me
OGNL Index
, this first character
at 0 index is extracted from the resulting array
XML validation
XML validation please tell me how to validate an XML against DTD by using link . you can learn more information about servlets structure... for more information.
servlets execution - JSP-Servlet
servlets execution the xml file is web.xml file in which the servlet name,servlet class,mapping etc which has to be done.
What u want...://
Thanks.
Amardeep
xml or database - XML
xml or database If I implement some web applications, which is a better way to retrieve and parse xml file directly using DOM or storing those xml files in Database and retrieve. My xml files will be about 100 - 200 and each
What is Index?
What is Index? What is Index
XML in flex
XML in flex Hi...
just tell me about
What is e4X and XML in flex?
Thanks
XML template
XML template Hi.....
please tell me about
What is XML template?
Thanks
XML and xlink
XML and xlink Hi....
please tell me about that
What is the differences Between XML and xlink?
Thanks
XML namespace
XML namespace Hi....
please anyone tell me about
What software is needed to process XML namespaces?
Thanks
XML namespace
XML namespace hi....
please tell me about that
What is an XML namespace prefix?
thanks
XML namespace
XML namespace Hi......
please tell me about that
What characters are allowed in an XML namespace prefix?
Thanks
XML namespace
XML namespace hi...
What is an XML namespace name?
please tell me about that
Thanks
servlets
servlets what is the duties of response object in servlets
servlets
servlets why we are using servlets
servlets
what are advantages of servlets what are advantages of servlets
Please visit the following link:
Advantages Of Servlets
Read XML in java - XML
Read XML in java Hi Deepak, I want to read a xml file which have... node,int index) {
String nodeName = node.getNodeName();
String...);
if (child.getNodeType() == Node.ELEMENT_NODE) {
retrieveValue(child,index
Servlets How to edit and delete a row from the existing table in servlets
servlets
servlets How do you communicate between the servlets?
We can communicate between servlets by using RequestDespatcher interface and servlet chaining
XML Signatures
XML Signatures Hi.....
please tell me about
What three essential components of security does the XML Signatures provide?
Thanks
Xml Parser
Xml Parser Hi...
please tell me about
What parser would you use for searching a huge XML file?
Thanks
XML namespace
XML namespace hi...
please anyone tell me about
Can I use the same prefix for more than one XML namespace?
Thanks
XLink in Xml
XLink in Xml Hi..
Please anyone tell me about
What is XLink in Xml?
Thanks
XLink in Xml
XLink in Xml Hi...
please tell me about
Why doesn't use XLink in Xml?
Thanks
XML namespace
XML namespace hi...
please tell me about that
What happens if there is no prefix on an element type name?
thanks... link:
Thanks
Importance of XML
Importance of XML Hi.......
I have a problem regarding
Why is XML such an important development?
please tell me about that
Thanks
XML namespace
XML namespace Hi....
please anyone tell me about
Can I use a relative URI as a namespace name?
has been accessed:" + accesses); }}web.xml<?xml version="1
Adobe Flex Component Index
Adobe Flex Components:
In this current tutorial we will get to know about various components about Flex, the Flex provided various types of components like... can put validations on different field so easily and effectively.
Index of Flex
index of javaprogram
index of javaprogram what is the step of learning java. i am not asking syllabus am i am asking the step of program to teach a pesonal student.
To learn java, please visit the following link:
Java Tutorial
read xml
read xml hi all, i want to ask about how to read an xml in java ME..
here is the xml file
<data>
<value>
<struct>
<member>
<name>
User_Name
SERVLETS
servlets
the servlets
Servlets | http://roseindia.net/tutorialhelp/comment/81210 | CC-MAIN-2014-42 | refinedweb | 1,239 | 75.3 |
I have Visual Studio 2019 community edition on a windows 10 laptop. I have the .net Desktop Development and Universal Windows Platform Development package bundles installed among with some C++ and Python stuff. I ran the MonoGame 3.7.1 visual studio installer then downloaded the monogame templates from the extension manager. At one point Visual Studio had me install a new windows sdk, and at another point it downloaded some NuGet packages. When I go to build any of the templates it throws an exception because it can’t find Xna in the Microsoft namespace. Is there any way of setting Monogame up without setting up VS 2017? I am very new to C#, trying to learn it, and this is the first library I’m trying to setup.
I was able to get it setup using this tutorial. Basically just temporally rename a copy of the Visual Studio 2019 folder.
Yeah, I don’t understand. The devs refuse to properly support VS2019. I think they are working on better support for the future but it would be nice to have proper '19 support since we’re already half way through 2020…
The directions are for downloading but end me up at NuGet, where there’s a million packages… I have no idea where to start as the documentation doesn’t match what’s out there.
Use the getting started link, it tells you all you need
The NuGet packages are basically zip files. Just change the file extension form .nupkg to .zip, and you can find all the binaries in there.
If you want an installer use 3.7.1: | https://community.monogame.net/t/setup-with-vs-2019/12632 | CC-MAIN-2022-40 | refinedweb | 272 | 73.68 |
It appears there is no intellisense when editing a Xamarin.Forms XAML file or did something go wrong with my install?
If there is none, is there an XSD that could be used when editing the file in the XML Text editor?
I suspect we will need help from MS to make it happen. Sorry
The way their tooling works just isn't really compatible with the PCL framework.
Answers
I'm having the exact same issue. There is no intellisense at all when trying to create a Xamarin.Form. Should there be designer support for this as well as selecting "View Designer" does not do anything.
I too am having this issue -- the designer does not work and there is no Intellisense. Note: I am using Visual Studio 2013 Update 2
Are you using ReSharper? There's currently a bug in ReSharper's version of IntelliSense that causes this. Note that you can disable ReSharper's IntelliSense without disabling all of it and without losing smart completion elsewhere.
There is no designer, this option will just have Visual Studio trying to open the .xaml file with its own WPF/WP/WinRT designer which won't work.
Any thoughts on adding support for the designer? It would make a HUGE value add as it would allow more designers to work on the UI for mobile apps.
I am using resharper -- what do I need to disable to get this to work?
I am not using Resharper. Here is the Visual Studio About information:
Microsoft Visual Studio Professional 2013
Version 12.0.30501.00 Update 2
Microsoft .NET Framework
Version 4.5.51641
Installed Version: Professional
LightSwitch for Visual Studio 2013 06177-004-0446025-02539
Microsoft LightSwitch for Visual Studio 2013
Office Developer Tools - May 2014 Update ENU 06177-004-0446025-02539
Microsoft Office Developer Tools for Visual Studio 2013 - May 2014 Update ENU
Team Explorer for Visual Studio 2013 06177-004-0446025-02539
Microsoft Team Explorer for Visual Studio 2013
Visual Basic 2013 06177-004-0446025-02539
Microsoft Visual Basic 2013
Visual C# 2013 06177-004-0446025-02539
Microsoft Visual C# 2013
Visual C++ 2013 06177-004-0446025-02539
Microsoft Visual C++ 2013
Visual F# 2013 06177-004-0446025-02539
Microsoft Visual F# 2013
Visual Studio 2013 Code Analysis Spell Checker 06177-004-0446025-02539-02539
Windows Phone SDK 8.0 - ENU
ASP.NET.
File Nesting 1.0
Automatically nest files based on file name and enables developers to nest and unnest any file manually
Microsoft Team Foundation Server 2013 Power Tools 12.0
Power Tools that extend the Team Foundation Server integration with Visual Studio.
Microsoft Visual Studio Process Editor 1.0
Process Editor for Microsoft Visual Studio Team Foundation Server
NuGet Package Manager 2.8.50313.46
NuGet Package Manager in Visual Studio. For more information about NuGet, visit.
PreEmptive Analytics Visualizer 1.2
Microsoft Visual Studio extension to visualize aggregated summaries from the PreEmptive Analytics product.
SQL Server Data Tools 12.0.30919.1
Microsoft SQL Server Data Tools
Web Essentials 2013 1.0
Adds many useful features to Visual Studio for web developers.
Windows Azure Mobile Services Tools 1.1
Windows Azure Mobile Services
XtraReports package 1.0
XtraReports package
ReSharper's IntelliSense should be enough. ReSharper -> Options -> IntelliSense -> General -> Select Visual Studio.
Tried that -- no luck (Even restarted VS)
I'm running visual studio pro, update 2 and I have no plugins other than xamarin installed. Any other things I could try to get intellisense to work?
I've completely disabled resharper but I'm still not getting any intellisense:
Same here...For now I switched to Xamarin Studio and Intelli-Sense works there.
SUPER PUMPED about Xamarin.Forms though
Same issue here -- completely turned off Resharper and still not working.
XAML Intellisense has a chance of working if you can open the .xaml file using the Xaml UI Designer editor. When I try to Open With on the .xaml file to select that, I get this error: "The file cannot be opened with the selected editor. Please choose another editor."
This works fine for opening a Xamarin Forms XAML page if the file is defined in another kind of project (say, a WPF project). It seems that Portable Class Libraries is deliberately denying the ability to use that editor. Note that I'm not expecting the designer to work. But opening any xaml file using that editor tends to make the code editing half of the designer work, including Intellisense. So use linked files to add these xml files to another type of project (say... a WPF project for example) and you can open them in the right editor and you're halfway there.
Once the editor can be opened, there's another step required for it to work (from my experience getting XAML Intellisense to work on other object models, anyway). You need to help the editor find the types represented by the tags. Some great documentation on this is available on MSDN. First let's look at the XAML produced by the Xamarin Forms' "Forms XAML Page" item template:
Notice the root tag has a namespace that is just a URI -- not "clr-namespace" bit. That's fine, but it means some other magic is required to associate the namespace with the assembly that the types come from. For this to work in the designer's code pane, this association comes from the assembly carrying the types. Specifically, the Xamarin.Forms.Core.dll assembly needs to define this attribute:
That attribute is regrettably missing from the assembly, so getting Intellisense to work while the xmlns attribute is the way it is in the item template (I think) is impossible.
You can preview some of what Intellisense will be like after this work is done (on Xamarin's side) by creating such a .xaml file inside a WPF project, adding the Xamarin.Forms NuGet package to it, and then opening it inside the XAML editor. Change the opening tag to read this:
Notice how I've changed the value of the
xmlnsattribute. This now tells XAML exactly where to find the
ContentPagetype, and so Intellisense now works in VS. But since I've changed the xmlns attribute, I expect (although I've not yet tried it) that this may cause deserialization to fail at runtime.
Given that the Core assembly is PCL and that attribute is defined in System.Xaml.dll, that's a no go. The only way that would work is if the consuming side did a string comparison instead of a type and we could define our own version of the attribute.
The IntelliSense works in Xamarin Studio, how to get it working on Visual Studio 2013?
Any one get it working?
Guess I'll use Xamarin Studio for XAML development until they figure out how to get things working in Visual Studio.
If things actually work well (binding and performance in particular), I can't describe how excited I am to be able to write XAML for shared UIs.
Any update on this? Has anyone got XAML intellisense working in VS2013?
I suspect we will need help from MS to make it happen. Sorry
The way their tooling works just isn't really compatible with the PCL framework.
Xamarin Studio Intellisense doesn't work and it gives error as soon as I start typing "<" for tag starting.
Not using Resharper.
Any suggestions?
I would rather have intellisense working before getting a Forms designer in vs.net. Without it, I might as well be typing in Notepad.
Intellisense not working. Wish it did. No resharper, fresh install of Xamarin on top of VS2013 update 2.
I'm going to add a +1 to this. It makes XAML a pretty frustrating experience when there is no IDE support other than color coding. I am using ReSharper, but disabling it doesn't help.
ReSharper also has some issues with the code behind files.
+1! Tomorrow I have a talk about Xamarin, but will not show so much about XAML because is complicate write XAML without intellicense. And Xamarin Studio only show me Android apps
and the experience is completly differente.... I prefer VS and Code behide
+1
Presently we have this situation:
I'm using Xamarin Studio 5.2 (build 379). From previous update in alpha channel XAML autocomplete has broken. It behaves like in simple XML document. No properties autocomplete and no enums autocomplete. Is it a known bug?
Another wish for XAML Intellisense. Much more important (and probably easier to achive) than Designer.
UserVoice is the place to 'vote' on feature requests - they'll get counted up and summarized for us so we know what to aim for next.
Thanks @CraigDunn . I have just suggested a new Idea =>
In Visual Studio, do the following:
Resharper -> Options -> Code Inspection -> Settings -> Edit Items To skip
In the "File masks to skip" section, enter *.xaml.cs
This will cause Visual Studio to recognize the contents of the generated file. Still no intellisense, but at least the editor doesn't complain of missing methods or properties anymore.
@SMouligneaux I gave my votes! Good idea.
Xamarin Studio 5.2 build 384 still have autocomplete issue in xaml. Is this problem just for me?
Adding myself to the list of user asking for Xaml intellisense in Forms.
Same here, +1 for intellisense at least...
+1. Xamarin Forms are really amazing, but without XAML intellisense, it spoils the party
Please don't +1 this thread. Instead, if you really want to give your vote, head over to the UserVoice that already has this issue.
Xamarin Studio 5.2 release still broken autocomplete in XAML
It's hard write code XALM without intellisense. Please Xamarin team fix it, it's essential for programmers.
We are currently qualifying Xamarin for our mobile business strategy and, as of now, even if we understand the potential power of this approach ("one X-Platform design to rule them all"), we have found critical drawbacks (No auto-completion, no online reference documentation with a clear list of attributes like, ...) that restrain us from using of Xamarin.Forms.
@CharlesKEAT.4951 there is API documentation, such as this Entry members page.
We are aware that people really want auto-complete for Xaml in Visual Studio; and we're also working hard to continually expand the documentation at developer.xamarin.com.
The xaml editor in the code view is just a xml editor so you don't really get intellisense but with the right schema it would sure act like it . If Xamarin provided us with the schema for we could just follow the instructions on the blog post below and fix it the same way we fixed the Visual Studio Android XML editor (This link talks about VS 2012 but it worked fine for me in 2013):
With the correct xsd file for this should work nicely for us in Visual Studio. Well for the standard Xamarin.Forms Xaml controls at least. | https://forums.xamarin.com/discussion/comment/56152/ | CC-MAIN-2019-43 | refinedweb | 1,827 | 65.93 |
SYNOPSIS
#include <sys/types.h>
#include <signal.h>
int kill(pid_t pid, int sig);
DESCRIPTION
The
For a process to have permission to send a signal to a pid-designated process, the real or effective user ID of the sending process must match the real or saved user ID of the receiving process. The exception is if the sending process has appropriate privileges. The process with ID 0 and the process with ID 1 are special processes. They are referred to as proc0 and proc1, respectively.
- If pid is greater than zero, sig is sent to the process whose process ID is equal to pid.
- If pid is zero, sig is sent to all processes (except an unspecified set of system processes) whose process group ID is equal to the process group ID of the sender and for which the process has permission to send a signal.
- If pid is -1,
kill()sends the signal to all processes whose real user ID is equal to the effective user ID of the sender.
- If pid is negative but not -1, sig is sent to all processes (except an unspecified set of system processes) whose process group ID is equal to the absolute value of pid and for which the process has permission to send a signal.
If the value of pid causes sig to be
generated for the sending process and if sig
is not blocked, either sig or at least one pending
unblocked signal is delivered to the sending process before the
PARAMETERS
RETURN VALUES
If successful,
- EINVAL
The value of sig is an invalid or unsupported signal number.
- EPERM
The user ID of the sending process is not privileged; its real or effective user ID does not match the real or saved user ID of the receiving process. Or, the process does not have permission to send the signal to any receiving process.
- ESRCH
No process or process group can be found that corresponds to the one that pid specifies.
CONFORMANCE
POSIX.1 (1996), with exceptions.
MULTITHREAD SAFETY LEVEL
Async-signal-safe.
PORTING ISSUES
The determination of whether
the sending process has permission to send a signal to the
receiving process ignores any uid or gid settings
that have been specified with calls to
Using
Sending the SIGKILL signal to non-NuTCRACKER Platform processes also
attempts to post a close message to a window owned by the process specified
by pid.
In cases where it is not possible to post this message, or where
the process does not exit in a timely fashion,
Sending any other signal to a non-NuTCRACKER Platform process fails with errno set to EPERM.
AVAILABILITY
PTC MKS Toolkit for Professional Developers
PTC MKS Toolkit for Professional Developers 64-Bit Edition
PTC MKS Toolkit for Enterprise Developers
PTC MKS Toolkit for Enterprise Developers 64-Bit Edition
SEE ALSO
- Functions:
getpgrp(), getpid(), killpg(), setpgrp(), setsid(), sigaction(), signal(), sigqueue()
PTC MKS Toolkit 10.1 patch 1 Documentation Build 2. | https://www.mkssoftware.com/docs/man3/kill.3.asp | CC-MAIN-2018-30 | refinedweb | 492 | 55.68 |
In this assignment you will write a tool to carry out simple mutation testing on Python programs. Given a program, your tool must generate mutants of that program such that the mutation adequacy score correctly rank-orders a number of held-out test suites for that program in terms of their quality.
You may work with a partner for this assignment. If you do you must use the same partner for all sub-components of this assignment. Only one partner needs to submit the report on Canvas, but if you both do, nothing bad happens.
It is your responsibility to submit Python code that works on the grading server. This is true even if (indeed, especially if) the grading server uses a different version of Python than your development environment.
This assignment uses Python because the focus is on the mutation algorithm and not the compiler front-end. In theory it would be just as easy to do this assignment on C++ code using LLVM (e.g., via clang) or the like. In practice that would just add out-of-scope overhead without reinforcing course concepts. If you are interested in such topics, consider the Compilers and Programming Languages electives.
The grading server uses Python 3.5.2 for this assignment. (Yes, this is a change from other Homeworks.)
You mutation testing tool will take the form of a Python program called mutate.py. Your mutate.py accepts two command line arguments: first, the name of a Python source program to mutate; second, the number of mutants to produce (see below).
Your mutate.py must create a number of new Python source files in the same directory that are mutants of the input program. The mutants must be named 0.py, 1.py, 2.py, and so on. Each mutant is a copy of the original program with one or more mutation operators (see below) applied. Any other output (e.g., logging to standard output) your mutate.py produces is ignored.
The data structure used to represent Python source files is the abstract syntax tree (AST).
You should use the ast module (to read Python source files into abstract syntax trees) as well as the astor module (to serialize abstract syntax trees out to Python source files).
Many students report that the so-called "missing Python AST docs" are quite helpful here.
Your program must be deterministic in the sense that if it is run with the same arguments it should produce the same outputs. (So if you want to use "random numbers", either set the seed to zero or somescuh at the start or use the index of the file you are creating as the random number/seed.)
The ast.parse, ast.NodeVisitor, ast.NodeTransformer, and astor.to_source portions of the interface are all likely to be quite relevant for this assignment.
At minimum, you must implement and support the following three mutation operators:
Note that you do not have to use all three of these operators with the same frequency (or even use them at all — you could set their probabilities to zero). You do, however, have to implement them as a minimal baseline.
For this assignment we will make use of the FuzzyWuzzy string matching library as a subject program. A version of the library merged into one file is available here; it is 686 lines long. You could also do git clone, but the merged-into-one-file version prevents you from having to write a mutator that handles multiple files, and is thus highly recommended.
In addition, two public test suites are provided: publictest-full.py and publictest-half.py. The latter was produced by removing every other test from the former. They are thus not independent high-quality test suites, and you are encouraged to make your own higher-quality test suites (e.g., using the techniques from Homeworks 1 and 2).
Recall that one goal of mutation testing is to assess the adequacy of a test suite. We would thus like the automatic results of our mutation testing to agree with our intuitive assessment that the full test suite is of higher quality than the half test suite.
Here is how an example run might go:
$ python mutate.py fuzzywuzzy.py 10 $ cp fuzzywuzzy.py saved.py ; for mutant in [0-9].py ; do rm -rf *.pyc *cache* ; cp $mutant fuzzywuzzy.py ; python publictest-full.py 2> test.output ; echo $mutant ; grep FAILED test.output ; done ; cp saved.py fuzzywuzzy.py 0.py FAILED (failures=2) 1.py FAILED (errors=24) 2.py 3.py FAILED (errors=35) 4.py FAILED (failures=5) 5.py 6.py FAILED (failures=22, errors=1) 7.py FAILED (failures=1) 8.py 9.py FAILED (errors=40) $ cp fuzzywuzzy.py saved.py ; for mutant in [0-9].py ; do rm -rf *.pyc *cache* ; cp $mutant fuzzywuzzy.py ; python publictest-half.py 2> test.output ; echo $mutant ; grep FAILED test.output ; done ; cp saved.py fuzzywuzzy.py 0.py 1.py FAILED (errors=11) 2.py 3.py FAILED (errors=17) 4.py FAILED (failures=3) 5.py 6.py FAILED (failures=11) 7.py FAILED (failures=1) 8.py 9.py FAILED (errors=21)
In this example we first create ten mutants. We then run each of those ten mutants against the full test suite, and notice that seven of the mutants are "killed" by at least one test (i.e., fail at least one test). Finally, we run each of those mutants against the half test suite, and notice that only six of the mutants are killed. Thus, in this example, the mutation adequacy score for the full suite is 0.7 and the mutation adequacy score for the half suite is 0.6, so mutation testing has assigned test suite qualities that order the test suites in a way that matches our intuition.
In the example above, note FAILED (failures=22, errors=1). The dinstinction between "failures" and "errors" is made by Python's Unit Testing framework and does not matter for our grading. Basically, a "failure" refers to failing the unit test while an "error" refers to any other exception. You are likely doing a better job if you get all failures and no errors, but our grading server just looks for FAILED (which includes both). See Python's Documentation for more information.
Ten mutants is not a large number for randomized testing. We could gain additional confidence by using a larger sample:
$ cp original_saved_fuzzywuzzy.py fuzzywuzzy.py $ python mutate.py fuzzywuzzy.py 100 $ cp fuzzywuzzy.py saved.py ; for mutant in [0-9]*.py ; do rm -rf *.pyc *cache* ; cp $mutant fuzzywuzzy.py ; python publictest-full.py ; done >& test.output ; grep FAILED test.output | wc -l ; cp saved.py fuzzywuzzy.py 46 $ cp fuzzywuzzy.py saved.py ; for mutant in [0-9]*.py ; do rm -rf *.pyc *cache* ; cp $mutant fuzzywuzzy.py ; python publictest-half.py ; done >& test.output ; grep FAILED test.output | wc -l ; cp saved.py fuzzywuzzy.py 38
In the example above, 46 of the mutants are killed by the full suite but only 38 are killed by the half suite.
Many students report that they find it easy to get a few points on this assignment but hard to get a high score — that is, hard to write a mutate.py that produces mutants that rank-order the high- and low-quality test suites.
If you find that your program is not producing enough high-quality mutants to assess the adequacy of a test suite:
You may want to avoid generating "useless" or "stillborn" mutants, such as those that do not parse, always exit with an error, are equivalent to a previously-generated mutant, etc. See Sections III and IV of the Jia and Harman survey for ideas. Here are some common student pitfalls. You should check locally to see if you are making any of these.
You must also write a short three-paragraph PDF report reflecting on your experiences creating a mutation tesitng tool for this assigment. Consider addressing topics such as:
Rubric:
The grading staff will select a small number of excerpts from particularly high-quality or instructive reports and share them with the class. If your report is selected you will receive extra credit.
Historically, many students find it difficult to produce a mutation testing program that works as well on our grading server as it does locally. Ultimately, it is your responsibility to overcome this challenge. However, to provide additional clarity, this assignment features a ``Sanity Check'' autograder submission. You may submit to the Sanity Check option as often as you like; your score there has no influence on your final grade (for good or for ill).
The Sanity Check submission does include significantly more debugging output than the normal submission. Click on the right arrow icons to expand them and read the output carefully. You can use this to debug issues such as bad imports, invalid mutants, and so on.
The Sanity Check submission setup is just like the final submission setup, except that it uses the AVL tree Python program from a previous homework, coupled with a very simple test suite. You can get all of those files here (hw3-sanity.zip) for your own local testing.
Submit a single mutate.py file to the autograder. Submit a single PDF report via canvas. In your PDF report, you must include your name and UM email id (as well as your partner's name and email id, if applicable).
For the autograder submission, we have manually prepared a number of private (i.e., held-out) test suites of known quality. For example, Private Test Suite A is known to be better than Private Test Suite B. You receive points if your mutant adequacy score shows that A is is better than B (i.e., if A kills more of your mutants than B). We check "A > B" and "A >= B" separately; the former is worth more points.
In this section we detail previous student issues and resolutions:
Question: When I submit my mutate.py to the sanity checker, I get:
Compute Mutation Score Exit status: 0 Stdout: ============================================= = Your mutate.py did not run on the server. = ============================================= Inspect the output nearby carefully to debug the problem. Stderr: Traceback (most recent call last): File "mutate.py", line 2, in
import strangelibrary ImportError: No module named 'strangelibrary'
Answer: In such cases you will want to read the output carefully. In this particular example, the problem is that the submitted mutate.py tries to import strangelibrary, but that library is not available on the grading server. Remove the import and try again.
Question: When I submit my mutate.py to the sanity checker, it somewhat works, but I see this if I scroll down to the bottom:
Traceback (most recent call last): File "privatetest-a.py", line 6, in
import avl File "/home/autograder/working_dir/avl.py", line 42 else: ^ IndentationError: expected an indented block
Answer: You are creating mutants that are not valid Python programs. In this example, the student is removing an entire statement right after an else: — but then Python gets confused because it is expectint a tabbed-over statement there. So the mutant is not a valid Python program. Check out the hints on how to deal with this sort of issue.
Question: My submission does not seem to create any mutants on the autograder and/or it can't seem to find them:
ls: cannot access '[0-9]*.py]': No such file or directory
Answer: This almost always means that your mutate.py has an error (such as importing a library not found on the autograder, or raising an exception) that means it is not running to completion.
This issue is, in some sense, the most common student problem. There is no silver bullet here: test locally and make use of the sanity check submission.
Question: It feels like the autograder is non-deterministic. I feel like I am submitting the same mutate.py twice and getting different results.
Discussion: There are many possible issues here that all result in the same observed symptom.
Answer 1: Your mutate.py may be non-deterministic. (This is rare, since student are careful about it.)
Answer 2: Your mutate.py may be creating mutants that are, themselves, non-deterministic. This is much trickier, and happens surprisingly often.
Answer 3: Your test automation may be using stale information or cached values. Even with the rm -rf *.pyc *cache*, you may be testing on mutants created by a previous run of mutate.py if you are not careful.
Answer 4: There may be differences between the autograder setup and your local setup. For example, the autograder uses export PYTHONHASHSEED=0 to try to determinize the order in which hashmaps are iterated.
Discussion: Ultimately, it may not be worth your time to track this down. Remember that we use your best submission, not your last one. Start early.
Question: When I run locally, I get
ImportError: No module named 'astor'
Answer: Make sure you install (again!) with pip3 and python3 rather than pip and python.
Question: I am trying to delete things, but I get this error:
assert node is None, node AssertionError:
Answer: You have ast.Pass but want ast.Pass() instead (note the parentheses). However, you may actually not want to "delete" things like this at all (look around for other hints).
Question: Is fuzzywuzzy.py being modified? When I run all of my mutants to test them it really looks like fuzzywuzzy is being changed.
Answer: Good observation. Your mutate.py does not change it directory, but the example shell script commands we have above do (look for cp which means "copy"). Just copy a saved version back over the original.
Question: When I run my mutate.py, I get this error when trying to print out my mutants:
"AttributeError: 'Assign' object has no attribute 'value' "
Answer: This error occurs when the AST library tries to pretty-print your abstract syntax tree data structure back out to (ASCII) Python source. The AST library expects each node object to have certain fields (properties) filled out. Sometimes a node operation that can look totally reasonable to you (e.g., making a new node, setting it as the child of some other node) can result in a node object not having all of the fields set. If you are changing the types of nodes directly, I would recommend that you instead use their friendly constructors — that may well end up fixing this problem for you. (This is explicitly a bit of a challenge; dig around first and get used to the AST library before asking for help here.)
Question: How can I get the parts of an AST node? Suppose I want to figure out the identified on the left-hand side of an assignment:
Assign(targets=[Name(id='x', ctx=Store())], value=Num(n=9))
Answer: Check out the node documentation. In this particular example, some students report success with node.targets[0].id to extract the id from an instance of the the Assign class.
Similarly, suppose you want to change the right-hand side of the assignment to "None", but leave the left-hand side alone. Have your node transformer do something like:
return ast.copy_location(ast.Assign(targets=node.targets, value=ast.NameConstant(value=None)), node)
Question: I've just started deleting statements, but now I get:
AttributeError: module 'string' has no attribute 'strip'
Answer: If you look closely, you'll see that fuzzywuzzy.py has if PY3: string = str on lines 14-15. If you make big changes there you end up changing which module the code will use, which can have far-reaching effects. Be careful! | https://web.eecs.umich.edu/~weimerw/2018-481/hw3.html | CC-MAIN-2019-43 | refinedweb | 2,625 | 67.55 |
5 AnswersNew Answer
How can we write length of a string without including a particular character For e.g length of "string" could be calculated as 5 by not including r.
12/9/2020 9:45:39 AMHarshita Sharma
5 AnswersNew Answer
s = "this is a short string" print(f'String has {len(s)} characters at all.') print(f'Without character "t" there are {len(s)-s.count("t")} characters, including spaces.')
Do it this way: - Create a variable to add the length to - Loop through the string - Use a conditional statement (if an element is not something) - Add it to the variable. - Print the variable Snippet: length = 0 for letter in string: if letter != the letter you don't want: length += 1 print (length) Happy Coding 😀
def getlen(s, c): return len(s) - s.count(c) print(getlen("string", 'r')) edit...see here for string methods..
Thanks
Thank you all..finally my code worked.
Learn Playing. Play Learning
SoloLearn Inc.4 Embarcadero Center, Suite 1455 | https://www.sololearn.com/Discuss/2619740/length-in-python | CC-MAIN-2021-10 | refinedweb | 166 | 69.68 |
Important: Please read the Qt Code of Conduct -
Dialog UI doesn't show up if it's pointer is allocated inside a function.
I don't know exactly how to search this problem so I will try to describe it here. I would appreciate any pointers (ironic) on what I am missing.
So I have a class named
Calculator_Winwhich inherits from
QMainWindow. It contains as class members various buttons etc. Some of them are connected to show a custom (Q)Dialog which has some functionality. And here lays my problem:
class Calculator_Win : public QMainWindow { Q_OBJECT public: explicit Calculator_Win( QWidget* parent = nullptr ); virtual ~Calculator_Win() override; ... private slots: void fireup_dialog( const PushButton* pbtn ); ... private: std::unique_ptr<Ui::Calculator_Win> m_ui; std::unique_ptr<ConvertDialog> converterDlg; //If the above pointer isn't allocated in Calculator_Win's Ctor, //the ui doesn't show up
Now, if I allocate
converterDlgin the ctor like:
Calculator_Win::Calculator_Win( QWidget* parent ) : QMainWindow { parent } , m_ui {std::make_unique<Ui::Calculator_Win>()} , converterDlg {std::make_unique<ConvertDialog>()} ... { // Body of Ctor m_ui->setupUi( this ); ....
the dialog shows up later when I click my buttons. If however I don't make the
converterDlgpointer to
ConvertDialoga class member, but rather I allocate it like this:
//Right now converterDlg is commented out from the class's variables void Calculator_Win::fireup_dialog( const PushButton* pbtn ) { auto converterDlg { std::make_unique<ConvertDialog>( pbtn, this ) }; converterDlg->setModal( true ); converterDlg->setWindowFlags( Qt::CustomizeWindowHint | Qt::WindowTitleHint | Qt::Dialog ); converterDlg->show(); }
nothing happens. The main window (
Calculator_Win) is responsive. In fact, I can click any button I want or move around the window and nothing is lagging. The slot
fireup_dialogis called, but the dialog is missing.
I am developing in KDevelop and I ran this with Helgrind among other checks. I got multiple errors about
.../src/main.cpp:17:2: Possible data race during write of size 8 at 0x8945198 by thread #1
The problematic line is this:
#include "calculator_win.h" int main( int argc, char* argv[] ) { QApplication app( argc, argv ); <---- qRegisterMetaType<PushButton>(); qRegisterMetaType<ButtonGroup>(); Calculator_Win w;
Could this be irrelevant? I am thinking that maybe the pointer gets out of scope when
fireup_dialogexits so nothing is show, but how the function exits if the
ConvertDialogis (should be) allocated and "active"?
Any ideas on how to debug this would be much appreciated. Thank you.
- Chris Kawa Moderators last edited by Chris Kawa
@Petross404_Petros-S said:
I am thinking that maybe the pointer gets out of scope when fireup_dialog exits so nothing is show
Yes, this is the cause. You're making a local unique pointer, so it deletes your dialog as soon as you get to the
}.
but how the function exits if the ConvertDialog is (should be) allocated and "active"?
There's nothing blocking in that function. The dialog is created, shown and the function exits. If you want to block there until the dialog is closed change
show()to
exec(). This creates a local event loop and blocks until the dialog is closed.
Otherwise don't put the pointer in a smart pointer and delete it manually when the dialog is closed (see e.g. the Qt::WA_DeleteOnClose attribute).
@Chris-Kawa said in Dialog UI doesn't show up if it's pointer is allocated inside a function.:
There's nothing blocking in that function. The dialog is created, shown and the function exits. If you want to block there until the dialog is closed change
show()to
exec(). This creates a local event loop and blocks until the dialog is closed.
Changing to
exec()method solved it.
One last question, are there are any downsides or other things I should have in mind when having a (local) second loop in my Qt app?
- Chris Kawa Moderators last edited by
@Petross404_Petros-S said:
are there are any downsides or other things I should have in mind when having a (local) second loop in my Qt app?
Not that I can think of. Modal dialogs are designed to work that way. It just changes the flow of your application, so you need to keep that in mind, but otherwise they're pretty simple. For non-modal dialogs it's more common to use
show()and let the app get back to the main event loop., but that's just because it's easier to reason about the flow of your app.
While you could come up with more convoluted designs usually you have only your main loop most of the time, a sporadic modal dialog run with
exec()and occasional brief window like a message box (yes, they also work this way). More than that would simply become hard to keep track of.
So the main window is blocked. The way I see this is that if for example I would like to open 2 or more dialogs at the same time, I should find another way to show them by not blocking the main loop.
I guess if I want to use the app in this way, I should just declare the pointer to
ConvertDialogas member variable and get done with it. It's a misconception I have that having many member variables is kind of a lazy solution. I mean how bloated can we allow a class to become?
Thank you once again for your explanation. Have a nice day.
- Chris Kawa Moderators last edited by Chris Kawa
So the main window is blocked.
Hold on a sec. Lets be clear here. Local event loop started by
exec()does not block event processing in main window or any other parts of your app. Main window can't get focus, but that's because you set your dialog to be modal, not because of a local event loop. All events are processed as usual, no matter how deep on an event loop stack you are. It's just that you don't leave the scope the loop is running in.
The way I see this is that if for example I would like to open 2 or more dialogs at the same time, I should find another way to show them by not blocking the main loop.
Just use
show()in that case, like you did. Just don't use a smart pointer on it so it doesn't delete your instances when you leave the scope.
I guess if I want to use the app in this way, I should just declare the pointer to ConvertDialog as member variable and get done with it.
If you need to have some sort of access to your dialog when it's shown then that's one way to do it, but if it's a standalone thing you don't need to keep any pointer to it. You can use the
Qt::WA_DeleteOnCloseattribute I mentioned so it deletes itself when it's closed or you can manually call
deleteLater()in its close event handler.
I mean how bloated can we allow a class to become?
There's simply no one answer to that. From technical standpoint you can stuff your class as much as fits in the memory. A pointer or two is not a lot when you think how much RAM a random computer has. You could have no classes at all for all CPU cares. It's all just bytes and addresses to it anyway.
The other consideration though is readability and maintainability of your code. Smaller classes compose better and are easier to understand, refactor and maintain. Things like dialogs or message boxes are temporary in nature so it's a bit silly to keep a pointer to one around when most of the time it's null, but sometimes it's just the most convenient thing to do.
All in all it's the beautiful dance of balancing those different concerns we programmers deal with every day :) | https://forum.qt.io/topic/120059/dialog-ui-doesn-t-show-up-if-it-s-pointer-is-allocated-inside-a-function/4 | CC-MAIN-2021-49 | refinedweb | 1,294 | 63.49 |
-file too big
<>
I've never gotten -odbc- to work nicely with the Mac version (I suspect this is due to using 3rd party/free drivers), so I usually use Roger Newson's -stcmd- (from SSC) to automate using the program StatTransfer to convert the excel files to comma/tab delimited files or directly to Stata .dta files in a loop.
You might be able to use -import excel- with the 'cellrange()' option to get around the 'file too big' error (?). You could import the top half of each file and the bottom half and then concatenate them together. You might have to experiment to find the range where the file becomes to big to import into Stata and then select a cell range that is smaller than this limit. So, in pseudo-code if you had 2 variables:
global files: "mydir" files "*.xlsx", respectcase
foreach x of global files {
import excel using "`x'", clear firstrow cellra(A1:B????)
sa "top", replace
import excel using "`x'", clear firstrow cellra(A????+1:B???????) // B??... should be the max rows in all your files (for me it's B1048000)
sa "bottom", replace
**append top/bottom together**
u "top", clear
append using "bottom"
sa "`x'.dta", replace
}
Of course finding the max number of rows and the number of variables in your large excel files becomes another challenge. I created some test data with 1048000 obs and 50 random vars. I -outsheet-ed this data to a tab delimited file. I then opened and saved them in Excel (Office 2011 for Mac OSX) in .xlsx format. Next, I saved this as xlsx and tried to import to Stata using the command:
import excel using "test.xlsx", clear firstrow
and it imported all the rows /vars without the "file too big" error. When I tried created a file with more than 1048000 rows, Excel only loaded part of the file (Office 2011 for Mac OSX -- maybe there are different capacities for different versions?), so I apparently cannot create a larger test file with Excel.
- Eric
__
Eric A. Booth
Public Policy Research Institute
Texas A&M University
ebooth@ppri.tamu.edu
Office: +979.845.6754
On Aug 22, 2011, at 8:30 AM, Ricardo Ovaldia wrote:
>
> Hello,
>
> I wrote an -do- file that first imports a series of excel sheets into Stata using the -import- command.
> However, some of the sheets are too big and I get the corresponding error message "File too big".
> I can convert the sheet to a tab delimited txt file and use -insheet- to import. That works, but this is tedious because I have lots of files and they will change from time to time.
> Is there a way (code) to create the tab delimited txt file from inside the -do- program? Or does anyone have an alternative that can be automated?
>
> Thank you,
> Ricardo
>
> Ricardo Ovaldia, MS
> Statistician
> Oklahoma City, OK
>
>
> *
> * For searches and help try:
> *
> *
> *
*
* For searches and help try:
*
*
* | http://www.stata.com/statalist/archive/2011-08/msg01006.html | CC-MAIN-2015-48 | refinedweb | 493 | 70.73 |
Sensitive data can include:.
Storing sensitive information in the source code of your application might not always be a good practice, anyone that has access to the source code can view the secrets in clear text.
Debug logs in apex code should not contain any sensitive data (usernames, passwords, names, contact information, opportunity information, PII, etc). The debug logs include standard salesforce logs using system.debug() methods or custom debug logs created by the application. Sensitive information should also be not be sent to 3rd party by emails or other means as part of reporting possible errors.
Long term secrets like username/passwords, API tokens and long lasting access tokens should not be sent via GET parameters in the query string. It is fine to send short lived tokens like CSRF tokens in the URL. Salesforce session id or any PII data should not be sent over URL to external applications.
External applications should not store Salesforce.com user credentials (usernames, passwords, or session ID's) in external databases. In order to integrate an external application with Salesforce.com user accounts, the OAuth flow should be used. More information about implementing OAuth can be found at here.
If your application copies and stores sensitive data that originated at salesforce.com, you should take extra precaution. Salesforce.com takes threats to data that originated at their site very seriously, and a data breach or loss could jeopardize your relationship with salesforce.com if you are a partner..
If your application stores the salesforce.com user password, your application may be vulnerable.
If your application collects other forms of sensitive data, your application may not be compliant with industry standards and the leakage of that sensitive data may cause a significant privacy incident with legal consequences.
Review the scheme used to store sensitive data and identify information collected in use cases and workflows.
As PII/HBI data varies from state to state and country to county, it is best to seek expert legal counsel to review sensitive data collected and stored.
Consider an application that must authenticate users. We have to store some form of the user’s password in order to authenticate them, i.e. in order to see if the user presented the correct password. We don’t want to store the password in plaintext form (i.e. unobfuscated or unencrypted), because if an attacker is able to recover the database of passwords (such as by using SQL injection or by stealing a backup tape), they would be able to undetectably hijack every user’s account. Therefore, we want to obfuscate the passwords in such a way that we can still authenticate users.
We could encrypt the passwords, but that would require an encryption key — and where would we store that? We would have to store it in the database or in some other place the application can get it, and then we’re pretty much back where we started: An attacker can recover the plaintext of the passwords by stealing the ciphertexts and the decryption key, and decrypting all the ciphertexts.
(Most or all database-level encryption schemes fall prey to the “But where is the key?” problem. Note that full-disk encryption, as opposed to encrypting database rows or columns with a key known the database client, is a separate and arguably more tractable problem.)
Therefore, developers have historically used a cryptographic hash function, a one-way function that is (supposedly) computationally infeasible to reverse. They then store the hash output:
hash = md5 # or SHA1, or Tiger, or SHA512, etc. storedPasswordHash = hash(password)
To authenticate users, the application hashes the provided password and compares it to the stored password:
authenticated? = hash(password) == storedPasswordHash
The plaintext password is never stored.
However, there is a problem with this scheme: the attacker can easily pre-compute the hashes of a large password dictionary. Then the attacker matches their hashes to those in their stolen database. For all matches, the attacker has effectively reversed the hash. This technique works as well as the password dictionary is good, and there are some very good password dictionaries out there.
To address this problem, developers have historically “salted” the hash:
salt = generateRandomBytes(2) storedPasswordHash = salt + hash(salt + password)
The goal is to make attackers have to compute a much larger dictionary of hashes: they now have to compute 2saltSize (e.g. 216 for a 2-byte salt) hashes for each item in their password dictionary.
However, a salted password hash only makes it more expensive to pre-compute the attack against a large password database. It does not protect from attempts to brute force individual passwords when the hash and salt are known. The only obstacle here is the cost of the computing resources required to perform these calculations, and a single round of MD5 or SHA-1 is no longer expensive enough to slow attackers down. Fast, cheap and highly parallel computation on specialized hardware or commodity compute clusters makes brute force search with a dictionary quite affordable and accessible, even to adversaries with few resources. (See Grembowski, referenced above, and and.)
Therefore, we need a solution that significantly slows down the attacker but does not slow down our application by too much. Fortunately, it turns out this is easy, and there is code to do it. The canonical solution is bcrypt by Niels Provos and David Mazières. The idea is that we tune the hashing function to be pessimal; Provos and Mazières use a modified form of the Blowfish cipher to pessimize its already-slow setup time. Using bcrypt is a fine solution, but it is also easy to build a tunably slow hash function using the standard library of most programming languages.
The benefit of this approach is that it slows down the attacker greatly, but for the application to verify a single password candidate still takes essentially no time. (Additionally, since login actions are such a small fraction of all application traffic, it would still be okay if verification took an entire 0.5 seconds or more.)
There are multiple ways to protect sensitive data within Force.com, depending on the type of secret being stored, who should have access, and how the secret should be updated.
Protected Custom Metadata Types
Within a namespaced managed package, protected custom metadata types are suitable for storing authentication data and other secrets. Custom metadata types can also be updated via the metadata api in the organization that created the type, and can be read (but not updated) at runtime via SOQL code within an apex class in the same namespace as the metadata type. Secrets which are common across all users of the package (such as an API key) needs to be stored in Managed Protected Custom Metadata Types. Secrets should never be hardcoded in the package code or displayed to the user.
For more information, see the Custom Metadata Implementation Guide
Protected Custom Settings
Custom settings. This is useful for secrets that need to generated at install time or initialized by the admin user.
Unlike custom metadata types, custom settings can be updated at runtime in your Apex class, but cannot be updated via the Metadata Api.
In order to allow authorized users to create and update sensitive information in the UI,: transient keyword
Finally, configure the security settings for this page to ensure it’s only accessible by limited profiles on an as needed basis.
For more information, see custom settings methods
Apex Crypto Functions
The Apex crypto class provides algorithms for creating digests, MACs, signatures and AES encryption. When using the crypto functions to implement AES encryption, keys must be generated randomly and stored securely in a Protected Custom Setting or Protected Custom Metadata type. Never hardcode the key in within an Apex class.
For more information and examples for implementing the crypto class, please visit: apex crypto classes
Encrypted Custom Fields
Encrypted custom fields are text fields that can contain letters, numbers, or symbols but are encrypted with 128-bit keys and use the AES algorithm. The value of an encrypted field is only visible to users that have the “View Encrypted Data” permission. We do not recommend storing authentication data in encrypted custom fields, however these fields are suitable for storing other types of sensitive data (credit card information, social security numbers, etc).
Named Credentials
Named Credentials are a safe and secure way of storing authentication data for external services called from your apex code such as authentication tokens. We do not recommend storing other types of sensitive data in this field (such as credit card information). Be aware that users with customize application permission can view named credentials, so if your security policy requires that the secrets be hidden from subscribers, then please use a protected custom metadata type or protected custom setting. For more information, see named credentials in the online help and training guide.
When storing sensitive information on a machine:
ASP.NET provides access to the Windows CryptoAPIs and Data Protection API (DPAPI). This is intended to be used for the storage of sensitive information like passwords and encryption keys if the DataProtectionPermission has been granted to the code. Generally, the machine key is used to encrypt and decrypt sensitive data at the risk that if the machine is compromised malicious code could potentially decrypt any stored secrets. More information on this topic can be found here:
The strongest solution for ASP.NET would be to rely on a hardware solution for securely storing cryptographic keys, such as a cryptographic smartcard or Hardware Security Module (HSM), that is accessible by using the underlying Crypto API with a vendor supplied CryptoAPI Cryptographic Service Provider (CSP).
A .NET version of the bcrypt library called bcrypt.net is available.
Java provides the KeyStore class for storing cryptographic keys. By default this uses a flat file on the server that is encrypted with a password. For this reason, an alternative Cryptographic Service Provider (CSP) is recommended. The strongest solution for Java would be to rely on a hardware solution for securely storing cryptographic keys, such as a cryptographic smartcard or Hardware Security Module (HSM), that is accessible by using the vendor's supplied CSP in that java.security configuration file. For more information on installing Java CSPs, consult the Java Cryptography Architecture (JCA) Reference Guide. When not using a CSP, if the product is a client application, you must use JAVA bindings to store the passphrase protecting the keystore in the vendor provided key store. Never store the passphrase in source code or in a property file. For server java solutions, follow the general guidance of making the passphrase protecting the keystore unavailable to the database process storing credentials.
A Java implementation of bcrypt is available called jBCrypt.
PHP does not provide cryptographically secure random number generators. Make sure to use /dev/urandom as the source for random numbers.
Use the mcrypt library for cryptography operations. Salted hashes and salts could be subsequently stored in a database.
A framework called phpass offers "OpenBSD-style Blowfish-based bcrypt" for PHP. For client apps, you must use native bindings to store user secrets in the vendor provided key store.
There is a copy of bcrypt specifically for Ruby called bcrypt-ruby. For client apps, you must use ruby bindings to store secrets in the vendor provided key store.
Use a module that interacts with the vendor provided keystores such as the python keyring module.
Use the Encrypted Local Store which contains bindings to use vendor provided keystores to store secrets. | https://developer.salesforce.com/page/Secure_Coding_Storing_Secrets | CC-MAIN-2018-51 | refinedweb | 1,919 | 53.21 |
AIFB DataSet
AIFB DataSet is a Semantic Web (RDF) dataset used as a benchmark in data mining. The dataset consists of a single approximately 3 megabyte large file. It records the organizational structure of AIFB at the University of Karlsruhe.
Get the data[edit]
The dataset is distributed from.
Get context[edit]
The dataset was used in Kernel Methods for Mining Instance Data in Ontologies. Find and read the part of the dataset on page 10.
Python[edit]
Setup a Python environment with rdflib installed and load the AIFB file and count the number of times the "affiliation" property is used:
from rdflib import Graph, URIRef g = Graph() g.load('aifbfixed_complete.n3', format='n3') len(list(g.triples((None, URIRef(""), None))))
The URI for the affiliations can be obtained with:
affiliations = g.triples((None, URIRef(""), None)) groups = set(affiliation[2] for affiliation in affiliations)
How many different affiliations are there?
Find the name of the affiliations via "". | https://en.wikiversity.org/wiki/AIFB_DataSet | CC-MAIN-2018-34 | refinedweb | 157 | 58.38 |
Proposals/SVG in ODF
Contents
Background
SVG in the OpenDocument Format dates back to 2005, when the OpenDocument TC, a technical committee in OASIS, decided to use SVG in the OpenDocument office format. Rather than use SVG as specified, however, they merged it with their own custom format Draw/Impress. They decided that many SVG-defined attributes were useful, but not the elements. Not realizing that SVG attributes are in the null namespace, they applied these attributes to Draw elements but put them in the SVG namespace.
- list of relevant posts to www-svg
- list of relevant posts to w3c-svg-wg
After some discussion between the OpenDocument TC and the SVG WG, this ended in an acceptable (if not entirely satisfying) result, in which the ODF specification changed the namespace in which they placed their referenced attributes from the SVG namespace to their own custom namespace, "urn:oasis:names:tc:opendocument:xmlns:svg-compatible:1.0".
Current State
Right now, ODF (and more specifically, the OpenOffice.org implementation) only supports SVG as an import and export format, not as a native format. An OOXML developer, Jesper Lund Stocholm, wrote a blog entry with in-depth analysis of this support, and determined that there doesn't seem to be true SVG support.
Inkscape also has compiled a list of correspondancies between ODF Draw and SVG.
While there is clearly some interest within the OOo development team to provide native SVG support, there also seems to be some resistance; at least some of these developers seem determined to retain the Draw/Impress format as the primary graphics format, and to devote the majority of effort there, as discussed in this Sun blog entry.
Our goal is to convince the OpenDocument TC to mandate full native support for SVG 1.1 and SVG Tiny 1.2 in ODF-Next. Important things for us to note include:
- we are not challenging the existing support for Draw/Impress; SVG would supplement that
- we are not proposing that SVG replace the whole format (there seemed to be some confusion about that on the Sun blog comments)
- we are willing to adapt SVG to meet their needs
- there are substantial network effect benefits to SVG
- there are people inside and outside the dedicated SVG community who want to see this happen and who would benefit
ODF Requirements
Andreas Neumann alerted us to a Call for Proposals for "ODF-Next", from OASIS's Mary McRae. ODF-Next is the provisional name for the version of the spec after ODF 1.2.
Deadlines
We have to submit our requirements by March 31st, 2009 to be considered for their report, which is due May 1st, 2009. This will be composed by the ODF Requirements Subcommittee.
Communication
Contacts
Previously, we had been in touch with Michael Brauer (Michael.Brauer@Sun.COM) about this issue. He still seems involved in this project, according to the OpenDocument TC feedback page. This page lists the following contacts:
- Robert Weir (IBM), Chair, robert_weir@us.ibm.com
- Michael Brauer (Sun), Chair, michael.brauer@sun.com
- Mary McRae (OASIS), OASIS Staff Contact, mary.mcrae@oasis-open.org
Additionally, there is a ODF Requirements Subcommittee chair:
- Bob Jolliffe, (South African Department of Science and Technology), Chair, bobj@dst.gov.za, bobjolliffe@gmail.com
Mailing List
We need to send our comments to by March 31, 2009. We can look through the archives to find how best to phrase and format our request.
Proposed Liaison Prose
+NAME Doug Schepers
+CONTACT schepers@w3.org
+CATEGORY (select one or more from below) editing/import-export/other
+SCOPE (select one or more from below) presentation/other
+USE CASE Dynamic, interactive, semantically-rich, Web-friendly, reusable graphics
We applaud the OpenDocument TC for their decision to use SVG, by adopting some SVG elements and attributes. As we understand it, one goal of the ODF specification is to reuse existing specification where appropriate, and in this case, it makes sense to specify complete support for SVG 1.1 and SVG Tiny 1.2 as they are specified, rather than only as part of ODF Draw format. In the next version of the ODF specification, there should be support for SVG as a regular image and as vector graphics (or "line art"), in addition to the ODF Draw format.
With native SVG support, ODF would enjoy several "network effects" though the increasing prevalence of SVG among authoring tools and viewers. Developing and maintaining ODF implementations would be made simpler, since there are many existing open-source SVG libraries, in both C and Java.
In contrast to ODF Draw format, SVG is natively web-publishable, with native support in Firefox, Opera, Safari, and Google Chrome, and in Internet Explorer through plugins. While ODF currently supports SVG as both an import and export format, this extra step makes effective round-tripping more difficult, with regards to using existing content, and editing in Inkscape, Illustrator, CorelDraw, Xara, and other major graphics authoring tools.
Additionally, there is good existing clipart content through various open online clipart repositories, which would add value to ODF by making it easier to author content through reuse. This would also tie ODF into the growing SVG and open-graphics communities. With the recent addition of SVG/VML drawings to Google Docs, this would also provide a common graphics format for two of the most popular office suites.
Where the SVG specification may not meet the needs of ODF, there are two options. First, ODF can simply extend SVG using its own namespaced elements and attributes. Second, the SVG WG is interested in working with the OpenDocument TC to add missing features to the SVG specification. We are already planning on adding some common features, like connector elements, which we see are supported in ODF, and we are open to hearing more use cases and requirements.
We feel that this is a pivotal opportunity for open document formats, and that a synergy between ODF and SVG will work to everyone's benefit.
Please let us know any issues or factors that would make adopting SVG as a first-class component of ODF difficult. We may be able to help remove barriers or clarify confusion.
+DESCRIPTION Reference SVG 1.1 and SVG Tiny 1.2 as mandated formats for ODF-Next, as a regular image and as vector graphics:
For extensions of SVG, ODF should follow the guidelines detailed in the SVG specification:
Currently, SVG is allowed in ODF, as stated in 9.3.2 Image, "While the image data may have an arbitrary format, it is recommended that vector graphics are stored in the [SVG] format and bitmap graphics in the [PNG] format." However, there is no mandate that it be supported, or details about the precise manner in which it should be supported. After a brief review of the OpenDocument specification, we recommend that you add more detail regarding SVG in the following sections:
4.5 Page-bound graphical content 5.8 Inline graphics and text-boxes 9.3.2 Image, to allow SVG as a link to an external resource, or embedded directly in a document 9.3.3 Objects, to allow SVG as Charts or Drawings 9.3.10 Client Side Image Maps 13 SMIL Animations, to match SVG's animation functionality.
The SVG WG is available to help provide more details during the OpenDocument specification process. | http://www.w3.org/Graphics/SVG/WG/wiki/index.php?title=Proposals/SVG_in_ODF&redirect=no | CC-MAIN-2015-22 | refinedweb | 1,226 | 51.38 |
Here is what I had to do:
In this project each individual will create a data analysis program that will at a minimum, 1) read data in from a text file, 2) sort data in some way, 3) search the data in some way, 4) perform at least three mathematical manipulations of the data, 5) display results of the data analysis in numeric/textual form, and 6) display graphs of the data. In addition, 7) your program should handle invalid input appropriately and 8) your program should use some “new” feature that you have not been taught explicitly in class. (Note: this is to give you practice learning new material on your own – a critical skill of today’s programmer.) If you do not have a specific plan in mind for your project, below is a specific project that meets all of the qualifications as long as 7) and 8) are addressed in the implementation.
Everyrthing is doen except I need to call my methods in my GradeTester. I am struggling with this a lot, and you would think I would know by now but everything I have tried has not worked. So, please please help me out! Thank You!
GradeBook:
public class GradeBook { public final int MAXARRAY_SZ = 20; double [] scores = new double [MAXARRAY_SZ]; int lastGrade = 0; double mean = 0; public GradeBook() { for (int i=0; i< scores.length; i++ ) { scores[i] = 0; } } public void addToGradeBook(int grade) { scores[lastGrade] = grade; lastGrade++; } public void sort() { for (int i = 0; i < lastGrade; i++) { for (int j=1; j< lastGrade; i++){ if (scores[j-1]>scores[j]) { double temp = scores[j]; scores[j]= scores[j-1]; scores[j-1]=temp; } } } } public boolean linearSearch(int key) { int index = 0; while(index < lastGrade) { if(scores[index] == key) { return true; } if(scores[index] > key) { return false; } index++; } return false; } public void outputHistogram(String inputFileName) { String z = ""; String y =""; for (int i=0; i < scores.length; i++); if (scores[lastGrade] > 70) { z += "a"; } else if (scores[lastGrade] < 50) { y += "b"; } System.out.println(inputFileName + "(" + z); System.out.println(inputFileName + "(" + y); } public String toString(){ //to string String grades = ""; //System.out.println(lastGrade); for (int i = 0; i < lastGrade; i++){ //go through each spot in array and print it //System.out.println("Scores" + i + scores[i]); grades = grades + scores[i]; } return grades; } public double mean() { //Calculating mean double gradesTotal = 0; for (int i=0; i<scores.length; i++) { gradesTotal = gradesTotal + scores[i]; } mean = gradesTotal/scores.length; return gradesTotal; } public double variance() { //Calculating standard deviation double variance = 0; for (int i=0; i<scores.length; i++) { variance = variance + (Math.pow((scores[i] - mean), 2)); } variance = variance / scores.length; double standardDeviation = Math.sqrt(variance); System.out.println(variance); return variance; } public double median(){ //Finding median score double median; if (scores.length % 2 == 0) median = ((scores[(scores.length/2) - 1]) + scores[(scores.length/2)]) / 2; else median = scores[(scores.length/2)]; return median; } }
GradeTester:
/** * @author Allison Cather * Date: 4/11/2015 * Course: CS 220 * Assignment: Final Lab */ /** *This class tests the class called GradeBook. *It creates a new object of GradeBook. *This class scans in the inputFile created with the array of grades. *It reads the file requested */ import java.util.*; import java.io.*; import java.lang.*; public class GradeTester { public static void main(String[] args) throws IOException { GradeBook science = new GradeBook(); Scanner console = new Scanner(System.in); System.out.println("Enter the name of the file"); String inputFileName = console.nextLine(); File inputFile = new File(inputFileName); Scanner scan = new Scanner(inputFile); //declaring that whatever the first number in the document is, is how many indexes the document has while (scan.hasNext()) { int x = scan.nextInt(); science.addToGradeBook(x); //System.out.println("x is " + x); //System.out.println(science); } console.close(); } } | https://www.daniweb.com/programming/software-development/threads/494668/calling-methods-in-java | CC-MAIN-2017-30 | refinedweb | 619 | 54.93 |
This.
I was thinking of this article when I wrote How to Convert String to Integer in Java and How to convert String to Double in Java but somehow it get delayed. Anyway, now I am happy to put these steps in an article.
I also started with HelloWorld in Java but After programming in Java for few years we all know more than that and subtle details about Java programming language but there are still many people who are learning Java programming and they often face the same problem which We have already solved. In This article, I will put a step by step solution to run a simple Java Program and Setup Java programming environment from scratch to help beginners who are trying to run Java program including popular Example of HelloWorld in Java.
Running Java Program from command prompt
Step by Step Guide to Run Java Program in PC
1. Download JDK from Oracle.
the first step is downloading the correct version of JDK and correct installer for your machine. Since Java is supported for multiple platforms you see a lot of installers available for JDK. if you are running on windows PC then you should download Windows Installer of 32-bit machine since most of Windows desktop and laptop are 32 bit and until you know that it's for Windows Server which can be 64 bit. If you are running on RedHat linux or Ubuntu then you can also download tar file.
2.The second step is to installing Java
If you are running on Windows PC then installing Java is just a cakewalk. just double click on Installer and it will install Java on your machine. it usually creates a folder under program files/Java/JDK_version , this folder is important because in many scripts this is refereed as JAVA_HOME and we will specify an environment variable JAVA_HOME pointing to this folder. If you are running in Linux or any Unix machine including AIX, Solaris etc. you just need to extract tar file and it will put all the binary in a folder this will be your JAVA_HOME in Linux.
3. Third Step is Setting PATH for Java.
for setting PATH you just need to append JAVA_HOME/bin in PATH environment variable. For step by step guide and details How to Set PATH for Java in Windows, Linux, and Unix.
4. Testing Java PATH
Before you run your first Java program it's better to test PATH for Java. Now open a command prompt in Windows just go to "Run" and type "cmd". Now type "java" or "javac" if you see large output means Java is in PATH and you are ready to execute Java program.
5. The fifth step is to write your first Java program
Best program to quickly test anything is HelloWorld , just type below program and save it into file called HelloWorld.java
public class Helloworld{
public static void main(String args[]){
System.out.println("I am running my first Java program');
}
}
Java starts execution from main function just like in C.
6. Sixth Step is to compile Java program
For compiling just type javac HelloWorld.java, it will compile this Java file and create a corresponding .class file for execution. Java finds classes by looking on CLASSPATH , by default Classpath points to "." current directory and that's why we are able to compile our Java Class. it reside on some other directory you may not be able to compile until you explicitly provide classpath by option –cp or specify that on Environment variable called CLASSPATH. for more details see How to Set ClassPATH in JAVA on Windows, Linux and Unix.
7. The seventh and final step is to run Java Program.
Now we are ready to run our first Java program. just type "java HelloWorld" and it will execute HelloWorld class and execute its main method which will print "I am running my first Java program".
Now you know how to run Java program in your own PC in just seven steps. If you face any error or issue , please let me know and I will try to help you.
That's all on this HelloWorld Example in Java and How to run Java program from command prompt, also If you have any JAR file for execution than you cal also run it by giving command java -jar HelloWorld here Helloworld must be defined as Main-Class inside Manifest file of JAR. If you have reached up to this state then you can also try How to debug a Java program
Further Learning
Java Fundamentals Part 1,2
Java Fundamentals: The Java Language
Head First Java
Related Java Tutorial
20 comments :
step by step tutorial, you better call it HelloWorld Example in Java, it would be more appropriated. I wanted to write HelloWorld in Java and found this quite helpful.
good tutorials..
For javascript and basic java tutorials.. visit
thanks
I was looking for How to run java program from command line and got this , I have a confusion is command prompt and command line is same thing or different. java on command line or java on command prompt will run alike or not, please advise
Command line and command prompt are the same.
Can I run my Java program written in notepad or using DOS Editor using above steps ? I understand I need to save by Java program to .java file, compile it using javac command and run it using java command but my doubt is I am coding in windows using notepad but I need to run my Java program in Solaris host which is a Unix machine, I heard Java program written in notepad in windows contains line separator as /r/n while line separator in Unix is /n, won't that create any issue while running Java program in Solaris box?
Can you please let us know How to run Java program in any IDE like Netbeans or Eclipse, I have coding in text editor as textpad or notepad and don't like writing Java program in VI or EMACS editor in Unix operating system e.g. Linux, AIX, BSD or even Solaris. What I want to learn is using Eclipse to run my Java program as soon as I finished coding, is it possible to do that without setting path or classpath etc?
command line arguments are those which you pass while running your Java program from command prompt using "java" command e.g.
java Helloworld abcd 1234
will run HelloWorld class and pass two command line parameters.
This isn't going to work because you opened your string with " but closed it with '
Also, I got this error:
Exception in thread "main" java.lang.NoClassDefFoundError: helloWorld
Caused by: java.lang.ClassNotFoundException: helloWorld: helloWorld. Program will exit.
Of course, my classpath is just fine, and matches what Eclipse is successfully using... But I really wanted to try something at the command line :/
i am having some problems with running the java program i created with command prompt can anyone help me ?
Can you please write about
How to run Java program from Windows 7 and Windows 8 ?
How to run Java program from UNIX, Linux and Solaris ?
I heard Java is platform independent but still I have trouble running Java program from Windows to Unix, please help
Best HelloWorld guide for Java Developers, I have seen so far. Thanks a ton dude.
I have read this tutorial. But i have an issue while i am saving the notepad file demo.java in D drive. Now how to compile by command prompt?
what if ..m not able to save my program in bin?
means m getting a dialogue box saying that u don not have authority to access it ..wuld u like to save in my documents ? wat shuld i do ? plz help
What program should it be typed into? I was using notepad but the .java part wasn't saving as part of the name for some reason.
Whenever I typed it into command prompt, it then said the file couldn't be found.
I am answering a couple questions asked by readers. (1) If using Notepad, when saving, on "Save as Type:" select "All files (*.*)", and make sure the name of the file is exactly the same as the class name. In the above case, the file name must be "Helloworld.java". (2) There is an error in the example file! The text in the line should read as follows: System.out.println("I am running my first Java program"); Note the closing " mark instead of '. (3) To open a command prompt in Windows 8, easiest (I think) is to right-click the Start icon (lower left corner) and select it from the choices. Then, navigate to where you have saved the Helloworld.java file. Perhaps this will be in your desktop or documents folders? The command to change directories is cd. The command prompt program usually starts you at c:\Users\yourname. If the file is in the Documents directory, type "cd Documents". If you type "dir" it will list all files and directories in your current file location.
When i try to run my test.java program (which compiles perfectly fine) i get the error, that 'the file C:\ProgramData\Oracle\Java\javapath\java.exe cannot be found'. I couldn't find any solution for this problem on the Internet, do you know what could cause the problem and how to fix it?
plz tell me i m facing an error while running helloworld program the error is
error while writing HelloWorld :HelloWorld.class(Access is denied)
public class Helloworld
^
1 error
Hello. My version of Java is jre1.8.0_40 I'm confused about what to install for the Path, would there be a conflict if I were to install a JDK to my version of Java? I saw something confusing at Oracle when I was about to download the said instructions above. It says that JDK (Download), Server JRE (Download) & JRE (Download). What should I do now?
@Anonymous, you need JDK if you want to do Java development e.g. writing Java code, compiling them to class file and run them using java command, but if you have a JAR file and you want to run it, JRE is enough, same is the case with Applet.
So, download and install JDK if you want to write Java code. You should define a JAVA_HOME variable and add %JAVA_HOME%/bin in PATH so that javac and other tool are available to your command prompt.
See following tutorials to learn more :
How to set JAVA_HOME see here | http://javarevisited.blogspot.co.uk/2011/11/run-java-program-from-command-prompt.html | CC-MAIN-2018-05 | refinedweb | 1,774 | 71.24 |
java -jar tagsoup-1.2.1.jar <page.html >page.xhtml" java -cp saxon9pe.jar net.sf.saxon.Query -s:"test.xhtm" -qs:"//*:div[@id='ps-content']"
Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.
Have a better answer? Share it in a comment.
From novice to tech pro — start learning today.
____file query.xq____
declare default element namespace '';
doc('page.html')//div[@id=
______________________
Command-line using Nailgun:
ng.exe --nailgun-port 2114 net.sf.saxon.Query -x:"org.ccil.cowan.tagsoup
Open in new window
but it gives this error:
"Error on line 1 of *module with no systemId*:
Failed to load org.ccil.cowan.tagsoup.Par
Query processing failed: Run-time errors were reported"
Note that TagSoup is an external component, I simply downloaded the file "tagsoup-1.2.1.jar" and copied it to the same folder of "saxon9pe.jar". Maybe I have to do something more...
How could I tell to Java and/or Saxon that it should consider that
if it is in the same dir, just put it after the CP together with the saxon pe
java -cp tagsoup-1.2.1.jar saxon9pe.jar net.sf.saxon.Query
have you managed to run a simpler XPath over PE? because I assumed you needed a reference to the license file too
This command-line works:
java -cp saxon9pe.jar;tagsoup-1.2.1
Now I only miss to replace the html string part with my file name. I tried random syntaxes without success. Any ideas?
PS: Gertone I already obtained and put in the same dir the file "saxon-license.lic" as you suggested :)
you can't use doc since it is not wellformed
saxon:parse-html(unparsed-
Error on line 1 column 17
XPST0017 XQuery static error near #...l(unparsed-text('test.
System function unparsed-text#1 is not available with this host language/version
Static error(s) in query
Open in new window(And the unparsed-text function may need to be qualified as above with the "fn:", try with it and without.)
but collection() recently got some properties
I believe collection('page.html;unpa
works in both XSLT and XQuery
try:
java -cp saxon9pe.jar;tagsoup-1.2.1
...\SaxonPE9-4-0-7J>java -cp saxon9pe.jar;tagsoup-1.2.1
net.sf.saxon.Query --xqueryVersion:3.0 -qs:"saxon:parse-html(fn:u
page.html'))//*:div[@id='p
Error on line 1 column 17:"fn:parse-html(fn:unpa
e.html'))//*:div[@id='ps-c
Error on line 1 column 14:"saxon:parse-html(coll
tml;unparsed=yes'))//*:div
Error on line 1 of *module with no systemId*:
FODC0002: The file or directory
file:/C:/Users/diego/Downl
exist
Query processing failed: Run-time errors were reported
___________
...\SaxonPE9-4-0-7J>java -cp saxon9pe.jar;tagsoup-1.2.1
net.sf.saxon.Query --xqueryVersion:3.0 -qs:"saxon:parse-html(coll
tml';'unparsed=yes'))//*:d
Error on line 1 column 39
XPST0003 XQuery syntax error near #...ion('page.html';'unpar
expected ")", found ";"
Static error(s) in query
Here is how it works in XQuery
Open in new window
I copied the amazon file as test2.html on my desktop
put the file uri with path, add a questionmark
put select with the file mask (could be a single file as in this example)
I have not tested this on teh commandline
(sitting in a hotel room on a thin wire)
but it should work
Given I did not test, I am a bit curious
this is teh XPath that should work in your single line
saxon:parse-html(collectio
Open in new window
However it returns this empty result:
<?xml version="1.0" encoding="UTF-8"?
I reposted the question here:
;)
But I was wondering... you want to do all of this command-line? One single command.
Does that mean you can not have an XSLT or XQuery file next to it? You just need to reference the XSLT file then and still call the actual process in one go. I would go for XSLT then, given it supports the unparsed text function
Note that you can still pass parameters to the XSLT, so the XSLT could be a stub file and the actual XPath could be passed as a parameter to the XSLT... it gives you all the dynamics you could possibly need
Any idea about the most efficient solution?
I don't think it matters
Just getting a single value... then XQuery sounds more natural to me
(note that you better make a full file uri from the file reference
I think this is the XQuery you would need
Open in new window | https://www.experts-exchange.com/questions/28154550/how-to-extract-an-XPATH-from-a-malformed-HTML-page-with-Saxon-PE-commandline.html | CC-MAIN-2018-17 | refinedweb | 786 | 55.95 |
0
Hello, I've been trying to read txt from a file, and breaking each line into words and storing them in Array.
Example. txt file
C001 John Smith 999999
C002 Mary Agnes 888888
Here is my code.
public class Customer implements iCommand{ static List<Customer> cust = new ArrayList<Customer>(); static private String cID, String cName, cPhonenum; public Customer(String id, String name, String phone_num){ this.cID = id; this.cName = name; this.cPhonenum = phone_num; } public static void main(String[] args){ Scanner f = null; try { f = new Scanner(new File("C:/x.txt")); } catch (FileNotFoundException e) { System.out.println("unable to open file"); e.printStackTrace(); } while (f.hasNextLine()){ String input = null; String[] words = input.split(""); Customer client = new Server( cID, cName, cPhonenum); clients.add(client); } } }
Can anyone help me because I haven't found what I'm looking for with my current code.
Thanks. | https://www.daniweb.com/programming/software-development/threads/484327/splitting-line-into-words-storing-array-into-arraylist | CC-MAIN-2016-50 | refinedweb | 143 | 69.68 |
NoKarma (Arthur Schreiber)
- Registered on: 06/08/2008
- Last connection: 11/07/2013
Issues
- Assigned issues: 0
- Reported issues: 20
Activity
11/07/2013
07:19 PM Ruby trunk Bug #9089: rb_fix2uint no longer raises a RangeError when given negative values
- That's weird. If you go back to the previous change that was made in numeric.c, the fix2uint specs do pass:
Arthur...
07:52 AM Ruby trunk Bug #9089: rb_fix2uint no longer raises a RangeError when given negative values
- =begin
I guess I somehow incorrectly formatted the issue description, so here it is again with proper formatting.
...
07:34 AM Ruby trunk Bug #9089 (Rejected): rb_fix2uint no longer raises a RangeError when given negative values
- Up until the change that was made in ((<URL:...
08/15/2008
09:57 PM Ruby trunk Bug #447 (Closed): [PATCH] Net::HTTPHeaders iterator methods should return Enumerators
- =begin
Net::HTTPHeader#canonical_each, Net::HTTPHeader#each_capitalized_name,
Net::HTTPHeader#each_capitalized, Ne...
09:47 PM Ruby trunk Bug #446 (Closed): [PATCH] [DOC] Net::HTTPHeaders#fetch does not return nil but raises IndexError
- =begin
As Hash#fetch, Net::HTTPHeaders#fetch does raise an IndexError when neither a default
value nor a block wa...
09:42 PM Ruby trunk Bug #445 (Closed): [PATCH] Net::HTTPHeaders#fetch raises NoMethodError instead of returning default values
- =begin
require "net/http"
class Example
include Net::HTTPHeader
attr_accessor :body
def i...
08:41 PM Ruby 1.8 Bug #444 (Rejected): [PATCH] CGI#radio_group raises a TypeError when passing false as checked value
- =begin
c = CGI.new("html4")
c.radio_group("test", ["bar", "label for bar", false])
=> TypeError: can't convert f...
08:35 PM Ruby 1.8 Bug #443 (Rejected): [PATCH] CGI#checkbox_group raises a TypeError when passing false as checked value
- =begin
c = CGI.new("html4")
c.checkbox_group("test", ["bar", "label for bar", false])
=> TypeError: can't conver...
08/07/2008
04:55 PM Ruby 1.8 Bug #385: Net::FTP#login raises TypeErrors
- =begin
Yes, that patch seems to be fine.
=end
07/18/2008
06:33 PM Ruby trunk Feature #255: CGI element generation methods should convert keys/values to Strings before escaping.
- =begin
Ok, the old patch is bugged.
Converting keys to Strings using #to_s might result in duplicated element attr... | https://bugs.ruby-lang.org/users/38 | CC-MAIN-2019-18 | refinedweb | 371 | 54.73 |
Sorting - Subtle Errors# COMMENTS
</p>
Time to wrap up sorting for a while. We just finished quicksort having gone through a series of lessons
- We started with Quickselect.
- Then we did a quicksort, copying to new arrays during the partition
- Then finally to an in place quicksort.
For the final quicksort we used a partition algorithm pretty much the same as the one described here.
We started testing using by building a randomly filled array like this:
Random rnd = new Random(); int a[] = new int[n]; for (int i
0;i<<span style="color: #7CB8BB;">n</span>;i++) { a[i]rnd.nextInt(100); } qsort(a);
And everything seemed terrific.
Just like when we did the mergesort, we started to increase n. First 20, then 100, then 1000 and so on.
All of a sudden, we started getting a stack overflow. We only made it to about 450,000. Mergesort got to arrays of about 40,000,000 items before we started to have memory problems.
Our algorithm was sound. It worked on everything up to about 450,000. Since Mergesort worked well into the tens of millions, quicksort should have as well.
What was wrong?
We changed the code a bit:
Random rnd = new Random(); int a[] = new int[n]; for (int i
0;i<<span style="color: #7CB8BB;">n</span>;i++) { a[i]rnd.nextInt(10000); } qsort(a);
Instead of an array of 450,000 values between 0 and 100, our elements now went fro 0 to 10,000.
All of a sudden things were good.
Why? It wasn't long before the student saw that 500,000 elements with values between 0 and 100 meant lots of duplicates. Our partition didn't account for that. If we had duplicate pivots, only one is moved into place, the rest are left unsorted taking us closer to worst case performance and blowing our stack.
Fortunately there was an easy fix:
public int partition(int[] a, int l, int r) { int tmp; int pivotIndex = l+rnd.nextInt(r-l); int pivot = a[pivotIndex]; tmp = a[r]; a[r] = a[pivotIndex]; a[pivotIndex]=tmp;
int wall
l; <span style="color: #7CB8BB;">int</span> <span style="color: #DFAF8F;">pcount</span>=1; <span style="color: #F0DFAF; font-weight: bold;">for</span> (<span style="color: #7CB8BB;">int</span> <span style="color: #DFAF8F;">i</span>=l;i<<span style="color: #7CB8BB;">r</span>;i++) { <span style="color: #F0DFAF; font-weight: bold;">if</span> (a[i]<pivot) { tmpa[i]; a[i]=a[wall]; a[wall]=tmp; wall++; } if (a[i]==pivot) pcount++; } // now copy over all the pivots int rwall
wall; tmpa[rwall]; a[wall]=a[r]; a[r]=tmp; rwall++; for (int i
rwall+1;i<=r;i++) { <span style="color: #F0DFAF; font-weight: bold;">if</span> (a[i]==pivot) { tmpa[rwall]; a[rwall]=a[i]; a[i]=tmp; rwall++; } } return (wall+rwall)/2; }
When we partition the array, move all the elements equal to the partition to the middle of the array.
That did the trick.
All of a sudden we were blazing through data sets upwards of 100,000,000 elements.
We're done for sorting for a while, at least until the heapsort but it's been a fun couple of weeksTweet | https://cestlaz.github.io/posts/2014-03-17-subtle-errors-sorting.html/ | CC-MAIN-2020-10 | refinedweb | 539 | 63.19 |
This is a discussion on Palindromes within the C++ Programming forums, part of the General Programming Boards category; Originally Posted by jewelz hmm..getting a compilation error..it's saying: error: expected identifier before '(' token indicating the line with while ...
Ok now on to fix the problem that I have been having since completing the first part of the assignment (output just palindromes)...the compiler is telling me:
pal.h:4: error: 'string' in namespace 'std' does not name a type
pal.h:5: error: 'string' is not a member of 'std'
pal.h:5: error: 's' was not declared in this scope
and its saying that i cant use the isPalindrome function:
error: 'isPalindrome' cannot be used as a function
if u guys need to look at my code for header file and implementation file for two functions, it's on the previous pages..
yeah but one of my classmates said he didn't need to include that in his pal.h and it ran fine..plus i thought header files are generally not supposed to have them anyway?
well i included the <string> and compiled it again, this time the only problem is that it's saying that there is an undefined reference to 'isPalindrome(std.....)
i dunno what to make of that error.. pal.h is included but idk whats going on..
And is isPalindrome prototyped in pal.h? More importantly, is it prototyped the way it is defined and the way it is called?
here is my code for the entire project:
pal.h
implementation file - pal.ccimplementation file - pal.ccCode:#ifndef GUARD_PAL_H_ #define GUARD_PAL_H_ #include<string> std::string reverse(const std::string& s); bool isPalindrome(const std::string& s); #endif
main function:main function:Code:#include "pal.h" #include <cstdlib> //function declaration std::string reverse(const std::string& s) { string s2 = ""; for (int i = 1; i < s.length(); i++) { s2 = s2 + s[s.length() - i]; } s2 = s2 + s[0]; return s2; } bool isPalindrome(const std::string& s) { return(s==reverse(s)); }
Code:#include "pal.h" #include <string> #include <cstdlib> #include <iostream> using std::endl; using std::string; using std::cout; using std::cin; int main() { typedef string::size_type string_size; string s; string_size max = s.size(); string longest = s; while((cin >> s) && (isPalindrome(s)== true)) { string_size size = s.size(); if (size > max) { max = size; longest = s; } } cout << "Longest Palindrome is " << "\"" << longest << "\"" << "whose length is " << max << endl; return 0; }
there is never a reason to compare a bool to a bool.
is identical tois identical toCode:isPalindrome(s)== trueCode:isPalindrome(s)
Oh, so linker error. Make sure pal.cc is in your project, or included in your command-line compilation.
Thanks guys i got it to compile, but i have a problem when running the program.. basically the program is supposed to read from the input and output the longest palindromes, along with it's length..however what it does is..it takes the first word inputted for example "abba" and then says that it is the longest palindrome right away and then waits for more input..i basically need the program to check through the list AFTER the user is done inputting words..also another problem is that the program exits if the user inputs a non-palindrome word.
Last edited by jewelz; 02-22-2009 at 08:54 PM.
i believe either you changed your code from what's posted above or you have misspoken.
yeah..i made a silly mistake =) anyway thanks for all the help guys..really appreciate it | http://cboard.cprogramming.com/cplusplus-programming/111932-palindromes-4.html | CC-MAIN-2014-52 | refinedweb | 586 | 66.54 |
In this post we look at two approaches to dealing with domain specific types - unboxed tagged types and case classes and how well they integrate with play framework 2.4 and slick 3.0.
by
Dominik Zajkowski
May 26, 2016
Tags : Scala Play framework Slick Macro
We can all agree that it’s useful to be able to express a number. Or a character. It could be argued that most code is built upon some set of primitives. And naturally simple types work well in a limited number of use cases: algorithms, tutorials, small/focused applications etc. The moment the domain outgrows the natural usage of a given primitive it becomes troublesome to keep in mind what the meaning behind a particular
Int is. We all know this, it’s been the driving force behind OOP since day one.
Recently I’ve been working on an application based on play framework 2.4.x and slick 3.0. Unsurprisingly, as the app grew the need to track and control domain specific data became more and more pressing.
It’s useful to be able to quickly start with something simple. Scala has type aliasing which provides a simplistic way of expressing intent.
Quick & easy but has some drawbacks:
The above code compiles fine but Mike might not be all that happy about it. The solution itself isn’t that bad: gives no type safety and serves only as a hint but it’s very cheap and can easily be employed as a ‘stub’ for a better solution. It’s important to stress that this approach doesn’t scale well:
domain specific aliases x
amount of developers x
features implemented equals a misassignment bound to happen.
After reading this post I’ve decided to try if this approach could work with
play and
slick. The gist of this approach is that it’s possible to attach ‘meta information’ to a primitive type and the typer will enforce it.
In practice it looks like this:
Mike can be at ease: produces:
Having the basics covered I got to the interesting parts.
Removes
.asInstanceOf[A] invocations and converts primitives into domain types:
Usage in table definition:
routes
This is where the trouble starts.
To be able to use custom types in
routes a
path binding needs to be provided:
routes file:
And the error:
It turns out that:
is what play framework generates in
Routes.scala.
The ramifications are quite annoying - instead of having type checking in
routes file it’s necessary to handle boxing manually:
Controller:
In tests:
It’s worth keeping in mind that
unboxes tagged types and
play json don’t align perfectly.
The proposed solution covers some of the aspects that would make it a valid solution for handling
domain specific types. It falls short in a very important spot: ease of testing. The test code base should be (in my opinion) easy to maintain and refactor and loosing type safety in this area is a deal breaker.
At this point I was out of ideas on how to push this solution further so I decided to give a completely different approach a try.
Case classes come with a set of limitations, but when the problem calls for type-safety, readability and ease of integration with common libraries (in this case
play and
slick), they quickly become valuable tools.
This way
routes can utilize the type system:
and in tests:
A lot of the code base in a DB centric application will call for values: names, identifiers, nicks, etc. Not all of these need to be processed and if not - the above approach makes building applications easier and less error prone.
The previous paragraph shows how to integrate
case classes with the stack but it introduces boilerplate. It’s not a lot but it seems wasteful and might be error prone. Maybe we can use some macro magic to make it go away?
Here’s my take on the problem, heavily inspired by this article.
def macros
Providing
def macros and utilizing them in the
annotation macro made the
json format visible for other already defined macros (e.g.
Json.format).
This way if another
class uses one of the annotated
case classes and defines an implicit
Json.format the compiler won’t complain.
One way to make the macro compilation order happy in a play application:
This solution uses macro paradise so it’s quite volatile (read experimental, subject to change etc.) but it makes adding new
simple domain specific types very straightforward:
path bindings,
json serialization and
slick integration just work (tm) for all primitive types.
One thing that was omitted from the macro is primitive type extension.
It would be so useful to be able to reason about a primitive and have the compiler police it’s domain constraints. Disappointing but understandable - library authors have a lot of interop requirements to appease and a niche feature that seems to be a tad outside of how scala programming should look like isn’t a priority.
Case classes may not be the perfect solution but the approach is popular enough for library authors to provide out-of-the-box helpers that just work (e.g. slick’s
MappedTo). And if not: it’s always possible (and quite easy) to figure out a macro or two that will meddle with the case class itself or its companion object and deal with boilerplate around the required implicits.
by
Dominik Zajkowski
May 26, 2016
Tags : Scala Play framework Slick Macro | https://blog.scalac.io/2016/05/26/simple-types-in-play.html | CC-MAIN-2018-26 | refinedweb | 918 | 59.64 |
In my previous article Good Bye MD5, I introduced you to the current findings on cryptology and MD5 collision detection. A debate started, and most of the people think that these findings are not a serious issue.
Microsoft agreed that this is an important issue:
". Source: Microsoft Scraps Old Encryption in New Code
We now have some proofs of concept, like a pair of X.509 colliding certificates and a spectacular example of a pair of postscript documents, with the same MD5 hash value, you can read about this in the excellent paper, Attacking Hash Functions by Poisoned Messages "The Story of Alice and her Boss".
There is a known result about MD5 hash function:
If MD5(x) == MD5(y) then MD5(x+q) == MD5(y+q)
So, if you have a pair of messages,
x and
y, with the same MD5 value, you can append a payload
q, the MD5 value remains the same, the size of q is arbitrary. You need a pair of vectors,
x and
y to do the exploit. You can try to find a pair for yourself, but we already have a pair of values, given by the Chinese investigators Joux and Wang. A practical use of this pair of vector values is explained in the paper MD5 To Be Considered Harmful Someday, by Dan Kaminsky.
In my blog, I have written about these issues, and now I want to show you how you can make an exploit using these vectors.
The proof of concept to be shown in this article has the following scenario:
This picture shows a scenario, where a pair of binary files with the same MD5 are generated, MD5(good.bin) == MD5(evil.bin):
First, we will build a generator program, this program takes a pair of executables, the first is a harmless program and the second the evil file, is a harmful program, and generates a pair of binary distribution files (.bin files). These are good.bin distribution file, and an evil.bin distribution file.
The code of the harmless program is simple:
namespace GoodExe { /// <summary> /// A Harmless program /// </summary> class Class1 { /// <summary> /// The main entry point for the application. /// </summary> [STAThread] static void Main(string[] args) { Console.WriteLine ("this is a good executable"); } } }
This is the code of the evil program, that simulates a harmful behavior:
using System; using System.Threading; namespace EvilExe { /// <summary> /// A harmfull program /// </summary> class Class1 { /// <summary> /// The main entry point for the application. /// </summary> [STAThread] static void Main(string[] args) { Console.WriteLine ("This is an evil file"); Console.WriteLine ("Formatting your hard drive..."); Thread.Sleep(2000); Console.WriteLine ("Just joking..."); } } }
We have a pair of vectors with the same MD5 value:
/// <summary> /// First prefix vector /// Taken from stripwire by Dan Kaminsky /// /// </summary> static byte[] vec87 ,x71 , 0x41 , 0x5a, 0x08 , 0x51 , 0x25 , 0xe8 , 0xf7 , 0xcd , 0xc9 , 0x9f , 0xd9 , 0x1d , 0xbd , 0xf2 ,xb4 ,xa8 , 0x0d , 0x1e , 0xc6 , 0x98 , 0x21 , 0xbc , 0xb6 , 0xa8 , 0x83 , 0x93 , 0x96 , 0xf9 , 0x65 , 0x2b , 0x6f , 0xf7 , 0x2a , 0x70 };
/// <summary> /// Second prefix vector /// Taken from stripwire by Dan Kaminsky /// /// </summary> static byte[] vec07 ,xf1 , 0x41 , 0x5a , 0x08 , 0x51 , 0x25 , 0xe8 , 0xf7 , 0xcd , 0xc9 , 0x9f , 0xd9 , 0x1d , 0xbd , /**/0x72 ,x34 ,x28 , 0x0d , 0x1e, 0xc6 , 0x98 , 0x21 , 0xbc , 0xb6 , 0xa8 , 0x83 , 0x93 , 0x96 , 0xf9 , 0x65 , /* flag byte*/0xab , 0x6f , 0xf7 , 0x2a , 0x70 };
Remember that given this pair of vectors, if we have a payload of any size, then MD5(vec1+payload) == MD5(vec2+payload). The payload is built in this way, the length of good file, the length of evil file, the content of the good file, and the content of the evil file.
The core of the generation program is shown below:
[STAThread] static void Main(string[] args) { if (args.Length != 2) Usage(); byte[] goodFile = ReadBinaryFile(args[0]); byte[] evilFile = ReadBinaryFile(args[1]); WriteBinary("good.bin", vec1, goodFile, evilFile); WriteBinary("evil.bin", vec2, goodFile, evilFile); ShowMD5("good.bin"); ShowMD5("evil.bin"); } private static void Usage () { Console.WriteLine("Usage: md5gen good_file evil_file"); Environment.Exit (-1); } private static void WriteBinary (string sOutFileName, byte[] prefix, byte[] goodFile, byte[] evilFile) { using (FileStream fs = File.OpenWrite (sOutFileName)) { using (BinaryWriter writer = new BinaryWriter(fs)) { writer.Write(prefix); writer.Write ( goodFile.Length ); writer.Write ( evilFile.Length ); fs.Write (goodFile, 0, goodFile.Length); fs.Write (evilFile, 0, evilFile.Length); fs.Close (); } } }
If we apply the generator program to the pair of programs, we generate a pair of files, good.bin and evil.bin in the following way:
C:\TEMP>md5clone goodexe.exe evilexe.exe MD5 Hash for good.bin is 1D8EE13FBA00DD022F002AAD0E3EF9C7 MD5 Hash for evil.bin is 1D8EE13FBA00DD022F002AAD0E3EF9C7).
Now, suppose we have changed the extractor program, with our own version. Our extractor receives the .bin distribution file, and extracts the good or evil program based on the prefix vector at the beginning of the .bin file. We use the byte at position 123 to detect the vector that is used for the prefix.
The code of the extractor is very simple:
[STAThread] static void Main(string[] args) { if (args.Length == 0) Usage(); ExtractFile(args[0], args[1]); } private static void ExtractFile (string sfilename, string soutputfile) { using (BinaryReader reader = new BinaryReader(File.OpenRead (sfilename))) { byte[] vec = reader.ReadBytes (128); int goodSize = reader.ReadInt32 (); int evilSize = reader.ReadInt32 (); /// open evil file if (vec[123] == 0xab) { reader.ReadBytes (goodSize); byte[] evil = reader.ReadBytes (evilSize); using (BinaryWriter writer = new BinaryWriter(File.OpenWrite (soutputfile))) { writer.Write (evil); writer.Close (); } } else { byte[] good = reader.ReadBytes (goodSize); using (BinaryWriter writer = new BinaryWriter(File.OpenWrite (soutputfile))) { writer.Write (good); writer.Close (); } } Console.WriteLine ("File written on {0}", soutputfile); } } private static void Usage () { Console.WriteLine( "Usage: md5extract file.bin output_file.exe"); Environment.Exit (-1); }
Suppose, you receive the good.bin file, then you apply the extractor on good.bin and the good.exe file is extracted. But if you receive the evil.bin file, then the extractor will extract the evil.exe, i.e. the harmful executable. Remember that MD5(evil.bin) == MD5(good.bin).
Recently, the world of cryptographic hash functions was on crisis. A lot of researchers announced "attacks" to find collisions for common hash functions such as MD5 and SHA-1. "For cryptographers, these results are exciting - but many so-called "practitioners" turned them down as practically irrelevant".
I hope, this proof of concept will convince you that there is a serious issue with MD5.
s. Lenstra, Wang and de Weger [LWdW,LdW] constructed colliding X.509 certificates".
This article shows how a failure on the software distribution chain, allows exploiting the current findings on cryptology about the MD5 hash function.
General
News
Question
Answer
Joke
Rant
Admin | http://www.codeproject.com/KB/security/HackingMd5.aspx | crawl-002 | refinedweb | 1,091 | 58.28 |
Silverlight 2 is far more versatile than Silverlight 1. It can handle data-sources with some subtlety. John Papa tackles the whole subject of data-binding with Silverlight. This article is a partial excerpt from John Papa's book Data-Driven Services with Silverlight 2 by O'Reilly, released in December 2008.
Unlike Silverlight 1, Silverlight 2 has controls, .NET CLR support and data binding features. This article is the first of a series that describes the basic elements of data binding with Silverlight 2.
While binding can be established using a manual push and pull process, the data binding capabilities of XAML and Silverlight offer more power and flexibility with less runtime code. This provides a more robust data bound user-interface with fewer failure points than with manual binding.
The process of Automated Data-Binding in Silverlight links a UI FrameworkElement to a data source entity and back. The data source entity contains the data that will flow to the FrameworkElement control for presentation. The data can also flow from the control in Silverlight back to the entity. For example, an entity may be bound to a series of controls, each of which is linked to a specific property on the entity, as shown in Figure 1.
The entity is set to the DataContext for a control. This then allows that control, or any child control of that control, to be bound directly to the entity. There are many important players in this process that will be introduced in this article, including the DataContext, binding modes, and dependency properties on FrameworkElement controls. Each of these plays a critical role in customizing how the data binding process operates in a Silverlight application.
Figure 1. Data binding in Silverlight 2
There are some basic rules to follow when you are setting up data binding in Silverlight. The first rule is that the target element of a data binding operation must be a FrameworkElement. The second rule says that the target property must be a Dependency Property.
The target of data binding must be a FrameworkElement. This many sound limiting but it is quite the opposite. The FrameworkElement has many subclasses that inherit from it. Figure 2 shows several controls that inherit from the FrameworkElement. The FrameworkElement extends the UIElement class and adds capabilities that allow it to control layout and support data binding.
Any control that derives from FrameworkElement can be used for layout on a page or user control, and can be involved in data binding as a target. There are other classes that derive from some of the subclasses shown in Figure 2, such as System.Windows.Controls.Textbox, too.
In data binding, both a data source and at least one target are required. The target can be a control or set of controls on a page (or within a user control). Basically, the data can travel in either direction between the source and the target. The sources of data are generally instances of objects such as a domain entity. The properties of the data source are referred to in the targets, so that each target control knows which property of the entity it should be bound to.
Figure 2. FrameworkElement Class Hierarchy
As mentioned previously, the second rule of data binding in Silverlight is that the target must be a Dependency Property. This might initially seem to be a restriction, especially since one of the first controls people think about when they think of data binding is the TextBox’s Text property. However if you take a look at the source code (using a tool like Lutz Roeder’s .NET Reflector) for the Text property of a TextBox you will see that it too is a Dependency Property. In fact most properties that you can think of are Dependency Properties, which is great, since that means you can use data binding with so many properties.
Dependency Properties are data-bound properties whose value is determined at runtime. The purpose of dependency properties is to provide a way to determine the value of a property based on inputs including, but not limited to, user preferences, resources, styles, or data binding. An example of a Dependency Property can be seen in the XAML code snippet below by looking at the Fill property.
The Rectangle control’s Fill property is a Dependency Property that is set to a specific color, in this case. The Fill property’s value could be determined using a resource or by data binding to an object. This would allow the color of the rectangle to be determined at runtime.
Dependency Properties are not declared as a standard .NET CLR type, but rather they are declared with a backing property of type Dependency Property. The code in Example 1 shows the public facing property Fill and its type Brush However you’ll see that its backing property is not Brush but rather the type Dependency Property. You can always identify a Dependency Property by looking at its backing property’s name. If the backing property name has the Property suffix then it is generally the backing property for a Dependency Property.
Example 1. DependencyProperty
C# code
public
{
get { return (Brush) this.GetValue(FillProperty); }
set { base.SetValue(FillProperty, (DependencyObject) value); }
}
VB Code
Public
Get
Return CType(Me.GetValue(FillProperty), Brush)
End Get
Set(ByVal value As Brush)
MyBase.SetValue(FillProperty, CType(value, DependencyObject))
End Set
End Property
Table 1 shows a quick reference of these terms applied to the code in Example 1
Term
Description
Explanation
Dependency Property
The property named Fill
A property that is backed by a field of type Dependency Property
DependencyProperty
The type of FillProperty
A type that defines the backing field
Dependency Property Identifier
The instance of the backing property,FillProperty . This is referred to in the CLR Wrapper code with the GetValue and SetValue methods.
An instance of the Dependency Property
CLR Wrapper
The setter and getter accessor code for the Fill property.
The getter and setter for the property
A dependency property can also get its value through a data-binding operation. Instead of setting the value to a specific color or a Brush, the value can be set through data-binding. When using data-binding, the property’s value is determined at runtime from the binding to the data source.
The following XAML example sets the Fill for a Rectangle using data-binding. The binding uses an inherited data context and an instance of an object data source (referred to as MyShape). The binding syntax and the DataContext will be explored later in this article.
Grid.Column="0" Grid.Row="0"
Besides basic data binding, styles and templates are a huge beneficiary of using dependency properties. Controls that use styles are indicated through a StaticResource (defined in app.xaml or defined locally). The style resources are often set to a Dependency Property to achieve a more elegant appearance.
Dependency Property values are determined using an order of precedence. For example a style resource may set the Background Dependency Property to White for a canvas control. However the Background color can be overridden in the control itself by setting the Background property to Blue. The order of precedence exists in order to ensure that the values are set in a consistent and predictable manner. The previous example of the Rectangle control shows that the locally-set property value has a higher precedence than a resource.
When creating a binding, a Dependency Property of a FrameworkElement must be assigned to the binding. This is the target of the binding operation. The source of the binding can be assigned through the DataContext property of the UI element or any UI element that is a container for the bound UI element.
One of the main pieces of functionality offered by the Dependency Property is its ability to be data bound. In XAML, the data binding works through a specific markup extension syntax. Alternatively, the binding can be established through .NET code. A set of XAML attributes exist in order to support the data binding features. A basic example of the usage of these extensions is shown in the pseudo-code examples below.
<someFrameworkElement property="{Binding}" .>
<someFrameworkElement property="{Binding Path=pathvalue}" .>
<someFrameworkElement
property="{Binding oneOrMoreBindingProperties}" .>
<someFrameworkElement property
="{Binding Path=pathvalue, oneOrMoreBindingProperties}" .>
The element must be a FrameworkElement (thus the name someFrameworkElement). The property would be replaced with the name of the property that will be the target of the binding. For example the element might be a TextBox and the property might be Text. To bind the value of the property to a source the binding markup extensions can be used.
The Binding attribute indicates that the value for the Dependency Property will be derived from a data binding operation. The binding gets its source from the DataContext for the element or the DataContext that is inherited from the closest parent element. To bind an element to an object that is the DataContext (and not to a property of the object), all that is needed is the Binding attribute (see the first line of XAML from the previous example). For example, this is usually the case when binding an object that is a list to a ListBox.
The second usage of the binding markup syntax is to specify a pathvalue. This can be the name of a property that exists on the bound object. For example, to bind a TextBox’s Text property to the CompanyName property of an object in the inherited DataContext the following code could be used:
Additionally, there are a handful of other binding properties (referred to in the previous example as oneOrMoreBindingProperties) that can be set with the XAML binding extensions in Silverlight. These properties are:
The Mode indicates the binding mode that specifies how the binding will operate. Valid values for the Mode property are OneTime, OneWay and TwoWay. An object reference can be set to the Source property. If the Source property is set the object reference will override the DataContext as the data source for this binding. All of these properties are optional. The default value for the Mode is OneWay while if the Source property is omitted the data source will defer to the DataContext.
Keep in mind that a Dependency Property follows an order of precedence to determine its value. If a Dependency Property is bound and in code the property is set to a value explicitly, the binding is removed. For example the tbCompany TextBox in the previous example is bound to the CompanyName property of the DataContext. If the Text property of tbCompany is set to Foo in code, then the binding is removed.
The DataContext refers to a source of data that can be bound to a target. The DataContext often is set to an instance of an entity. Once set, the DataContext can be bound to any controls that have access to it. It can be used to bind all controls within a container control to a single data source. This is useful when there are several controls that all use the same binding source. It could become repetitive to indicate the binding source for every control. Instead, the DataContext can be set for the container of the controls.
Each FrameworkElement has a DataContext. This includes the instances of the UserControl class that the examples in this article have demonstrated, since the UserControl class inherits from the Control class which in turn inherits from the FrameworkElement class. This means that, on a single UserControl, there could be objects assigned to dozens of DataContext properties of various FrameworkElement controls. For example the UserControl, a layout control such as a Grid, and a series of interactive controls such as the TextBox, CheckBox and ListBox controls might all have their DataContext property set.
To use the DataContext, the XAML must also be modified using the binding markup extension syntax. The newly modified XAML for the UserControl is shown in the code example below. This code is only the portion of the entire XAML file that shows only the elements where binding takes place.
<TextBox x:
<TextBox x:
This XAML shows that the Text property of each TextBox is bound to a property of the data source. The data source is not listed anywhere in this XAML code. Therefore it is inferred that the Binding will use the DataContext that is closest in the inheritance hierarchy to the Target. If the TextBox itself has its DataContext property set, it will use the object from its own DataContext.
Example 2. DataContext Binding
C#
person = new Person { FirstName = "Ella",
LastName = "Johnson", Company = "Hoo Company" };
this.DataContext = person;
ByVal e As RoutedEventArgs)
person = New Person With {.FirstName = "Ella", _
.LastName = "Johnson", .Company = "Hoo Company"}
Me.DataContext = person
End
The code in Example 2 shows the event handler that will execute when the UserControl is loaded. First an instance of the Person class is created and initialized. Then the DataContext property (also a Dependency Property) of the UserControl is set to the person instance. This gives each TextBox’s Binding a valid DataContext to use as the data source. Figure 3 shows the result of the binding. The DataContext is set for a container control (the UserControl itself).
Figure 3. DataContext Binding
Silverlight 2 offers a variety of data binding features that all stem from some basic concepts as discussed in this article. All instances of the FrameworkElement class support data binding as a target while all properties of FrameworkElements that are dependency properties can be a target property of a data binding operation. The DataContext is a very powerful way to bind a source object to one or more elements are multiple levels in XAML. These are the fundamental tools to data binding with Silverlight 2.
Author profile: John Papa
John Papa, Senior .NET Consultant at ASPSOFT, is a Microsoft MVP [C#], MCSD.NET, and an author of several data access technology books. John has over 10 years' experience in developing Microsoft technologies as an architect, consultant, and a trainer. He is the author of the Data Points column in MSDN Magazine and can often be found speaking at user groups, MSDN Web Casts, and industry conferences such as VSLive and DevConnections. John is a baseball fanatic who spends most of his summer nights rooting for the Yankees with his family and his faithful dog, Kadi. You can contact John at johnpapa.net.
His new book Data-Driven Services with Silverlight 2 has recently been published. | http://www.simple-talk.com/dotnet/.net-framework/data-and-silverlight-2-data-binding/ | crawl-002 | refinedweb | 2,409 | 54.63 |
> From: Peter Reilly [mailto:peter.reilly@corvil.com]
> >wouldn't this here work?
> >
> ><macrodef name="example">
> > <element name="files" implicit="yes"/>
> > <sequential>
> > <task xmlns="URI-for-prefix-x">
> > <files/>
> > <task>
> > <copy todir="z">
> > <files/>
> > </copy>
> > </sequential>
> ></macrodef>
> no (in ant 1.6.1) see:
>
>
> >A nested element discovered by reflection is looked up in
> >
> >(1) the task's namespace
> >
> >(2) the namespace associated with Ant's core, no matter what the
> >prefix of Ant's core may currently be and no matter what the default
> >namespace currently is.
> >
> >And (2) would only kick in if (1) fails.
> >
> >I could support this proposal.
> Excellent!
Cool! I've been waiting for that ;-)
Not really, since I was lucky enough I could substitute <bm:lsync> with
<sync>, thus my <sources> macrodef element was used in tasks from the
default Ant NS. I'd like to be able to reuse such a macrodef element in
tasks from different namespaces tough (in the same macro of course).
Peter, why wouldn't Stefan alternate solution work? I don't think I
followed.
I have another XML NS weirdness in Ant I'd like to report, before I
completely forget it (I meant to report it earlier...) It's coming from the
same "compile" macro of the other problem. Here's the definition:
<!--
* Define the <compile> macro...
* @attr jaxb whether to run the jaxb schema compiler
* @elem schemas patternset/selector of XML schemas for <jaxb>
* Must be part of the "antlib:com.lgc.buildmagic" namespace.
-->
<macrodef name="compile">
...
<attribute name="jaxb" default="false" />
<element name="schemas" optional="true" />
<sequential>
<!-- Compile the XML schemas into Java code, if any -->
<mkdir dir="build/generated/@{name}" />
<bm:jaxb
<bm:schemas
<schemas/>
</bm:schemas>
...
</bm:jaxb>
</sequential>
</macrodef>
The weirdness (at least to me), comes when you try to use this macro,
because as the comment above warns, you must NS qualify the <schemas> macro
element at the point of use:
<compile name="dsp-core" jaxb="true" ...>
<schemas xmlns="antlib:com.lgc.buildmagic">
<include name="com/lgc/infra/persistence/**/doc-files/*.xsd" />
</schemas>
</compile>
So according to XML rules, <schemas> in the macrodef has no NS, while you
*must* use the proper NS when you use the macro, otherwise it doesn't work.
I find this confusing.
Would your patch solve this too?
BTW, note the 'jaxb' macro attribute, and the ifTrue="@{jaxb}", and
jaxb="true" nodes. I already reported that I wished to be able to infer
whether to perform a given task when a particular macro element exists.
Thanks, --DD
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class P ( ...' public boolean broken( T theArg ) { return (theArg.getClass().getName().equals("T"));and
program(t){ print t.type.name }.
class Collection { // Returns and removes an object previously put in the collection. public Object get(); // Inserts an object into the collection. public void put(Object); } class Queue { head = 0; tail = 0; array = {}; public Object get(){ if (head==tail) throw Error(); return array[head++]; } public void put(Object){ array[tail++]=Object; } } class Stack { integer index = 0; Object[] array = {}; public Object get(){ if (index==0) throw Error() return array[--index]; } public void put(Object){ return array[index++]; } }There is no valid assumption that one can make from the interface of Collection that will ever be violated by Stack or Queue. This approach can explain the issue with Alastair's counter-example:
class Collection { // Returns and removes an object previously put in the collection. public Object get(); // Inserts an object into the collection. public void put(Object); // Returns a Strng containing the name of the implementation of this class. public Class getClass(); } class Queue { head = 0; tail = 0; array = {}; public Object get(){ if (head==tail) throw Error(); return array[head++]; } public void put(Object){ array[tail++]=Object; } public String getClass(){ return "Queue"; } } class Stack { integer index = 0; Object[] array = {}; public Object get(){ if (index==0) throw Error() return array[--index]; } public void put(Object){ return array[index++]; } public String getClass(){ return "Stack"; } }The fact the their behaviour is the same under that interface is trivially true; that the information made available due to the result of the 'getClass()' function is part of the interface is trivially false. The trick is that in this context, the behaviour of getClass() is specified to be an open set, whereas get() and put() are a closed set. The behaviour of get() and put() is completely determined by the closed set of 'what have we put in so far'. Stack and Queue would therefore not be subtypes of Collection if they violated this, either by returning an object from get() that had not been added by means of put(). getClass(), on the other hand is an open set. Therefore, any program making valid use of the interface must be prepared to accept any output which satisfies the predicate of that open set, namely, that there is a definition of a class, whose name is represented by the returned String. And here is the important part: any program that breaks given the output of any subclass of collection is making invalid use of that interface. More formally, any program which uses the output of getClass() must either map it to a closed set, or include an open set as part of its interface. Note that the opposite is not true: a closed set can never possibly generate an open set; to do otherwise would invalidate the HaltingProblem. Given this, we can come up with a simple definition of behaviour which has the property described above: the behaviour of a type is the [set of [mapping of a open or closed set to a function names]]. ." For any program defined in terms of Collection's, the behaviour (as defined above) is unchanged if used with Queue or Stack. If it makes use of getClass(), and makes a decision on the basis of that output, then it's behaviour can already be described as returning an open or closed set.
String closedSetBehaviour(Collection){ string = Collection.getClass(); if (string=="Queue") return true; else return false; } String openSetBehaviour(Collection){ string = Collection.getClass(); if (string=="ClearableQueue?") return ((ClearableQueue?) Collection).clearAll(); else return false; }Remember, that this is defined in terms of Collection, and therefore the result of any cast-like activity is an open set. There behaviour is therefore not changed in either example: the first will always return a known closed set, the other an open set. In short, we're talking about 'behaviour' as in the behaviour of functions of the form "f(x) = a / bx", as opposed to the behaviour of the function in which "f(x) = 6 / 3x == 1 where x=2". Another phrasing would be: Behaviour is the set of things that a subtype could do, not the set of things that it will do. --WilliamUnderwood P.S., for the TuringChallenged, I define an open set loosly as a set that could always fill up the memory of any available computer, wheras a closed set can always be completely enumerated on a sufficiently powerful real computer.
class P ( ...' public boolean broken( T theArg ) { return (theArg.getClass().getName().equals("T"));and the second is
program(t){ print t.type.name }The challenge for anyone who wishes to defend the declaration is to present a mathematical definition of subtyping that permits subtypes of T to be substituted for T in the above two programs without altering their behavior. Alistair believes this is not only impossible, it is trivially easy to see that it is impossible. Their "behavior" is actually unaltered. The "behaviour is not changed" does not mean the program allways return a constant. It's very basic. The behavior of a program is a relation between its inputs, outputs, and possibly the context of execution. If I write F(x)= x+1 the behavior of F is the predicate:
OUTPUT = INPUT + 1which holds true for every x that doesn't generate a type checking error (of course we can't substitute x with a string). It doesn't have to be the predicate "OUTPUT = constant". This is the very basic logical flaw in asserting that the above two programs disproves whatever. By the way, you can't have a counterexample to a definition. --Costin for addresses two practical things that in his opinion break the LSP: mutability and reflection. As a matter of fact Liskov and Wing do address mutability in the above paper, it is true that they don't address reflection. However, reflection cannot break the LiskovWingSubtyping, because LWS is a logical design choice. I addressed that in the discussion of LiskovSubstitutionPrinciple. It is arguable that LSW might be too tough of a restriction in order to allow practical usage, i.e we'll rarely meet a type that is a LWS subtype of another in practical design, and we might want to use a lesser relation: is kind-of between types, that would allow a more flexible framework for OO designers and programmers to work with. However, the proponents of this approach have yet to come up with practical examples where LWS is too strict, and have yet to construct and logically justify an alternative.
F(x:X) = ( x.type.name == "X" ), which, you imply, should return true. But for many people other than you, it's obvious that's not necessarily true, not in Java, not in Smalltalk, not in any hypothetical language that would actually enforce LWS. That doesn't mean that the behavior of F has changed, because the behavior of F is what we can prove of F (and of course we can't prove that it should return true). Even from a heuristic point of view, claiming that F should always return true serves no purpose whatsoever. So we have to either say that LWS is an unuseful concept because it doesn't allow your little program to always return true, or we have to live with the fact that F will not always return true in a system adhering to LWS. Yes, F doesn't always return true, we can't therefore claim that the behavior of F is to always return true in the hypothetical system supporting LWS. Only if we could justifiably claim (or better, actually prove ) that F should return true, then we could assert that the behavior has changed. So what's the big deal about that, Alistair ? F doesn't always return true, just get over it. Do you have a valid claim why is it so important that F should always return true ? No, you don't. You didn't in your paper and you didn't some time ago when we had the same discussion on the LiskovSubstitutionPrinciple. If you came with something like If we hold LWS, than Pythagora's theorem is no longer a theorem, then you'd have had a point. But instead you come up with a stupid little program that will not always return true, and in fact, it shouldn't. And to supplement it, you derail the discussion with politics and personal itches. At least did you hask the opinion of the persons you talk about so unpleasantly? Maybe they have more patience than I did to explain the obvious to you. But I wouldn't blame them if they didn't. --CostinCozianu In fact, I did ask JeannetteWing?, in 1999 before submitting my paper. She wrote back: "Dear Alistair, I read what you wrote. There's nothing inherently wrong with what you're saying. It's just a matter of how useful or convenient it is to have a notion of substitutability/subtyping when one must always consider the additional argument (context)." Please read her words, - there's nothing inherently wrong with what I'm saying - (she chooses to pursue her research anyway). And thank you very much, you now seem to accept it, too, judging from your latest append. -- AlistairCockburn I think that only if you twist her words, you can draw the conclusion that she agreed to all your claims that LSP is broken, or mathematically unsound and others like that. If you twist what I said maybe you can say the same about me. The fact that your proposed subtyping relation (with the addition of context) might be a valid one, albeit not necessarily useful, does not invalidate LWS. This is also what you didn't get it right in your paper, that various researchers don't necessarily contradict each other with their proposed concept of subtyping, they just have alternative approaches, it's exactly the same as the fact that no 2 OO languages can agree on what is the a class. And the same with the fact that we have euclidean geometries and non-euclidean geometries. If I want to calculate the height of a building using optical instruments and for many other practical and purposeful task, I'll have the euclidean geometry anytime. Likewise if I have to choose between a system with LWS and a system like yours with subtyping depending on context, you can guess what I'd choose. You fail to produce convincing evidence where subtyping is not possible under LWS definition but is desirable under yours. To do so you might want to start your own constructive argument (how about AlistairSubtyping? page), and give up on bashing LWS with ridiculous claims, like "is mathematically unsound", "is broken", etc. The fact that she chose to pursue her research anyways says that she didn't see much value in your proposal, and it's your responsibility to promote your ideas, not hers. But you don't need to mislead people with bashing their work in order to do that. --CostinCozianu I think at this point, Costin, I'm willing to let our disagreement stand [AgreeToDisagree]. --AlistairCockburn
class P ( ...' public boolean broken( T theArg ) { return (theArg.getClass().getName().equals("T")); } }The behaviour of broken(T) is that it will return true if the name of the class of the parameter is T. Renaming to better describe the behaviour therefore:
class P ( ...' public boolean isClassNamedT( T theArg ) { return (theArg.getClass().getName().equals("T")); } }--WilliamUnderwood | http://c2.com/cgi-bin/wiki?LiskovWingSubtyping | CC-MAIN-2016-22 | refinedweb | 1,913 | 59.64 |
interp(1T) Tcl Built-In Commands interp(1T) __________________________________________________________________________________________________________________________________________________ NAME
interp - Create and manipulate Tcl interpreters SYNOPSIS
interp option ?arg arg ...? _________________________________________________________________ DESCRIPTION
This command makes it possible to create one or more new Tcl interpreters that co-exist with the creating interpreter in the same applica- tion. The creating interpreter is called the master and the new interpreter is called a slave. A master can create any number of slaves, and each slave can itself create additional slaves for which it is master, resulting in a hierarchy of interpreters. Each interpreter is independent from the others: it has its own name space for commands, procedures, and global variables. A master inter- preter may create connections between its slaves and itself using a mechanism called an alias. An alias is a command in a slave inter- preter which, when invoked, causes a command to be invoked in its master interpreter or in another slave interpreter. The only other con- nections between interpreters are through environment variables (the env variable), which are normally shared among all interpreters in the application. environ- ment. exam- ple, evalu- ated. THE INTERP COMMAND
The interp command is used to create, delete, and manipulate slave interpreters, and to share or transfer channels between interpreters. It can have any of several forms, depending on the option argument: interp alias srcPath srcToken Returns a Tcl list whose elements are the targetCmd and args associated with the alias represented by srcToken (this is the value returned when the alias was created; it is possible that the name of the source command in the slave is different from srcToken). interp alias srcPath srcToken {} Deletes the alias for srcToken in the slave interpreter identified by srcPath. srcToken refers to the value returned. The command returns a token that uniquely identifies the command created srcCmd, even if the command is renamed afterwards. The token may but does not have to be equal to srcCmd. interp aliases ?path? This command returns a Tcl list of the tokens of all the source commands for aliases defined in the interpreter identified by path. The tokens correspond to the values returned when the aliases were created (which may not be the same as the current names of the commands). com- mandsur- sion. Note that the script will be exe- cuted in the current context stack frame of the path interpreter; this is so that the implementations (in a master interpreter) of aliases in a slave interpreter can execute scripts in the slave that find out information about the slave's current state and stack frame. interp exists path Returns 1 if a slave interpreter by the specified path exists in this master, 0 otherwise. If path is omitted, the invoking inter- preter is used. interp expose path hiddenName ?exposedCmdName? | Makes the hidden command hiddenName exposed, eventually bringing it back under a new exposedCmdName name (this name is currently | accepted only if it is a valid global name space name without any ::), in the interpreter denoted by path. If an exposed command | with the targeted name already exists, this command fails. Hidden commands are explained in more detail in HIDDEN COMMANDS, below. | interp hide path exposedCmdName ?hiddenCmdName? | Makes the exposed command exposedCmdName hidden, renaming it to the hidden command hiddenCmdName, or keeping the same name if hid- | denCmdName is not given, in the interpreter denoted by path. If a hidden command with the targeted name already exists, this com- | mand fails. Currently both exposedCmdName and hiddenCmdName can not contain namespace qualifiers, or an error is raised.. Hidden commands are explained in more detail in HIDDEN COMMANDS, below. | interp hidden path | Returns a list of the names of all hidden commands in the interpreter identified by path. | interp invokehidden path ?-global? hiddenCmdName ?arg ...? | Invokes the hidden command hiddenCmdName with the arguments supplied in the interpreter denoted by path. No substitutions or evalua- | tion are applied to the arguments. If the -global flag is present, the hidden command is invoked at the global level in the target | interpreter; otherwise it is invoked at the current call frame and can access local variables in that and outer call frames. Hidden | commands are explained in more detail in HIDDEN COMMANDS, below. interp issafe ?path? Returns 1 if the interpreter identified by the specified path is safe, 0 otherwise. interp marktrusted path | Marks the interpreter identified by path as trusted. Does not expose the hidden commands. This command can only be invoked from a | trusted interpreter. The command has no effect if the interpreter identified by path is already trusted. interp recursionlimit path ?newlimit? Returns the maximum allowable nesting depth for the interpreter specified by path. If newlimit is specified, the interpreter recur- sion omit- ted, the invoking interpreter is used. interp target path alias Returns a Tcl list describing the target interpreter for an alias. The alias is specified with an interpreter path and source com- mand name, just as in interp alias above. The name of the target interpreter is returned as an interpreter path, relative determine the exact behavior of the command. The valid forms of this com- mand are: slave aliases Returns a Tcl list whose elements are the tokens of all the aliases in slave. The tokens correspond to the values returned when the aliases were created (which may not be the same as the current names of the commands). slave alias srcToken Returns a Tcl list whose elements are the targetCmd and args associated with the alias represented by srcToken (this is the value returned when the alias was created; it is possible that the actual source command in the slave is different from srcToken). slave alias srcToken {} Deletes the alias for srcToken in the slave interpreter. srcToken refers to the value returned INVOCA- TION below for details. The command returns a token that uniquely identifies the command created srcCmd, even if the command is renamed afterwards. The token may but does not have to be equal to srcCmd.. Note that the script will be executed in the current context stack frame of slave; this is so that the implementations (in a master interpreter) of aliases in a slave interpreter can execute scripts in the slave that find out information about the slave's current state and stack frame. slave expose hiddenName ?exposedCmdName? | This command exposes the hidden command hiddenName, eventually bringing it back under a new exposedCmdName name (this name is cur- | rently accepted only if it is a valid global name space name without any ::), in slave. If an exposed command with the targeted | name already exists, this command fails. For more details on hidden commands, see HIDDEN COMMANDS, below. | slave hide exposedCmdName ?hiddenCmdName? | This command hides the exposed command exposedCmdName, renaming it to the hidden command hiddenCmdName, or keeping the same name if | the argument is not given, in the slave interpreter. If a hidden command with the targeted name already exists, this command fails. | Currently both exposedCmdName and hiddenCmdName can not contain namespace qualifiers, or an error is raised. Commands to be hidden | are looked up in the global namespace even if the current namespace is not the global one. This prevents slaves from fooling a mas- | ter interpreter into hiding the wrong command, by making the current namespace be different from the global one. For more details | on hidden commands, see HIDDEN COMMANDS, below. | slave hidden | Returns a list of the names of all hidden commands in slave. | slave invokehidden ?-global hiddenName ?arg ..? | This command invokes the hidden command hiddenName with the supplied arguments, in slave. No substitutions or evaluations are | applied to the arguments. If the -global flag is given, the command is invoked at the global level in the slave; otherwise it is | invoked at the current call frame and can access local variables in that or outer call frames. For more details on hidden commands, | see HIDDEN COMMANDS, below. slave issafe Returns 1 if the slave interpreter is safe, 0 otherwise. slave marktrusted | Marks the slave interpreter as trusted. Can only be invoked by a trusted interpreter. This command does not expose any hidden com- | mands in the slave interpreter. The command has no effect if the slave is already trusted. slave recursionlimit ?newlimit? Returns the maximum allowable nesting depth for the slave interpreter.process invocation might be allowed for a carefully selected and fixed set of programs. A safe interpreter is created by specifying the -safe switch to the interp create command. Furthermore, any slave created by a safe inter- preter The following commands are hidden by interp create when it creates a safe interpreter: cd encoding exec exit fconfig- | ure file glob load open pwd socket source These Note::cre- | ate :- | BreakAfter tcl_wordBreakBefore can pack- | ages. dis- cussion of management of extensions for safety see the manual entries for Safe-Tcl and the load Tcl command. A safe interpreter may not alter the recursion limit of any interpreter, com- mand procedure in the target interpreter, and that command procedure is invoked with the new set of arguments. An error occurs if there is no command named targetCmd in the target interpreter. No additional substitutions are performed on the words: the target command proce- dure. | HIDDEN COMMANDS
| Safe interpreters greatly restrict the functionality available to Tcl programs executing within them. Allowing the untrusted Tcl program | to have direct access to this functionality is unsafe, because it can be used for a variety of attacks on the environment. However, there | are times when there is a legitimate need to use the dangerous functionality in the context of the safe interpreter. For example, sometimes | a program must be sourced into the interpreter. Another example is Tk, where windows are bound to the hierarchy of windows for a specific | interpreter; some potentially dangerous functions, e.g. window management, must be performed on these windows within the interpreter con- | text. | com- | mand mas- | ter evalu- | ating any arguments passed in through the alias invocation. Otherwise, malicious slave interpreters could cause a trusted master inter- | preter com- | mand cur- | rent namespace be different from the global one. CREDITS
This mechanism is based on the Safe-Tcl prototype implemented by Nathaniel Borenstein and Marshall Rose. EXAMPLES
Creating and using an alias for a command in the current interpreter: SEE ALSO
load(1T), safe(1T), Tcl_CreateSlave(3TCL) KEYWORDS
alias, master interpreter, safe interpreter, slave interpreter ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +--------------------+-----------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +--------------------+-----------------+ |Availability | SUNWTcl | +--------------------+-----------------+ |Interface Stability | Uncommitted | +--------------------+-----------------+ NOTES
Source for Tcl is available on. Tcl 7.6 interp(1T) | https://www.unix.com/man-page/opensolaris/1t/interp/ | CC-MAIN-2019-47 | refinedweb | 1,752 | 52.7 |
(Not recommended) Set imaginary data elements in
mxDOUBLE_CLASS array
mxSetPi is not available in the interleaved complex API. Use
mxSetComplexDoubles instead. For more information, see Compatibility Considerations.
#include "matrix.h" void mxSetPi(mxArray *pm, double . Instead, call this function to replace existing values with new
values. Examples of allocating heap space include setting the
ComplexFlag to
mxCOMPLEX or setting
pi to a non-
NULL value.
The
mxSetPi function does not free any memory allocated for
existing data that it displaces. To free existing memory, call
mxFree on the pointer returned by
mxGetPi.
pm— Pointer to MATLAB® array
mxArray *
Pointer to a MATLAB array of type
mxDOUBLE_CLASS, specified as
mxArray *.
pi— Pointer to data array
double *
Pointer to the first
mxDouble element of the imaginary
part of the data array within an
mxArray, specified as
double *.
leaks and other memory errors can result.
Not recommended starting in R2018a
Use the
mxSetComplexDoubles function in the interleaved complex API instead
of
mxSetPr and
mxSetPi.
Example
arrayFillSetPr.c
To build the MEX file, call
mex with the
-R2018a option.
mxSetPiwith interleaved complex API
Errors starting in R2018a
The
mxSetPi function is only available in the separate
complex API. To build
myMexFile.c using this function,
type:
mex -R2017b myMexFile.c
Existing MEX files built with this function continue to run. | https://ch.mathworks.com/help/matlab/apiref/mxsetpi.html | CC-MAIN-2021-17 | refinedweb | 216 | 50.43 |
Unanswered: Dragging and dropping nodes only withing the same parents.
Unanswered: Dragging and dropping nodes only withing the same parents.
Hello,
I found on this forum an old post showing how to allow drag and drop only within same parent but it is from version 2.X.
I was wondering if in version 3.4, there was a more elegant way to do it.
Exemple :
Node1
Node1.1
Node1.2
Node2
Node2.1
Node2.2
I would like to allow changing the order of the children of Node1 and Node 2 with drang and drop, but I want to disable draging children of Node2 in Node1.
Thank you
Hi fvaliquette,
I had same problem. I wrote custom TreeDropTarget to prevent insert action.
Code:
public class CustomTreeDropTarget<M> extends TreeDropTarget<M> { public CustomTreeDropTarget(Tree<M, ?> tree) { super(tree); } @Override protected void handleInsert(DndDragMoveEvent event, final TreeNode<M> item) { if (item.getModel().equals(root)) { if (activeItem != null) { clearStyle(activeItem); } status = -1; activeItem = null; appendItem = null; Insert.get().hide(); event.getStatusProxy().setStatus(false); } else { super.handleInsert(event, item); } } } | http://www.sencha.com/forum/showthread.php?256017-Dragging-and-dropping-nodes-only-withing-the-same-parents | CC-MAIN-2015-14 | refinedweb | 175 | 52.76 |
User Interfaces
Business Space
Business Space is a UI framework designed for end users to interact with BPM functions. Business Space is a specialization of the IBM Lotus Mashups technologies. Business Space is built from a set of one or more "spaces". Each space contains one or more pages. Each page contains one or more widgets that are laid out on the page.
Each BPM product installed adds one or more Business Space widgets to the catalog of available widgets.
Events
Widgets can communicate with each other through the publish/subscribe of events between them. When a widget is registered with Business Space, its registration describes which events it can publish to and which events it can subscribe upon. When a widget is added to a page, it can then be wired to other widgets. One widget will act as the publisher of the event, and the other act as the subscriber. Two widgets can only be wired together if they support the same type of event.
See Also – Business Space
Flex Custom Widgets in Business Space - Using Flex within Business Space
References – Business Space
Custom Widgets
The widgets provided by IBM for business space are not the only widgets possible. You can create and use your own widgets to augment the existing functions. There are a number of steps and piece-parts required to build a new widget.
A widget is configured to Business Space by providing an XML configuration file that corresponds to the iWidget specification. Contained within this file are a number of properties that are used by the Business Space runtime to control how the widget behaves and is displayed.
In addition to the visual characteristics of the widget, we should realize that a widget can send events to other widgets as well as received events from other widgets. This is a form of publish and subscribe. The XML document also holds the information on what a widget can send to other widgets and can receive from other widgets.
An example iWidget XML control file may look as follows:
<?xml version="1.0" encoding="UTF-8" ?> <iw:iwidget <iw:content <![CDATA[ <div>Hello World</div> ]]> </iw:content> </iw:iwidget>
A deep understanding is recommend of the structure and semantics of this control file. IBM provides a rich function GUI editor that hides the majority of the details allowing values to be entered in a much more pleasing manner. See iWidget editor.
In addition to the iWidget XML control file, there is a second file which is a Business Space specific Catalog XML file. The purpose of this file is to tell Business Space about the nature of the widget so that Business Space can present this widget in its catalogs of available widgets.
Finally there is one more XML file of importance to us when building custom Business Space widgets. This file is the Endpoint Registration XML file. The purpose of this file is to provide information to the widget about where it should connect to at runtime in order to communicate with a WPS server instance. Business Space widgets typically make REST style communication calls to the WPS server.
iWidget Mode
One of the core concepts of an iWidget is its mode. Think of the mode of a widget as being a "state" that the widget as a whole may be in. Depending on the value of the mode, the widget can render itself in different ways. For example, if a widget is in view mode, then it might be displaying business data. If the same widget is in configuration mode, it might be displaying configuration data for itself such as which database to read data from.
A widget can be told its mode ... which is another way of saying how the widget is to represent itself for a particular task. As an example, setting its mode to:
Business space defines these three modes of operation.
iWidget Structure
The iWidgets supplied for Process Server can be found in the directory <ProcessServer>/BusinessSpace/widgets. These serve as a useful source of reference and should be examined to see how IBM has built its own widgets.
What follows next is a breakdown on the logical content of the iWidget XML documents. Note that these conform to the iWidget specification v2.0 which is very different from the previous version that was used in previous product releases.
The XML control file begins with an
iwidget
The <iw:iwidget> element is the root container in the document used to describe the iWidget. It has many possible attributes for its configuration.
Attributes:
Example
<iw:iwidget xmlns:
resource
<iw:resource
Attributes:
Example
<iw:resource
eventDescription
Attributes:
event
content
This tag contains the content that will be displayed/loaded in the Widget. This is usually HTML. The <iw:content> element is a child of the <iw:iwidget> element.
Attributes:
iWidget Modules/Data Structures
Managed Item Set
The ManagedItemSet is part of the iWidget specification. It defines data that is managed by the widget itself. This includes saving the data for later retrieval. This can be used for setting the configuration/properties of the widget so that later it can be restored.
The ManagedItemSet for an iWidget can be retrieved from the widget's iContext using the getiWidgetAttributes() function.
ManagedItemSet getiWidgetAttributes();
For example,
var myAttributes = this.iContext.getiWidgetAttributes();
Although the iWidget spec shows that the setItemValue function can take an object to save, reality is that there is a limitation of the iWidget container. To help with this, we should encode the object that we want to save as a string and save the string value as the attribute. In JavaScript, we can employ the JSON encoding and leverage the dojo.toJson function to encode a JavaScript object. When we retrieve the value, we can use the dojo.fromJson function to get the JavaScript object back again.
For example:
var x = new Object(); x.a = "Hello"; x.b = "World"; var myAttributes = this.iContext.getiWidgetAttributes(); myAttributes.setItemValue("test", dojo.toJson(x), false); myAttributes.save(); // Retrieve … var y = dojo.fromJson(myAttributes.getItemValue("test"));
Also note that saving attributes is recommended when the widget is in 'edit' mode. The actual persisting of these attributes back to the server only occurs when the widget goes from the edit mode back to view mode.
Functions on ManagedItemSet
ManagedItemSet setItemValue(in String itemName, in Object value, in boolean readOnly /*optional*/); Object getItemValue(in String itemName); ManagedItemSet removeItem(in String itemName); String[] getAllNames(); boolean isReadOnly(in String itemName); null save(in Function callbackFn /*optional*/); boolean addListener(in Function listener); boolean removeListener(in Function listener); ManagedItemSet clone();
function(in String managedItemSetName, in boolean success);
addListener This method returns a boolean indicating whether or not the request to add a listener to changes in iWidget v1.0 Specification the ItemSet was successful. Note that the signature for such a listener is:
module { null listener(in iEvent ev); }
removeListener This method returns a boolean indicating whether or not the request to remove a listener was successful.
clone This method returns a new ManagedItemSet that is a duplicate of the current ManagedItemSet. While this method does provide for cloning all the values within the ManagedItemSet, in general this will only clone the data fields for complex Objects, both type information and any embedded logic will most likely be lost.
iWidget iContext
ManagedItemSet getiWidgetAttributes(); ManagedItemSet getUserProfile(); ManagedItemSet getiDescriptor(); ItemSet getItemSet(in String name, in Boolean private); Object iScope(); String processMarkup(in String markup);
null processiWidgets(in DOMNode node); Element getElementById(in String id); Element[] getElementByClass(in String className); Element getRootElement(); null requires(in String requiredItem, in String version /*optional*/, in String uri, in Function callbackFn /*optional*/); iEvents iEvents; IO io; xml xml; String widgetId;
getiDescriptor This method returns the ManagedItemSet that provides access to attributes that both the iContext and the iWidget need to understand. If there is no ManagedItemSet related to the iWidget's descriptive items, this method MUST create an empty set and return it.
getItemSet This method returns an ItemSet corresponding to the requested name. If it does not already exist, an ItemSet will be created and associated with the supplied name. If a new ItemSet is created, the "private" parameter controls whether or not the ItemSet can be exposed to other components. If the ItemSet already exists, the "private" parameter is ignored. If access to the desired ItemSet is denied or the ItemSet cannot be created, null is returned.
function(requiredItem, uri, resourceHandle /* when appropriate */)
The following names refer to optional functionality defined here:
io
xml
iEvents This field contains an object that provides access to event services in a manner allowing the iWidgets on the page to interact in a loosely coupled manner while also providing control to whomever is defining the overall page/application. Types related to eventing are defined in a separate section below.
io This optional field contains an object that provides access to io services in a manner allowing the page as a whole to remain consistent, particularly in the face of server-side coordination between related application components. See also: iWidget IO.
xml This optional field is a placeholder for future definitions providing explicit support for XML-oriented processing. This version of the specification provides no such definitions, but they are expected in future versions. Extensions supported by more advanced iContexts SHOULD follow the pattern used for the iEvents and IO portions of these definitions. This allows iWidgets to determine the support for a "foo" extension defined by a group named "bar" using a construct of the form:
var fooSupported = (iContext._bar & iContext._bar.foo);
widgetId This field appears to be the Dojo Dijit ID for the Dijit Widget
Constants
iContext.constants.mode.VIEW = "view" iContext.constants.mode.EDIT = "edit" iContext.constants.mode.HELP = "help" iContext.constants.ATTRIBUTES = "attributes" iContext.constants.IDESCRIPTOR = "idescriptor" iContext.constants.USERPROFILE = "userprofile" iContext.constants.keys.SHIFT = 1 iContext.constants.keys.ALT = 2 iContext.constants.keys.CTRL = 4 iContext.constants.keys.META = 8 iContext.constants.keys.CAPSLOCK = 16
iEvents
module iEvents { null publishedEvents(in iEventDescription eventDesc[]); null handledEvents(in iEventDescription eventDesc[]); null fireEvent( in String name, /* event name, preferrably a serialized QName */ in String type, /* optional reference to type, preferrably a serialized QName */ in Object payload /* optional ... the event's data */); }
io
XMLHttpRequest XMLHttpRequest(); URI rewriteURI(in URI uri); XMLHttpRequest request(in requestVerb, in URI uri, in Function callbackFn, in String message /*optional*/, in [{headerName, value}] requestHeader /*optional*/);
Notes
Getting the URL for the widget
The URL for the widget can be obtained using:
var rootString = io.rewriteURL("");
Misc
After changing the Business Space Registry, much of the documentation says to execute an expensive restart of the server. Experience so far seems to be showing that simply stopping and then restarting the application called
IBM_BSPACE_WIDGETS appears to be sufficient.
iWidget editor
In the latest versions of ID and RAD, there is a an iWidget editor built into the development tooling. The iWidget editor is documented in the RAD InfoCenter. This editor visualizes the iWidget XML description file in a custom editor that is designed to show the values of an iWidget. In addition, an iWidget control file can be created as a new artifact. To create a new iWidget, select New from a Web project. You must be in the Web Perspective. In the list of available artifacts, the iWidget entry can be found:
If the entry does not show up in the list, choose it from the New artifact list. It can be found in the Web folder.
This launches a wizard in which details of the new iWidget can be entered:
In the editor, the iWidget has a drop-down selection for the type of iWidget. The selections available are:
Once created, a new XML artifact appears in the project. To open this file in the iWidget editor, select
Open With → Other and select iWidget Editor
Here is an example of an iWidget file opened in the editor with some data entered:
BSpaceWidgetRegistry
getWidgetRegistry() Returns the business space registry for the widget that contains the instance of this class.
getWidgetRegistryServiceURI() Returns the service URI that returns all the widget registries.
getWidgetRootURI() Returns the URI to the location of the widget definition XML.
getWidgetInfoByWidgetId(widgetId) Undocumented.
getServiceEndpoint(key) Returns the endpoint that matches the given key.
getServiceURLRoot() Returns the service URI root of the business space.
isInBSpace() Returns true if this widget is hosted in business space. False otherwise.
getDefinitionXMLPath() Returns the path to this widget's definition XML.
BSpaceGeneralHelper
Registering Widgets
In WPS 7.0, a new wsadmin task was introduced that performs the installation actions more elegantly than previous releases. The command is called
AdminTask.installBusinessSpaceWidgets.
The syntax for the new WSAdmin task is as follows:
AdminTask.installBusinessSpaceWidgets('[ -nodeName *nodeName *-serverName *serverName *-widgets pathToWidgetZipFile]')
The input to this file is a manually created ZIP file. To create the ZIP file, first create a new folder. In that folder, create the following sub-folders:
ear Contains the EAR file for the Widget Web Project. This EAR contains the iWidget XML file and the JavaScript amongst possible others.
catalog Contains the catalog_nameOfWidget.xml file. The structure and content of this file is described at The Catalog File.
endpoints Contains the endpoint XML file
help (optional)
Once done, ZIP up the data so that these folders are the immediate children in the ZIP. This is the ZIP file to be passed to the installBusinessSpaceWidgets script in the -widgets parameter.
The effect of running this command will be to install the EAR contained within the ZIP as well as register the new Business Space widget. Experience shows that although the EAR application is installed, it is not automatically started. It must be started before the widget can be used in Business Space.
An almost identical command is available to remove (un-install) a previously installed widget. Like the install script, the un-install script takes the ZIP file as input.
AdminTask.uninstallBusinessSpaceWidgets('[ -nodeName *nodeName *-serverName *serverName *-widgets pathToWidgetZipFile]')
Updating the information about the widget in WPS can also be achieved through scripting:
AdminTask.updateBusinessSpaceWidgets('[ -nodeName *nodeName *-serverName *serverName *-catalogs pathToCatalogXMLFile]')
The same command can be used to update the endpoints XML file:
AdminTask.updateBusinessSpaceWidgets('[ -nodeName *nodeName *-serverName *serverName *-endpoints pathToEndpointsXMLFile]')
After installing or updating a widget (at least in test), restart the server.
When installing a widget, the catalog file is copied into:
<Profile>/BusinessSpace/Node/Server/mm.runtime.prof/config
Deleting the file from this location will also delete the widget. The file called catalog_default.xml should also be edited to remove the associated includes.
Similarly, a directory called:
<Profile>/BusinessSpace/Node/Server/mm.runtime.prof/endpoints
contains the endpoint files.
The Catalog File
The XML Catalog file that is used to register a widget does not appear to be any known industry standard. It appears to be IBM specific and very technical in nature at that. No publicly understood documentation is known to exist that describes this mysterious content. By examination (and guesswork), the Catalog XML file seems to contain the following information.
In WPS v7.0, a new catalog structure was designed that differs from that of previous releases. The name of the XML file should be:
catalog_nameOfWidget.xml
Documentation on this is currently poor. Its general structure appears to be:
<catalog id="???"> <resource-type>Catalog</resource-type> <category name="???"> <title>Text</title> <description>Text</description> <entry id="{namespace}name" unique- <title>Text</title> <description>Text</description> <definition>Path???</definition> <preview>Path???</preview> <icon>Path???</icon> <previewThumbnail>Path???</previewThumbnail> <shortDescription>Text</shortDescription> <metadata name="com.ibm.bspace.version">1.0.0.0</metadata> <metadata name="com.ibm.bspace.owner">IBM</metadata> <metadata name="com.ibm.bspace.serviceEndpointRefs"> [{ "name": "serviceUrlRoot", "required": "false", "refId": "endpoint://{namespace}name", "refVersion": "1.0.0.0" }] </metadata> </entry> <category> </catalog>
The text entries in the XML Catalog can be NLS encoded using the following format:
<nls-stringHuman Readable Text</nls-string>
The fields in the Catalog structure are as follows:
It is also used in the category selection in a couple of places:
and
catalog/category/entry/description
The description shows up in the category selection
catalog/category/entry/definition This entry points to the path of the iWidget XML file available from a URL. This links together the Catalog data and the iWidget XML description data. It is from here that the runtime can obtain the iWidget XML description document.
Registry Endpoints XML
The endpoint registry XML example looks as follows:
<?xml version="1.0" encoding="UTF-8"?> <BusinessSpaceRegistry xmlns="" xmlns: <Endpoint> <id>{namespace}name</id> <type>{namespace}name</type> <version>1.0.0.0</version> <url>/WebPath/</url> <description>Description</description> </Endpoint> </BusinessSpaceRegistry>
BusinessSpaceRegistry/Endpoint/id The ID of this endpoint information. This is what is references in the Registry Widget XML in the tag serviceEndpointRef/refId.
JavaScript for a new widget
When a widget is loaded by Business Space, that widget usually supplies some JavaScript code to be executed. As the Business Space widget is loaded and used, callbacks are executed into this code. It is this code that controls the user interactions and makes REST calls to back-end servers and updates the HTML of the page to display or change content. JavaScript does not natively have similar concepts to Java of package names and class names. Dojo provides a similar mapping using the two Dojo methods called
dojo.provide and
dojo.declare. Using these methods provides the ability to declare the Java equivalent of a Class type in a package. This is used with custom Widgets in the iWidget specification. In the iWidget definition, there is an attribute called
iScope. This takes the name of the declared JavaScript class. When an instance of a Business Space widget is created on the page, a corresponding instance of the JavaScript class object is also created.
dojo.provide("com.kolban.SampleWidget"); dojo.declare("com.kolban.SampleWidget", [dijit._Widget], { "onLoad": function() { dojo.mixin(this, new com.ibm.bspace.common.util.widget.BSpaceCommonUtilityLoader()); this.require("com.ibm.bspace.common.util.widget.BSpaceGeneralHelper"); }, "onUnload": function() {}, "onReload": function() {}, "onRefreshNeeded": function() {}, "onSizeChanged": function() {} });
Functions
The JavaScript written to implement the widget contains callback functions that are called by the Business Space framework. The names of these functions are architected. What follows is a brief description of the different callbacks available.
In addition, for each of the modes, a callback function is available for when the mode is selected:
onview
onedit
Modes
A widget can be in any one of a number of modes. The common modes are view and edit. To switch mode, the iContext event called onModeChanged can be invoked.
this.iContext.iEvents.fireEvent("onModeChanged", null, "{newMode: 'view'}");
HTML rewriting
It is possible that there is HTML re-writing going on in the environment. I seem to see that the widget.xml contains:
_IWID_
is being replaced with a UUID which I believe to be the iWidget ID (what ever that means). This same widgetID can be obtained from iContext.widgetId.
Debugging iWidget JavaScript
Assuming you are running the iWidget in FireFox with FireBug installed, adding the JavaScript code statement:
debugger;
causes a breakpoint to be reached which stops the execution and throws you into the FireBug JavaScript debugger.
Adding the JavaScript:
console.log("Text");
caused the text to be logged to the FireBug console.
Event handling
A widget can send (publish) and receive (handle) events from other widgets. IBM's supplied Business Space widgets both publish and handle events. This means that custom widgets can be wired together with the IBM widgets to react or cause reaction. In order for two widgets to be wired together, one needs to publish an event interface and the other needs to handle the exact same event interface. The configuration that describes published and handled events is performed in the iWidget XML document. There are two tags of interest. These are:
eventDescription
event
The eventDescription contains:
<iw:eventDescription <!-- one per locale --> <iw:alt </iw:eventDescription>
id This appears to be a unique ID for the eventDescription. It must match the value used in the eventDescName in the event tag.
payLoadType This describes the type of data that can be incoming.
lang A locale (eg. "en")
description A textual description of the event
title Unknown. Although this shows up in the spec, it does not show up in the iWidget editor.
The event contains
<iw:event
id The identity of the event. This must match between event sender and receiver.
To send an event one uses the method called:
iContext.iEvents.fireEvent()
The function defined in the onEvent attribute of the event tag accepts a single parameter defined as follows:
module iEvent { String name; String type; Object payload; String source; }
When the JavaScript function named in the <iw:event onEvent=...> entry is called, it is passed a JavaScript Object as a parameter. This object contains at least the following:
The iWidget specification provides a set of predefined events that callback into the JavaScript code without event specifications in the XML file having to be coded. These are:
{ "newMode": value }
Called when the mode of the widget has changed
{ "newWidth": value, "newHeight": *value *}
Dojo Level Workarounds
The level of Dojo distributed with Business Space is back-level compared to the latest possible Dojo release. At the time of writing, the level of Dojo supplied is 1.4.3. Many of the expected Dojo functions simply aren't there. Here are some of them (but by no means all) and some suggested workaround:
None at this time.
Debugging and Problem determination
If after building a custom widget, things are not working as expected, here are some tips to follow to see what might be going wrong:
In the catalog file, there is an entry called <definition>. This defines a WEB path to the iWidget xml file. Open a browser and attempt to access this file. For example:
After making changes to the definitions, consider restarting the Business Space server. When changes actually take effect is not completely known.
When logging JavaScript objects, consider using the FireBug command:
console.debug(object)
This will log the object to the console in an expanded form that allows one to interrogate the object's contents very easily.
While developing Custom Widgets, changes are frequently made to the code files. If a browser caches code, then re-testing can be a challenge. In FireFox 3, the Function Key 5 (F5) causes a re-load of the current page bypassing any cached files.
Assuming you are running the iWidget in FireFox with FireBug installed, adding the JavaScript code statement:
debugger;
causes a breakpoint to be fired when reached which stops the execution and throws you into the FireBug JavaScript debugger.
If the widget appears but there is no flex content, check that the expected SWF file is the one named.
See Also:
Custom Widget Walk through
In this section we will walk through the creation of a trivial custom widget from beginning to end to demonstrate the creation of such an entity. It assumes familiarity with the previous topics
We create a new Dynamic Web based project to hold our new widget. We call the project MyTestWidget and have it associated with a deployable EAR called MyTestWidgetEAR. This project will host the JavaScript and iWidget XML file.
Now we need to create the JavaScript file that will be called to handle events.
dojo.provide("com.sample.MyTestWidget"); dojo.declare("com.sample.MyTestWidget", null, { onLoad: function () { console.log("onLoad called"); }, onUnload: function() { console.log("onUnload called!"); }, onview: function() { console.log("onview"); }, onedit: function() { console.log("onEdit called!"); }, onReload: function() { console.log("onReload called"); }, onRefreshNeeded: function() { console.log("onRefreshNeeded called!"); console.log("Root: " + this.getWidgetRootURI()); console.log("here: " + this.iContext.io.rewriteURI("")); }, onSizeChanged: function(event){ console.log("onSizeChanged called"); console.log("New sizes: width=" + event.payload.newWidth + " height=" + event.payload.newHeight); }, /** * Sample Event handler … */ handleEvent: function(event) { console.log("handleEvent called! : " + event.payload); } });
Create the iWidget XML file. Right click in the Web Content folder of the new project and select create
New > Other. From the Web folder of the New dialog, find and select iWidget.
The name of the new iWidget should be MyTestWidget.
Open the newly created iWidget XML file with the iWidget editor. This may have to be done with the
Open > Other and then select the editor explicitly.
Give values to some of the iWidget attributes such as name and iScope. The iScope parameter MUST has the Dijit name of the widget. Save the result and close the editor.
Here is the data contained in the iWidget XML file:
<?xml version="1.0" encoding="UTF-8" ?> <iw:iwidget <iw:content <![CDATA[ <div>Hello World</div> ]]> </iw:content> <iw:resource </iw:iwidget>
Create a General Project called
MyTestWidgetPackage. This project will be used to hold Business Space widget installation and packaging artifacts.
In the new project, create three simple folders called:
catalog
ear
endpoints
The result should look as follows:
In the catalog folder, create a file called
catalog_MyTestWidget.xml and in the folder called endpoints create a file called
endpoints.xml. These should be created as simple files.
Copy the following XML fragment into the content of the file
catalog_MyTestWidget.xml. This fragment is a template for what we need and will be further edited.
<?xml version="1.0" encoding="UTF-8"?> <catalog id="myWidget"> <resource-type>Catalog</resource-type> <category name="myWidget"> <title> <nls-stringMy Widget</nls-string> </title> <description> <nls-stringMy Widget description.</nls-string> </description> <entry id="{mynamespace}myWidget" unique- <title> <nls-stringMy Widget Title 2</nls-string> </title> <description> <nls-stringMy Widget Description 2</nls-string> </description> <definition>/WebRoot/myWidget.xml</definition> <preview>/WebRoot/images/preview_myWidget.gif</preview> <icon>/WebRoot/images/icon_myWidget.gif</icon> <previewThumbnail>/WebRoot/images/thumb_myWidget.gif</previewThumbnail> <shortDescription> <nls-stringMyWidget", "refVersion":"1.0.0.0" }] </metadata> </entry> </category> </catalog>
Change the following:
All references to myWidget to be MyTestWidget
All references to WebRoot to be MyTestWidget
The result will be:
<?xml version="1.0" encoding="UTF-8"?> <catalog id="MyTestWidget"> <resource-type>Catalog</resource-type> <category name="MyTestWidget"> <title> <nls-stringMy Test Widget</nls-string> </title> <description> <nls-stringMy Test Widget description.</nls-string> </description> <entry id="{mynamespace}MyTestWidget" unique- <title> <nls-stringMy Test Widget Title 2</nls-string> </title> <description> <nls-stringMy Test Widget Description 2</nls-string> </description> <definition>/MyTestWidget/MyTestWidget.xml</definition> <preview>/MyTestWidget/images/preview_myWidget.gif</preview> <icon>/MyTestWidget/images/icon_myWidget.gif</icon> <previewThumbnail>/MyTestWidget/images/thumb_myWidget.gif</previewThumbnail> <shortDescription> <nls-stringMy MyTestWidgetTestWidget", "refVersion":"1.0.0.0" }] </metadata> </entry> </category> </catalog>
Copy the following XML fragment into the endpoints.xml file:
<?xml version="1.0" encoding="UTF-8"?> <BusinessSpaceRegistry xmlns="" xmlns: <Endpoint> <id>{mynamespace}myWidget</id> <type>{mynamespace}myWidget</type> <version>1.0.0.0</version> <url>/WebRoot/</url> <description>Location of MyWidget</description> </Endpoint> </BusinessSpaceRegistry>
Change all occurrences of myWidget to MyTestWidget and the WebRoot to also be MyTestWidget. The result will be:
<?xml version="1.0" encoding="UTF-8"?> <BusinessSpaceRegistry xmlns="" xmlns: <Endpoint> <id>{mynamespace}MyTestWidget</id> <type>{mynamespace}MyTestWidget</type> <version>1.0.0.0</version> <url>/MyTestWidget/</url> <description>Location of MyWidget</description> </Endpoint> </BusinessSpaceRegistry>
Now we want to generate the EAR file for the MyTestWidget Web project and save the result in the file system underneath the ear folder in the packaging project.
Refreshing the packaging project now shows that the EAR is contained in the ear folder:
Generate a ZIP file containing just these folders and their contents. This can be done through the ID Export option. Remember to select "Create only selected directories" to ensure that no extra directories are created that we do not want.
If examined in a ZIP tool, the following would be shown:
Once the ZIP file has been created, the Widget is ready to be installed. Use the wsadmin script to install the widget. Make sure that the script is pointing to the ZIP file that was just created. See Registering Widgets. After installation has been completed, restart the WPS server to ensure that all changes have taken effect. Once the server has been restarted, Business Space can be launched. In the page editing section, we will now see a new widget that can be added to a page:
Once added, we can see it in place within the Business Space environment:
It isn't a very exciting widget … but it is indeed a custom widget.
Using RAD 8.0.3 to create an iWidget
Mashup Center
See also:
Multiple Browser instances and BPM
When developing or working with BPM solutions, it is not uncommon to want to work with multiple browsers open on your desktop to a variety of BPM applications. Such applications can include:
In a secure WAS environment, each of these applications requires you to authenticate with the target WAS server before the application can be used. Unfortunately, this can cause a problem. To understand this, let us examine how WAS authentication through a browser works.
When you login to WAS and provide a user name and password, that data is sent to WAS only once. WAS validates that the user name and password match and generates a security token. This token is probably no more than a long sequence of characters. When the browser subsequently interacts with WAS, the token is passed back from the browser back to WAS. On seeing this token, WAS now knows who you are and trusts the previous authentication. This means that the userid and password only ever flowed to WAS once. All transmissions between the browser and WAS occur over the encrypted HTTPS (SSL) transport and hence the content of the token is never exposed on the network and can't be sniffed and replayed by other users.
When the token is originally generated by WAS and sent back to the browser, the token is saved locally by the browser in the form of a cookie. This cookie containing the token is what is sent back to WAS when the browser makes subsequent calls back to WAS.
So far ... no problems.
Now imagine bringing up two browser windows or tabs running in the same browser. If we sign-on to a WAS based application on one window, a token is created and saved in the local cookie store. If we sign-on to WAS in the second window, again a token is created and saved in the local cookie store. The problem is ... is that there is only one cookie store shared by all browser windows/instances. So if you sign-in as user "A" in one browser instance and then sign-in as user "B" in a second browser instance, the token/cookie for user "A" is replaced with the token/cookie for user "B".
From a users perspective, this manifests itself as either getting unexpected results when working with WAS applications in different browser windows or else we get additional requests to authenticate as the cookies are constantly being expired and refreshed.
Fortunately, there is a solution.
When we use the FireFox browser, each instance of the browser can have its own private profile. Think of this as a complete set of configurations including the storage area where cookies are saved. If we want to have multiple browsers up and running then we can launch multiple instances of FireFox, each with its own profile.
The FireFox program has two command line flags that should be supplied:
-ProfileManager
-no-remote
The first parameter causes FireFox to display the ProfileManager dialog which allows us to create and select the profile to be used.
The second parameter forces FireFox to use a second profile even if an existing instance of FireFox is already running. Without this flag, a second profile will be ignored and FireFox will use the profile in effect for the first instance started.
The ProfileManager dialog is shown next:
Use the Create Profile button to create as many profiles as desired. To start FireFox with a specific profile, select it and click the Start Firefox button.
Note that multiple tabs in a single instance of FireFox will always share the same profile so utilize multiple profiles and hence multiple browser instances to keep them separate.
Business Space Supplied Widgets
Business Space comes with a variety of Widgets. As other BPM products are installed, so too are additional sets of Widgets.
Business Configuration
Business Rules
Human Task Management
The Human Task Management category of Business Space contains the following widgets:
Escalations List
Human Workflow Diagram
A BPEL process can contain a set of Human Tasks. The Human Workflow Diagram widget allows us to visualize the human tasks within instances of BPEL processes and see where we are within the process with respect to the human tasks being executed. It dynamically examines the process associated with a selected task and draws a picture of where that task is within the process relative to other tasks.
The following illustrates an example of the Human Workflow Diagram.
The widget responds to the following events:
An example wiring of this widget would be to a Tasks List widget with:
Tasks List (Item Selected) → Human Workflow Diagram (Open)
My Team's Tasks
My Work Organizer
Process Definitions List
Processes List
Task Definitions List
Task Information
Tasks List
|| |Action Requested|| |Focus Changed|| |Items Selected|| |Task Released|| |Task Delegated|| |Task Terminated|| |Task Deleted|| |Task Claimed|| |Escalation Started||
Problem Determination
Solution Administration
Solution Operation
User Management
Viewers
Web Viewer
The Web Site viewer widget displays the contents of a web site. The web site displayed can be configured in the settings for the widget or can be passed in via an event definition.
Script Adapter
The Script Adapter widget can be wired to receive events published by any other widget. When it receives an event, it can then forward that event onwards to any other wired widget. The value of this is two-fold. First, it can be used during widget development for debugging. When one widget publishes an event, the fact that the event was published and its payload can be logged by the Script Adapter. Secondly, JavaScript source code can be supplied as a configuration parameter to the Script Adapter widget. This JavaScript can operate against the payload data and potentially massage or transform its content. The passed in data is available in a variable called payload. Payload will be a String. If it contains JSON encoded data, then the data will have to be expanded. An example of this is:
var myObject = eval('(' + payload + ')');
Visual Step
JSPs
See Also:
WebSphere Portal
See also:
Liferay
Liferay is an Open Source Portal environment.
Installing Liferay on WAS
Liferay can be installed on WAS v8 environment. Since we are working with IBM BPM, chances are good that our familiarity with WAS v8 will be higher than other Java EE platforms.
We start our installation by creating a new WAS profile. I'll assume you know how to do that. Create the profile with no special augmentations.
Download the Liferay package without a bundled Java EE environment. This can be found in the Additional Files page at the Liferay web site:
A Zip file called "
liferay-portal-depenencies" is supplied which contains JAR files that need to be added to the WAS class path. As of writing, these are:
These should be copied to
<WAS>/lib/ext
Now we start the WAS Server. Experience has shown that the default max heap size of 256MB is not enough. I increased to 512MB. Once started, bring up the WAS Admin console and install the Liferay WAR file. Accept all the default options. The WAR is pretty large, it make take a few moments to upload and then parse for installation.
Using the Liferay Tomcat bundle
One of the bundles available for Liferay is an integrated Tomcat environment. After extracting the content to a folder, we can launch the Tomcat environment using:
<Liferay>/tomcat/bin/startup
Developing Liferay Portlets
First we will want to install the Liferay development environment. The full recipe for this can be found in the Liferay documentation but here are some notes that I used to get it working. First I downloaded Eclipse for Java EE 4.2.1. Once launched, I used the Eclipse in-built updated to install the Liferay IDE from the following Eclipse update site: IDE/1.6.1/updatesite/
Liferay supports the JSR-286 Portlet Specification
See also:
Lotus Forms
See Also:
Dojo
Custom Dojo development environment
At times we want to work with the Dojo generated by WID. WID places these files in a Web Project for deployment to the WPS server for subsequent retrieval by Business Space. If we want to modify the generated HTML files, we find that we are constantly redeploying the Web project so that the changes become visible. During development of UIs, we constantly find ourselves wishing to make changes so this update/publish sequence can be annoying. Fortunately, there is an elegant solution.
When the web project containing the HTML is published to WPS, the files for the HTML can be accessed from the file system under the WPS profile directory. Changes made to these files are immediately picked up.
In the following walk-through, assume that the Web Project hosting the Dojo/HTML files is called DojoHolder and that an example HTML file is called MyHTML.html. DojoHolder is hosted by the EAR called DojoHolderApp.
{WPS Profiles}/{Profile Name}/installedApps/{Cell Name}/DojoHolderApp.ear/DojoHolder.war
we will find the files in the DojoHolder Web Project. Editing these will provide real-time changes to the files as served by WPS.
Rather than editing these files with notepad or some similar editor, we ideally want to edit them with a JavaScript editor such as is found in WID. It has been found that if we create a new WID Static Web project we can then link in these file system files to the web project and edit within WID. This Web Project will never be published and is only a wrapper to allow us access to the files.
See also:
See also:
Flex and Business Space
Flex is UI technology from Adobe that allows a developer to create fantastic user interfaces very easily. Flex is the combination of:
Widgets that use Flex
Here is a list of widgets that are known to use Flex. There may very well be others. This list is useful if reverse engineering is needed to see how a technique was done.
Flex Custom Widgets in Business Space
Business Space is the BPM framework for hosting “Widgets” that allow end users to interact with IBM’s BPM products.
Business Space provides the ability to create new customer written widgets that can add or replace functions for end user interaction. These are new widgets are generally called ‘custom widgets’. The creation of a general custom Business Space widget is described in detail at Custom Widgets.
The goal of this section is to provide additional knowledge on creating end user interfaces using Flex and that will be hosted as Custom Widgets in a Business Space environment.
Using Flex components, a user interface can very quickly be created. The next question is how can this be visualized in the IBM Business Space?
The answer to this is to understand that a Business Space Custom Widget is a combination of the following technologies:
To create a custom widget, the developer must be aware of all of these technologies and more. This is a steep learning curve.
Fortunately, there is a relatively easy solution.
What if we could create a Business Space custom widget that could generically host a Flex application? If designed and implemented properly, the task of creating a new custom widget utilizing Flex would solely be that of building a Flex application solution and the custom widget could simply be told which Flex application to load. This would dramatically reduce the burden of implementation and allow the UI designers to focus exclusively in their area of comfort and expertise … that being Flex.
At a high level, this solution would look as follows:
A Business Space user will open the web page to the Business Space environment and either add a new widget or see existing widgets on their page. These widgets are written in the combination of JavaScript and Dojo. The widget will insert an Adobe Flash Player object into the page using HTML and the flash player will then load the Flex application. The Flex application can communicate directly with the BPM environment using REST or other communication calls as well as interact with the Widget that loaded it.
Again, it needs to be stressed, that the designer of the user interface need only concentrate on their logical function and not be aware at all of the Widget and Business Space interactions. All they see is the clean world of Flex programming.
We will call such a generic Flex wrapper for Business Space by the name BSFlex.
Building a new Custom Widget for Flex
The construction of a new Custom Widget needs WID for its design and configuration. Create a new Dynamic Web project. In that Dynamic Web Project, add the following supplied files into the WebContent folder:
After adding the files to the project, the file structure should look as follows:
The files that were added were:
Now we need to rename these files. Let us assume that our new widget is going to be called “MyTest”
The mapping of file names becomes:
|| |images/Icon_160x125.png|unchanged| |images/Icon_20x20.png|unchanged| |images/Icon_64x48.png|unchanged| |BSpaceCommonUtilityLoader.js|unchanged| |Flex.js|MyTest.js| |Flex_iWidget.xml|MyTest_iWidget.xml|
The resulting contents of the project after renaming looks like:
Next we must edit the content of some of these files.
The files that must be edited are:
MyTest.js
MyTest_iWidget.xml
Within these files, the places to be changed are marked with
** CHANGE **
The change is to replace the word “flex” or “Flex” with “myTest” or “MyTest”.
Copy the XXXRegistryEndpoints.xml and XXXRegistryWidgets.xml file to the WPS <Profile>/BusinessSpace/registryData folder/directory.
Stop and restart the WAS application called BusinessSpaceManager.
From the Flex perspective, an Adobe Flex Builder project has been supplied which contains the necessary functions for the framework to execute. Rename the FlexWidget.mxml file to be the same name as the target widget.
Environment of the Flex application
When the Flex application has been loaded, it is passed some properties from the Business Space widget. These properties can be used by the Flex programmer to communicate with BPM and Business Space.
The properties passed in can be found in the Application.application.parameters object
|| |Property|Type|Description| |iWidgetId|String|The ID of the Dijit widget in the Business Space| |widgetBaseUri|String|The URL of the Web application associated with the Business Space widget| |baseUri|String|Protocol/host/port to the server hosting business space|
Widget Instance Configuration
Every Business Space widget has configuration data available to it. The BSFlex wrapper needs to be informed when the user has selected configuration in Business Space.
In our Flex application, we must register a callback from Business Space which is informed when a configure request has been issued. The following code should be added that is invoked early:
ExternalInterface.addCallback("doConfigure", doConfigure);
The function registered is called (with no parameters) when configuration is requested because the user has selected Configure from the menu for the widget. The name of the callback must be doConfigure. When the doConfigure function in Flex is called, it should visualize the configuration to allow the user to change properties. This is the next section.
Our BSFlex wrapper provides an object called <local:Configuration>. This visual component loads and saves data from the Business Space persistent store.
Custom configuration for the BS Widget is achieved through modification of this widget to display the configuration desired.
The exposed (public) information for this object is:
function loadAttributes(): void
Load the attributes for this instance of the widget.
var attributes:Object
This variable holds the attributes of the widget. This object can be used globally to get the values saved for this widget during configuration. The object should never be written to outside of the context of a configuration edit.
event: endConfigure
Event issued when the configuration has completed (Apply or Cancel pressed).
The basic visual looks as follows:
When the Apply button is pressed, the values of the attributes object are saved back to Business Space. If the Cancel button is pressed, nothing is saved back to the server.
When either Apply or Cancel are pressed, an event is generated called endConfigure that flags the configuration as over.
It is anticipated that this component will be included in a ViewStack container and shown when configuration of the Widget is requested. When the endConfigure event is received, the widget will be hidden from the stack.
Example:
Imagine that our widget has three attributes called “a”, “b” and “c”. The Configuration.mxml Flex source file would be modified to present visualization of these values. The data for the values must be held off the “attributes” variable as this is the data that is loaded and saved when the widget is used. The “attributes” variable is public from this flex file and hence can be read and written to globally. From a Flex programmer’s perspective, the only customization needed is to code the function called setAttributes() which is also in Configuration.mxml. This function should populate the attributes object from the current settings of the configuration visuals.
Making REST requests
In many cases, the Flex BS Widget will want to make REST requests back to the server to send and receive information. This is easily achieved in Flex through the HTTPService object.
Here is an example:
import mx.rpc.http.HTTPService; import mx.rpc.AsyncToken; import mx.rpc.events.ResultEvent; var h1:HTTPService = new HTTPService(); var baseUri:String = Application.application.parameters["baseUri"]; h1.url = baseUri + "/rest/bpm/monitor/models"; var asyncToken:AsyncToken = h1.send(); asyncToken.addResponder(new mx.rpc.Responder( function(result:ResultEvent): void { var respData:Object = JSON.decode(String(result.result)); // Do something … return; }, function(fault:FaultEvent): void { trace("Fault caught: " + ObjectUtil.toString(fault)); }));
Although this may look a little scary at first, it can be quickly understood. First we create an instance of the HTTPService object which knows how to make a REST request. Next we get the base URI that will be the server target of the request. We then append to this the target specific data and set this to be the url property on the HTTPService object. We then send the request which returns an asyncToken object. To this we add the callback function that will be invoked when the response is available.
When using REST, we often find that we want to subvert browser security, thankfully that is handled by the Ajax Network Proxy supplied with Business Space. This can be reached at:
/mum/proxy
For example:
Prior to 7.5.1, the Proxy was wide open meaning that any redirections were possible. From 7.5.1 onwards, Proxy configuration was tightened. The proxy configuration file is called "proxy-config.xml" and can be found at:
<Profile Name>/BusinessSpace/<nodeName>/<serverName>/mm.runtime.prof/config
After making these changes, the AdminTask.updateBlobConfig wsadmin command must be executed. Details of this can be found in the BPM InfoCenter. An example would be:
AdminTask.updateBlobConfig('[-serverName server1 -nodeName win7-x64Node01 -propertyFileName "C:\IBM\WebSphere\AppServer\profiles\ProcCtr01\BusinessSpace\win7-x64Node01\server1\mm.runtime.prof\config\proxy-config.xml" -prefix "Mashups_"]') AdminConfig.save()
To switch off security for the Proxy, an entry such as the following may be added to
proxy-config.xml:
<proxy:policy <proxy:actions> <proxy:method>GET</proxy:method> <proxy:method>POST</proxy:method> <proxy:method>PUT</proxy:method> <proxy:method>DELETE</proxy:method> </proxy:actions> <proxy:headers> <proxy:header>Cache-Control</proxy:header> <proxy:header>Pragma</proxy:header> <proxy:header>User-Agent</proxy:header> <proxy:header>Accept*</proxy:header> <proxy:header>Content*</proxy:header> <proxy:header>X-Method-Override</proxy:header> <proxy:header>X-HTTP-Method-Override</proxy:header> <proxy:header>If-Match</proxy:header> <proxy:header>If-None-Match</proxy:header> <proxy:header>If-Modified-Since</proxy:header> <proxy:header>If-Unmodified-Since</proxy:header> <proxy:header>Slug</proxy:header> <proxy:header>SOAPAction</proxy:header> </proxy:headers> <proxy:cookies> <proxy:cookie>LtpaToken</proxy:cookie> <proxy:cookie>LtpaToken2</proxy:cookie> <proxy:cookie>JSESSIONID</proxy:cookie> </proxy:cookies> </proxy:policy>
If you are using the Chrome web browser, it has a command line option called "
--disable-web-security" that switches off web security (Same Origin Policy) for that instance of the browser. This is useful for development but should never be used or suggested for production. In later versions of Chrome, we must also ass "
--user-data-dir".
You will know it is working because you will see a warning message:
See also:
Handling returned XML
Some of the REST requests return XML data. By default, this XML is parsed into an Object. If we want the pure XML text, we need to set the resultFormat property of the HTTPService object to “text”. It has been found that the XML returned contains carriage-return/line-feed characters (i.e “\r\n”). To remove the carriage-return, the following AS3 can be used:
var data1:String = String(result.result); var p1:RegExp = new RegExp("\r", "g"); data1 = data1.replace(p1, "");
Cross domain security
A Flex application that wishes to call a service in a machine other than that from which the Flex application was loaded will be disallowed by default. This protects the Flex sandbox from breaking security protocols. For development testing, create a file called crossdomain.xml and have it available for download from the machine that the REST request is targeted to. The content of the file should look as follows:
<?xml version="1.0"?> <cross-domain-policy> <allow-access-from </cross-domain-policy>
Be aware that this will allow ANY Flex application to connect to the server. This is usually fine for testing. Before setting up cross domain security, first test to see if the application works without it. For BPM apps it seems to work fine probably due to explicit authentication.
Problems with PUT and DELETE requests
Unfortunately, Flex’s HTTPService object disallows both PUT and DELETE requests. What this means is that a complete section of WPS REST interfaces appear to be inaccessible. Fortunately, WPS claims to accept the X-Method-Override capability.
|| |Bug
The problem with this is that it appears not to actually work. PMR 79493,004,000 has been raised to address the problem. As of 2009-07-02 this has been partially fixed with an APAR available from support called IZ52208. This problem no longer exists in the latest versions of WPS with the latest fixpacks applied.|
An example of this would be
h1.method = "POST"; h1.headers = {"X-Method-Override": "PUT"};
Widget to Widget Event Handling
Event handling is the idea that a Business Space widget can be a source or destination of events. An event is simply the transmission of some data from one widget to another. The data can be anything that the Flex programmer chooses to transmit.
Sending Events
A Flex application can send an event directly to another widget. The way to achieve this is illustrated in the following code fragment:
var iWidgetId:String = FlexGlobals.topLevelApplication.parameters.iWidgetId; ExternalInterface.call("_" + iWidgetId + "_iContext.iEvents.publishEvent", "eventName", "parms");
Old technique
Sending an event is accomplished in two parts. First the flex application will make a call back to the JavaScript wrapper:
var iWidgetId:String = FlexGlobals.topLevelApplication.parameters.iWidgetId; ExternalInterface.call("_" + iWidgetId + "_iContext.iScope().funcName", parms);
In the JavaScript file, we need to code something like the following to actually execute the event publish.
this.iContext.iEvents.publishEvent(eventName, payload);
This needs to be wrapped in the function that the Flex application will invoke through the ExternalInterface call.
eventPublish_markerClicked: function(payload) { this.iContext.iEvents.publishEvent("com.kolban.map.MarkerClicked", payload); }
Convention has us declare the function with the name:
eventPublish_<event name>
The iWidget.xml file for the custom widget must be modified to declare that the widget is capable of publishing events. Code similar to the following should be added:
<iw:eventDescription <iw:event
The name of the event to be published is found in the iw:event@id location.
Unfortunately, we can't call the fireEvent wrapper function directly. This is because the function is defined on the JavaScript object that represents the widget and not on the page itself. In WPS 7.0, when a Business Space widget is on a page, the JavaScript object that represents that widget is hooked of the root of the HTML DOM tree. It appears to have a name of
_iWidgetId_IContext
This object has a function upon it called iScope(). This returns the JavaScript object that we wish to access.
From this a Flex application can call the functions in that widget directly. From within Flex, we can then call functions on that object as shown in the following example:
var iWidgetId:String = FlexGlobals.topLevelApplication.parameters.iWidgetId; ExternalInterface.call("_" + iWidgetId + "_iContext.iScope().testFunc", "Hello World");
The iWidgetId can be passed into flex from the JavaScript variable
this.iContext.io.id
Receiving Events
Receiving events sent from another Widget is a little trickier.
In the receiving Flex application, a function needs to be created with the signature:
private function <name>(payload:Object) : void
This is the function that is to be called when an event transmitted by a partner widget has been received. It is in this function that the Flex code for processing the event will be written.
This function needs to be exposed to the surrounding JavaScript with a call to the Flex provided class called ExternalInterface such as:
ExternalInterface.addCallback("<name>", name);
This will allow the surrounding JavaScript to call the method when an event arrives. A suitable place for adding this code is in the init() method.
In the iWidget XML file, the fact that this widget can now subscribe to incoming events must also be registered:
<iw:eventDescription </iw:eventDescription> <iw:event
In the JavaScript for the iWidget, a callback handler must be defined:
eventSubscribe_mapInput: function(event) { var swfId = this.iContext.widgetId + "_" + this.widgetName; if (dojo.isIE) { window[swfId].eventSubscribe_mapInput(event.payload); } else { document[swfId].eventSubscribe_mapInput(event.payload); } }
Working with WPS Human Task / Process Data
WebSphere Process Server has the notion of Business Objects. Both a BPEL process and a Human Task can take one or more Business Objects as input and return one or more Business Objects as outputs. On occasion (and especially with Human Tasks) we may wish the input to be presented to the user and have a response returned to the process or task (we will focus now on just tasks, but the same applies to processes).
WPS internally represents a Business Object definition as an XML Schema and a Business Object instance as an XML document corresponding to that schema. When we make REST calls to WPS to get Human Task input data, we are returned an instance of an XML document. If we want to send new data to the Human Task as output data for that task, we would supply an XML document.
Through the REST APIs we can ask for an instance of task data. The following code fragment illustrates how this can be done:
h1.url = "" + tkiid + "/input"; h1.method = "GET"; h1.resultFormat = HTTPService.RESULT_FORMAT_E4X; var asyncToken:AsyncToken = h1.send(); asyncToken.addResponder(new mx.rpc.Responder( function(result:ResultEvent) : void { var myXML:XML = XML(result.result); // Do something with the XML }, function(fault:FaultEvent) : void { trace("Got a fault!"); } ));
What we end up with is a Flex XML object. If the variable holding this data is held at the highest level and defined as bindable … for example:
[Bindable] private var myXML:XML;
Then the fields in the data can be accessed through Flex bindings.
Let us now work through an example of this. Imagine we have a Business Object that is defined as follows:
It is used in a Human Task Interface that looks like:
The XML document retrieved via a REST call to WPS might look as follows:
<?xml version="1.0" encoding="UTF-8"?> <p:mailing_._type xsi: <input> <street>9200 Glenhaven</street> <city>Fort Worth</city> <state>TX</state> <zip>76182</zip> </input> </p:mailing_._type>
It looks pretty scary … but if we take it apart we have the following:
<root> <input> <street> <city> <state> <zip>
What we find is that the immediate children of the document are the input parameters. The tags are named after the names of the parameters. In this case the tag called input matches the parameter called input found on the Interface.
The children of the parameter tags are the data. In this case, a data type called Address which matches the BO definition.
When this is assigned to a Flex XML object, we can then address the fields contained within such as:
[Bindable] var myData:XML = … var street:String = myData.input.street; var state:String = myData.input.state;
If we then use Flex Binding, we can display a field in a TextInput Flex component with the following:
<mx:TextInput
Mapping Data types and controls
A WPS Business Object field has a finite collection of possible common scalar data types associated with it. These include:
When we look at the input and output data associated with a task, we must realize that the Business Object is serialized to and from an XML document. This then asks the question, what is valid for a given BO field type in the associated XML item?
String
Any character string is allowable.
Int
Any positive or negative numeric characters are allowable
Date
Date is more interesting. The format of the date expected in XML is “YYYY-MM-DD”. This is not the default format of a Flex DateField. DateField has a property called formatString which can be set to “YYYY-MM-DD” to generate the correct format for the XML document.
Working with repeating/array data
Working with AnyType
Performing input validation
Single User Workflow
Single User Workflow is the idea of being presented with a page, completing that page and then immediately being presented with a succeeding page without having to manually claim the task.
InitiateAndClaimFirst
In: processTemplateName
In: InputMessage
Out: AIID
Out: ActivityName
Out: InputMessage
CompleteAndClaimSuccessor
In: AIID
In: OutputMessage
Out: AIID
Out: ActivityName
Out: InputMessage
CompleteAndClaimSuccessor
…
CompleteAndClaimSuccessor
<End>
Flex related REST Problems
Validate that the format of data being sent or received matches the expected format for the HTTPService request.
Use the FireFox 3.5 FireBug tool which can show Flash related communications.
Only a large subset of the BFM and HTM APIs are available via the REST interface. If the other BFM and HTM calls are needed, we seem to be stuck. As a possible workaround, we can create our own REST based servlet that when called, makes the correct local EJB calls. This is not an easy/obvious proposition.
Elixir
References – Elixir
References – Flex Widgets
Custom Process Portals
The IBM BPM framework provides what it calls the "Process Portal". This is an IBM supplied web based application that provides users with the abilities to:
It looks as follows:
The IBM supplied Process Portal is feature rich and extremely powerful. However there is a commonly encountered problem with consumers actually using it. Simply put, it may not be the company's strategic direction for interacting with users. Imagine a clerk responsible for processing insurance claims. This clerk has been trained to use the existing user interfaces of the existing applications. It would not be surprising if multiple distinct applications could be worked upon through this one user interface. If IBM BPM is to be considered as a component in a solution, it may not be desired to use Process Portal for a variety of non-functional business reasons. From a raw technical perspective, it will work just fine … but if Process Portal were used, we have the unfortunate story of the clerk user having to switch from one application to another to perform their work. In addition, extra training will have to be supplied to the clerks to teach them how to use the new user interface. All of this adds up to expense and introduces opportunities for errors. There is low quality in saying "Enter new claim data in this application" but "View claim history in that application".
Fortunately, there is an elegant solution. The IBM BPM product provides programming interfaces (APIs) that can be used by technical programming staff to perform the tasks that are achieved through IBM's supplied Process Portal. These APIs are exposed through the REST style of remote function call. By having such an API available, consumers can build or augment their own existing user interface applications to include access to the features provided by IBM BPM. This section will continue to discuss and dive deeper into that notion.
First of all let us ask ourselves what are the key concepts that we must take into account:
See also:
Types of Custom Portal
Let us start with some simple thoughts on different types of portals. At the highest level we have two basic kinds. Those known as "thick clients" and those that are "browser based". Thick clients are native executables installed locally on consumers desktops. These are applications that may use Windows/.NET APIs, Java Swing or Java SWT (as examples). The second type of process portal are those that run within the browser environment. These are the more common types of custom portals. These can also be broken down into categories based on whether the web page (HTML) is build in the browser (Web 2.0 style) or built on the server.
Browser built HTML technologies includes:
Server built HTML includes:
JSP
JSF
Portlets (JSR168, JSR286) hosted by portal providers
Irrespective of the type of UI technology used, the high level concepts and design remain the same.
Once the task has been selected, we now choose how to display the task data itself. This will either be the Coach UI as an in-line web page perhaps using
iFrame technology or else it will be custom controls/UI using the REST API to get the data for a specific task.
Generic Widgets for Custom Portals
With the idea of Custom Portals in mind, maybe we can design a framework for generic portals? This framework would be as flexible as possible and hide the majority of details from the consumer. To make the solution as flexible as possible, let us assume that we introduce the notion of a "Widget". A Widget is the user interface building block that is responsible for some function.
The Task List Widget
Here is a picture of the IBM Process Portal task list:
As we see, it is very attractive but what does it "logically" contain? If we strip away the superficial colors and styling, what is left?
The answer is that it is a visual container that lists a series of tasks that a user can work upon. This is a core thought. The concept of the Task List is a "container of tasks". It is responsible for determining a list of tasks and then showing each task. If a building block Widget of a Task List were to be created, what would it consist of?
Ignoring its visual appearance, we could define it to have:
With this minimal interface, the Task List widget would then be functional.
After a Task List requests tasks from a BPM Server, the Task List must now display each Task retrieved.
We will now assume the existence of a second type of Widget that we will call the TaskItem. The Task List will create an instance of a TaskItem for each Task that it wishes to display. Since the TaskItem is a widget, it is responsible for displaying its content. Again ignoring the visual appearance of the TaskItem, we could define it as having the following signature:
By generalizing these two functions, we now have all we need to create arbitrary visualizations of a Task List.
Here is an example visualization of a new Task List using these principles:
The Task Table Widget
When we think of a custom portal, we must consider the selection of tasks by a user. The user wishes to see these tasks in a desirable form. Given that the user may have some number of tasks available for them to work upon, one style of task list presentation is that known as the table. The table is pretty much what it sounds like. It is a rectangular array of information composed of rows and columns. Each row will represent a single task and each column will hold some attribute of that task.
The Task Table widget is an alternative to the Task List widget. It presents a table of tasks to the user and allows the user to select a task through the "
Open" button.
This widget has a callback function called "
onTaskSelected" which is invoked and passed an object which contains the taskId of the task that was selected.
The widget exposes a method called "
refreshTasks()" which, when invoked, will retrieve the current set of tasks and refresh the table with the new information.
An example of usage would be:
|| |<div data- <script type="dojo/method"> this.refreshTasks(); </script> <script type="dojo/connect" data- console.log("Connect called: " + value.taskId); myCoachViewer.set("taskId", value.taskId); </script> </div>|
This fragment will create the TaskTable widget, call its
refreshTasks() method and, when a task is selected, call a CoachViewer to show the Coach associated with the task.
The CoachViewer widget
The CoachViewer widget is used to load and view the Coaches for an associated task. It allocates an area of the browser display and when asked to show a Coach, that area then hosts the Coach details. It has a property called "
taskId" that must be set using the widget's "
set()" method. When a new
taskId is supplied, the widget will display the content of the associated Coach.
An example of usage would be:
|| |<div data- </div>|
This can be combined with the
TaskTable widget (see previous) to select which task to show.
The CoachViewer also has a callback function called "
onCompleted" which is called when the user completes the task. This can be used to signal a refresh of the task list or some other function. The parameter passed to the callback is an object which contains:
status – The status of the completion. This may be
"
completed" – to indicate that the coach completed succesfully
"
error" – to indicate that an error was encountered. If the status is error, two additional properties will be available:
A property of the CoachView called "
showStandby" can be set to "
true" to show a "standby" overlay while the Coach is loading.
A property called "
showError" is defined which is a boolean. If set to
true and an error is encountered, a dialog box showing the nature of the error will be displayed. If set to
false, no such dialog will be shown. In either setting, an error will be returned via the
onCompleted callback.
Determining when the current Coach has completed
When writing a custom Portal, the current Coach is usually shown in an
iFrame. When the Coach completes, we somehow need to tell our portal framework that this has happened. It seems that when a Coach completes, it posts a message to the DOM "
window" containing the
iFrame. This is the same window being used by the portal. The following code will register a callback for such an entry:
var onCompleted = function (m) { debugger; } if (typeof window.addEventListener != 'undefined') { window.addEventListener('message', onCompleted, false); } else if (typeof window.attachEvent != 'undefined') { window.attachEvent('onmessage', onCompleted); }
A more modern solution using Dojo would be:
on(window, "message", function(m) { … });
In jQuery, we would use:
jQuery(window).on("message", function(data) {…});
The data passed in here will contain
data.originalEvent.data as the JSON string.
Unfortunately, the callback is invoked on a number of occasions by different parties, not just when we expect, so we have to be careful to check the response.
The passed in "
m" message contains a field called "
data" which appears to contain a single string which is a JSON encoded piece of data that contains:
name – so far we have seen instances of:
taskID
applicationInstanceId
parameters – Can be array of strings. For onError it appears to be a message and a message code.
Unfortunately there is one more wrinkle. In all releases tested so far (up to and including 8.5.5), the "onCompleted" response message includes invalid JSON data. Specifically, the "taskID" property is returned as the text "undefined" with no quotes around it. This breaks JSON.parse(). As such, we can't rely on using JSON parses to parse the data and need to string grep it for what we need.
Using the Custom Portal widgets
Now that we have described the functions of the custom portal widgets, what remains is to describe how to use them.
A Widget is added to a Web Page (a source HTML file). Since the widgets are Dojo, the first thing we have to do is to add the mandatory boiler plate to load the Dojo environment:
<script type="text/javascript" src="/teamworks/script/coachNG/dojo/1.8.6/dojo/dojo.js" data- </script> <link rel="stylesheet" href="/teamworks/script/coachNG/dojo/1.8.6/dojo/resources/dojo.css" /> <link rel="stylesheet" href="/teamworks/script/coachNG/dojo/1.8.6/dijit/themes/claro/claro.css" />
The above must be added to in the
<head> section of the page. The URL to Dojo is good as of IBM BPM 8.5.
Because we are using custom widgets that are not part of the default Dojo distribution, we need to tell the environment where to load those widgets from. This is achieved using the AMD technology. In addition to saying where the custom widgets are located, we also have to say which of those widgets are going to be used in the page. Again in the <head> section, we add the following:
<script type="text/javascript"> require({ packages : [ { name : 'kolban', location : '/StaticTests/kolban' } ] }); require([ "kolban/widget/ProcessStart" ]); </script>
Because we are using Dojo, we must also specify the Dojo theme that we are going to use. The HTML
<body> tag should have the Dojo theme added to it:
<body class="claro">
We are now ready to include any widgets we wish, for example:
<div data- <script type="dojo/connect" data- console.log("Process Started!"); console.dir(processDetails); </script> </div>
Putting it all together, a sample would look like:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <title>Test_ProcessStart</title> <meta http- <script type="text/javascript" src="/proxy/teamworks/script/coachNG/dojo/1.8.3/dojo/dojo.js" data- </script> <link rel="stylesheet" href="/proxy/teamworks/script/coachNG/dojo/1.8.3/dojo/resources/dojo.css" /> <link rel="stylesheet" href="/proxy/teamworks/script/coachNG/dojo/1.8.3/dijit/themes/claro/claro.css" /> <script type="text/javascript"> require({ packages : [ { name : 'kolban', location : '/StaticTests/kolban' } ] }); require([ "kolban/widget/ProcessStart" ]); </script> </head> <body class="claro"> <h1>Test ProcessStart</h1> <p>The ProcessStart Widget presents a visible list of start-able processes. Clicking on one of these entries causes a new instance of that process to start. </p> <hr /> <div data- <script type="dojo/connect" data- console.log("Process Started!"); console.dir(processDetails); </script> </div> <hr /> </body> </html>
Writing custom portals using Coaches
In principle, a custom portal can itself be written as a Coach.
Within a custom portal we can imagine the user being presented with a list of tasks upon which they can work. After selecting such a task, a new window might open which will show the details of the new task. The URL to be used to open the window can be found using the REST API to query upon the client settings of the taskId to be launched. This REST API returns a URL for exactly this purpose. However, there appears to be a problem (as of 8.0.1.1). When the newly opened Coach completes, it seems to cause a "refresh" or "reset" of the Coach that launched it. This means that if we write a Coach which acts as a process portal, select a task and then open that task in a new window, when that new window ends, the original process portal Coach is reset. We do not yet know of a circumvention.
Addition: 2013-10-15: It appears that if we open a new window for a Coach if we set that window's "opener" property to null, the refresh will not happen.
Apache Flex
Flex is a function rich UI development environment that runs within a browser, native on the desktop and within Mobile platforms including Android and iOS. Originally developed by Adobe, it was Open Sourced and provided to the Apache group. The latest information on Flex can be found here:
There are a variety of fee and free development tools for building Flex applications. These include:
Flex for Mobile
One of the key reasons for considering Flex is for building mobile applications (i.e. those that can run on Android or iOS). Flex provides a write-once/run-anywhere model. It should be stressed that a logical "runtime" of the Adobe AIR environment is used but to all intents and purposes building such apps may be considered closer to native Apps than attempting to build HTML5 based applications.
The Flex support for Mobile appears to be first class but restricts the components that can be used. Here is a quick summary of those supported:
|| |StageWebView|Web Browser| |BusyIndicator|| |Button|| |ButtonBar|| |Callout|| |CalloutButton|| |CheckBox|| |DateSpinner|| |HSlider|| |Image|| |Label|| |List|| |RadioButton/RadioButtonGroup|| |SpinnerList|| |TextArea|| |TextInput|| |ToggleSwitch||
|| |DataGroup|| |Group|| |HGroup|| |Scroller|| |Spacer|| |TileGroup|| |VGroup||
Installing FlashDevelop
FlashDevelop is a free, Open Source development environment for Flex based applications:
Google Charts
Google provides a charting package. The URL for this is:
To use this technology, we need to perform some work:
<script type="text/javascript" src=""></script>
google.load('vizualization', '1.0', {'packages': ['corechart']});
google.setOnLoadCallback(function() { … code goes here ... });
Providing data to Google Charts
All Google charts expect data encapsulated in a DataTable object. The name of this object is "google.visualization.DataTable". There are a number of ways to build and populate this object. We will touch upon some of them. For full details, see the full Google documentation.
var data = new google.visualization.DataTable(); data.addColumn('string', 'Name'); data.addColumn('number', 'age'); data.addRows(1); data.setCell(0, 0, 'Bob'); data.setCell(0, 1, 34);
Google Chart – Gauge
The Gauge control provides a "dial" or "gauge" which contains a label and a value. The value is shown as well as a needle that provides a relative indication of where the value falls:
Package: google.load('visualization', '1', {packages: ['gauge']});
var chart = new google.visualization.Gauge(node); chat.draw(data, options);
Page 54 | https://learn.salientprocess.com/books/ibm-bpm/page/user-interfaces | CC-MAIN-2019-22 | refinedweb | 12,475 | 55.24 |
Interpolate data given on an Nd box grid, uniform or non-uniform, using numpy and scipy
Project description
Intergrid: interpolate data given on an N-d rectangular grid
Purpose: interpolate data given on an N-d rectangular grid, uniform or non-uniform, using the fast scipy.ndimage.map_coordinates. Non-uniform grids are first uniformized with numpy.interp.
Keywords, tags: interpolation, rectangular grid, box grid, python, numpy, scipy
Background:
the reader should know some Python and NumPy
(IPython is invaluable for learning both).
For basics of interpolation, see
Bilinear interpolation
on Wikipedia. For
map_coordinates, see the example under
multivariate-spline-interpolation-in-python-scipy
on stackoverflow.
Example
Say we have rainfall on a 4 x 5 grid of rectangles, lat 52 .. 55 x lon -10 .. -6, and want to interpolate (estimate) rainfall at 1000 query points in between the grid points.
from intergrid.intergrid import Intergrid # .../intergrid/intergrid.py # define the grid -- griddata = np.loadtxt(...) # griddata.shape == (4, 5) lo = np.array([ 52, -10 ]) # lowest lat, lowest lon hi = np.array([ 55, -6 ]) # highest lat, highest lon # set up an interpolator function "interfunc()",
- find the square of
griddatait's in, e.g. [52.5, -8.1] -> [0, 3] [0, 4] [1, 4] [1, 3]\
- do bilinear (multilinear) interpolation in that square, using
scipy.ndimage.map_coordinates.
Check:
interfunc( lo ) == griddata[0, 0]
interfunc( hi ) == griddata[-1, -1] i.e.
griddata[3, 4]
Parameters
Methods
After setting up
interfunc = Intergrid(...), either
query_values = interfunc.at( query_points ) # or query_values = interfunc( query_points )
do the interpolation. (The latter is
__call__ in python.)
Non-uniform rectangular grids
What if our griddata above is at non-uniformly-spaced latitudes,
say [50, 52, 62, 63] ?
Intergrid can "uniformize" these
before interpolation, like this:
lo = np.array([ 50, -10 ]) hi = np.array([ 63,
Mapping details
- a callable function: e.g.
np.logdoes
query_points[:,j] = np.log( query_points[:,j] )
- a sorted array describing a non-uniform grid:
query_points[:,j] =
np.interp( query_points[:,j], [50, 52, 62, 63], [0, 1, 2, 3] )
Download
git clone # ? pip install --user git+ # ? pip install --user intergrid # tell python where the intergrid directory is, e.g. in your ~/.bashrc: # export PYTHONPATH=$PYTHONPATH:.../intergrid/ # test in python or IPython: from intergrid.intergrid import Intergrid # i.e. .../intergrid/intergrid.py
Splines.
<small>
Fine print: is global, with IIR falloff ~ 1 / 4^distance.
(I don't know of test images that show a visible difference to local C-R).
Confusingly, the term "Cardinal spline" is sometimes used
for local (C-R, FIR),
and sometimes for global (IIR prefilter, then B-spline).
Intergrid( ... prefilter = False | True | 1/3 )
specifies the kind of spline, for
order >= 2:
prefilter=0 or
False, the default:.
Prefiltering is a clever transformation
such that
Bspline( transform( data )) = exactfitspline( data ).
It is described in a paper by M. Unser,
Splines: A perfect fit for signal and image processing ,
1999.
</small>
Uniformizing a grid with PWL, then uniform-splining, is fast and simple, but not as smooth as true splining on the original non-uniform grid. The differences will of course depend on the grid spacings and on how rough the function is.
Notes.
Beware of overflow: interpolating uint8 s can give values outside the range 0 .. 255.
(Interpolation in
d dimensions can overshoot by (9/8)^d .) with
order=1 looks at 32 corner values, with average weight 3 %.
If the weights are roughly equal
(which they will tend to be, by the central limit theorem ?),
sharp edges or gradients will be blurred, and colors mixed to a grey fog.
To see how different interpolators affect images, run matplotlib
plt.imshow( interpolation = "nearest" / "bilinear" / ... ) .
Kinds of grids ...
Run times
See also
scipy.ndimage.interpolation.map_coordinates
scipy reference ndimage
stackoverflow.com/questions/tagged/scipy+interpolation
interpol 2014 -- intergrid + barypol
Google "regrid | resample"
pip search interpol (also gets string interpolation)
and testcases most welcome
— denis-bz-py at t-online dot de
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/intergrid/ | CC-MAIN-2022-27 | refinedweb | 672 | 51.44 |
Command Duration¶
In some types of games a command should not start and finish immediately. Loading a crossbow might take a bit of time to do - time you don’t have when the enemy comes rushing at you. Crafting that armour will not be immediate either. For some types of games the very act of moving or changing pose all comes with a certain time associated with it.
The simple way to pause commands with yield¶
Evennia allows a shortcut in syntax to create simple pauses in commands.
This syntax uses the
yield keyword. The
yield keyword is used in
Python to create generators, although you don’t need to know what
generators are to use this syntax. A short example will probably make it
clear:
class CmdTest(Command): """ A test command just to test waiting. Usage: test """ key = "test" locks = "cmd:all()" def func(self): self.msg("Before ten seconds...") yield 10 self.msg("Afterwards.")
The important line is the
yield 10. It tells Evennia to “pause” the
command and to wait for 10 seconds to execute the rest. If you add this
command and run it, you’ll see the first message, then, after a pause of
ten seconds, the next message. You can use
yield several times in
your command.
This syntax will not “freeze” all commands. While the command is “pausing”, you can execute other commands (or even call the same command again). And other players aren’t frozen either.
Note: this will not save anything in the database. If you reload the game while a command is “paused”, it will not resume after the server has reloaded.
The more advanced way with utils.delay¶
The
yield syntax is easy to read, easy to understand, easy to use.
But it’s not that flexible if you want more advanced options. Learning
to use alternatives might be much worth it in the end.
Below is a simple command example for adding a duration for a command to finish.
from evennia import default_cmds, utils class CmdEcho(default_cmds.MuxCommand): """ wait for an echo Usage: echo <string> Calls and waits for an echo """ key = "echo" locks = "cmd:all()" def func(self): """ This is called at the initial shout. """ self.caller.msg("You shout '%s' and wait for an echo ..." % self.args) # this waits non-blocking for 10 seconds, then calls self.echo utils.delay(10, callback=self.echo) # call echo after 10 seconds def echo(self): "Called after 10 seconds." shout = self.args string = "You hear an echo: %s ... %s ... %s" string = string % (shout.upper(), shout.capitalize(), shout.lower()) self.caller.msg(string)
Import this new echo command into the default command set and reload the server. You will find that it will take 10 seconds before you see your shout coming back. You will also find that this is a non-blocking effect; you can issue other commands in the interim and the game will go on as usual. The echo will come back to you in its own time.
About utils.delay()¶
utils.delay(delay, callback=None, *args, **kwargs) is a useful
function. It will wait
delay seconds, then call a function you give
it as
callback(*args, **kwargs).
If you are not familiar with the syntax
*argsand
**kwargs, see the Python documentation here.
Looking at it you might think that
utils.delay(10, callback) in the
code above is just an alternative to some more familiar thing like
time.sleep(10). This is not the case. If you do
time.sleep(10)
you will in fact freeze the entire server for ten seconds! The
utils.delay()is a thin wrapper around a Twisted Deferred that
will delay execution until 10 seconds have passed, but will do so
asynchronously, without bothering anyone else (not even you - you can
continue to do stuff normally while it waits to continue).
The point to remember here is that the
delay() call will not “pause”
at that point when it is called. The lines after the
delay() call
will actually execute right away. What you must do is to tell it which
function to call after the time has passed (its “callback”). This may
sound strange at first, but it is normal practice in asynchronous
systems. You can also link such calls together as seen below:
from evennia import default_cmds, utils class CmdEcho(default_cmds.MuxCommand): """ waits for an echo Usage: echo <string> Calls and waits for an echo """ key = "echo" locks = "cmd:all()" def func(self): "This sets off a chain of delayed calls" self.caller.msg("You shout '%s', waiting for an echo ..." % self.args) # wait 2 seconds before calling self.echo1 utils.delay(2, callback=self.echo1) # callback chain, started above def echo1(self): "First echo" self.caller.msg("... %s" % self.args.upper()) # wait 2 seconds for the next one utils.delay(2, callback=self.echo2) def echo2(self): "Second echo" self.caller.msg("... %s" % self.args.capitalize()) # wait another 2 seconds utils.delay(2, callback=self.echo3) def echo3(self): "Last echo" self.caller.msg("... %s ..." % self.args.lower())
The above version will have the echoes arrive one after another, each separated by a two second delay.
> echo Hello! ... HELLO! ... Hello! ... hello! ...
Blocking commands¶
As mentioned, a great thing about the delay introduced by
yield or
utils.delay() is that it does not block. It just goes on in the
background and you are free to play normally in the interim. In some
cases this is not what you want however. Some commands should simply
“block” other commands while they are running. If you are in the process
of crafting a helmet you shouldn’t be able to also start crafting a
shield at the same time, or if you just did a huge power-swing with your
weapon you should not be able to do it again immediately.
The simplest way of implementing blocking is to use the technique covered in the Command Cooldown tutorial. In that tutorial we implemented cooldowns by having the Command store the current time. Next time the Command was called, we compared the current time to the stored time to determine if enough time had passed for a renewed use. This is a very efficient, reliable and passive solution. The drawback is that there is nothing to tell the Player when enough time has passed unless they keep trying.
Here is an example where we will use
utils.delay to tell the player
when the cooldown has passed:
from evennia import utils, default_cmds class CmdBigSwing(default_cmds.MuxCommand): """ swing your weapon in a big way Usage: swing <target> Makes a mighty swing. Doing so will make you vulnerable to counter-attacks before you can recover. """ key = "bigswing" locks = "cmd:all()" def func(self): "Makes the swing" if self.caller.ndb.off_balance: # we are still off-balance. self.caller.msg("You are off balance and need time to recover!") return # [attack/hit code goes here ...] self.caller.msg("You swing big! You are off balance now.") # set the off-balance flag self.caller.ndb.off_balance = True # wait 8 seconds before we can recover. During this time # we won't be able to swing again due to the check at the top. utils.delay(8, callback=self.recover) def recover(self): "This will be called after 8 secs" del self.caller.ndb.off_balance self.caller.msg("You regain your balance.")
Note how, after the cooldown, the user will get a message telling them they are now ready for another swing.
By storing the
off_balance flag on the character (rather than on,
say, the Command instance itself) it can be accessed by other Commands
too. Other attacks may also not work when you are off balance. You could
also have an enemy Command check your
off_balance status to gain
bonuses, to take another example.
Abortable commands¶
One can imagine that you will want to abort a long-running command before it has a time to finish. If you are in the middle of crafting your armor you will probably want to stop doing that when a monster enters your smithy.
You can implement this in the same way as you do the “blocking” command above, just in reverse. Below is an example of a crafting command that can be aborted by starting a fight:
from evennia import utils, default_cmds class CmdCraftArmour(default_cmds.MuxCommand): """ Craft armour Usage: craft <name of armour> This will craft a suit of armour, assuming you have all the components and tools. Doing some other action (such as attacking someone) will abort the crafting process. """ key = "craft" locks = "cmd:all()" def func(self): "starts crafting" if self.caller.ndb.is_crafting: self.caller.msg("You are already crafting!") return if self._is_fighting(): self.caller.msg("You can't start to craft " "in the middle of a fight!") return # [Crafting code, checking of components, skills etc] # Start crafting self.caller.ndb.is_crafting = True self.caller.msg("You start crafting ...") utils.delay(60, callback=self.step1) def _is_fighting(self): "checks if we are in a fight." if self.caller.ndb.is_fighting: del self.caller.ndb.is_crafting return True def step1(self): "first step of armour construction" if self._is_fighting(): return self.msg("You create the first part of the armour.") utils.delay(60, callback=self.step2) def step2(self): "second step of armour construction" if self._is_fighting(): return self.msg("You create the second part of the armour.") utils.delay(60, callback=step3) def step3(self): "last step of armour construction" if self._is_fighting(): return # [code for creating the armour object etc] del self.caller.ndb.is_crafting self.msg("You finalize your armour.") # example of a command that aborts crafting class CmdAttack(default_cmds.MuxCommand): """ attack someone Usage: attack <target> Try to cause harm to someone. This will abort eventual crafting you may be currently doing. """ key = "attack" aliases = ["hit", "stab"] locks = "cmd:all()" def func(self): "Implements the command" self.caller.ndb.is_fighting = True # [...]
The above code creates a delayed crafting command that will gradually
create the armour. If the
attack command is issued during this
process it will set a flag that causes the crafting to be quietly
canceled next time it tries to update.
Assorted Notes¶
In these examples we only used
utils.delay(), which is a very simple
wrapper around Twisted’s
reactor.callLater(). If you know your
Twisted one might imagine using more advanced features such as
callback/errback chains to more efficiently handle various command
states and conditions. | http://evennia.readthedocs.io/en/latest/Command-Duration.html | CC-MAIN-2018-13 | refinedweb | 1,736 | 67.04 |
Build a chat app with sentiment analysis using Next.js
To follow this tutorial you will need Node and either npm or Yarn installed on your machine.
Realtime applications have been around for quite a long time as we can see in contexts such as multi-player games, realtime collaboration services, instant messaging services, realtime data analytics tools, to mention a few. As a result, several technologies have been developed over the years to tackle and simplify some of the most challenging aspects of building apps that are sensitive to changes in realtime.
In this tutorial, we’ll build a very simple realtime chat application with sentiments. With sentiment analysis, we will be able to detect the mood of a person based on the words they use in their chat messages.-chat-app # cd into the new directory cd realtime-chat-app # Initiate a new package and install app dependencies npm init -y npm install react react-dom next pusher pusher-js sentiment npm install express body-parser cors dotenv axios make reference to them at several points in our code.
Next create a Next.js to set up }); }) .catch(ex => { console.error(ex.stack); process.exit(1); });
Modify npm scripts
Finally, we will modify the
"scripts" section of the
package.json file to look like the following snippet:
/* package.json */ "scripts": { "dev": "node server.js", "build": "next build", "start": "NODE_ENV=production node server.js" }.
Before we add content to the index page, we will build a
Layout component that can be used in our app pages as a kind of template. Go ahead and create a
components directory in your app root. Chat'}<
index.js file we created earlier:
/* pages/index.js */ import React, { Component } from 'react'; import Layout from '../components/Layout'; class IndexPage extends Component { state = { user: null } handleKeyUp = evt => { if (evt.keyCode === 13) { const user = evt.target.value; this.setState({ user }); } } render() { const { user } = this.state; const nameInputStyles = { background: 'transparent', color: '#999', border: 0, borderBottom: '1px solid #666', borderRadius: 0, fontSize: '3rem', fontWeight: 500, boxShadow: 'none !important' }; return ( <Layout pageTitle="Realtime Chat"> <main className="container-fluid position-absolute h-100 bg-dark"> <div className="row position-absolute w-100 h-100"> <section className="col-md-8 d-flex flex-row flex-wrap align-items-center align-content-center px-5"> <div className="px-5 mx-5"> <span className="d-block w-100 h1 text-light" style={{marginTop: -50}}> { user ? (<span> <span style={{color: '#999'}}>Hello!</span> {user} </span>) : `What is your name?` } </span> { !user && <input type="text" className="form-control mt-3 px-3 py-2" onKeyUp={this.handleKeyUp}</section> </div> </main> </Layout> ); } } export default () => ( <IndexPage /> );
We created a component
IndexPage for the index page of our app. We initialized the state of the component with an empty
name property. The
name property is meant to contain the name of the currently active user.
We also added an input field to receive the name of the user, if no user is currently active. Once the input field is filled and the
enter or
return key is pressed, the name supplied is stored in state.
If we test the app on our browser now, we should see a screen that looks like the following screenshot.
Building the Chat component
We will go ahead and build the chat component. Create a new
Chat.js file inside the
components directory and add the following content:
/* components/Chat.js */ import React, { Component, Fragment } from 'react'; import axios from 'axios'; import Pusher from 'pusher-js'; class Chat extends Component { state = { chats: [] } componentDidMount() { this.pusher = new Pusher(process.env.PUSHER_APP_KEY, { cluster: process.env.PUSHER_APP_CLUSTER, encrypted: true }); this.channel = this.pusher.subscribe('chat-room'); this.channel.bind('new-message', ({ chat = null }) => { const { chats } = this.state; chat && chats.push(chat); this.setState({ chats }); }); this.pusher.connection.bind('connected', () => { axios.post('/messages') .then(response => { const chats = response.data.messages; this.setState({ chats }); }); }); } componentWillUnmount() { this.pusher.disconnect(); } } export default Chat;
Here is a simple break down of what we’ve done:
We first initialized the state to contain an empty
chatsarray property. This
chatsproperty will be populated with chat messages as they keep coming. When the component mounts, we set up a Pusher connection and
channelsubscription inside the
componentDidMount()lifecycle method.
You can see that we are subscribing to a Pusher channel called
chat-roomfor our chat application. We are then binding to the
new-messageevent on the channel, which is triggered when a new chat message comes in. Next, we simply populate the state
chatsproperty by appending the new chat.
Also, on the
componentDidMount()method, we are binding to the
connectedevent on the Pusher client, when it is freshly connected, to fetch all the chat messages from history by making a
POST /messagesHTTP request using the
axioslibrary. Afterwards, we populate the state
chatsproperty with the chat messages received in the response.
The
Chat component is not completed yet. We still need to add a
render() method. Let’s do that quickly. Add the following snippet to the
Chat component class.
/* components/Chat.js */ handleKeyUp = evt => { const value = evt.target.value; if (evt.keyCode === 13 && !evt.shiftKey) { const { activeUser: user } = this.props; const chat = { user, message: value, timestamp: +new Date }; evt.target.value = ''; axios.post('/message', chat); } } render() { return (this.props.activeUser && <Fragment> <div className="border-bottom border-gray w-100 d-flex align-items-center bg-white" style={{ height: 90 }}> <h2 className="text-dark mb-0 mx-4 px-2">{this.props.activeUser}</h2> </div> <div className="border-top border-gray w-100 px-4 d-flex align-items-center bg-light" style={{ minHeight: 90 }}> <textarea className="form-control px-3 py-2" onKeyUp={this.handleKeyUp} placeholder="Enter a chat message" style={{ resize: 'none' }}></textarea> </div> </Fragment> ) }
As seen in the
render() method, we require an
activeUser prop to identify the currently active user. We also rendered a
<textarea> element for entering a chat message. We added an
onKeyUp event handler to the
<textarea> to send the chat message when you press the
enter or
return button.
On the
handleKeyUp() event handler, we construct a
chat object containing the
user sending the message (currently active user), the
message itself, and then the
timestamp for when the message was sent. We clean up the
<textarea> and then make a
POST /message HTTP request, passing the
chat object we created as payload.
Let’s add the
Chat component to our index page. First, add the following line to the
import statements in the
pages/index.js file.
/* pages/index.js */ // other import statements here ... import Chat from '../components/Chat';
Next, locate the
render() method of the
IndexPage component. Render the
Chat component in the empty
<section> element. It should look like the following snippet:
/* pages/index.js */ <section className="col-md-4 position-relative d-flex flex-wrap h-100 align-items-start align-content-between bg-white px-0"> { user && <Chat activeUser={user} /> } </section>
You can reload the app now in your browser to see the changes.
Defining the messaging routes
For now, nothing really happens when you try to send a chat message. You don’t see any message or any chat history. This is because we have not implemented the two routes we are making requests to.
We will go ahead and create the
/message and
/messages routes. Modify the
server.js file and add the following just before the call to
server.listen() inside the
then() callback function.
/* server.js */ // server.get('*') is here ... const chatHistory = { messages: [] }; server.post('/message', (req, res, next) => { const { user = null, message = '', timestamp = +new Date } = req.body; const sentimentScore = sentiment.analyze(message).score; const chat = { user, message, timestamp, sentiment: sentimentScore }; chatHistory.messages.push(chat); pusher.trigger('chat-room', 'new-message', { chat }); }); server.post('/messages', (req, res, next) => { res.json({ ...chatHistory, status: 'success' }); }); // server.listen() is here ...
First, we created a kind of in-memory store for our chat history, to store chat messages in an array. This is useful for new clients that join the chat room to see previous messages. Whenever the Pusher client makes a
POST request to the
/messages endpoint on connection, it gets all the messages in the chat history in the returned response.
On the
POST /message route, we are fetching the chat payload from
req.body through the help of the
body-parser middleware we added earlier. We then use the
sentiment module to calculate the overall sentiment score of the chat message. Next, we reconstruct the
chat object, adding the
sentiment property containing the sentiment score.
Finally, we add the chat to the chat history
messages, and then trigger a
new-message event on the
chat-room Pusher channel, passing the
chat object in the event data. This does the real time magic.
We are just a few steps away from completing our chat application. If you load the app on your browser now and try sending a chat message, you don’t see any feedback yet. That’s not because our app is not working. It is working perfectly. It’s simply because we are not yet rendering the chat messages on the view. Let’s head on to that and finish this up.
Displaying the chat messages
Create a new
ChatMessage.js file inside the
components directory and add the following content to it.
/* components/ChatMessage.js */ import React, { Component } from 'react'; class ChatMessage extends Component { render() { const { position = 'left', message } = this.props; const isRight = position.toLowerCase() === 'right'; const align = isRight ? 'text-right' : 'text-left'; const justify = isRight ? 'justify-content-end' : 'justify-content-start'; const messageBoxStyles = { maxWidth: '70%', flexGrow: 0 }; const messageStyles = { fontWeight: 500, lineHeight: 1.4, whiteSpace: 'pre-wrap' }; return <div className={`w-100 my-1 d-flex ${justify}`}> <div className="bg-light rounded border border-gray p-2" style={messageBoxStyles}> <span className={`d-block text-secondary ${align}`} style={messageStyles}> {message} </span> </div> </div> } } export default ChatMessage;
The
ChatMessage component is a very simple component requiring two props:
message for the chat message and
position for the positioning of the message - either
right or
left. This is useful for positioning the messages of the active user on one side and then the messages of other users on the other side as we would do in a moment.
Finally, we will modify the
components/Chat.js file to render the chat messages from the state. Make the following changes to the
Chat component.
First add the following constants before the class definition of the
Chat component. Each constant is an array of the code points required for a particular sentiment emoji. Also ensure to import the
ChatMessage component.
/* components/Chat.js */ // Module imports here ... import ChatMessage from './ChatMessage'; const SAD_EMOJI = [55357, 56864]; const HAPPY_EMOJI = [55357, 56832]; const NEUTRAL_EMOJI = [55357, 56848]; // Chat component class here ...
Then, add the following snippet between the chat header
<div> and the chat message box
<div> we created earlier in the
Chat component.
/* components/Chat.js */ {/** CHAT HEADER HERE **/} <div className="px-4 pb-4 w-100 d-flex flex-row flex-wrap align-items-start align-content-start position-relative" style={{ height: 'calc(100% - 180px)', overflowY: 'scroll' }}> {this.state.chats.map((chat, index) => { const previous = Math.max(0, index - 1); const previousChat = this.state.chats[previous]; const position = chat.user === this.props.activeUser ? "right" : "left"; const isFirst = previous === index; const inSequence = chat.user === previousChat.user; const hasDelay = Math.ceil((chat.timestamp - previousChat.timestamp) / (1000 * 60)) > 1; const mood = chat.sentiment > 0 ? HAPPY_EMOJI : (chat.sentiment === 0 ? NEUTRAL_EMOJI : SAD_EMOJI); return ( <Fragment key={index}> { (isFirst || !inSequence || hasDelay) && ( <div className={`d-block w-100 font-weight-bold text-dark mt-4 pb-1 px-1 text-${position}`} style={{ fontSize: '0.9rem' }}> <span className="d-block" style={{ fontSize: '1.6rem' }}> {String.fromCodePoint(...mood)} </span> <span>{chat.user || 'Anonymous'}</span> </div> ) } <ChatMessage message={chat.message} position={position} /> </Fragment> ); })} </div> {/** CHAT MESSAGE BOX HERE **/}
Let’s try to understand what this code snippet is doing. First, we are going through each
chat object in the state
chats array property. We check if the sender of the message is the same as the currently active user and use that to determine the position of the displayed chat message. As you can see, the active user’s messages will appear on the right.
We also use the
sentiment score in the chat object to set the mood of the user while typing the message to either
happy,
sad or
neutral using the earlier defined constants.
We conditionally render the
name of the user before the chat message based on one of the following conditions being met.
isFirst- the current chat message is the first in the list
!inSequence- the current chat message directly follows a message from another user
hasDelay- the current chat message has a delay of over
1 minutefrom the previous message of the same user
Also notice how we are using the
[String.fromCodePoint()]( method added in ES6 to get the emoji from the code points we defined in our constants earlier.
We are finally done with our chat app. You can go ahead to test what you have built on your browser. Here are some screenshots showing a chat between 9lad, Steve and Bob.
9lad
Steve
Bob
Conclusion
In this tutorial, we have been able to build a very simple chat application with chat sentiment using Next.js(React), Pusher and Sentiment Node module. While this tutorial focuses on just the basics, there are a lot of advanced stuffs you can do to make a better chat app. You can check the source code of this tutorial on GitHub.
Do check the documentation for each technology we used in this project to learn more about other ways of using them. I hope that this tutorial is of help to you.
May 2, 2018
by Christian Nwamba | https://pusher.com/tutorials/chat-sentiment-analysis-nextjs/ | CC-MAIN-2022-21 | refinedweb | 2,286 | 50.12 |
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psamty10 replied to d000hg's topic in GDNet LoungeOnly one solution: targeted assasination
Fast + Powerful Browser-Based 3D games
psamty10 replied to Jedimace's topic in General and Gameplay ProgrammingQuote:Original post by JParishy You can try Unity3D. It can make games for Windows and Mac OS X as well as browser games (requires it's own plugin, which is easy to install). The only catch is that is only runs on Mac OS X at the moment, but that probably won't be for long. They have been working on porting it over to Windows for a while now. Unity can only be authored on a Mac, but can be deployed on Windows.
J2ME to BREW porting
psamty10 replied to vivekmandya's topic in General and Gameplay ProgrammingIts your job, not mine. Therefore, if you don't ask nicely, theres no reason for me to answer. Specifically, the next time you post a question in the forums, remember to: 1) Frame the question properly 2) Understand that people will not break their necks to fix your problems 3) Have a question of limited scope (e.g. How do I port a game from J2ME to BREW is not a limited scope question) I used to work in a shop that ported games across handsets as a way to get into the software industry around 6 years ago. Some of the ports were from J2ME to BREW and vice-versa. This is not a trivial task. I would suggest you first learn BREW - which is a shitty SDK compared to J2ME - and then build a small game in BREW. Following this, you should attempt to port from J2ME with your newly acquired knowledge. This will not happen in less than 2-3 months.
- Quote:Original post by Oluseyi Denied. Not that I don't think RMS is crazy, but he doesn't "run" open source or the open source community. (Hell, he opposes the term.) QFT. RMS does not lead the community. His extreme viewpoint is shared by very few, few people would want to lead the life of an ascetic like RMS. This is evidenced by projects like Mono, which would not exist if RMS had his way. It is also evidenced by the number of open source projects that use a slightly less imposing license like the LGPL and BSD licenses as opposed to the hardcore GPL v3 promoted by RMS.
- Quote:Original post by Mithrandir Quote:Original post by necreia I'm pretty sure many of us wrote him off as bias zealotry when he broke out the use of "loonix" on a regular and 'serious' scale. I'm sorry, but when the entire community is packed full of people who rejoice at the fact that their efforts are putting people out of jobs and companies out of business, I reserve the right to call them loons. Write me off if you want, but I dare you to deny that the people running their community, like RMS, aren't crazy as hell. Did you read the article? The commercial company was trying to sell a code-editor. No, not an IDE. A code-editor. You know, like emacs. Not exactly an innovative product. If your product is too shitty to compete with open source, you should make no money from it. There is always going to be a market for proprietary software - most application software requiring interdisciplinary teams will continue to be dominated by companies, not the FOSS movement. However, as an applications developer, I find open source tools invaluable, especially when it comes to providing implementations of an industry-standard (eg. XML and WSDL parsers). As a small company, open source allows us to compete with the big boys without paying $$$ on software licenses. Open source basically will kill the tools and custom libraries market. Which as far as I'm concerned, is a good thing. Relying on proprietary libraries when you don't have source is an application developers biggest nightmare. Also, it is not the OSS community's responsibility to ensure job security for anyone else. Computers themselves have automated millions of people out of jobs. I didn't see anyone whining then...
Creating a game Engine ... how hard can it be ?
psamty10 replied to TDS's topic in For Beginners's ForumQuote:Original post by issch Quote:Original post by TDS but i really don't have the money to buy Engines ... as the game is totally free , the project is also free (no one takes money) If you do not have enough money to buy an engine, how will you have enough money to pay programmers to write one for you, or even write your game? There are a lot of free engines...
to which school to?
psamty10 replied to brainydexter's topic in GDNet LoungeI thought SMU had a pretty big time game dev program:
Abstract prototypes in XML (with XML Schema)
psamty10 replied to Sneftel's topic in General and Gameplay ProgrammingYou could have an element that contains a reference to an instance of itself. <xsd:schema xmlns: <xsd:complexType <xsd:sequence> <xsd:element</xsd:element> <xsd:element <xsd:element </xsd:sequence> </xsd:complexType> </xsd:schema>
Abstract prototypes in XML (with XML Schema)
psamty10 replied to Sneftel's topic in General and Gameplay ProgrammingQuote:Original post by mrcriminy It looks as if you are trying to fit an object oriented design into XML, which can't result in a pretty/easy validating XSD. XML does OO design just fine (example below): <xsd:element <xsd:complexType> <xsd:sequence> .... </xsd:sequence> </xsd:complexType> </xsd:element> <xsd:element <xsd:complexContent> <xsd:extension <xsd:sequence> .... </xsd:sequence> </xsd:extension> </xsd:complexContent> </ xsd:element> What it doesn't do well is allow you to be terse. Verbosity is its middle name. I would suggest an authoring tool to do this bit.
New To Programming: What Language Is Right For Me?
psamty10 replied to modmiddy's topic in For Beginners's ForumI see very few advantages of picking C# over Java for a beginning programmer other than the fact that one of them starts with the letter C. My vote is for Python or C, as each of them are good examples of the style of programming they support.
Vista + OpenGL app = freeze on startup half the time?
psamty10 replied to Aph3x's topic in Graphics and GPU ProgrammingProbably a part of Vista's super-security framework. It's a feature, not a bug.
- Quote:Original post by Vampyre_Dark Quote:Original post by psamty10.Young grasshopper? I've been coding for ten years now. The class view type functionality used to be really slow and unstable in some of my IDEs before there was express versions of so I never used it. I always had my clean h files anyways, which offered the same functionality. This question was brought up in the first place because I played with Managed C++ and C# last year for a bit, and I could have sworn I was using headers for all my classes in C#, but I only did it in the Managed C++ project. [lol] What a horrible language that is. I didn't mean it as an insult. I am but a grasshopper myself at around 9-10 years of coding experience. The wise old ones have much to teach us.
-.
- Quote:Original post by Kelly G Have you been reading this? No, what I pasted was straight from one of the Boost examples. Boost is considered the C++ gold standard. The solution to writing unmaintainable code and ensure a job for life is simply to use C++ ;)
- #include < iostream > #include <vector> #include <map> #include <boost/assign/std/vector.hpp> #include <boost/assert.hpp> using namespace std; using namespace boost::assign; int main() { vector<int> v; v += 1,2,3,4,5,6,7,8,9; map<string,int> m; insert( m ) ( "Bar", 1 ) ( "Foo", 2 ) ; std::cout << "This shit is crazy\t" << v[4] << "\t" << m["Bar"] << "\n"; } Now that's some crazy code. Yes, "," is an operator. So is "()()"
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Convention Based Filters
Title: Convention Based Filters
Not too long ago Joshua Flanagan spoke at the Austin .Net User Group about how the Dovetail crew use conventions to simplify their development process. The approach is simple in concept (of course the devil’s in the details)
This inspired me to apply the approach in my current project. Our project has several screens that very similar: a table, some buttons to perform actions, and a set of filters. When we implemented the first screen, it was obvious that building the filters were going to get old really fast. This looked like a good place to try and make things a little easier.
I started by creating a class for the fields that were on a filter and used the properties in the class to create an NHibernate Criteria search. The only real requirement here is that the property names in the filter class had to match the names in the Nhiberante mapped object.
This was pretty easy to setup. All we needed to do was build up the Criteria from the property names and the values.
public IEnumerable<ICriterion> CreateFilter(object filter, Type objectToFilter) { var criterion = new List<ICriterion>(); var props = filter.GetType().GetProperties(); foreach (var pi in props) { var val = pi.GetValue(filter, null); if (ShouldNotAddToFilter(pi, val)) continue; criterion.Add(new SimpleExpression(pi.Name, val, "=")); return criterion; }
Now this will create a very simple criteria by creating where statement with a bunch of Property = value OR Property2 = value2. While this is functional and does cover most of our needs, it is pretty limited in what it could do. One issue is that it only goes one level deep in your persistence model hiearchy. You would not be able to apply filters to anything modeled as components. Also there were a few fields that needed to be queried using expressions other than equals. We needed to do like filters as well as greater than / less than queries too. So we need to provide some metadata for the properties to make variations on the criteria output. The easiest way to do that is to decorate the filter properties with some attributes.
We created a set of Attribute classes that allowed us to create different types of Criteria Expressions. The type of expression needed was created inside the attribute. We can then use the power of polymorphism to avoid a big if or switch statement and keeps the query building code clean.
public class QueryFilterAttribute : Attribute { public virtual ICriterion GetCriteria(string propertyName, object val) { return Restrictions.Eq(propertyName, val); } public Type ComponentModel { get; set; } }
public class LikeQueryFilterAttribute : QueryFilterAttribute { public override ICriterion GetCriteria(string propertyName, object val) { return new LikeExpression(propertyName, val.ToString(), MatchMode.Anywhere); } }
These attributes allow us to change the Criteria Expression or Apply the filter to a Component Type. The full source code is at the gist below.
This relatively simple construct saved us a lot time, especially when you think about how much code we would have written after about 10 or 12 of these by hand. When you start to put these types of conventions in your entire codebase, they add up to a lot of time savings. Just another example of how working smarter, not harder can make your life a little bit easier.
<script src=""> </script> | https://lostechies.com/johnteague/2011/06/12/convention-based-filters/ | CC-MAIN-2018-34 | refinedweb | 550 | 54.63 |
Interface for interaction between a graphics document and a user. More...
#include <RDocumentInterface.h>
Interface for interaction between a graphics document and a user.
Typically one document interface exists for every document that is open in an MDI application. The document interface owns and links the various scenes, views and the currently active action.
A document interface can own multiple graphics scenes, each of which can have multiple views attached to it. The views forward all user events (mouse moves, mouse clicks, etc.) to the document interface for processing. The document interface dispatches the events to the currently active action object.
Adds a listener for coordinate events.
This can for example be a document specific widget that displays the current coordinate, e.g. rulers.
Adds the given entity to the preview of all scenes / view.
Adds a box to the preview that represents a zoom box displayed while drawing a window to magnify an area.
Applies the given operation to the document.
The operation might for example do something with the current selection.
Auto zooms in the view that currently has the focus.
After calling this function, all exports go into the preview of the scene instead of the scene itself.
Resets the document to its original, empty state.
Clears cached variables to ensure they are re-initialized before the next use.
Clears the preview of all scenes.
Notifies all property listeners that no properties are relevant at this point.
This can for example clear the property editor and other property listeners.
Deletes all actions that have been terminated.
De-select all entities, for convenience.
Deselects the given entities and updates the scenes accordingly.
Deselects the given entity and updates the scenes accordingly.
After calling this function, all exports go into the scene again and not the preview anymore.
The event is also used to determine the maximum distance from the cursor to the entity in the view in which the event originated.
\par Non-Scriptable:
This function is not available in script environments.
Gets the current snap object.
Helper function for mouseReleaseEvent.
Triggers an appropriate higher level event for mouse clicks for the given
action. The event type depends on the action's current ClickMode.
Highlights the given reference point.
Imports the given file if there is a file importer registered for that file type.
Makes sure that the current preview survives one mouse move.
Locks the position of the relative zero point.
Forwards the given mouse double click
event to the current action.
Forwards the given mouse move
event to the current action.
Forwards the given mouse press
event to the current action.
Forwards the given mouse release
event to the current action.
Notifies all coordinate listeners that the coordinate has changed to
position.
Triggers an objectChangeEvent for every object in the given set.
Forwards the given gesture to the current action.
Forwards the given gesture to the current action.
Helper function for mouseMoveEvent.
Triggers an appropriate preview event for the given action and the current click mode the action is in.
Previews the given operation by applying the operation to a temporary document that is linked to the (read only) document.
Forwards the given
event to the current action to signal that a property value has been changed.
Transaction based redo.
Regenerates all scenes attached to this document interface by exporting the document into them.
Regenerates the given part of all scenes attached to this document interface by exporting the given list of entities into them.
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
Regenerates all views.
Registers a scene with this document interface.
Repaints all views.
Selects all and updates the scenes / views accordingly.
Selects the given entities and updates the scenes accordingly.
Sets the click mode of the current action to the given mode.
Sets the current action.
This action will receive all events until it finishes.
Sets the current block that is in use for all views attached to this document interface.
Sets the current block based on the given block name.
Sets the current layer based on the given layer name.
Sets the current UCS (user coordinate system) that is in use for all views attached to this document interface.
Sets the current view based on the given view name.
Force cursor to be shown.
Used for e.g. snap to intersection manual where we want to show the cursor eventhough we are in entity picking mode.
Sets the action that is active if no other action is active.
Sets the current snap object.
The document interface takes ownership of the object.
Sets the current snap restriction object.
The document interface takes ownership of the object.
Notifies all property listeners that the properties of the given entity should be shown.
Uses the current snap to snap the given
position to a grid point, end point, etc.
Forwards the given gesture to the current action.
Forwards the given tablet
event to the current action.
Called immediately after the user has activated a new UCS to be used as current UCS.
Transaction based undo.
Unlocks the position of the relative zero point.
Unregisters a scene from this document interface.
Marks all entities with any kind of caching as dirty, so they are regenerated next time regenerate is called.
Forwards the given mouse wheel
event to the current action.
Zooms in at the view that currently has the focus.
Zooms out at the view that currently has the focus.
Zooms to the previously visible viewport.
Zooms to the given
region.. | http://www.qcad.org/doc/qcad/latest/developer/class_r_document_interface.html | CC-MAIN-2014-10 | refinedweb | 928 | 60.82 |
27 August 2012 05:00 [Source: ICIS news]
SINGAPORE (ICIS)--Here is Monday’s midday ?xml:namespace>
CRUDE: WTI Oct $97.48/bbl, up $1.33/bbl; BRENT Oct $115.18/bbl, up $1.59/bbl
Crude futures strengthened on Monday morning amid supply concerns resulting from disruption caused by Tropical Storm Isaac in the
NAPHTHA: $982.50-985.50/tonne CFR
Open-spec prices for the first-half October contract rose in the morning session on Monday on the back of rising crude futures.
BENZENE: $1,180-1,200/tonne FOB
Bids and offers firmed from the previous week on the back of stronger crude futures and persistently tight prompt supply in the region. Offers for October-loading lots were at $1,199-1,200/tonne FOB
TOLUENE: $1,125-1,140/tonne FOB
Prices were assessed stable amid range-bound discussions from the previous week despite stronger crude futures. A bid for October-loading lots emerged at $1,136/tonne FOB
ETHYLENE: $1,280-1,300/tonne CFR NE Asia, stable
Selling targets are reiterated at above $1,300/tonne CFR NE Asia for cargoes arriving in the latter half of September but some Chinese buyers were cautious to commit to such levels despite supply shortfalls, a trader said.
PROPYLENE: $1,390-1,410/tonne CFR NE Asia, stable
Selling ideas remained at the low $1,400s/tonne CFR NE Asia, while buying ideas were below $1,400 | http://www.icis.com/Articles/2012/08/27/9590088/noon-snapshot-asia-markets-summary.html | CC-MAIN-2014-41 | refinedweb | 240 | 62.17 |
Separation of concerns in node.js
I’ve been playing with typescript and node.js and I wanted to talk a little about how I’ve broken up my app source. It’s always good to modularize an application into smaller bits, and while node lets you do a lot, quickly, with just a little bit of code, as your application grows you really can’t put all your logic in one big
app.ts.
App.ts
Instead of the normal application example you see for node projects, I wanted to make it clearer what the initialization of my application does. My app start is structured like this:
/** * Module dependencies. */ import db = module("./storage/storageContainer"); import auth = module("./auth/oauthDefinitions"); import requestBase = module("./routes/requestBase"); var express = require('express') , routes = require('./routes') , http = require('http') , path = require('path') , log = require("./utils/log.js") , fs = require('fs') , passport = require('passport'); var app = express(); class AppEntry{ constructor(){ this.initDb(); this.setupRoutes(); this.defineOAuth(); this.startServer(); } // initialization functions } var application = new AppEntry();
The upside to this kind of simple structure is that it’s easy to see what the entrypoint structure is. Adding new initialization logic is encapsulated and isn’t intermingled among route configurations, OAuth authorization code, server start, database initialization, etc. Having a monolithic app can quickly get into a tangled mess.
You may have noticed that I didn’t pass in any required modules or references to the application. This is because I’m relying on the class initialization closure to capture the variables to keep function signatures clean. I opted to use a class instead of a module for no particular reason other than I like classes and forgot modules existed when I did this.
Storage
Even though I’m using mongoose as my mongoDB ORM, I still have tried to move all the storage logic in special storage classes. This means that any outside access to storage has to go through classes that wrap the storage calls. I’ve mentioned it before, but I think it’s always good practice to not entangle an application with specific 3rd party libraries (if you can avoid it). Also having storage classes means I can hide away internal mongo calls, if necessary, and let me do extra data manipulation outside of the context that wants the data.
To make accessing the storage classes easy for myself, I have split them up into separate classes based on what they most commonly access. For example, there is a
userStorage class, and a
trackStorage class, etc. Each class contains relevant CRUD and helper methods to aggregate the data in forms that I commonly use them.
Unfortunately, the way node works is that in each module you work in, if you wanted access to a storage class you’d have to import each one independently (one import for users, one import for dataPoints, etc). That’s a pain. Instead, I’ve wrapped the storage classes with a single exported singleton container.
// storageContainer.ts import schemaImport = module("./schema"); import users = module("./userStorage"); import tracks = module("./trackStorage") export var storage:schemaImport.db = new schemaImport.db(); export var userStorage:users.userStorage = new users.userStorage(); export var schema = schemaImport; export var trackStorage:tracks.trackStorage = new tracks.trackStorage();
Anywhere I want access to storage classes, I only need to import one module:
import db = module("./storage/storageContainer"); // ... db.userStorage.getUserByUsername(...)
Adding new storage classes and updating the singleton container means I have access to these everywhere I need them without having to worry about importing and instantiating modules.
Definition files
Like the storage classes, the same pattern goes for definition files. I’ve made a folder called
def and created an
all.d.ts that just has reference path’s to all my other definition mappings.
///<reference path="./mongoose.d.ts"/> ///<reference path="./nodeUnit.d.ts"/> ///<reference path="./schemaDef.d.ts"/> ///<reference path="./passport.d.ts"/>
Any other file that needs definition mappings can include the one all aggregate. Since it costs nothing and is just a compiler hint, there’s no resource hit.
Routes
And again, I do the same kind of pattern with routes. I have a folder setup like this:
routes ├── index.js ├── indexRoutes.ts ├── userRoutes.ts ├── ... etc
Where index.js looks like this:
var userRoutes = require("./userRoutes"); var indexRoutes = require("./indexRoutes"); var trackRoutes = require("./trackRoutes"); var partialsRoutes = require("./partialsRoutes"); module.exports = function(app){ new userRoutes.userRoutes(app); new indexRoutes.indexRoutes(app); new trackRoutes.trackRoutes(app); new partialsRoutes.partialsRoutes(app); };
From my main application, I import the routes module and pass it the app reference. I know that app is global in a node application, however, I don’t like relying on globals. It was just as easy to pass app as an argument and I prefer that flow control.
routes = require('./routes') routes(app);
In each of the route modules, I then go back to typescript
import db = module("../storage/storageContainer"); import base = module("./requestBase"); export class userRoutes { constructor(app:ExpressApplication) { var requestUtils = new base.requestBase(); app.get('/logout', (req:any, res) => { req.logout(); res.redirect('/'); }); app.get("/users", requestUtils.ensureAuthenticated, (req, res) => { res.send(req.user.name); }); }
So at this point I’m using the definition files from DefinitelyTyped for my express application. Also you can see that I’m injecting custom middleware into my routes for things that I want to make sure are authenticated. The point being that the routes class is now self encapsulated, and we don’t need to modify the main entry point to the application anymore. We update the routes index page and create a route object and that’s it.
Conclusion
It’s been fun playing in node, and while I see myself doing some things the .NET way, I’m also trying to embrace the node way. However, when it comes to module organization the node projects I’ve seen have been seriously lacking. While it does mean more boilerplate upfront, I think making sure to split up your files helps maintain a separation of concerns and your project extensible.
Hi Anton,
It looks like you’ve developed some typescript definition files for libraries like passport that aren’t in. To avoid people duplicating effort do you have any plans to publish these, or submitting them to DefinitelyTyped?
Thanks
Kevin, I didn’t really do much with regards to passport or monogoose (and I haven’t kept up to date with any of the library updates). The mongoose definitions I used are available but they are a pretty small subset of what is available. I was just adding as I went. If I revisit the project and add more to it I’ll definitely submit them to DefinitelyTyped as it’s an excellent resource! | http://onoffswitch.net/separation-concerns-node-js/ | CC-MAIN-2013-48 | refinedweb | 1,117 | 58.89 |
Hi, I am trying to get this board working with C++. I installed the k8055-git package from the aur and the example program works fine with my board. Unfortunately this example is written in C so I still have no clue, how to work with this c++ library from the package.
The package containing a library written in C code, which is used in the example. Then there is another library which seems to translating between C and C++. (I am not quite familiar with classes and libraries, so please excuse me if I paste the wrong parts of the code.)
#include "k8055.h" class K8055 { public: K8055(); ~K8055(); int read( void ); int write( void ); //[...] static char* Version( void ); static int SearchDevices( void ); int OpenDevice( int board_address ); int CloseDevice(); //[...] int SetDigitalChannel( int channel ); //[...] private: struct k8055_dev dev; };
#include "k8055++.h" K8055::K8055() { } K8055::~K8055() { k8055_close_device( &dev ); } //[...] int K8055::SearchDevices( void ) { return k8055_search_devices(0); } int K8055::OpenDevice( int board_address ) { return k8055_open_device( &dev, board_address ); } int K8055::CloseDevice() { return k8055_close_device( &dev ); //[...] int K8055::SetDigitalChannel( int channel ) { return k8055_set_digital_channel( &dev, channel ); } //[...]
And my code:
#include <iostream> #include "k8055++.h" int main() { using std::cout; using std::endl; K8055 device; int dev_addr = SearchDevices(); cout << dev_addr << endl; cout << "Open Device: " << device.OpenDevice(dev_addr) << endl; device.SetDigitalChannel(3); }
produces:
clang++ -std=c++11 -stdlib=libc++ -lc++abi -Wall -pedantic -lk8055++ -lk8055 -o test02 test02.cpp && ./test02 0 Open Device: -1 zsh: segmentation fault (core dumped) ./test02
I have no idea, what I am doing wrong. Please help. Thank you in advance!
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Looking at
Post subject: Re: K8055 search devices
New multicard function and procedures
SearchDevices
Syntax
FUNCTION SearchDevices(): Longint;
Description
The function returns all connected devices on the computer. The returned value is a bit field.
Returned value
· Bin 0000, Dec 0 : No devices was found
· Bin 0001, Dec 1 : Card address 0 was found.
· Bin 0010, Dec 2 : Card address 1 was found.
· Bin 0100, Dec 4 : Card address 2 was found.
· Bin 1000, Dec 8 : Card address 3 was found.
Example : return value 9 = devices with address 0 and 3 are connected.
This is likely to be same for your code.
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What are you trying to do? Are you planning on writing a C application, or a C++ application?
C is directly callable from C++. All k8055++.cpp does is take the C calling conventions and wraps them in a class to make them look for C++ish.
Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
You assume people are rational and influenced by evidence. You must not work with the public much. -- Trilby
----
How to Ask Questions the Smart Way
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My intention is writing in C++. I found the way to connect with the board. Insteat using
K8055 device; cout << "Open Device: " << device.OpenDevice(3) << endl; // [...]
I am know using
K8055 * device = new K8055(); cout << "Open Device: " << device->OpenDevice(3) << endl; // or cout << "Close Device: " << (*device).OpenDevice(3) << endl; // or cout << "Open Device: " << device[0].OpenDevice(3) << endl;
I have (actually) no clue, why it works when I using a pointer. Perhaps you can give me a hint?
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My guess is the segfault happens here in k8055_set_digital_channel.
The C++ wrapper does not initialize the k8055_dev struct, especially the dev_no member (see k8055_alloc). Since your K8055 C++ object lives on the stack, the dev_no member has some random value and OpenDevice fails (see here), leading to the segfault. However, if you allocate the K8055 object on the heap, everything is probably initialized to 0.
Imho, the C++ wrapper looks really bad. I suggest using the C api or writing a proper wrapper.
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I was working on a project where I had to process about 1,000 records. Eventually this set of records grew to several thousand. In some cases, the time complexity of routines that processed this data was O(n2). Using an array to randomly access these records was no longer feasible. It was time to go back to my computer science course notes to work with a more exciting data structure. You are probably here because you are in the same situation. (I'm no longer in that situation. Now I have to process several hundred thousand records!)
In my search for work already done that I could fall back on, the only serious C++ hash template class I could find was in SGI's extension to STL. Like much of STL, I found it difficult to understand. Unlike STL, I found it difficult to use as well. If you have a lightweight task to perform, you have to go through a relatively cumbersome process of defining this, implementing that, etc. I wanted something that could be quickly defined and instantiated -- I would have to write my own.
There are some things that other hash tables can do that this one cannot:
hash_multisetis free from this restriction. If you try adding an element which has a key that already exists in the table, then only the first key will ever be referenced in a random access lookup.
This article assumes that you know how a hash table works. If you don't, then you should familiarize yourself and consider the possibility that a hash table is not even an appropriate solution. Since you must also supply the hash function, you must know what those are all about. You don't have to write your own. There are plenty available on the Internet, but you'll need to incorporate them, understand their principles, and judge if they are appropriate to your data.
I've written these templates to be friendly to all compilers, environments and flavours of C++. However, I have only actually tried the code in GNU C++ and Visual C++. The only environmental requirement is that they must have access to the STL vector template class. There is also an
include <assert.h>, which is part of the ANSI standard. If, for whatever reason, that causes a compiler error, you can easily comment out the line and define your own assert macro to keep the compiler happy.
There are 3 hash table templates that you can use. The Doxygen-generated documentation is included with the source code. However, let's get you started on a "Hello world," which you can use as an outline to hash table applications.
First, you'll already have your class defined, to which you will need fast random access, called
T in the template code (or the "data class"). The declaration to such a class might look like this:
class Student { public: Student(); string m_sName;//this will be the unique key to the hash table entry int m_nGrade; int m_nID; };
Next, we will declare your hash class:
#include <ahashp.h> class StudentHash : public _HashP<Student> { public: StudentHash(); private: virtual bool COMPAREREFERENCESPREATTRIBUTES CompareReferences( const Student &ref1, const char *ref2) const COMPAREREFERENCESPOSTATTRIBUTES; virtual bucket_array_unit HASHREFERENCEPREATTRIBUTES GetHashReference( const char *ref) const HASHREFERENCEPOSTATTRIBUTES; virtual bucket_array_unit HASHREFERENCEPREATTRIBUTES GetHashReference( const Student &ref) const HASHREFERENCEPOSTATTRIBUTES; };
Note that you can dispense with those
*ATTRIBUTES macros if you expect never to use them. However, if you do use them, there's a chance that you might forget that you'll need to update your old code and forget about this class. So, if you are a stickler for correctness, make sure you leave them in.
Also note that there are actually two template parameters being passed to
_HashP. The second one defaults to
const char *. You'll also notice that those template parameters are the types of the parameters being passed to the virtual methods. This is not a coincidence. The template parameters decide the types of the parameters passed to the virtuals. Finally, define your class.
CompareReferences() is used so that when
_HashP needs to match a key with a particular element in the hash table, it can. The STL way of doing things might require that
Student have a comparison operator. This way, instead of making changes to your data class, you can just implement a pure virtual in your hash class.
bool StudentHash::CompareReferences(const Student &ref1, const char *ref2) const { return ref1.m_sName == ref2; }
Now for the hash function. These return an index to the bucket array. Notice that the modulus operation with
GetBucketSize() will usually be necessary:
StudentHash::bucket_array_unit StudentHash::GetHashReference(const char *ref) const { sdbm(ref)%GetBucketSize(); } StudentHash::bucket_array_unit StudentHash::GetHashReference(const Student &ref) const { return GetHashReference(ref.m_sName.c_str()); //just call GetHashReference(const char *) }
It is up to you to choose which hash function to use.
Sdbm() is an attractive choice for keys which are
strings, with good performance and good randomization, so I recommend that one. And there: your hash class is implemented! All you need to do is use it, and for that you should read about the
Add(),
Get() and
SetBucketSize() methods.
I've made use of 4 macros whose names are of the form
*ATTRIBUTES. You can define these as compiler-specific attributes, which may make the calling of the pure virtuals slightly more efficient. One such implementation might be of the GNU attribute
__attribute__((fastcall)) or the Visual C++
__fastcall. Use of attributes can be very dangerous in GNU, and probably to a lesser extent in Visual C++, so you should be very careful that you know what you are doing when using those. So far, I've been using
__attribute__((fastcall)) quite happily without incident, so due diligence should yield safe usage.
This hash table is of the chaining variety. The chains are maintained by linked list. This construct is ideal for roles where the number of lookups on the table do not greatly exceed the insertions and deletions on the table.
If you'd like to make improvements to my code, I'll give you some tips on understanding it.
Hungarian notation is a favourite of mine, but I prefer an improvement that I call Canadian notation.
I've tried to clean up the code. However, I have left in some debug code that I was reluctant to trim, since I've been able to make use of it at one time or another. Unlike all the other methods, it's not very well documented and, in some cases, usage might not be very intuitive. So, keep in mind that you can ignore it without losing any key points in understanding the code.
One can iterate through a hash table using the "hasherators," which borrow from the STL iterators. I found the iterator concept difficult to digest at first, but it is probably the best way to sequentially traverse such a random access data structure efficiently, should it be necessary.
The C++ culture seems to believe in only making
public pure virtuals. This would probably be why, if you've enabled such a warning, GNU C++ will always give you a warning about a class with virtual methods not having a virtual destructor, even if the virtual methods are not
public or the destructor is not
public. So far, I have not discovered a reason why pure virtuals should not be
private, so that the
abstract class can call them, rather than having the owner call them through what is probably a pointer to the instance. This philosophy makes pure virtuals like callbacks, and still takes full advantage of the strengths of
abstract classes.
One might notice that I used the STL array template
vector, but did not use the linked list. I found the linked list frustrating at the time and was getting a lot of debug errors about the improper use of iterators. So, I just dumped it and created my own linked list. Also, I'm not entirely certain of the efficiency of STL's linked list, but I am of the one I wrote.
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One thing that every business app eventually needs is an ability to search for something and show results using paging. The reason for that is that too many rows in search result set can bring any application to its knees. Hence, you should always page search results. If you are building a web application, there is always a temptation to use a data grid control to show those results. If you are using Angular, you can use ngGrid. I, however, do not feel that data grid is a good idea for web applications designed to run on any device, including smart phones. A grid with even four columns, such as First Name, Last Name, Edit button and Delete button will now look very good on the phone. On top of that, it is not going to be very usable because the text is going to be small and button are not going to present large enough targets for touch. Hence, I am not going to use a data grid, but instead I will present search results in Google search style. So, I am going to demonstrate in this post how to solve this problem to come up with the following solution.
I took this screenshot use pretty small browser window, about the size of a phone. It looks just as well on a large screen.
So, I presenting the results in a “well”, showing last and first name in line with two buttons, to edit and delete below. I have real mad design skills, don’t I?
OK, now let’s talk about solution. First, let’s take a look at the view behind this screen. It is quite simple, using just a few Twitter Bootstrap styles.
<div> <h1>Contacts</h1> </div> <button class="btn btn-success addButton" data-Add</button> <div class="verticalMargin"> <form class="form-inline" role="search"> <div class="input-group"> <span class="input-group-btn"> <button type="submit" class="btn btn-default" data-<span class="glyphicon glyphicon-search"></span> Search</button> </span> <input type="text" placeholder="Enter name" data- </div> </form> </div> <div class="verticalMargin"> <span><label>Total found: </label>{{totalFound}} ({{pageCount}} pages)</span> </div> <ul data-pagination></ul> <div> <div class="well" data-ng-cloak <div class="h2">{{contact.LastName}}, {{contact.FirstName}}</div> <div> <button class="btn btn-primary" data-Edit</button> <button class="btn btn-danger" data-Delete</button> </div> </div> </div> @*<ul data-pagination</ul>*@ <ul data-pagination></ul>
What you see above is search input box. The user can type in part of last or first name. The button is using glyph icons that ship with bootstrap. The search results will be shown using ngRepeat directive. This is where I have my “well” with placeholders for my data – last and first name. All this is pretty easy, right?
As far as Web Api controller goes, we have to make sure it does just a few things – we need to accept criteria, such as page number, page size and partial name and pass it into the database layer. I am not going to spend a lot of time on that, I will just show method signature that we will call from JavaScript and return values.
public ApiResult<PagedResult<ContactInfo>> Get([FromUri] PagedCriteria criteria) { return Execute(() => Mapper.Map<PagedResult<ContactInfo>>( _contactRepository.GetContacts(criteria.PageNumber, criteria.PageSize, criteria.Name))); }
The call to repository is pretty simple, mapping call just converts data model to business model. My return value is more interesting. I actually use this approach all the time. I create a return value with predefined shape, so I can easily handle /examine it in JavaScript. In this case, I use combination of two classes – generic result and paging result. Paging result has result set and total number of rows and pages. I use totals to give the user some more information about they search request. Here is the shape of the two classes:
public class ApiResult<T> { public ApiResult(T result, bool success = true, string errorMessage = "") { Result = result; Success = success; ErrorMessage = errorMessage; } public bool Success { get; set; } public string ErrorMessage { get; set; } public T Result { get; set; } }
public class PagedResult<T> { public PagedResult(IEnumerable<T> result, int totalRows, int totalPages) { Result = result; TotalRows = totalRows; TotalPages = totalPages; } public int TotalRows { get; set; } public IEnumerable<T> Result { get; set; } public int TotalPages { get; set; } }
Then in JavaScript I can write code like – if(result.Success) { do something }. You get the idea. A little convention makes your life a lot easier on JavaScript side. My Web Api methods never throw exceptions, they trap all of them and result ApiResult with success property set to false and error property set to something meaningful I can show to the user.
OK, enough with C#. Let’s take a look at the Angular code. There are two main players there – controller and a directive. Controller does just a few things, it calls service component to get the data and just sets up totals and result set properties. Total of about 10 lines of code. I wrote it in TypeScript, but you can look in my download to find compile JS version of all the files as well.
class ContactsController extends app.core.controllers.CoreController { constructor(private http: IHttp, private utilities: IUtilities, private $scope: IContactScope, $location: ng.ILocationService) { super($scope); $scope.pageSize = 10; $scope.pageCount = 0; $scope.currentPage = 1; $scope.search = (pageNumber: number, pageSize: number, name: string, eventToRaise: string) => { http.get('/Contacts/Get', (result: IHttpPagedResult<app.contacts.models.IContactInfo>) => { if (result.Success) { $scope.contacts = result.Result.Result; $scope.pageCount = result.Result.TotalPages; $scope.totalFound = result.Result.TotalRows; $scope.currentPage = pageNumber; $scope.$broadcast(eventToRaise); } }, true, { pageNumber: pageNumber, pageSize: pageSize, name: name }); }; $scope.search(1, $scope.pageSize, $scope.name, 'searchCompleted'); $scope.performSearch = ()=> { $scope.search(1, $scope.pageSize, $scope.name, 'searchCompleted'); }; $scope.gotoPage = function (pageNumber: number) { $scope.search(pageNumber, $scope.pageSize, $scope.name, 'pageLoadCompleted'); }; } }); }]);
See, I was not kidding – very little code here. You can see that in my search function I just call my Angular service custom component that simplifies the Api for me a bit, so that I do not have to write .success and .error all the time. After the call is done, I check Success property, then set my totals – pages and rows – and my data – contacts property. Then I broadcast an event down my scope (view model for my screen). Guess what is listening to the even call – my directive of course. My performSearch function is what my search button on the view is bound to. Name property is also on the scope, and it is bound to the search box.
Directives is an interesting animal in Angular. The goal of directive is to manipulate HTML. Of course, in this case, it also needs to have access to the controller. More specifically, to a few properties on the controller as well as the events controller raises. There are two events there – one for brand new search, the other to load a page based on page number user selected. It does make a difference to my directive. To access this data, I am going to rely on attributes. It is an easy way to communicate from controller to a directive. You can also use isolated scopes, but then I will have an issue with events. So, I need attributes to access the current page, total pages, and the function that will get the page selected by the user properties of the controller. You can guess by the names of course as well. Here is how it will look in HTML:
<ul data-pagination</ul>*
What would be nice, is to also rely on naming conventions. So, if the next search controller wants to use directive and they can use the same default names for all three properties, we can shorten HTML to just:
<ul data-pagination></ul>
Doesn’t that look nice, if you see what this tiny line of code does in the screenshot above? What is also interesting is that I only needed about 150 lines of JavaScript, well technically TypeScript to implement this fancy code. If you are wondering why I used <ul> tag, take a look at paging documentation for Bootstrap. I could have used a custom tag, such as <pagination/>, but this does not work in IE 8 without extra effort, so I use use <ul> to make my life easier. So, here come 150 lines of JS. I will explain what it does below.
export class PaginationDirective extends app.directives.BaseDirective { currentPage; number; totalPages: number; currentlyShownPages: number[]; static createButton(label: string, clickEvent: (eventObject: JQueryEventObject) => void): ng.IAugmentedJQuery { var button = angular.element('<li><a href=#>' + label + '</a></li>'); button.click({ page: label }, clickEvent); return button; } constructor() { super(); var that = this; that.currentPage = 0; this.') { pageNumber = that.currentPage + 1; if (pageNumber > that.totalPages) { pageNumber = that.totalPages; } } else if (page === '>>') { pageNumber = that.totalPages; } else if (page === '<<') { pageNumber = 1; } else if (page === '<') { pageNumber = that.currentPage - 1; if (pageNumber < 1) { pageNumber = 1; } } else { pageNumber = parseInt(page); } that.currentPage = pageNumber; scope.$apply(searchFunc + '(' + pageNumber.toString() + ')'); } }; var hasPageButton = function (): boolean { var returnValue: boolean = false; angular.forEach(instanceElement.children(), function (item: any) { var jqueryObject = angular.element(item); if (jqueryObject.text() === that.currentPage.toString()) { returnValue = true; } }); return returnValue; }; var refresh = function (goToFirstPage: boolean) { if (instanceAttributes.$attr['pageCount']) { that.totalPages = scope.$eval(instanceElement.attr(instanceAttributes.$attr["pageCount"])); } else { that.totalPages = scope.$eval("pageCount"); } if (instanceAttributes.$attr['currentPage']) { that.currentPage = scope.$eval(instanceElement.attr(instanceAttributes.$attr["currentPage"])); } else { that.currentPage = scope.$eval("currentPage"); } if (that.totalPages > 0) { var resetPage: boolean = goToFirstPage || (that.currentPage > that.totalPages); if (resetPage) { that.currentPage = 1; } var needToReset: boolean = (!hasPageButton()) || goToFirstPage; if (needToReset) { instanceElement.empty(); var maxButtons: number = 5; var firstPageNumber: number = that.currentPage; while ((firstPageNumber + 4) > that.totalPages) { firstPageNumber--; } if (firstPageNumber < 1) { firstPageNumber = 1; } that.currentlyShownPages = []; for (var i = firstPageNumber; i <= that.totalPages; i++) { if (i < firstPageNumber + maxButtons) { that.currentlyShownPages.push(i); } else { break; } } instanceElement.append(PaginationDirective.createButton('<<', handleButtonClick)); instanceElement.append(PaginationDirective.createButton('<', handleButtonClick)); for (var j = 0; j < that.currentlyShownPages.length; j++) { var button = PaginationDirective.createButton(that.currentlyShownPages[j].toString(), handleButtonClick); instanceElement.append(button); } instanceElement.append(PaginationDirective.createButton('>', handleButtonClick)); instanceElement.append(PaginationDirective.createButton('>>', handleButtonClick)); } angular.forEach(instanceElement.children(), function (item: any) { var jqueryObject = angular.element(item); var text: string = jqueryObject.text(); if (that.currentPage === that.totalPages && (text === ">" || text === ">>")) { jqueryObject.addClass('disabled'); } else if (that.currentPage === 1 && (text === "<" || text === "<<")) { jqueryObject.addClass('disabled'); } else { jqueryObject.removeClass('disabled'); } if (text === that.currentPage.toString()) { jqueryObject.addClass('active'); } else { jqueryObject.removeClass('active'); } }); } else { instanceElement.empty(); } }; scope.$on('pageLoadCompleted', function () { refresh(false); }); scope.$on('searchCompleted', function () { refresh(true); }); }; } }
There are three main functions in it. handleButtonClick function is what I bind to the page buttons I create. In this function I call controller’s goToPage function, passing the page number from the button. I use scope.$eval to do that. There is a bit of code there to handle previous, next, last and first buttons as well. There is also a bit of code to handle clicks on disabled buttons. Yes, those still fire, but we can eat them. They fire because disabled is a built-in style in Bootstrap. hasPageButton is a helper function that checks to see if a specific page button exists inside pagination <ul> element. Refresh function just rebuild the page buttons. It is fired in two cases – when a user clicks on a page button or when a use performs new search. It takes a parameter to distinguish between the two. First, this function checks to see if the page you selected is listed in the list of current 5 page buttons. The reason this occurs is because the user can be looking at pages 1 through 5, but hit ‘next’ button to go to page 6. In this case I am rebuilding the page buttons, preparing for the next group. createButton helper function is what creates the UL and wires up event handler. And, finally, if there are not pages to show, I am hiding entire <ul> by calling empty() on it. There is a bit extra code to deal with lack of jQuery. Angular ships with jqLite, which is missing some functionality I need for this directive, such as full children() implementation or full find() implementation.
You can download entire project here. This functionality is in Contacts screen. | http://www.dotnetspeak.com/angular/building-pagination-directive-in-angular-and-twitter-bootstrap/ | CC-MAIN-2019-09 | refinedweb | 2,030 | 51.24 |
C# REPL
C# GUI Shell
This documents the features available in the C# interactive shell that is part of Mono’s C# compiler. An interactive shell is usually referred to as a read eval print loop or repl. The C# interactive shell is built on top of the Mono.CSharp library, a library that provides a C# compiler service that can be used to evaluate expressions and statements on the flight as well as creating toplevel types (classes, structures, enumerations).
Using it
To use the C# compiler in interactive mode, you need to start it with the the “csharp” command from the command line:
$ csharp Mono C# Shell, type "help;" for help Enter statements below. csharp>
Statements and expression can take multiple lines, for example, consider this LINQ query that displays all the files modified in the /etc directory in the last week. The prompt changes from “csharp” to “ >” to indicate that new input is expected:
csharp> using System.IO; csharp> from f in Directory.GetFiles ("/etc") > let fi = new FileInfo (f) > where fi.LastWriteTime > DateTime.Now-TimeSpan.FromDays(7) select f; { "/etc/adjtime", "/etc/asound.state", "/etc/mtab", "/etc/printcap", "/etc/resolv.conf" } csharp>
A GUI version of this tool is called
gsharp and is available when
you install the
mono-tools package:
Details
Presets
When you startup the interactive shell, the System, System.Linq and System.Collections and System.Collections.Generic namespaces have already been imported for you.
Command line editing
The interactive shell supports an Emacs-like command line editor, just like the Bash shell or other Unix tools so it should integrate naturally into your shell experience.
In Mono 2.6 the csharp shell also includes auto-completion. This is triggered by using the tab key.
In Mono 4.4.0, completion is automatically triggered with the “.” key as well, and if there are matches, a popup window will show up allowing users to select a value.
Using Declarations
Unlike compile mode when the using statement are only allowed before any declarations have been parsed, in interactive mode you can enter using statements as you go. The using statements only will have an effect for any future uses.
The using declarations must appear on their own and can not be mixed with regular statements in a single line, for example:
csharp> using System; csharp> Console.WriteLine ("hello"); hello csharp>
Is a valid use of the using statement, but the following is invalid:
csharp> using System; Console.WriteLine ("hello");
Local Variable Declarations
You can use the local variable declaration in the interactive shell, but the compiler will turn all top-level declarations into static class fields. This is necessary as every statement is actually hosted in an individual class and an individual method.
The semantics have been extended to allow
var declarations, so it is
possible to write:
csharp> var a = "hello, world";
And have
a’s type be resolved to string.
When using the interactive shell, it is possible to redeclare variables to have different meaning than the one they had previously on the session, the following for example is valid:
csharp> var a = "hello world"; csharp> var a = 1;
The new declaration of a will override the older declaration.:
csharp> var list = new int [] {1,2,3}; csharp> var b = from x in list > where x > 1 > select x; csharp> b;
Built-in Methods
A few static methods and public fields can be used from the shell, these are:
- LoadAssembly (string): Loads the given assembly, equivalent to passing the -r:NAME to the compiler.
- LoadPackage(string): Loads the given package, equivalent to passing the -pkg:NAME to the compiler.
- ShowVars (): shows all the current variable declarations in scope.
- ShowUsing (): show the current using statements in effect.
- Describe (object o): Shows the type definition for an object.
csharp> var a = 1; csharp> var b = "hello"; csharp> ShowVars (); int a string b csharp>
The GUI version includes a handful of other methods:
- Plot (DoubleFunc f1 [,f2 [,f3 [,f4]]]): Plots one or more functions in the buffer.
In the GUI it is also possible to register your own custom transformation objects for rendering the expression results. This allows you to render objects differently:
- RegisterTransformHandler (RenderHandler rh): Use this to register a custom transformer for an object.
- UnregisterTransformHandler (RenderHandler rh): Use this to unregister a trasformer handler.
The GUI version is able to embed Gtk.Widgets when a rendering handler has been registered. The shell will call all registered methods and pass the result of an operation, and if the operation returns a Gtk.Widget that is used instead of the string representation.
This can be layered multiple times, the following example shows how to register a handler to render true and false:
Notice that a simple call that returns a widget will not embed the widget itself:
csharp> LoadPackage ("gtk-sharp-2.0"); csharp> new Gtk.Window ("Click me"); { } csharp>
This is to avoid having your widgets automatically parented into the shell.
At least one transformation step must be applied before a Gtk.Widget will be considered for embedding.
Built-in Properties
- object quit {get;} terminates the program.
- string help {get;} shows the help for available commands.
- string Prompt {get;set} a variable that holds the current primary prompt.
- string ContinuationPrompt {get;set} a variable that holds the current continuation prompt.
The GUI version introduces a few more:
- bool Attached {get;} if the code is running attached to another process.
- Gtk.Widget MainWindow {get;} the Gtk.Widget representing the toplevel GUI shell.
Grammar
The Interactive Shell allows valid C# statements as well as expressions to be entered interactively. Unlike the batch-compiled C#, plain expressions are allowed, for example, this is valid input in the interactive mode that is invalid on batch mode:
csharp> 1 == 2; false csharp>
Startup Files
On startup the csharp shell will load any C# script files (ending with .cs) and pre-compiled libraries (ending with .dll) that are located in the ~/.config/csharp directory (on Windows this is the value of Environment.GetFolderPath (Environment.SpecialFolder.ApplicationData)).
The assemblies are loaded first, and then the scripts are executed. This allows your scripts to depend on the code defined in the assemblies.
C# script files are merely files that contains statements and expressions, they can not contain full class definitions, those should be stored and precompiled in DLL files. | https://www.mono-project.com/docs/tools+libraries/tools/repl/ | CC-MAIN-2020-50 | refinedweb | 1,054 | 55.34 |
Sproing is a very simple and intuitive Flash game. It’s also rather addictive. The object of the game is to destroy green orbs by hitting them hard enough with a blue orb which is connected to the mouse via a spring force. You’ll have to play the game to see what I mean. In this tutorial I’m going to show you how to make the blue orb spring to the mouse. Obviously, I wont show you how to make the complete game. The demo below shows exactly what we’ll be making:
We’ll be making the demo with ActionScript 3.0, which means you’ll need Flash CS3, Flex Builder or the free Flex SDK. However, I’ll explain how to use the code specifically with Flash CS3. I assume you have at least a basic working knowledge of ActionScript 3.0. If you have experience with ActionScript 2.0, then you shouldn’t find it too difficult to follow through.
Before I begin explaining the code step-by-step, I’d like you to get the demo up and running yourself. The first step is to create a new Flash document, with which we’ll associate the program’s main class. Open up Flash and create a new document (
File > New > ActionScript 3.0). Save this .fla file as ‘SproingDemo.fla’ (
File > Save As). Bring up the Properties Panel (
CTRL+F3), and under Document class, enter ‘SproingDemo’ (the name of the program’s main class). If a warning dialog appears (as shown in the image below), just click OK.
Set the frame rate to 30fps, and leave the other document properties at their defaults.
That’s all we need to do with the .fla file. Now we will create the main class. This is as simple as saving the class definition in a file called ‘SproingDemo.as’ (note the .as extension). Here’s the main class in it’s entirety:
Note: The program’s main class definition must be placed in a text file named after the main class, with a .as extension.
An additional class is used to represent the orb which is sprung to the mouse. Save this class in a file called ‘Orb.as’. Here it is:
You should now have three files: SproingDemo.fla, SproingDemo.as and Orb.as (all placed in the same directory). Open SproingDemo.fla and press
CTRL+ENTER to see the demo in action (or
Control > Test Movie). Assuming all went well, let’s begin exploring the code (if you encountered problems, make sure you followed the above instructions exactly).
The main class
We’ll be using several built-in classes in this program, so we must import them using the
import directive:
In the demo, you’ll notice there are two orbs. The small orb is used to represent the position of the mouse. This orb is created as an instance of the Shape class, which is perfect for such a simple graphical object. I’ve given the large orb a class of it’s own: Orb, a subclass of Shape. Since the large orb is sprung to the mouse, we need to keep track of it’s velocity (it’s speed along the x and y axes). So to the Orb class, I have added two instance variables,
vx and
vy. Both of which are of type
Number (there’ll need to hold fractional values).
The main class extends the Sprite class, so we need to import that. For animation, we’ll use the
Event.ENTER_FRAME event, which is why we need the Event class. Finally, the Mouse class is used to hide the mouse pointer.
The main class declares five instance variables.
orb1 and
orb2 hold references to the small and large orb, respectively.
lineCanvas holds a reference to a Shape object in which we’ll draw a line between the two orbs.
spring is used to determine the strength of the spring force between the two orbs. The greater this value, the greater the force. To force the large orb to settle down,
damping is applied to its velocity (you can think of
damping as a kind of frictional force, which works against the spring force).
Following the five instance variables is the main class’s constructor, which simply invokes
init().
init() takes care of initializing the program. It creates the small orb by assigning a Shape object to
orb1, and then invokes drawing methods on the Graphics instance of the Shape object. The first two methods,
lineStyle() and
beginFill(), set the color of the orb’s stroke and fill, as well as the thickness of the stroke. Feel free to change the arguments passed to these methods to change the appearance of the small orb. The large orb is then created, by assigning an instance of the Orb class to
orb2, passing in arguments to the set the orb’s appearance (I’ll explain the Orb class shortly).
The two orbs are connected visually by a line, which is drawn to
lineCanvas. So a Shape object is assigned to
lineCanvas.
Now that the three graphical elements of the program have been created, they are added to the display list so that they can be seen on screen.
The large orb needs to be below both the small orb and the connecting line, so it’s added first, followed by the small orb and then the connecting line (which appears on top).
enterFrameListener() registers with the main class instance to receive
Event.ENTER_FRAME notifications, so that it is executed repeatedly, each time the screen is about to be updated. It is in this listener that we place the animation code.
Finally, the mouse pointer is hidden by invoking the
hide() method of the Mouse class.
The
enterFrameListener() method is the heart of the program. It is executed on every frame. First it sets the small orb’s position equal to the mouse’s position, as retrieved from the DisplayObject class’s instance variables,
mouseX and
mouseY. This causes the small orb to follow the mouse. Next, the large orb is moved a little closer to the small orb, as determined by a simple spring formula. The difference between the orbs positions along both axes is multiplied by
spring. The resulting value is the amount by which the large orb should be accelerated towards the small orb on this frame. As the distance between the two orbs decreases, so does the acceleration. However, the large orb is moving at greatest speed when it has reached the small orb, which it passes, causing the spring force to pull it back towards the small orb. The acceleration along the x and y axes is applied by adding to
vx and
vy, respectively. Damping is achieved by applying
damping to
vx and
vy, which reduces the orbs velocity on every frame. The large orb’s position is finally updated by adding
vx and
vy to the orb’s
x and
y properties, respectively.
Last but not least,
drawLine() is invoked. It draws a line between the two orbs.
The Orb class
This class is very simple. It consists of just three instance variables. We’ve met both
vx and
vy.
radius simply holds the orbs radius. Although
radius is not used in this program, it can be convenient to have access to this property, such as when performing collision detection. The constructor has four parameters, all of which are optional (since default values are supplied). However, if you supply a value for a parameter, you must supply values for all preceding parameters. These parameters are used to set the orb’s radius, fill color, stroke thickness, and stroke color. The constructor sets
radius equal to the parameter with the same name. The
radius variable and
radius parameter are disambiguated by using the
this keyword (which refers to the current object). A circle is then drawn in the center of the Orb object using
drawCircle().
Notice that
radius,
vx, and
vy are defined using the
internal access-control modifier: this is to make them accessible within the main class. That’s all there is to it.
I hope you’ve enjoyed working through this tutorial, and I’m sure you’ll take the program a lot further. If you have any questions, leave a comment.
Nice tutorial. I would like to contact you. Can you mail me at info@emanueleferonato.com?
Thanks for the Sproing link and nice tutorial! Interestingly I’m about to start learning AS3 myself so this will be particularly relevant for developing Sproing 2!
@Gordon
I’m glad to hear your developing Sproing 2, and I wish you the best in learning AS3! I can highly recommend Essential ActionScript 3.0 by Colin Moock, I have learned a great deal from it. Also, Colin’s site is a nice resource
OMG, its Emanuele Feronato! I love your site!
ANyway, i tried to limit where the mouse goes (though I am a n00b) with this (in the SproingDemo.fla):
if(mouseX > 200)
{
mouseX = 200
}
if(mouseX 200)
{
mouseY = 200
}
if(mouseY
@n00b
Both
mouseXand
mouseYare read-only properties. They indicate the x and y coordinates of the mouse relative to a given display object.
If you want to constrain the large orb to a specific boundary, then you’d check the orb’s position and update it appropriately within the ENTER_FRAME listener.
First set some constants to represent the boundary, like so:
These would go along with the instance variables at the beginning of the main class definition.
Then, within the ENTER_FRAME listener, just before the call to
drawLine(), place the following:
If you need any more help, let me know.
Man, I love this.
I have a quetsion though. I tried changing the color but I didnt know how. I looked in the code in orb and saw one that said fill, but when I played the movie I had 2 mistakes. So I change it back and it works, can you help me in any way…
Thanks
@Ben
Changing the color of the orb is as simple as changing the second argument passed into the Orb constructor. Locate line 27 of the main class. It looks like this:
So, if I wanted the orb to be green, line 27 would look like this:
Say I had a bunch of exploding boxes all around the screen. How could I program the big ball to react to them and explode them?
@Raptor
You’d want to set up some collision detection between the big ball and the boxes. You could use the
hitTestObject()method of the DisplayObject class. What I would do is create a new function called “checkCollisions”. In this function, we’d loop through an array of boxes, testing each box against the big ball for collision. If a collision takes place, we’d instruct the box which was hit, to explode, by going to and playing from the first frame of the explosion animation. After which, the box would remove itself from the Stage, and the array of boxes.
checkCollisions()would be called just after
drawLine().
If you need any more help with this, let me know.
Hi! i dont understand the array too much, if anybody want to explain me a little bit about it i will be so pleasant!
@Santy
Here’s a nice intro to using arrays in AS.
Hope this helps. | http://technomono.com/blog/build-a-game-like-sproing/ | crawl-002 | refinedweb | 1,903 | 73.68 |
Outstanding from last week:
Minutes from 20 January meeting.
GV suggest move "one size fits all" thread to IG. no need. has ended.
JW propose way for handling mechanism for moving threads between IG and WG. JW track incoming requests for participation.
WC update the discussion of table linearization in the Techniques. done.
WC take resolution to ER (defn in WCAG is the one to use). done.
WL give electronic reference to Jakob Nielsen's new book.
IJ resubmit proposal for 11.1. Refer to Ian's original proposal from 28 July. open.
JW proposal for dealing with relationships between 3.3, 5.3, and 11.1. done.
WC takes action to make sure test results are incorporated into the user agent support page. Done.
WC put daniel's PICS conformance scheme into errata. Done.
CMN to write RDF schema in relation to WCAG and IJ's unified conformance scheme. Refer to Charles' message from 17 January. Done - group needs to review and comment.
WC write, post, and link from WCAG home page "how to get into ETA." Open.
WC make reading ETA issues public, but adding issues only working group. Done.
GV javascript discussion on uaccess-l. on our site, we're using javascript and style sheets that transforms gracefully. We get lots of hits by a variety of browsers.
DB we face the same problems and are looking at similar solutions.
GV someone needs to document these solutions so that people can use them. It's troubling that Netscape freezes when it uses some style sheet stuff.
GV document once set up, then bring it to the list for review, then post to IG.
WC I have documented what I did with MWC - it uses scripts, style sheets, etc. We could start discussions with that.
JW we ought to post to the list.
GV we need to find more examples of pages that work.
JW work will continue on this solution, it will be reviewed by IG for compatibility issues, and then we'll add all that that passes muster to Techniques document.
GV first send to this list.
All on the call are likely to go.
IJ shall we send individual invitations to the people who have responded to call for participation?
/* yes */
DB give it more time on the list.
GV yes, let's head towards it. pull the plug if we don't get a sufficient showing.
@@WC move ahead w/plans for 20th March face-to-face
WC describes issues that ER wants clarification on.
GV "title" is a short descriptive title, "caption" is a description of one to two sentence description of the table, "summary" provides an overview of the content. "title" a few words, "caption" a couple sentences, "summary" as long as it has to be.
WC what info included in "summary"? /* reads from HTML 4 spec */
GV "the purpose of the table is to show x, y, z and is laid out in the following fashion."
JW relationships among the different items, especially those which are not mentioned, should be mentioned in summary. CAPTION should not be required. summary rather important, especially if complicated table.
WL where is summary?
WC it is an attribute of the TABLE element.
IJ there are reasons for doing that. CAPTION always rendered. "summary" so wouldn't be rendered.
JW follow gregg's suggestion. context dependent. should convey aspects of structure and relationships not obvious. especially if table put through table linearizer and relationships are lost.
IJ the attributes like alt and longdesc were not designed by this WG. many of them are inherited (like SMIL from HTML) w/out testing. Therefore, do we need to inhereit the issues.
WL how do browsers deal with summary?
IJ there is no rendering information for it in the HTML spec. XML says don't do in attributes, use elements. therefore, this is going off in a different direction. I don't think we should clarify the meaning of these things.
WL if we try to deal with caption, summary, title then it's an exercise in ivory tower discussions if the browsers don't use them.
JW if it's complicated it needs a summary.
WL does the summary does something do like what would happen if you hire a really good reader?
IJ you could do a "d-link"
JW the idea is that table linearizer would show the summary. thus, that can eliminate the support problem. as far as what to do for ER: agree with gregg's proposal.
WC not only take to ER, also add to Techniques doc.
IJ also interaction with PF.
JW 1. write up in techniques. 2 send to ER. 3. take to PF
@@WC write up proposal for changes to Techniques doc re: TABLE summaries, captions, and title. send to list. once group happy pass along to ER.
JW willing to take advise to PF. summary should be element rather than attribute.
IJ there is a general project for HTML re: how HTML attributes interact. we don't say don't use title if use alt. alt, londesc, title all had different uses. for table, should we take this to the list to generate more ideas? are we suggesting changes to HTML?
JW summary could evolve into an element. it's a question of PF tracking what is said in relation to these elements so that when it comes up in future formats they're advise is consistent with our techniques document.
WL someone said that summary does not bear the same relation to table as longdesc to IMG.
IJ partly because longdesc is a URI. modularization of XHTML..there is a table module and a forms module. they are in last call. has PF done any work on table module?
JW they have.
IJ last call ends 1 Feb.
JW PF in meeting right now.
IJ can PF say that we need to establish a consistent and adequate approach to providing equivalents. now that's in in XML we can say "create a namespace" for these things.
@@JW remind PF that table information be supported in consistent way with other access elements/attributes.
JW IJ has postponed his action item until next week. therefore, postpone this discussion.
Tracking levels of CSS implementation and inconsistencies among different implementations for user agent support page and techniques document (is this already being carried out externally, E.G. by the W3C style activity or other organisations)?
JW my understanding is that the w3c css activity is tracking CSS implementations. that would be useful for techniques.
@@IJ talk with style lead to find out if recording support.
WC webreview has a list of support, although a bit outdated and not granular enough for my tastes.
WL are people supporting it?
IJ moving in that direction.
JW GR said Opera claim css1, and mozilla claiming css2 on the way.
@@WC point rob to the info in techniques doc (webreview's safe list and the w3c css test suite) as he implements if he finds ommissions or things to add, we can add them.
@@WC keep pestering companies to provide information about their browser support.
GV let's schedule 1 1/2 hours, but try to keep 1 hour.
IJ has anyone else requested this time?
@@WC will request this time for 1 1/2 hours.
resolved: discuss on list. probably best for UA list rather than WCAG.
$Date: 2000/11/08 08:30:14 $ Wendy Chisholmp | http://www.w3.org/WAI/GL/meetings/20000127.html | CC-MAIN-2018-05 | refinedweb | 1,241 | 77.64 |
Algorithmic Problem Solving studies the implementation and application of algorithms to a variety of problems. Topics covered will include:
Evaluation is based on participation in programming contests, quizzes, and exams.
Students who would like to develop their programming and algorithmic skills by having a new set of programming challenges presented to them in each class. Basic algorithms and comfort with Java or C++ is a prerequisite.uesday and Thursday, 3:30PM-4:45PM, CIWW 101
Friday, 5:10PM-7:10PM, CIWW 101
Steven and Felix Halim's Competitive Programming (Third Edition) for $26.99. Also available as an eBook (PDF) for $19.99.
For John: Wednesdays from 9am to 10am in WWH 328 and Mondays from 7:30pm to 8:30pm in the 13th floor lounge. Please email me in advance just to give me a heads up.
Codebooks are allowed for standard algorithms, but all of the submitted code must be your own. Collaboration is allowed on all assigments except the midterm and final, but each student must submit his/her own code. Programming assignments will be submitted through Virtual Judge. More information will be posted here for each assignment. If you are enrolled in the course, please register an account on Virtual Judge with username netid_CS480S16. If you are just following the course but are not enrolled, any username will do, but please do not suffix it with _CS480S16.
Each week there will be a programming homework hosted on the Virtual Judge, with links given below. As stated above, please register an account on Virtual Judge with username netid_CS480S16. Your grade will be based on the number of problems solved correctly.
All programs must take their input from standard input, and must write their output to standard output. Java programs must be contained in a public class entitled Main, and they must be in the default package. C++ programs must have a function main, and Java programs must have a method main. If you get Judging Error 1, it means the judging queue is backed up, and you can simply click refresh to be rejudged. If you get Judging Error 2, it means their are server-side communication errors, and your submission should be automatically rejudged when the communication problems are fixed. On Judging Error 2, if you see other people getting submissions through, you may want to resubmit. The student ranking (not used to determine your HW grade) is determined by how quickly you submit each problem (measured from the start of the competition), and how many incorrect submissions you have made (penalized 20 minutes for each incorrect submission).
Lectures and assignments will be posted here. Based on material used with permission from Bowen Yu, Brett Bernstein and Sean McIntyre. | https://cs.nyu.edu/courses/spring16/CSCI-UA.0480-004/ | CC-MAIN-2019-43 | refinedweb | 453 | 62.78 |
⚠️ SPOILER ALERT ⚠️
This is a post with my solutions and learning from the puzzle. Don't continue reading if you haven't tried the puzzle on your own yet.
If you want to do the puzzle, visit adventofcode.com/2020/day/7.
My programming language of choice is
python and all examples below are in python.
TOC
- Key learning
- Puzzle
- Part 1
- Part 2
- Alternative: Regex
- Alternative: Networkx
- Python tips
Key learning
- Depth first search
- Possibly on part 1: Breadth first search
This puzzle can be viewed as a "graph" problem with nodes and edges. A simple way for beginners to start is utilizing a queue or recursive function.
Puzzle
The puzzle describes relationship between bags in different colors. A bag in one color can contain a certain amount of bags in other colors.
Example.
Part 1
The puzzle is to find all bags that can directly or indirectly contain a
shiny gold bag. This can be viewed as a graph where bags are nodes and their relationships are edges.
An visualisation with example data:
-> green bag -> grey bag / \ blue bag - -> shiny gold bag \ / -> purple bag / / white bag -------------------
Our goal is to traverse from
shiny gold to the left and counting all nodes it finds. In this visualisation the answer is:
white bag, blue, green, grey
Parsing input
A big part of the problem is deciding on data structure and how to parse the input into that structure.
For part 1 I aimed for this data-structure:
bags = { "light red": "1 bright white bag, 2 muted yellow bags.", "dark orange": "3 bright white bags, 4 muted yellow bags.", "bright white": "1 shiny gold bag.", "muted yellow": "2 shiny gold bags, 9 faded blue bags.", ... }
To keep track of which bags that contain a
shiny gold bag I used a
set to avoid duplicates. Below is the code to parse in the data. This approach does the simple parsing for bare minimum for part 1:
# Extract a list of lines from file lines = [x.strip() for x in open('07.input', 'r').readlines()] bags = {} for l in lines: bag, contains = l.split('contain') bag = bag.replace(' bags','') bags[bag] = contains
Solution: Breadth first
Some bags will directly contain
shiny gold. Those bags can in turn be contained in other bags, which will indirectly contain
shiny gold.
This solution uses a work queue to traverse the "graph". Once we find a bag that can contain
shiny gold we add it to the queue to check if it can be contained by another bag. We keep on doing so until the work queue is empty. For every bag we find we store it in the
answer-set
This is a so called breadth first search. In this case I use a
queue.
answer = set() # Bags containing 'shiny gold' q = ['shiny gold'] # Work queue for traversing bags while len(q) != 0: current = q.pop(0) for bag in bags: if bag in answer: # Skip if already counted. continue if current in bags[bag]: # If bag contains current-bag, q.append(bag) # add to queue and answer answer.add(bag) print "Answer part 1: %d" % len(answer)
Solution: Depth first
Another solution is the depth first search. Both algorithms do fine in this puzzle and input-size. But in coming advent-of-code-puzzles, it is possible that only one will be sufficient enough. Therefore we practice both now.
This example is a
depth first where I use a
recursive function:
bags = {} for l in lines: bag, contains = l.split('contain') bag = bag.replace(' bags','') bags[bag] = contains def deep_search(bag, bags): contains = [] for b in bags: if bag in bags[b]: # Add b to our list contains.append(b) # Add all children to b in our list contains.extend(deep_search(b, bags)) # Remove duplicates return set(contains) print "Answer: ", len(deep_search('shiny gold', bags))
Part 2
Parsing input
For part 2 I aimed for this data-structure:
bags = { "light red": { "bright white": 1, "muted yellow": 2 }, "dark orange": { "bright white": 3, "muted yellow": 4 }, "bright white": { "shiny gold": 1 }, "muted yellow": { "shiny gold": 2, "faded blue": 9 }, ... }
In this way I can call
bags['muted yellow']['shiny gold'] to find out how many
shiny gold bags
muted yellow contain.
This is a ugly "simple" way of solving it. Further down is an regex example which is cleaner.
bags = {} q = [] for l in lines: # Clean line from unnecessary words. l = l.replace('bags', '').replace('bag', '').replace('.','') bag, contains = l.split('contain') bag = bag.strip() if 'no other' in contains: # If bag doesn't contain any bag bags[bag] = {} continue contains = contains.split(',') contain_dict = {} for c in [c.strip() for c in contains]: amount = c[:2] color = c[2:] contain_dict[color] = int(amount) bags[bag] = contain_dict
Solution
A good data structure enables us to do a clean solution. Here is an example with
a recursive function to count all bags:
def recursive_count(bag, bags): count = 1 # Count the bag itself contained_bags = bags[bag] for c in contained_bags: multiplier = contained_bags[c] count += multiplier * recursive_count(c, bags) return count # Minus one to not count the shiny gold bag itself result = recursive_count('shiny gold', bags) - 1 print "Result part 2: %d " % result
Alternative: With regex
A lot easier way to parse the data is using regex. Here is an example:
import re from collections import defaultdict bags = defaultdict(dict) for l in lines: bag = re.match(r'(.*) bags contain', l).groups()[0] for count, b in re.findall(r'(\d+) (\w+ \w+) bag', l): bags[bag][b] = int(count) def part1(): answer = set() def search(color): for b in bags: if color in bags[b]: answer.add(b) search(b) search('shiny gold') return len(answer) def part2(): def search(bag): count = 1 for s in bags[bag]: multiplier = bags[bag][s] count += multiplier * search(s) return count return search('shiny gold' ) - 1 # Rm one for shiny gold itself
Alternative: Network X
NetworkX is a good library for handling graphs. Haven't used it myself so much, but it appears quite often in the solutions megathread once there is a graph-problem.
There is a lot of documentation, but by reading solutions on the megathread you'll learn what common features to use.
Make sure you understand the above example with regex first before reading this. Here is an example solution with networkx:
import re from collections import defaultdict import networkx as nx # Parse data bags = defaultdict(dict) for l in lines: bag = re.match(r'(.*) bags contain', l).groups()[0] for count, b in re.findall(r'(\d+) (\w+ \w+) bag', l): bags[bag][b] = { 'weight': int(count)} # Create a graph in networkx G = nx.DiGraph(bags) def part1(): # Reverse edges RG = G.reverse() # Get predecessors predecessors = nx.dfs_predecessors(RG, 'shiny gold') # Count predecessors return len(predecessors) print(part1()) def part2(): def search(node): count = 1 # Iterate neighbors for node for n in G.neighbors(node): # Multiply weight with recursive search count += G[node][n]['weight'] * search(n) return count return search('shiny gold') - 1 print(part2())
Some benefit in using networkx is that it gives us more powerful tools than just traversing the graph. If we would like to find the shortest path, then this one-liner would help:
print(nx.shortest_path(G, source='bright red', target='shiny gold'))
Links:
- networkx.org/documentation/networkx-2.3/reference/classes/digraph.html#
- [networkx.org/documentation/networkx-2.3/reference/algorithms/generated/networkx.algorithms.shortest_paths.generic.shortest_path.html](
More python tools
These are tools worth having in back of your head while doing advent of code.
defaultdict: Useful when you don't want to think about initiating all values first.
deque: Useful when you want to pop left and right from a queue.
heapq: Amazing for tool or solving problems that involve extremes such as largest, smallest, optimal, etc.
Thanks for reading!
I hope these solutions were helpful for you.
Complete code can be found at: github.com/cNille/AdventOfCode/blob/master/2020/07.py
Discussion (1)
This is an awesome post! Thanks for sharing your insights! | https://dev.to/cnille/advent-of-code-2020-day-07-3da8 | CC-MAIN-2021-17 | refinedweb | 1,337 | 65.01 |
Connections / Transactions¶
You can write queries anywhere in your program. When you want to execute them you need a database connection.
Database connection¶
You can tell Slick how to connect to the JDBC database of your choice by creating a Database object, which encapsulates the information. There are several factory methods on scala.slick.jdbc.JdbcBackend.Database that you can use depending on what connection data you have available.
Using a JDBC URL¶
You can provide DataSource¶
You can provide a DataSource object to forDataSource. If you got it from the connection pool of your application framework, this plugs the pool into Slick.
val db = Database.forDataSource(dataSource: javax.sql.DataSource)
When you later create a Session, a connection is acquired from the pool and when the Session is closed it is returned to the pool.
Using a JNDI Name¶
If you are using JNDI you can provide a JNDI name to forName under which a DataSource object can be looked up.
val db = Database.forName(jndiName: String)
Session handling¶
Now you have a Database object and you can use it to open database connections, which Slick encapsulates in Session objects.
Automatically closing Session scope¶
The Database object’s withSession method creates a Session, passes it to a given function and closes it afterwards. If you use a connection pool, closing the Session returns the connection to the pool.
val query = for (c <- coffees) yield c.name val result = db.withSession { session => query.list()( session ) }
You can see how we are able to already define the query outside of the withSession scope. Only the methods actually executing the query in the database require a Session. Here we use the list method to execute the query and return the results as a List. (The executing methods are made available via implicit conversions).
Note that by default a database session is in auto-commit mode. Each call to the database like insert or insertAll executes atomically (i.e. it succeeds or fails completely). To bundle several statements use Transactions.
Be careful: If the Session object escapes the withSession scope, it has already been closed and is invalid. It can escape in several ways, which should be avoided, e.g. as state of a closure (if you use a Future inside a withSession scope for example), by assigning the session to a var, by returning the session as the return value of the withSession scope or else.
Implicit Session¶
By marking the Session as implicit you can avoid having to pass it to the executing methods explicitly.
val query = for (c <- coffees) yield c.name val result = db.withSession { implicit session => query.list // <- takes session implicitly } // query.list // <- would not compile, no implicit value of type Session
This is optional of course. Use it if you think it makes your code cleaner.
Transactions¶
You can use the Session object’s withTransaction method to create a transaction when you need one. The block passed to it is executed in a single transaction. If an exception is thrown, Slick rolls back the transaction at the end of the block. You can force the rollback at the end by calling rollback anywhere within the block. Be aware that Slick only rolls back database operations, not the effects of other Scala code.
session.withTransaction { // your queries go here if (/* some failure */ false){ session.rollback // signals Slick to rollback later } } // <- rollback happens here, if an exception was thrown or session.rollback was called
If you don’t have a Session yet you can use the Database object’s withTransaction method as a shortcut.
db.withTransaction{ implicit session => // your queries go here }
Manual Session handling¶
This is not recommended, but if you have to, you can handle the lifetime of a Session manually.
val query = for (c <- coffees) yield c.name val session : Session = db.createSession val result = query.list()( session ) session.close
Passing sessions around¶
You can write re-useable functions to help with Slick queries. They mostly do not need a Session as they just produce query fragments or assemble queries. If you want to execute queries inside of them however, they need a Session. You can either put it into the function signature and pass it as a (possibly implicit) argument. Or you can bundle several such methods into a class, which stores the session to reduce boilerplate code:
class Helpers(implicit session: Session){ def execute[T](query: Query[T,_]) = query.list // ... place further helpers methods here } val query = for (c <- coffees) yield c.name db.withSession { implicit session => val helpers = (new Helpers) import helpers._ execute(query) } // (new Helpers).execute(query) // <- Would not compile here (no implicit session)
Dynamically scoped sessions¶
You usually do not want to keep sessions open for very long but open and close them quickly when needed. As shown above you may use a session scope or transaction scope with an implicit session argument every time you need to execute some queries.
Alternatively you can save a bit of boilerplate code by putting
import Database.dynamicSession // <- implicit def dynamicSession : Session
at the top of your file and then using a session scope or transaction scope without a session argument.
db.withDynSession { // your queries go here }
dynamicSession is an implicit def that returns a valid Session if a withDynSession or withDynTransaction : scope is open somewhere on the current call stack.
Be careful, if you import dynamicSession and try to execute a query outside of a withDynSession or withDynTransaction scope, you will get a runtime exception. So you sacrifice some static safety for less boilerplate. dynamicSession internally uses DynamicVariable, which implements dynamically scoped variables and in turn uses Java’s InheritableThreadLocal. Be aware of the consequences regarding static safety and thread safety.
Connection Pools¶
Slick does not provide a connection pool implementation of its own. When you run a managed application in some container (e.g. JEE or Spring), you should generally use the connection pool provided by the container. For stand-alone applications you can use an external pool implementation like DBCP, c3p0 or BoneCP.
Note that Slick uses prepared statements wherever possible but it does not cache them on its own. You should therefore enable prepared statement caching in the connection pool’s configuration and select a sufficiently large pool size. | http://slick.typesafe.com/doc/2.0.0/connection.html | CC-MAIN-2014-41 | refinedweb | 1,041 | 57.37 |
WP8 Voice Commands: Phrase Lists
Today, I ’m going to show you how to extend the app we built in yesterday’s post, using something we call Phrase Lists. Using a Phrase List, we’ll be able to let users of our “Search On” application “Search on” 15 more sites, not just search on Amazon.com.
Here are a couple examples of how that’ll play out for users of the app…
To search on Amazon, it’ll work just like it did yesterday (with a small tweak to the prompt):
User: "Search On Amazon"
Phone: "Search Amazon for what?"
User: "Electronics" (or whatever the user wants)
Phone: "Searching Amazon for Electronics" (or whatever the user said she wanted)
But with the changes today, you’ll also be able to search on a bunch of sites. Here are the sites we’ll add today: Amazon, Bing, CNN, Dictionary.com, Ebay, Facebook, MSN, Twitter, Weather.com, YouTube, or Zillow. Feel free to add more when you’re typing it up on your computer.
User: "Search On CNN"
Phone: "Search CNN for what?"
User: "Presidential Election Results”
Phone: "Searching CNN for Presidential Election Results"
… or …
User: "Search On Weather.com"
Phone: "Search Weather.com for what?"
User: "Seattle 10 day forecast”
Phone: "Searching Weather.com for Seattle 10 day forecast"
Sound Good? OK… Let’s get started.
First of all, if you haven’t built the app from yesterday, go do that now. Start here…
Now, let’s update our Voice Command Definition file. We’re going to make 4 changes to the VCD file. 1.) We’re going to update the examples phrases that get displayed to users in the built in speech UX in WP8, 2.) We’re going to add a Phrase List that will contain the list of sites that we want to be able to search, 3.) We’ll refer to that PhraseList from our searchSite <Command>, specifically, from our <ListenFor> elements, and, finally 4.) We’ll change the text feedback in the <Feedback> element to react dynamically to what the user said.
Here we go …
To update the example phrases, simply find the existing <Example> elements from the vcd.xml file, and replace them this:
<Example>Amazon, Bing, CNN, Dictionary.com, Ebay, Facebook,
MSN, Twitter, Weather.com, YouTube, or Zillow</Example>
Now, let’s actually define the PhraseList. You can have up to 10 PhraseLists in your VoiceCommands CommandSet, and the PhraseLists must be after all the Command elements in the XML file. If there are more than 10, or they’re not in the right spot in the VCD file, Visual Studio should give you a red underlined squiggly line that will tell you what’s wrong when you hover over it. If for some reason you miss this, at runtime the call to InstallCommandSetsFromFileAsync will throw an exception. In our sample, we’re not trying to catch those, so if you don’t have a debugger hooked up, you’ll miss it.
We’ll name our PhraseList “siteToSearch”, and define it like this:
1: <PhraseList Label="siteToSearch">
2: <Item>Amazon</Item>
3: <Item>Bing</Item>
4: <Item>CNN</Item>
5: <Item>Dictionary.com</Item>
6: <Item>Ebay</Item>
7: <Item>Facebook</Item>
8: <Item>Google</Item>
9: <Item>Hulu</Item>
10: <Item>IMDB</Item>
11: <Item>Kayak</Item>
12: <Item>Linked In</Item>
13: <Item>MSN</Item>
14: <Item>Netflix</Item>
15: <Item>Twitter</Item>
16: <Item>Weather.com</Item>
17: <Item>YouTube</Item>
18: <Item>Zillow</Item>
19: </PhraseList>
Next, let’s update our Command, with ListenFor elements that reference this list.
The text inside a ListenFor element is used as a constraint for the recognizer. In yesterday’s example, we used a simple string, “Amazon”, as the content for our one and only ListenFor element. That meant that the user had to say “Search On”, which is the command prefix for our application, followed by “Amazon”. If you have several things you want the user to be able to say, you can do one, or both, of the following 2 things: have more than one <ListenFor> element in your command, and/or have your <ListenFor> element refer to a PhraseList by it’s Label.
Let’s see what that looks like for our updated application. Replace the <ListenFor> from yesterday, with the following:
1: <ListenFor>{siteToSearch}</ListenFor>
2: <ListenFor>{siteToSearch} dot com</ListenFor>
The first <ListenFor> element only contains a reference to the PhraseList. The second <ListenFor>, though, both references the same PhraseList, but it also has the words “dot com” after that PhraseList reference. What does this do? Well, it tells the recognizer that it’s OK for the user to say any one of the items inside the PhraseList with the siteToSearch Label, followed by the phrase “dot com”. Because we have both of these <ListenFor> elements, it essentially makes the “dot com” and optional phrase. We could have specified using an “optional” notation, using square brackets, like this:
1: <ListenFor>{siteToSearch} [dot com]</ListenFor>
Either of these two representations is essentially result in the same constraint being communicated to the speech recognizer.
OK. We’ve updated our examples, we’ve added our PhraseList for the sites to search, and we’ve updated our phrases for our command. Last thing we need to do is to update the <Feedback> element.
Similar to the <ListenFor> elements’ use of the PhraseList Label, we can substitute what was said from the PhraseList into the text feedback as well. Let’s update our <Feedback> element, and it should be pretty obvious what I mean:
1: <Feedback>Search on {siteToSearch} for what?</Feedback>
What that’ll do is this: Once the VoiceCommandService determines that one of your commands was recognized, it’ll take the text inside the corresponding <Feedback> element, and it’ll replace all occurrences of curly brace delimited PhraseLists with the text for the item that was actually recognized from the user speaking. That way, if I said “Search On Amazon”, the VoiceCommandService will replace the “{siteToSearch}” part of “Search on {siteToSearch} for what?” feedback string with “Amazon”. It’s a lot like C# string formatting, except using PhraseList Labels instead of order based parameter references, like 0, 1, 2.
OK. Now, our VCD file is all up to date. Great. Now let’s turn our attention to the code in MainPage.xaml.cs.
Let’s start off by adding a Dictionary of strings that we’ll use to look up the URL for the site we’ll be searching. And, if let’s have a backup way of searching if we can’t find that URL. Scroll down to the bottom of the MainPage class, and add the following:
1: private string _defaultUrlTemplateForUnknownSites = "{0}";
2:
3: private Dictionary<string, string> _siteUrlTemplateDictionary = new Dictionary<string, string>()
4: {
5: { "Amazon", "{0}" },
6: { "Bing", "{0}" },
7: { "CNN", "{0}" },
8: { "Dictionary.com", "{0}" },
9: { "Ebay", "{0}" },
10: { "Facebook", "{0}" },
11: { "Google", "{0}" },
12: { "Hulu", "{0}" },
13: { "IMDB", "{0}" },
14: { "Linked In", "{0}" },
15: { "MSN", "{0}" },
16: { "Twitter", "{0}" },
17: { "Weather", "{0}" },
18: { "YouTube", "{0}" },
19: { "Zillow", "{0}/" },
20: };
Now, let’s add a method that’ll do the lookup for us:
1: private string GetUrlTemplateFromSiteName(string siteName)
2: {
3: return _siteUrlTemplateDictionary.ContainsKey(siteName)
4: ? _siteUrlTemplateDictionary[siteName]
5: : string.Format(_defaultUrlTemplateForUnknownSites, siteName + "%20{1}");
6: }
Great. Now let’s update our SearchSiteVoiceCommand method to figure out what site we’re actually searching, update how we speak the feedback based on the site name, use our new GetUrlTemplateFromSiteName method to find the right URL template, and then stick the search string into the URL template appropriately. When it’s all done, it should look like this:
1: private async void SearchSiteVoiceCommand(IDictionary<string, string> queryString)
2: {
3: string text = await RecognizeTextFromWebSearchGrammar();
4: if (text != null)
5: {
6: string siteName = queryString["siteToSearch"];
7: await Speak(string.Format("Searching {0} for {1}", siteName, text));
8:
9: string siteUrlTemplate = GetUrlTemplateFromSiteName(siteName);
10: NavigateToUrl(string.Format(siteUrlTemplate, text, siteName));
11: }
12: }
One additional thing I’ll do, that we don’t absolutely need to at this point, but I think it’s good practice, is to make sure that we actually have a “siteToSearch” item in our query string dictionary in our HandleVoiceCommand method.
1: private void HandleVoiceCommand(IDictionary<string, string> queryString)
2: {
3: if (queryString["voiceCommandName"] == "searchSite" &&
4: queryString.ContainsKey("siteToSearch"))
5: {
6: SearchSiteVoiceCommand(queryString);
7: }
8: }
One more change, and then we can test it out.
Since we were only searching Amazon.com yesterday, it was probably OK for us to open up the Amazon.com home page if you started the Search On application from the Start menu, not by voice. But … It doesn’t make as much sense now, since we can search 15 different sites. Right?
So, I’ll update the code to search for blog posts by me about Windows Phone 8 on my MSDN blog instead. A bit self serving, I know, but … Hey … It’s my sample app, right? :-)
First, I’ll define a class variable to hold the new location we’ll open in that situation:
1: private string _defaultUrlForNewNavigations =
2: "'s%20Rhapsody%20Windows%20Phone%208%20site:blogs.msdn.com";
And then, I’ll update the OnNavigatedTo method to use that new class variable (see line 11 in the snippet below):: NavigateToUrl(_defaultUrlForNewNavigations);
12: }
13: else if (e.NavigationMode == NavigationMode.Back && !System.Diagnostics.Debugger.IsAttached)
14: {
15: NavigationService.GoBack();
16: }
17: }
Now we’re ready to try it out.
If you haven’t typed this in all along the way, you can scroll down below and copy/paste into Visual Studio and give it a go that way.
Press F5, and you should see a Bing Search for my blog. Yeah.
Now, on the phone, Press and hold the “Start” menu, and let’s try out our examples from above.
You: "Search On Amazon"
Phone: "Search Amazon for what?"
You: "Electronics" (or whatever you want)
Phone: "Searching Amazon for Electronics" (or whatever you said you wanted)
Great. That one still works! Let’s try out the others…
User: "Search On CNN"
Phone: "Search CNN for what?"
User: "Presidential Election Results”
Phone: "Searching CNN for Presidential Election Results"
Did that one work as well? Mine did. :-) Last one … we’ll try here today…
User: "Search On Weather.com"
Phone: "Search Weather.com for what?"
User: "Seattle 10 day forecast”
Phone: "Searching Weather.com for Seattle 10 day forecast"
Excellent. Well … except it’s going to rain this week. Bummer. But the speech part worked. If only I could say “Clouds, stop raining!!” I’m sure I can do the speech part of that one; it’s the actual stop raining part I don’t know how to do. Yet. :-)
Well. That’s it for today. Hopefully, you now know how to use PhraseLists with the VoiceCommandService. And … Our “Search On” application is starting to actually become useful. I wonder how far we can take this …
Drop me some feedback below and let me know what you’d like to see, and I’ll try to work that into posts in the future.
Happy coding! … Oh yeah … I almost forgot … Here’s the full listing for the code, and the VCD file.
1: using System;
2: using System.Collections.Generic;
3: using System.Net;
4: using System.Windows;
5: using System.Windows.Navigation;
6: using Microsoft.Phone.Controls;
7: using Windows.Phone.Speech.VoiceCommands;
8: using Windows.Phone.Speech.Recognition;
9: using Windows.Phone.Speech.Synthesis;
10: using System.Threading.Tasks;
11: using Microsoft.Phone.Tasks;
12:
13: namespace SearchOn
14: {
15: public partial class MainPage : PhoneApplicationPage
16: {
17: public MainPage()
18: {
19: InitializeComponent();
20:
21: VoiceCommandService.InstallCommandSetsFromFileAsync(new Uri("ms-appx:///vcd.xml"));
22: }
23:
24: protected override void OnNavigatedTo(NavigationEventArgs e)
25: {
26: base.OnNavigatedTo(e);
27:
28: if (e.NavigationMode == NavigationMode.New && NavigationContext.QueryString.ContainsKey("voiceCommandName"))
29: {
30: HandleVoiceCommand(NavigationContext.QueryString);
31: }
32: else if (e.NavigationMode == NavigationMode.New)
33: {
34: NavigateToUrl(_defaultUrlForNewNavigations);
35: }
36: else if (e.NavigationMode == NavigationMode.Back && !System.Diagnostics.Debugger.IsAttached)
37: {
38: NavigationService.GoBack();
39: }
40: }
41:
42: private void HandleVoiceCommand(IDictionary<string, string> queryString)
43: {
44: if (queryString["voiceCommandName"] == "searchSite" &&
45: queryString.ContainsKey("siteToSearch"))
46: {
47: SearchSiteVoiceCommand(queryString);
48: }
49: }
50:
51: private async void SearchSiteVoiceCommand(IDictionary<string, string> queryString)
52: {
53: string text = await RecognizeTextFromWebSearchGrammar();
54: if (text != null)
55: {
56: string siteName = queryString["siteToSearch"];
57: await Speak(string.Format("Searching {0} for {1}", siteName, text));
58:
59: string siteUrlTemplate = GetUrlTemplateFromSiteName(siteName);
60: NavigateToUrl(string.Format(siteUrlTemplate, text, siteName));
61: }
62: }
63:
64: private async Task<string> RecognizeTextFromWebSearchGrammar()
65: {
66: string text = null;
67: try
68: {
69: SpeechRecognizerUI sr = new SpeechRecognizerUI();
70: sr.Recognizer.Grammars.AddGrammarFromPredefinedType("web", SpeechPredefinedGrammar.WebSearch);
71: sr.Settings.ListenText = "Listening...";
72: sr.Settings.ExampleText = "Ex. \"electronics\"";
73: sr.Settings.ReadoutEnabled = false;
74: sr.Settings.ShowConfirmation = false;
75:
76: SpeechRecognitionUIResult result = await sr.RecognizeWithUIAsync();
77: if (result != null &&
78: result.ResultStatus == SpeechRecognitionUIStatus.Succeeded &&
79: result.RecognitionResult != null &&
80: result.RecognitionResult.TextConfidence != SpeechRecognitionConfidence.Rejected)
81: {
82: text = result.RecognitionResult.Text;
83: }
84: }
85: catch
86: {
87: }
88: return text;
89: }
90:
91: private async Task Speak(string text)
92: {
93: SpeechSynthesizer tts = new SpeechSynthesizer();
94: await tts.SpeakTextAsync(text);
95: }
96:
97: private void NavigateToUrl(string url)
98: {
99: WebBrowserTask task = new WebBrowserTask();
100: task.Uri = new Uri(url, UriKind.Absolute);
101: task.Show();
102: }
103:
104: private string GetUrlTemplateFromSiteName(string siteName)
105: {
106: return _siteUrlTemplateDictionary.ContainsKey(siteName)
107: ? _siteUrlTemplateDictionary[siteName]
108: : string.Format(_defaultUrlTemplateForUnknownSites, siteName + "%20{1}");
109: }
110:
111: private string _defaultUrlForNewNavigations = "'s%20Rhapsody%20Windows%20Phone%208%20site:blogs.msdn.com";
112: private string _defaultUrlTemplateForUnknownSites = "{0}";
113:
114: private Dictionary<string, string> _siteUrlTemplateDictionary = new Dictionary<string, string>()
115: {
116: { "Amazon", "{0}" },
117: { "Bing", "{0}" },
118: { "CNN", "{0}" },
119: { "Dictionary.com", "{0}" },
120: { "Ebay", "{0}" },
121: { "Facebook", "{0}" },
122: { "Google", "{0}" },
123: { "Hulu", "{0}" },
124: { "IMDB", "{0}" },
125: { "Linked In", "{0}" },
126: { "MSN", "{0}" },
127: { "Twitter", "{0}" },
128: { "Weather", "{0}" },
129: { "YouTube", "{0}" },
130: { "Zillow", "{0}/" },
131: };
132: }
133: }
vcd.xml
1: <?xml version="1.0" encoding="utf-8"?>
2:
3: <VoiceCommands xmlns="">
4:
5: <CommandSet xml:
6:
7: <CommandPrefix>Search On</CommandPrefix>
8: <Example>Amazon, Bing, CNN, Dictionary.com, Ebay, Facebook, MSN, Twitter, Weather.com, YouTube, or Zillow</Example>
9:
10: <Command Name="searchSite">
11: <Example>Amazon, Bing, CNN, Dictionary.com, Ebay, Facebook, MSN, Twitter, Weather.com, YouTube, or Zillow</Example>
12: <ListenFor>{siteToSearch}</ListenFor>
13: <ListenFor>{siteToSearch} dot com</ListenFor>
14: <Feedback>Search on {siteToSearch} for what?</Feedback>
15: <Navigate Target="MainPage.xaml" />
16: </Command>
17:
18: <PhraseList Label="siteToSearch">
19: <Item>Amazon</Item>
20: <Item>Bing</Item>
21: <Item>CNN</Item>
22: <Item>Dictionary.com</Item>
23: <Item>Ebay</Item>
24: <Item>Facebook</Item>
25: <Item>Google</Item>
26: <Item>Hulu</Item>
27: <Item>IMDB</Item>
28: <Item>Kayak</Item>
29: <Item>Linked In</Item>
30: <Item>MSN</Item>
31: <Item>Netflix</Item>
32: <Item>Twitter</Item>
33: <Item>Weather.com</Item>
34: <Item>YouTube</Item>
35: <Item>Zillow</Item>
36: </PhraseList>
37:
38: </CommandSet>
39:
40: </VoiceCommands> | https://docs.microsoft.com/en-us/archive/blogs/robch/wp8-voice-commands-phrase-lists | CC-MAIN-2020-16 | refinedweb | 2,499 | 56.76 |
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