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• Android - need UI help/advice

  - by Donal Rafferty

  I have been working on Android for the past couple of months getting to know how various components work. One area I am completely lacking in knowledge is any sort of User Interface or graphical interface creation. As an excercise I have been asked to break down the HTC call screen into what components it contains and rebuild as close as possible. Here is a picture of the HTC call screen: From my understanding the above UI has a custom title bar where "Meteor" and the call time appears. Then the main image in the middle block along with a text view showing the called party, in this case "Voice Mail" and the number. The bottom is then a custom view maybe with three custom buttons used within it. Would I be correct in my above assumptions? So the parts I should look into start programming are a custom title bar and a custom view with three custom buttons to place at the bottom? What layout would be reccomended? I hope this question is seen as relative to Stack Overflow, if it is not then I will delete it. Thanks in advance

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• What is a good starter-project in Perl?

  - by Vivin Paliath

  A buddy of mine wants to learn Perl. He asked me how to go about it. I told him: To learn Perl, you must first write Perl code. This was seconded by another buddy of mine who writes a lot of good Perl code. It's very zen, but not helpful. The problem is that this is exactly how I learnt to write Perl. At my very first job I had to implement something in Perl and I pretty much just jumped into it and waded and stumbled around until I figured it out. I was thinking that the best way for him to learn Perl would be to do a small project in Perl. The problem is, I can't think of anything that would be a good starter-project in Perl. For just basic learning and understanding concepts, I have recommended going to PerlMonks, to read Learning Perl, and also to look at Perl Best Practices. Aside from this, I think a good starter-project would be useful for him to get a grasp of the language. Any suggestions?

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• Passenger: "Missing these required gems redgreen"

  - by Michael Stum

  Hello, total ruby newbie, trying to setup a Rails/MongoDB application on Mac OS X Snow leopard. Installed Ruby 1.9.1 and RubyGems 1.3.7, which ruby and which gem point to the same directory. I'm using the Snow Leopard built-in apache and Passenger 2.2.11. I'm using the rails template from the mongo-site which seems to work okay overall. The exact error that passenger gives me is: /Users/User/Sites/feuerapp/vendor/rails/railties/lib/rails/gem_dependency.rb:119:Warning: Gem::Dependency#version_requirements is deprecated and will be removed on or after August 2010. Use #requirement **Notice: C extension not loaded. This is required for optimum MongoDB Ruby driver performance. You can install the extension as follows: gem install bson_ext If you continue to receive this message after installing, make sure that the bson_ext gem is in your load path and that the bson_ext and mongo gems are of the same version. Missing these required gems: redgreen You're running: ruby 1.9.1.376 at /usr/local/bin/ruby rubygems 1.3.7 at /Users/User/.gem/ruby/1.9.1, /usr/local/lib/ruby/gems/1.9.1 Runrake gems:installto install the missing gems. The weird thing is that redgreen is installed and looks fine to me: Dahlia:feuerapp User$ ls -la vendor/gems/ total 0 drwxr-xr-x 7 User staff 238 May 18 22:56 . drwxr-xr-x 5 User staff 170 May 18 23:00 .. drwxr-xr-x 11 User staff 374 May 18 22:56 factory_girl-1.2.4 drwxr-xr-x 11 User staff 374 May 18 22:56 mocha-0.9.8 drwxr-xr-x 7 User staff 238 May 18 22:56 mongo_mapper-0.7.6 drwxr-xr-x 7 User staff 238 May 18 22:56 redgreen-1.2.2 drwxr-xr-x 11 User staff 374 May 18 22:56 shoulda-2.10.3 Commenting out this line in environment.rb "solves" the issue, but that's not really want I want: config.gem 'redgreen' I don't understand anything of gems yet, but from my limited understanding, redgreen should be there and found?

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• Objective-C Protocols within Protocols

  - by LucasTizma

  I recently began trying my hand at using protocols in my Objective-C development as an (obvious) means of delegating tasks more appropriately among my classes. I completely understand the basic notion of protocols and how they work. However, I came across a roadblock when trying to create a custom protocol that in turn implements another protocol. I since discovered the solution, but I am curious why the following DOES NOT work: @protocol STPickerViewDelegate < UIPickerViewDelegate > - ( void )customCallback; @end @interface STPickerView : UIPickerView { id < STPickerViewDelegate > delegate; } @property ( nonatomic, assign ) id < STPickerViewDelegate > delegate; @end Then in a view controller, which conforms to STPickerViewDelegate: STPickerView * pickerView = [ [ STPickerView alloc ] init ]; pickerView.delegate = self; - ( void )customCallback { ... } - ( NSString * )pickerView:( UIPickerView * )pickerView titleForRow:( NSInteger )row forComponent:( NSInteger )component { ... } The problem was that pickerView:titleForRow:forComponent: was never being called. On the other hand, customCallback was being called just fine, which isn't too surprising. I don't understand why STPickerViewDelegate, which itself conforms to UIPickerViewDelegate, does not notify my view controller when events from UIPickerViewDelegate are supposed to occur. Per my understanding of Apple's documentation, if a protocol (A) itself conforms to another protocol (B), then a class (C) that conforms to the first protocol (A) must also conform to the second protocol (B), which is exactly the behavior I want and expected. What I ended up doing was removing the id< STPickerViewDelegate > delegate property from STViewPicker and instead doing something like the following in my STViewPicker implementation where I want to evoke customCallback: if ( [ self.delegate respondsToSelector:@selector( customCallback ) ] ) { [ self.delegate performSelector:@selector( customCallback ) ]; } This works just fine, but I really am puzzled as to why my original approach did not work.

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• Graph colouring algorithm: typical scheduling problem

  - by newba

  Hi, I'm training code problems like UvA and I have this one in which I have to, given a set of n exams and k students enrolled in the exams, find whether it is possible to schedule all exams in two time slots. Input Several test cases. Each one starts with a line containing 1 < n < 200 of different examinations to be scheduled. The 2nd line has the number of cases k in which there exist at least 1 student enrolled in 2 examinations. Then, k lines will follow, each containing 2 numbers that specify the pair of examinations for each case above. (An input with n = 0 will means end of the input and is not to be processed). Output: You have to decide whether the examination plan is possible or not for 2 time slots. Example: Input: 3 3 0 1 1 2 2 0 9 8 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 Ouput: NOT POSSIBLE. POSSIBLE. I think the general approach is graph colouring, but I'm really a newb and I may confess that I had some trouble understanding the problem. Anyway, I'm trying to do it and then submit it. Could someone please help me doing some code for this problem? I will have to handle and understand this algo now in order to use it later, over and over. I prefer C or C++, but if you want, Java is fine to me ;) Thanks in advance

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• Correlating traditional Windows joystick axes with HID

  - by Wade Williams

  I'm a bit confused on the description of joystick axes and I'm hoping that someone has a link or document which could help clear my confusion. I'm not a Windows guy, so trying to port some traditional Windows gameport code has me a bit confused. We all know about the common first three axes: X Y Z My understanding was that in the gameport-style interface the three other axes are: R U V However, looking in my IOHIDUsageTables (OS X), I see: kHIDUsage_GD_X = 0x30, /* Dynamic Value */ kHIDUsage_GD_Y = 0x31, /* Dynamic Value */ kHIDUsage_GD_Z = 0x32, /* Dynamic Value */ kHIDUsage_GD_Rx = 0x33, /* Dynamic Value */ kHIDUsage_GD_Ry = 0x34, /* Dynamic Value */ kHIDUsage_GD_Rz = 0x35, /* Dynamic Value */ kHIDUsage_GD_Vx = 0x40, /* Dynamic Value */ kHIDUsage_GD_Vy = 0x41, /* Dynamic Value */ kHIDUsage_GD_Vz = 0x42, /* Dynamic Value */ kHIDUsage_GD_Vbrx = 0x43, /* Dynamic Value */ kHIDUsage_GD_Vbry = 0x44, /* Dynamic Value */ kHIDUsage_GD_Vbrz = 0x45, /* Dynamic Value */ kHIDUsage_GD_Vno = 0x46, /* Dynamic Value */ This has me a bit confused due to the three R axis (though that does not appear to be uncommon) and the lack of a U axis. Two questions: 1) Can anyone confirm to what axis the traditional U axis would be? I saw one document describe it as "the axis for rudder pedals" leading me to believe it would be Rz. 2) Can anyone describe in more detail the typical usages of the V and Vbr axes? I understand the descriptions are "vector" and "relative vector,' respectively, but I'm having difficult visualizing what that means in terms of a physical device. All enlightenment and documentation pointers welcome.

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• Why is Available Physical Memory (dwAvailPhys) > Available Virtual Memory (dwAvailVirtual) in call G

  - by Andrew

  I am playing with an MSDN sample to do memory stress testing (see: http://msdn.microsoft.com/en-us/magazine/cc163613.aspx) and an extension of that tool that specifically eats physical memory (see http://www.donationcoder.com/Forums/bb/index.php?topic=14895.0;prev_next=next). I am obviously confused though on the differences between Virtual and Physical Memory. I thought each process has 2 GB of virtual memory (although I also read 1.5 GB because of "overhead". My understanding was that some/all/none of this virtual memory could be physical memory, and the amount of physical memory used by a process could change over time (memory could be swapped out to disc, etc.)I further thought that, in general, when you allocate memory, the operating system could use physical memory or virtual memory. From this, I conclude that dwAvailVirtual should always be equal to or greater than dwAvailPhys in the call GlobalMemoryStatus. However, I often (always?) see the opposite. What am I missing. I apologize in advance if my question is not well formed. I'm still trying to get my head around the whole memory management system in Windows. Tutorials/Explanations/Book recs are most welcome! Andrew

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• Are there more Cocoa and Cocoa Touch videos which are worth looking at?

  - by dontWatchMyProfile

  To gain a better understanding, I think it would be a good idea to watch every cocoa video available on the net. I tend to find session videos from conferences or good podcast videos only by accident, so maybe someone has a handy list of links to great ressources. I already know all the WWDC stuff and the stuff from stanford, but a lot of universities around the world publish session videos as well in local languages. Also, there are like thousands of conferences around the world with great session videos. This list should compensate for all those who can't afford beeing at WWDC. Therefore, guys, let's create a handy list to fill the gaps for everyone! This is community wiki, so just list them all! I'll start with: English 360 Conferences (360iDev) Videos Oredev with some good iPhone dev session videos German Macoun 2009 with some interesting session videos, if you can speak German Please don't hesitate to post links to videos in other languages than English. Many of us speak more languages, so go ahead! We'll be excited!

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• Is there a detailed description of optimizations in the Android build process?

  - by Daniel Lew

  I've been curious as to all the optimizations that go into the building of an .apk. I'm curious because of two things I've tried in the past to bring down the size of my .apk: I have had a few large json assets in projects before, as well as a static sqlite database. I tried bringing down the size of the apk by gzipping them before the build process, but the resulting size is exactly the same. I just today tried pngcrush on my /drawable/ folders. The resulting build was exactly the same size as before. I would think that perhaps #1 could be explained by the zip process, but simply zipping the /drawable/ folders in #2 result in different-sized files. Perhaps the build process runs something akin to pngcrush? Regardless, I was wondering if anyone knew where to find a detailed description of all the optimizations in the Android build process. I don't want to waste my time trying to optimize what is already automated, and also I think it'd help my understanding of the resulting apk. Does anyone know if this is documented anywhere?

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• Positioning SVG Elements

  - by Rob Wilkerson

  In the course of toying with SVG for the first time (using the Raphael library), I've run into a problem positioning dynamic elements on the canvas in such a way that they're completely contained within the canvas. What I'm trying to do is randomly position n words/short phrases. Since the text is variable, its position needs to be variable as well so what I'm doing is: Initially creating the text at point 0,0 with no opacity. Checking the width of the drawn text element using text.getBBox().width. Setting a new x coordinate as Math.random() * (canvas_width - ( text_width/2 ) - pad). Altering the x coordinate of the text to the newly set value (text.attr( 'x', x ) ). Setting the opacity attribute of the text to 1. I'll be the first to admit that my math acumen is limited, but this seems pretty straightforward. Somehow, I still end up with text running off beyond the right edge of my canvas. For simplicity above, I removed the bit that also sets a minimum x value by adding it to the Math.random() result. It is there, though, and I see the same problem on the leading edge of the canvas. My understanding (such as it is), is that the Math.random() bits would generate a number between 0 and 1 which could then be multiplied by some number (in my case, the canvas width - half of the text width - some arbitrary padding) to get the outer bound. I'm dividing the width of the text in half because its position on the grid is set at its center. I hope I've just been staring at this for too long, but is my math that rusty or am I misunderstanding something about the behavior of Math.random(), SVG, text or anything else that's under the hood of this solution?

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• Read large file into sqlite table in objective-C on iPhone

  - by James Testa

  I have a 2 MB file, not too large, that I'd like to put into an sqlite database so that I can search it. There are about 30K entries that are in CSV format, with six fields per line. My understanding is that sqlite on the iPhone can handle a database of this size. I have taken a few approaches but they have all been slow 30 s. I've tried: 1) Using C code to read the file and parse the fields into arrays. 2) Using the following Objective-C code to parse the file and put it into directly into the sqlite database: NSString *file_text = [NSString stringWithContentsOfFile: filePath usedEncoding: NULL error: NULL]; NSArray *lineArray = [file_text componentsSeparatedByString:@"\n"]; for(int k = 0; k < [lineArray count]; k++){ NSArray *parts = [[lineArray objectAtIndex:k] componentsSeparatedByString: @","]; NSString *field0 = [parts objectAtIndex:0]; NSString *field2 = [parts objectAtIndex:2]; NSString *field3 = [parts objectAtIndex:3]; NSString *loadSQLi = [[NSString alloc] initWithFormat: @"INSERT INTO TABLE (TABLE, FIELD0, FIELD2, FIELD3) VALUES ('%@', '%@', '%@');",field0, field2, field3]; if (sqlite3_exec (db_table, [loadSQLi UTF8String], NULL, NULL, &errorMsg) != SQLITE_OK) { sqlite3_close(db_table); NSAssert1(0, @"Error loading table: %s", errorMsg); } Am I missing something? Does anyone know of a fast way to get the file into a database? Or is it possible to translate the file into a sqlite format that can be read directly into sqlite? Or should I turn the file into a plist and load it into a Dictionary? Unfortunately I need to search on two of the fields, and I think a Dictionary can only have one key? Jim

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• Help a C# developer understand: What is a monad?

  - by Charlie Flowers

  There is a lot of talk about monads these days. I have read a few articles / blog posts, but I can't go far enough with their examples to fully grasp the concept. The reason is that monads are a functional language concept, and thus the examples are in languages I haven't worked with (since I haven't used a functional language in depth). I can't grasp the syntax deeply enough to follow the articles fully ... but I can tell there's something worth understanding there. However, I know C# pretty well, including lambda expressions and other functional features. I know C# only has a subset of functional features, and so maybe monads can't be expressed in C#. However, surely it is possible to convey the concept? At least I hope so. Maybe you can present a C# example as a foundation, and then describe what a C# developer would wish he could do from there but can't because the language lacks functional programming features. This would be fantastic, because it would convey the intent and benefits of monads. So here's my question: What is the best explanation you can give of monads to a C# 3 developer? Thanks! (EDIT: By the way, I know there are at least 3 "what is a monad" questions already on SO. However, I face the same problem with them ... so this question is needed imo, because of the C#-developer focus. Thanks.)

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• Questions on usages of sizeof

  - by Appu

  Question 1 I have a struct like, struct foo { int a; char c; }; When I say sizeof(foo), i am getting 8 on my machine. As per my understanding, 4 bytes for int, 1 byte for char and 3 bytes for padding. Is that correct? Given a struct like the above, how will I find out how many bytes will be added as padding? Question 2 I am aware that sizeof can be used to calculate the size of an array. Mostly I have seen the usage like (foos is an array of foo) sizeof(foos)/sizeof(*foos) But I found that the following will also give same result. sizeof(foos) / sizeof(foo) Is there any difference in these two? Which one is preffered? Question 3 Consider the following statement. foo foos[] = {10,20,30}; When I do sizeof(foos) / sizeof(*foos), it gives 2. But the array has 3 elements. If I change the statement to foo foos[] = {{10},{20},{30}}; it gives correct result 3. Why is this happening? Any thoughts..

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• Help with dynamic-wind and call/cc

  - by josh

  I am having some trouble understanding the behavior of the following Scheme program: (define c (dynamic-wind (lambda () (display 'IN)(newline)) (lambda () (call/cc (lambda (k) (display 'X)(newline) k))) (lambda () (display 'OUT)(newline)))) As I understand, c will be bound to the continution created right before "(display 'X)". But using c seems to modify itself! The define above prints (as I expected) IN, X and OUT: IN X OUT And it is a procedure: #;2> c #<procedure (a9869 . results1678)> Now, I would expect that when it is called again, X would be printed, and it is not! #;3> (c) IN OUT And now c is not a procedure anymore, and a second invokation of c won't work! #;4> c ;; the REPL doesn't answer this, so there are no values returned #;5> (c) Error: call of non-procedure: #<unspecified> Call history: <syntax> (c) <eval> (c) <-- I was expecting that each invokation to (c) would do the same thing -- print IN, X, and OUT. What am I missing?

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• function's return address is different from its supposed value, buffer overflow,

  - by ultrajohn

  Good day everyone! I’m trying to understand how buffer overflow works. I’m doing this for my project in a computer security course I’m taking. Right now, I’m in the process of determining the address of the function’s return address which I’m supposed to change to perform a buffer overflow attack. I’ve written a simple program based from an example I’ve read in the internet. What this program does is it creates an integer pointer that will be made to point to the address of the function return address in the stack. To do this, (granted I understand how a function/program variables get organized in the stack), I add 8 to the buffer variable’ address and set it as the value of ret. I’m not doing anything here that would change the address contained in the location of func’s return address. here's the program: Output of the program when gets excecuted: As you can see, I’m printing the address of the variables buffer and ret. I’ve added an additional statement printing the value of the ret variable (supposed location of func return address, so this should print the address of the next instruction which will get executed after func returns from execution). Here is the dump which shows the supposed address of the instruction to be executed after func returns. (Underlined in green) As you can see, that value is way different from the value printed contained in the variable ret. My question is, why are they different? (of course in the assumption that what I’ve done are all right). Else, what have I done wrong? Is my understanding of the program’s runtime stack wrong? Please, help me understand this. My project is due nextweek and I’ve barely touched it yet. I’m sorry if I’m being demanding, I badly need your help.

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• Are SharePoint site templates really less performant than site definitions?

  - by Jim

  So, it seems in the SharePoint blogosphere that everybody just copies and pastes the same bullet points from other blogs. One bullet point I've seen is that SharePoint site templates are less performant than site definitions because site definitions are stored on the file system. Is that true? It seems odd that site templates would be less performant. It's my understanding that all site content lives in a database, whether you use a site template or a site definition. A site template is applied once to the database, and from then on the site should not care if the content was created using a site template or not. So, does anybody have an architectural reason why a site template would be less performant than a site definition? Edit: Links to the blogs that say there is a performance difference: From MSDN: Because it is slow to store templates in and retrieve them from the database, site templates can result in slower performance. From DevX: However, user templates in SharePoint can lead to performance problems and may not be the best approach if you're trying to create a set of reusable templates for an entire organization. From IT Footprint: Because it is slow to store templates in and retrieve them from the database, site templates can result in slower performance. Templates in the database are compiled and executed every time a page is rendered. From Branding SharePoint:Custom site definitions hold the following advantages over custom templates: Data is stored directly on the Web servers, so performance is typically better. At a minimum, I think the above articles are incomplete, and I think several are misleading based on what I know of SharePoints architecture. I read another blog post that argued against the performance differences, but I can't find the link.

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• How should I implement reverse AJAX in a Django application?

  - by Carson Myers

  How should I implement reverse AJAX when building a chat application in Django? I've looked at Django-Orbited, and from my understanding, this puts a comet server in front of the HTTP server. This seems fine if I'm just running the Django development server, but how does this work when I start running the application from mod_wsgi? How does having the orbited server handling every request scale? Is this the correct approach? I've looked at another approach (long polling) that seems like it would work, although I'm not sure what all would be involved. Would the client request a page that would live in its own thread, so as not to block the rest of the application? Would it even block? Wouldn't the script requested by the client have to continuously poll for information? Which of the approaches is more proper? Which is more portable, scalable, sane, etc? Are there other good approaches to this (aside from the client polling for messages) that I have overlooked?

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• SQL Server 2005 standard filegroups / files for performance on SAN

  - by Blootac

  Ok so I've just been on a SQL Server course and we discussed the usage scenarios of multiple filegroups and files when in use over local RAID and local disks but we didn't touch SAN scenarios so my question is as follows; I currently have a 250 gig database running on SQL Server 2005 where some tables have a huge number of writes and others are fairly static. The database and all objects reside in a single file group with a single data file. The log file is also on the same volume. My interpretation is that separate data files should be used across different disks to lessen disk contention and that file groups should be used for partitioning of data. However, with a SAN you obviously don't really have the same issue of disk contention that you do with a small RAID setup (or at least we don't at the moment), and standard edition doesn't support partitioning. So in order to improve parallelism what should I do? My understanding of various Microsoft publications is that if I increase the number of data files, separate threads can act across each file separately. Which leads me to the question how many files should I have. One per core? Should I be putting tables and indexes with high levels of activity in separate file groups, each with the same number of data files as we have cores? Thank you

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• How to launch correct version of Msbuild

  - by Rory Becker

  When I type... Msbuild<Enter> ... At the command prompt, I get... Microsoft (R) Build Engine Version 2.0.50727.4927 [Microsoft .NET Framework, Version 2.0.50727.4927] Copyright (C) Microsoft Corporation 2005. All rights reserved. This is all very well and good except that when I run this against a vs2010 .sln file, the error message indicates: MyProject.sln(2): Solution file error MSB5014: File format version is not recognized. MSBuild can only read solution files between versions 7.0 and 9.0, inclusive. 0 Warning(s) 1 Error(s) It would appear that the version of msbuild that is being called, is not capable of understanding my solution file. I figured that I would check out my path and see where msbuild is being picked up from. However, it seems that no part of my path points at a location where msbuild is to be found. How is the command line finding the copy of msbuild that it is using and how can I change this version so that the latest version is used?

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• Objective-C memory model

  - by TofuBeer

  I am attempting to wrap my head around one part of the Objective-C memory model (specifically on the iPhone, so no GC). My background is C/C++/Java, and I am having an issue with the following bit of code (also wondering if I am doing this in an "Objective-C way" or not): - (NSSet *) retrieve { NSMutableSet *set; set = [NSMutableSet new]; // would normally fill the set in here with some data return ([set autorelease]); } - (void) test { NSSet *setA; NSSet *setB; setA = [self retrieve]; setB = [[self retrieve] retain]; [setA release]; [setB release]; } start EDIT Based on comments below, the updated retrieve method: - (NSSet *) retrieve { NSMutableSet *set; set = [[[NSMutableSet alloc] initWithCapacity:100] autorelease]; // would normally fill the set in here with some data return (set); } end EDIT The above code gives a warning for [setA release] "Incorrect decrement of the reference count of an object is not owned at this point by the caller". I though that the "new" set the reference count to 1. Then the "retain" call would add 1, and the "release" call would drop it by 1. Given that wouldn't setA have a reference count of 0 at the end and setB have a reference count of 1 at the end? From what I have figured out by trial and error, setB is correct, and there is no memory leak, but I'd like to understand why that is the case (what is wrong with my understanding of "new", "autorelease", "retain", and "release").

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• Perl, module export symbol

  - by Mike

  I'm having trouble understanding how to export a package symbol to a namespace. I've followed the documentation almost identically, but it seems to not know about any of the exporting symbols. mod.pm #!/usr/bin/perl package mod; use strict; use warnings; require Exporter; @ISA = qw(Exporter); @EXPORT=qw($a); our $a=(1); 1; test.pl $ cat test.pl #!/usr/bin/perl use mod; print($a); This is the result of running it $ ./test.pl Global symbol "@ISA" requires explicit package name at mod.pm line 10. Global symbol "@EXPORT" requires explicit package name at mod.pm line 11. Compilation failed in require at ./test.pl line 3. BEGIN failed--compilation aborted at ./test.pl line 3. $ perl -version This is perl, v5.8.4 built for sun4-solaris-64int

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• Help! I've learned jQuery... now I want to learn JavaScript

  - by Derek Adair

  I am a self-taught web developer/programmer. I started out about two years ago by learning how to make simple dynamic websites with HTML/CSS/PHP. Then I started dabbling with animation... Enter jQuery I've become quite proficient with jQuery over the last year and I've even started making my own plugins. I've spent most of my effort learning how to beautify websites with fancy effects and what not. Upon tackling my first full-blown application, I realized how under-developed my knowledge of JavaScript actually is. jQuery has allowed me to rely on its framework so heavily that I rarely use any interesting functions, techniques, or whatever that are 'native' to the JavaScript language. For example: I have a basic understanding of what a closure is... but I am unsure where this technique can actually benefit me. Although as I understand it, that's what my jQuery plugins do with (function ($){//plugin code here})(jQuery). I've seen many posts/blogs/whatever about memory leaks and circular references which is concerning. I'm frustrated because I can wrap my head around the basic concepts of what these are just by reading the articles, but I'm finding that the deeper I go the more I don't understand. The vocabulary alone is burdensome. Let alone how to actually use these techniques/functions/language features. I am trying to figure out what I don't know I'm looking to gather any advice, techniques, articles, books, videos, snippets, examples, potential pitfalls... really anything you have regarding application development with JavaScript/jQuery.

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• What makes these two R data frames not identical?

  - by Matt Parker

  UPDATE: I remembered dput() about the time Sharpie mentioned it. It's probably the row names. Back in a moment with an answer. I have two small data frames, this_tx and last_tx. They are, in every way that I can tell, completely identical. this_tx == last_tx results in a frame of identical dimensions, all TRUE. this_tx %in% last_tx, two TRUEs. Inspected visually, clearly identical. But when I call identical(this_tx, last_tx) I get a FALSE. Hilariously, even identical(str(this_tx), str(last_tx)) will return a TRUE. If I set this_tx <- last_tx, I'll get a TRUE. What is going on? I don't have the deepest understanding of R's internal mechanics, but I can't find a single difference between the two data frames. If it's relevant, the two variables in the frames are both factors - same levels, same numeric coding for the levels, both just subsets of the same original data frame. Converting them to character vectors doesn't help. Background (because I wouldn't mind help on this, either): I have records of drug treatments given to patients. Each treatment record essentially specifies a person and a date. A second table has a record for each drug and dose given during a particular treatment (usually, a few drugs are given each treatment). I'm trying to identify contiguous periods during which the person was taking the same combinations of drugs at the same doses. The best plan I've come up with is to check the treatments chronologically. If the combination of drugs and doses for treatment[i] is identical to the combination at treatment[i-1], then treatment[i] is a part of the same phase as treatment[i-1]. Of course, if I can't compare drug/dose combinations, that's right out.

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• Weird switch behavior in .NET 4

  - by RaYell

  I have a problem understanding what's causes the compilation error in the code below: static class Program { static void Main() { dynamic x = ""; var test = foo(x); if (test == "test") { Console.WriteLine(test); } switch (test) { case "test": Console.WriteLine(test); break; } } private static string foo(object item) { return "bar"; } } The error I get is in switch (test) line: A switch expression or case label must be a bool, char, string, integral, enum, or corresponding nullable type. Intellisence shows me that foo operation will be resolved on runtime, which is fine because I'm using a dynamic type as a param. However I don't understand how if condition compiles fine when switch doesn't. Code above is just simplified version of what I have in my application (VSTO) which appeared after migrating the app from VSTO3 to VSTO4 when one method in VSTO was changed to return dynamic type values instead of object. Can anyone give me an explanation what's the problem. I know how to resolve it but I'd like to understand what's happening.

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• Unit Testing a Java Chat Application

  - by Epitaph

  I have developed a basic Chat application in Java. It consists of a server and multiple client. The server continually monitors for incoming messages and broadcasts them to all the clients. The client is made up of a Swing GUI with a text area (for messages sent by the server and other clients), a text field (to send Text messages) and a button (SEND). The client also continually monitors for incoming messages from other clients (via the Server). This is achieved with Threads and Event Listeners and the application works as expected. But, how do I go about unit testing my chat application? As the methods involve establishing a connection with the server and sending/receiving messages from the server, I am not sure if these methods should be unit tested. As per my understanding, Unit Testing shouldn't be done for tasks like connecting to a database or network. The few test cases that I could come up with are: 1) The max limit of the text field 2) Client can connect to the Server 3) Server can connect to the Client 4) Client can send message 5) Client can receive message 6) Server can send message 7) Server can receive message 8) Server can accept connections from multiple clients But, since most of the above methods involve some kind of network communication, I cannot perform unit testing. How should I go about unit testing my chat application?

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