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  • Why is django giving me an attribute error when I call _set.all() for its children models?

    - by user1876508
    I have two models defined from django.db import models class Blog(models.Model): title = models.CharField(max_length=144) @property def posts(self): self.Post_set.all() class Post(models.Model): title = models.CharField(max_length=144) text = models.TextField() blog = models.ForeignKey('Blog') but the problem is, when I run shell, and enter >>> blog = Blog(title="My blog") >>> post = Post(title="My first post", text="Here is the main text for my blog post", blog=blog) >>> blog.posts I get the error Traceback (most recent call last): File "<console>", line 1, in <module> File "/home/lucas/Programming/Python/Django/djangorestfun/blog/models.py", line 9, in posts self.Post_set.all() AttributeError: 'Blog' object has no attribute 'Post_set' >>> Now I am having the following problem >>> from blog.models import * >>> blog = Blog(title="gewrhter") >>> blog.save() >>> blog.__dict__ {'_state': <django.db.models.base.ModelState object at 0x259be10>, 'id': 1, 'title': 'gewrhter'} >>> blog._state.__dict__ {'adding': False, 'db': 'default'} >>> post = Post(title="sdhxcvb", text="hdbfdgb", blog=blog) >>> post.save() >>> post.__dict__ {'blog_id': 1, 'title': 'sdhxcvb', 'text': 'hdbfdgb', '_blog_cache': <Blog: Blog object>, '_state': <django.db.models.base.ModelState object at 0x259bed0>, 'id': 1} >>> blog.posts >>> print blog.posts None Second update So I followed your guide, but I am still getting nothing. In addition, blog.posts gives me an error. >>> from blog.models import * >>> blog = Blog(title="asdf") >>> blog.save() >>> post = Post(title="asdf", text="sdxcvb", blog=blog) >>> post.save() >>> blog.posts Traceback (most recent call last): File "<console>", line 1, in <module> AttributeError: 'Blog' object has no attribute 'posts' >>> print blog.all_posts None

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  • Downloading Python 2.5.4 (from official website) in order to install it

    - by brilliant
    I was quite hesitant about whether I should post this question here on "StackOverflow" or on "SuperUser", but finally decided to post it here as Python is more a programming language rather than a piece of software. I've been recently using Python 2.5.4 that is installed on my computer, but at the moment I am not at home (and won't be for about two weeks from now), so I need to install the same version of Python on another computer. This computer has Windows XP installed – just like the one that I have at home. The reason why I need Python 2.5.4 is because I am using “Google App Engine”, and I was told that it only supports Python 2.5 However, when I went to the official Python page for the download, I discovered that certain things have changed, and I don’t quite remember where exactly from that site I had downloaded Python 2.5.4 on my computer at home. I found this page: http://www.python.org/download/releases/2.5.4/ Here is how it looks: (If you can’t see it here, please check it out at this address: http://brad.cwahi.net/some_pictures/python_page.jpg ) A few things here are not clear to me. It says: “For x86 processors: python-2.5.4.msi For Win64-Itanium users: python-2.5.4.ia64.msi For Win64-AMD64 users: python-2.5.4.amd64.msi” First of all, I don’t know what processor I am using – whether mine is “x86” or not; and also, I don’t know whether I am an “Win64-Itanium” or an “Win64-AMD64” user. Are Itanium and AMD64 also processors? Later it says: “Windows XP and later already have MSI; many older machines will already have MSI installed.” I guess, it is my case, but then I am totally puzzled as to which link I should click as it seems now that I don’t need those three previous links (as MSI is already installed on Windows XP), but there is no fourth link provided for those who use “Windows XP” or older machines. Of course, there are these words after that: “Windows users may also be interested in Mark Hammond's win32all package, available from Sourceforge.” but it seems to me that it is something additional rather than the main file. So, my question is simple: Where in the official Python website I can download Python 2.5.4, precisely, which link I should click?

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  • How to read the 3D chart data with directX?

    - by MemoryLeak
    I am reading a open source project, and I found there is a function which read 3D data(let's say a character) from obj file, and draw it . the source code: List<Vertex3f> verts=new List<Vertex3f>(); List<Vertex3f> norms=new List<Vertex3f>(); Groups=new List<ToothGroup>(); //ArrayList ALf=new ArrayList();//faces always part of a group List<Face> faces=new List<Face>(); MemoryStream stream=new MemoryStream(buffer); using(StreamReader sr = new StreamReader(stream)){ String line; Vertex3f vertex; string[] items; string[] subitems; Face face; ToothGroup group=null; while((line = sr.ReadLine()) != null) { if(line.StartsWith("#")//comment || line.StartsWith("mtllib")//material library. We build our own. || line.StartsWith("usemtl")//use material || line.StartsWith("o")) {//object. There's only one object continue; } if(line.StartsWith("v ")) {//vertex items=line.Split(new char[] { ' ' }); vertex=new Vertex3f();//float[3]; if(flipHorizontally) { vertex.X=-Convert.ToSingle(items[1],CultureInfo.InvariantCulture); } else { vertex.X=Convert.ToSingle(items[1],CultureInfo.InvariantCulture); } vertex.Y=Convert.ToSingle(items[2],CultureInfo.InvariantCulture); vertex.Z=Convert.ToSingle(items[3],CultureInfo.InvariantCulture); verts.Add(vertex); continue; } And why it need to read the data manually in directX? As far as I know, in XDA programming, we just need to call a function a load the resource. Is this because it is in DirectX, there is no function to read resource? If yes, then how to prepare the 3D resource ? in XDA we just need to use other software draw the 3D picture and then export. but what should I do in DirectX?

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  • Daylight saving time and Timezone best practices

    - by Oded
    I am hoping to make this question and the answers to it the definitive guide to dealing with daylight saving time, in particular for dealing with the actual change overs. If you have anything to add, please do Many systems are dependent on keeping accurate time, the problem is with changes to time due to daylight savings - moving the clock forward or backwards. For instance, one has business rules in an order taking system that depend on the time of the order - if the clock changes, the rules might not be as clear. How should the time of the order be persisted? There is of course an endless number of scenarios - this one is simply an illustrative one. How have you dealt with the daylight saving issue? What assumptions are part of your solution? (looking for context here) As important, if not more so: What did you try that did not work? Why did it not work? I would be interested in programming, OS, data persistence and other pertinent aspects of the issue. General answers are great, but I would also like to see details especially if they are only available on one platform. Summary of answers and other data: (please add yours) Do: Always persist time according to a unified standard that is not affected by daylight savings. GMT and UTC have been mentioned by different people. Include the local time offset (including DST offset) in stored timestamps. Remember that DST offsets are not always an integer number of hours (e.g. Indian Standard Time is UTC+05:30). If using Java, use JodaTime. - http://joda-time.sourceforge.net/ Create a table TZOffsets with three columns: RegionClassId, StartDateTime, and OffsetMinutes (int, in minutes). See answer Check if your DBMS needs to be shutdown during transition. Business rules should always work on civil time. Internally, keep timestamps in something like civil-time-seconds-from-epoch. See answer Only convert to local times at the last possible moment. Don't: Do not use javascript date and time calculations in web apps unless you ABSOLUTELY have to. Testing: When testing make sure you test countries in the Western and Eastern hemispheres, with both DST in progress and not and a country that does not use DST (6 in total). Reference: Olson database, aka Tz_database - ftp://elsie.nci.nih.gov/pub Sources for Time Zone and DST - http://www.twinsun.com/tz/tz-link.htm ISO format (ISO 8601) - http://en.wikipedia.org/wiki/ISO_8601 Mapping between Olson database and Windows TimeZone Ids, from the Unicode Consortium - http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/windows_tzid.html TimeZone page on WikiPedia - http://en.wikipedia.org/wiki/Tz_database StackOverflow questions tagged dst - http://stackoverflow.com/questions/tagged/dst StackOverflow questions tagged timezone - http://stackoverflow.com/questions/tagged/timezone Other: Lobby your representative to end the abomination that is DST. We can always hope...

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  • Opera Mobile, offline web app development, and memory

    - by Jake Krohn
    I'm developing a data collection app for use on a HP iPAQ 211. I'm doing it as an offline web app (go with what you know) using Opera Mobile 9.7 and Google Gears. Being it is an offline app, it is very dependent on Javascript for much of its behavior. I'm using the LocalServer, Database, and Geolocation components of Gears, as well as the JQuery core and a couple of plugins for form validation and other usability tweaks (no jQuery UI). I've tried to be conservative with my programming style and free up or close resources whenever possible, but Opera just slowly dies after about 10-20 minutes of use. The Javascript engine stops responding, pages only half-load, and eventually stop loading completely. I'm guessing it's a resource issue. Quitting and relaunching the browser solves the problem, but only temporarily. The iPAQ ships with 128 MB of RAM, about 85-87 MB of which is available immediately after a reset. With only Opera running, there still remains about 50 MB that is left unused. My questions are thus: Is it possible to get Opera to address this unused RAM? Are there configuration settings in Opera or in the Windows Registry itself that will help improve performance? I know where to tweak, but the descriptions of the opera:config variables that I've found are less than helpful. Is is laughable to ask about memory management and jQuery in the same sentence? If not, does anyone have any suggestions? Finally, are my plans too ambitious, given the platform I have to work with? I know that Gears and Windows Mobile 6 are on their way out, but they (theoretically) suffice for what I need to do. I could ditch them in favor of an iPhone/iPod Touch, Mobile Safari, and HTML5 but I'd like to try to make this work first. I didn't think that Opera was a dog when it comes to JS performance, but perhaps it's worse than I thought. That this motley collection of technologies works at all is a minor miracle, but it needs to be faster and more stable. I appreciate any suggestions.

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  • From a 3D modeler to an iPhone app - what are best practices?

    - by bonkey
    I am quite new in 3D programming on iPhone and I would like to ask for hints about organizing a work between designers and programmers on that platform. Most of all: what kind of tools, libraries or plugins cooperate the best on both sides. Although I consider the question as looking for general best-practices advice I would like to find a solution for my current situation which I describe further, too. I've already done some research and found following libraries: SIO2 Khronos OpenGL ES 1.x SDK for PowerVR MBX Unity3D Oolong Game Engine I've checked modellers or plugins to them giving output formats readable by those tools: obj2opengl Wavefront OBJ to plain header file converter Blender with SIO2 exporter iphonewavefrontloader Cheetah3D PVRGeoPOD for 3DS / Maya Unfortunately I still have no clear vision how to combine any of that tools to get a desinger's work in an application. I look for a way of getting it in the most possible complete way: models, lights, scenes, textures, maybe some simple animations (but rather no game-like physics), but I still got nothing. And here comes my situation: I would like to find right way to present few (but quite complicated) models from a single scene. The designers mostly use 3DS Max 9, sometimes 10 (which partly prevents using PVRGeoPOD) and are rather reluctant to switch to something else but if there's no other choice I suppose it would be possible. The basic rule I've already found in some places "use Wavefront OBJ" not always works. I haven't got any acceptable results with production files, actually. The only things worked fine were some mere examples. Some of my models did imported incomplete, sometimes exporters hung or generated enormous files not really useful on an iPhone, sometimes enabling textures (with GL_TEXTURE_2D) just crashed an app. I know it might be a problem with too complicated models or my mistakes coming from inexeperience but I am not able to find any guidelines for that process to have streamlined cooperation with designers. I am even willing to write some things from scratch in pure OpenGL-ES if it's necessary, but I would like to avoid what might be avoided and get the most from the model files. The best would be the effect I saw on some SIO2 tutorials: export, build & go. But at that moment I've got only "import, wrong", "import, where are textures?", "import, that almost looks fine, export, hang" and so on... Is it really so much frustrating or I am just missed something obvious? Can anybody share his/her experience in that field and tell what kind of software uses for "making things happen"?

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  • iGoogle Stack Overflow Gadget [closed]

    - by Charango
    Since SO's question database is becoming an excellent first point of call for finding answers to coding problems, some people (like me) might like to be able to fire up searches from their iGoogle home page, among the other searches you might launch from there. I've created a very simple gadget to do this, and put the source below. My hope is that this might provide a foundation on which community members with better ideas for performing this function, or ideas for enhancing it, can update it. Perhaps we could make it configurable to search via a site scope search from Google and / or a question search, for instance. I've hosted and registered this first version but if anyone makes changes and can host a new version / new pics elsewhere, please feel free. <?xml version="1.0" encoding="UTF-8"?> <Module> <ModulePrefs title="Stack Overflow Search" author="Community Wiki" author_email="[email protected]" author_affiliation="Stack Overflow" author_location="The Internet" author_aboutme="All sorts" author_link="http://stackoverflow.com" author_quote="Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law." description="Stack Overflow is rapidly becoming one of the best resources for finding answers to your programming questions. This gadget adds a question search box to your iGoogle homepage" screenshot="http://arkios-solutions.com/misc/sogadget/SOGadget.png" thumbnail="http://arkios-solutions.com/misc/sogadget/SOGadget_Thumbnail.png" singleton="true" title_url="http://stackoverflow.com" /> <Content type="html"><![CDATA[ <img src="http://i.stackoverflow.com/Content/Img/stackoverflow-logo-250.png" alt="Stackoverflow Logo"/> <div style="font-family:arial;font-size:0.8em;"> This gadget allows you to search the Stack Overflow question database. </div> <form name='SOQueryForm' action="http://stackoverflow.com/search" method="get" target="new"> <p>Your question: <input type='text' size='34' name='q' /></p> <p><input type='submit' value='Go' /></p> </form> ]]> </Content> </Module> The source / installable gadget xml are also hosted here.

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  • Using in app purchase to unlock features vs. using free & paid app versions for iPhone

    - by yabada
    I have an app that I was going to release as a free (lite) version with some of the total functionality and a paid full version with advanced functionality. Now, with in app purchase for free apps I am thinking of going that route with the ability to unlock features as needed. I'm not talking about a trial version that expires.I want people to be able to try out the app and get an idea of the interface and functionality before deciding to purchase the full functionality of each major section of the app, basically. Here's an analogy of what my app would be like. Let's say you have a cooking app that teaches you to cook in different styles. There could be major section for French, Italian, and Chinese. Each section could have some rudiments unlocked in the free app so users can see the UI and basics of the functionality. Then, the user could decide to purchase each major section (or not) individually with in app purchase or buy the full versioned app (with the free/paid model). One concern I have with offering a free app with in app purchase would be with feedback. I would be very clear in my description in the app store that there is in app purchase for full features but I'm worried that less serious users could/would leave negative feedback. I suppose that's always a risk but curious about any experience with this. It also seems that it could be a whole lot more complicated keeping track of what portions of the app are locked and unlocked with in app purchase. I know I'd have to have all the code for the full functionality and "lock" the portions that haven't been purchased. How do people usually lock portions of their code? I'm not talking about the process of purchasing (I've read the In App Purchase Programming Guide) but after the purchase has been made. Would I just keep track of what the user has purchased and put conditionals on the sections that are initially locked? Or is there another way to do this as well? My instinct is for the in app purchase (particularly since users could purchase the major sections that they want individually).

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  • Fixed point math in c#?

    - by x4000
    Hi there, I was wondering if anyone here knows of any good resources for fixed point math in c#? I've seen things like this (http://2ddev.72dpiarmy.com/viewtopic.php?id=156) and this (http://stackoverflow.com/questions/79677/whats-the-best-way-to-do-fixed-point-math), and a number of discussions about whether decimal is really fixed point or actually floating point (update: responders have confirmed that it's definitely floating point), but I haven't seen a solid C# library for things like calculating cosine and sine. My needs are simple -- I need the basic operators, plus cosine, sine, arctan2, PI... I think that's about it. Maybe sqrt. I'm programming a 2D RTS game, which I have largely working, but the unit movement when using floating-point math (doubles) has very small inaccuracies over time (10-30 minutes) across multiple machines, leading to desyncs. This is presently only between a 32 bit OS and a 64 bit OS, all the 32 bit machines seem to stay in sync without issue, which is what makes me think this is a floating point issue. I was aware from this as a possible issue from the outset, and so have limited my use of non-integer position math as much as possible, but for smooth diagonal movement at varying speeds I'm calculating the angle between points in radians, then getting the x and y components of movement with sin and cos. That's the main issue. I'm also doing some calculations for line segment intersections, line-circle intersections, circle-rect intersections, etc, that also probably need to move from floating-point to fixed-point to avoid cross-machine issues. If there's something open source in Java or VB or another comparable language, I could probably convert the code for my uses. The main priority for me is accuracy, although I'd like as little speed loss over present performance as possible. This whole fixed point math thing is very new to me, and I'm surprised by how little practical information on it there is on google -- most stuff seems to be either theory or dense C++ header files. Anything you could do to point me in the right direction is much appreciated; if I can get this working, I plan to open-source the math functions I put together so that there will be a resource for other C# programmers out there. UPDATE: I could definitely make a cosine/sine lookup table work for my purposes, but I don't think that would work for arctan2, since I'd need to generate a table with about 64,000x64,000 entries (yikes). If you know any programmatic explanations of efficient ways to calculate things like arctan2, that would be awesome. My math background is all right, but the advanced formulas and traditional math notation are very difficult for me to translate into code.

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  • Is Ogre's use of Exceptions a good way of using them?

    - by identitycrisisuk
    I've managed to get through my C++ game programming career so far virtually never touching exceptions but recently I've been working on a project with the Ogre engine and I'm trying to learn properly. I've found a lot of good questions and answers here on the general usage of C++ exceptions but I'd like to get some outside opinions from here on whether Ogre's usage is good and how best to work with them. To start with, quoting from Ogre's documentation of it's own Exception class: OGRE never uses return values to indicate errors. Instead, if an error occurs, an exception is thrown, and this is the object that encapsulates the detail of the problem. The application using OGRE should always ensure that the exceptions are caught, so all OGRE engine functions should occur within a try{} catch(Ogre::Exception& e) {} block. Really? Every single Ogre function could throw an exception and be wrapped in a try/catch block? At present this is handled in our usage of it by a try/catch in main that will show a message box with the exception description before exiting. This can be a bit awkward for debugging though as you don't get a stack trace, just the function that threw the error - more important is the function from our code that called the Ogre function. If it was an assert in Ogre code then it would go straight to the code in the debugger and I'd be able to find out what's going on much easier - I don't know if I'm missing something that would allow me to debug exceptions already? I'm starting to add a few more try/catch blocks in our code now, generally thinking about whether it matters if the Ogre function throws an exception. If it's something that will stop everything working then let the main try/catch handle it and exit the program. If it's not of great importance then catch it just after the function call and let the program continue. One recent example of this was building up a vector of the vertex/fragment program parameters for materials applied to an entity - if a material didn't have any parameters then it would throw an exception, which I caught and then ignored as it didn't need to add to my list of parameters. Does this seem like a reasonable way of dealing with things? Any specific advice for working with Ogre is much appreciated.

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  • CodeGolf: Brothers

    - by John McClane
    Hi guys, I just finished participating in the 2009 ACM ICPC Programming Conest in the Latinamerican Finals. These questions were for Brazil, Bolivia, Chile, etc. My team and I could only finish two questions out of the eleven (not bad I think for the first try). Here's one we could finish. I'm curious to seeing any variations to the code. The question in full: ps: These questions can also be found on the official ICPC website available to everyone. In the land of ACM ruled a greeat king who became obsessed with order. The kingdom had a rectangular form, and the king divided the territory into a grid of small rectangular counties. Before dying the king distributed the counties among his sons. The king was unaware of the rivalries between his sons: The first heir hated the second but not the rest, the second hated the third but not the rest, and so on...Finally, the last heir hated the first heir, but not the other heirs. As soon as the king died, the strange rivaly among the King's sons sparked off a generalized war in the kingdom. Attacks only took place between pairs of adjacent counties (adjacent counties are those that share one vertical or horizontal border). A county X attacked an adjacent county Y whenever X hated Y. The attacked county was always conquered. All attacks where carried out simultanously and a set of simultanous attacks was called a battle. After a certain number of battles, the surviving sons made a truce and never battled again. For example if the king had three sons, named 0, 1 and 2, the figure below shows what happens in the first battle for a given initial land distribution: INPUT The input contains several test cases. The first line of a test case contains four integers, N, R, C and K. N - The number of heirs (2 <= N <= 100) R and C - The dimensions of the land. (2 <= R,C <= 100) K - Number of battles that are going to take place. (1 <= K <= 100) Heirs are identified by sequential integers starting from zero. Each of the next R lines contains C integers HeirIdentificationNumber (saying what heir owns this land) separated by single spaces. This is to layout the initial land. The last test case is a line separated by four zeroes separated by single spaces. (To exit the program so to speak) Output For each test case your program must print R lines with C integers each, separated by single spaces in the same format as the input, representing the land distribution after all battles. Sample Input: Sample Output: 3 4 4 3 2 2 2 0 0 1 2 0 2 1 0 1 1 0 2 0 2 2 2 0 0 1 2 0 0 2 0 0 0 1 2 2 Another example: Sample Input: Sample Output: 4 2 3 4 1 0 3 1 0 3 2 1 2 2 1 2

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  • How to create a Uri instance parsed with GenericUriParserOptions.DontCompressPath

    - by Andrew Arnott
    When the .NET System.Uri class parses strings it performs some normalization on the input, such as lower-casing the scheme and hostname. It also trims trailing periods from each path segment. This latter feature is fatal to OpenID applications because some OpenIDs (like those issued from Yahoo) include base64 encoded path segments which may end with a period. How can I disable this period-trimming behavior of the Uri class? Registering my own scheme using UriParser.Register with a parser initialized with GenericUriParserOptions.DontCompressPath avoids the period trimming, and some other operations that are also undesirable for OpenID. But I cannot register a new parser for existing schemes like HTTP and HTTPS, which I must do for OpenIDs. Another approach I tried was registering my own new scheme, and programming the custom parser to change the scheme back to the standard HTTP(s) schemes as part of parsing: public class MyUriParser : GenericUriParser { private string actualScheme; public MyUriParser(string actualScheme) : base(GenericUriParserOptions.DontCompressPath) { this.actualScheme = actualScheme.ToLowerInvariant(); } protected override string GetComponents(Uri uri, UriComponents components, UriFormat format) { string result = base.GetComponents(uri, components, format); // Substitute our actual desired scheme in the string if it's in there. if ((components & UriComponents.Scheme) != 0) { string registeredScheme = base.GetComponents(uri, UriComponents.Scheme, format); result = this.actualScheme + result.Substring(registeredScheme.Length); } return result; } } class Program { static void Main(string[] args) { UriParser.Register(new MyUriParser("http"), "httpx", 80); UriParser.Register(new MyUriParser("https"), "httpsx", 443); Uri z = new Uri("httpsx://me.yahoo.com/b./c.#adf"); var req = (HttpWebRequest)WebRequest.Create(z); req.GetResponse(); } } This actually almost works. The Uri instance reports https instead of httpsx everywhere -- except the Uri.Scheme property itself. That's a problem when you pass this Uri instance to the HttpWebRequest to send a request to this address. Apparently it checks the Scheme property and doesn't recognize it as 'https' because it just sends plaintext to the 443 port instead of SSL. I'm happy for any solution that: Preserves trailing periods in path segments in Uri.Path Includes these periods in outgoing HTTP requests. Ideally works with under ASP.NET medium trust (but not absolutely necessary).

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  • json problems with making a ruby on rails application

    - by Prince Merdz
    So I'm using Bitnami to learn Ruby on Rails. I have also previously tried the manual installation for ruby and rails and was met by the same problem so I thought I should try first the easy package deal of Bitnami. Anyway my problem with json is that it causes the bundle install to fail. First the auto bundle install that rails new does fails because of an ssl error. Which is easily solved by changing the source in the gemfile which is https to http. However when I try to bundle install it does another error when it tries to install json. C:\RubyStack-3.2.7-0\projects\testing>bundle install Fetching gem metadata from http://rubygems.org/......... Using rake (0.9.2.2) Using i18n (0.6.0) Using multi_json (1.3.6) Installing activesupport (3.2.8) Using builder (3.0.0) Installing activemodel (3.2.8) Using erubis (2.7.0) Using journey (1.0.4) Using rack (1.4.1) Using rack-cache (1.2) Using rack-test (0.6.1) Using hike (1.2.1) Using tilt (1.3.3) Using sprockets (2.1.3) Installing actionpack (3.2.8) Using mime-types (1.19) Using polyglot (0.3.3) Using treetop (1.4.10) Using mail (2.4.4) Installing actionmailer (3.2.8) Using arel (3.0.2) Using tzinfo (0.3.33) Installing activerecord (3.2.8) Installing activeresource (3.2.8) Using bundler (1.1.5) Using coffee-script-source (1.3.3) Using execjs (1.4.0) Using coffee-script (2.2.0) Using rack-ssl (1.3.2) Installing json (1.7.5) with native extensions Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension . C:/RUBYST~1.7-0/ruby/bin/ruby.exe extconf.rb creating Makefile make 0 [main] echo 5244 open_stackdumpfile: Dumping stack trace to echo.exe.sta ckdump make: *** [generator-i386-mingw32.def] Error 5 Gem files will remain installed in C:/RUBYST~1.7-0/ruby/lib/ruby/gems/1.9.1/gems /json-1.7.5 for inspection. Results logged to C:/RUBYST~1.7-0/ruby/lib/ruby/gems/1.9.1/gems/json-1.7.5/ext/j son/ext/generator/gem_make.out An error occured while installing json (1.7.5), and Bundler cannot continue. Make sure that `gem install json -v '1.7.5'` succeeds before bundling. This is the gem_make.out file it produces after trying to install json (btw windows also produces an error that echo.exe has stopped working while running the gem install json) C:/RUBYST~1.7-0/ruby/bin/ruby.exe extconf.rb creating Makefile make 0 [main] echo 5244 open_stackdumpfile: Dumping stack trace to echo.exe.stackdump make: *** [generator-i386-mingw32.def] Error 5 I can't even start learning ror for the setup is already a huge pain. (btw I have no prior experience with web frameworks, just desktop programming). help?

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  • The most efficient method of drawing multiple quads in OpenGL

    - by CPatton
    I'm not very keen with OpenGL and I was wondering if someone could give me some insight on this. I'm a 'seasoned' programmer, I've read the redbook about VBOs and the like, but I was wondering from a more experienced person about the best/most efficient way of achieving this. I've been producing this 2d tile-based game engine to be used in several projects. I have a class called "ScreenObject" which is mainly composed of a Dictionary<Point, Tile> The Point key is to show where to render the Tile on the screen, and the Tile contains one or more textures to be drawn at that point. This ScreenObject is where the tiles will be modified, deleted, added, etc.. My original method of drawing the tiles in the testing I've done was to iterate through the ScreenObject and draw each quad at each location separately. From what I've read, this is a massive waste of resources. It wasn't horribly slow in the testing, but after I've completed the animation classes and effect classes, I'm sure it would be extremely slow. And one last thing, if you wouldn't mind.. As I said before, the Tile class can contain multiple textures to be drawn at the Point location on the screen. I recognize possibly two options for me here. Either add a quad at that location for each texture to be drawn, or, somehow.. use a multiple texture for the same quad (if it's possible). Even if each tile contained one texture only, that would be 64 quads to be drawn on the screen. Most of the tiles will contain 2-5 textures, so the number of total quads would increase dramatically with this method. Would it be feasible to add a quad for each new texture, or am I ignoring a better way to do this? Just need some help understanding this if you don't mind :) I've tried to be as concise as possible, and I'd greatly appreciate any responses.. and even some criticism. Programming is often a learning process and one who develops seems to never stops learning. Thanks for your time.

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  • Rail test case fixtures not loading

    - by Deano
    Rails appears to not be loading any fixtures for unit or functional tests. I have a simple 'products.yml' that parses and appears correct: ruby: title: Programming Ruby 1.9 description: Ruby is the fastest growing and most exciting dynamic language out there. If you need to get working programs delivered fast, you should add Ruby to your toolbox. price: 49.50 image_url: ruby.png My controller functional test begins with: require 'test_helper' class ProductsControllerTest < ActionController::TestCase fixtures :products setup do @product = products(:one) @update = { :title => 'Lorem Ipsum' , :description => 'Wibbles are fun!' , :image_url => 'lorem.jpg' , :price => 19.95 } end According to the book, Rails should "magically" load the fixtures (as my test_helper.rb has fixtures :all in it. I also added the explicit fixtures load (seen above). Yes Rails complains: user @ host ~/Dropbox/Rails/depot > rake test:functionals (in /Somewhere/Users/user/Dropbox/Rails/depot) /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -Ilib:test "/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/rake-0.8.3/lib/rake/rake_test_loader.rb" "test/functional/products_controller_test.rb" Loaded suite /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/gems/1.8/gems/rake-0.8.3/lib/rake/rake_test_loader Started EEEEEEE Finished in 0.062506 seconds. 1) Error: test_should_create_product(ProductsControllerTest): NoMethodError: undefined method `products' for ProductsControllerTest:Class /test/functional/products_controller_test.rb:7 2) Error: test_should_destroy_product(ProductsControllerTest): NoMethodError: undefined method `products' for ProductsControllerTest:Class /test/functional/products_controller_test.rb:7 ... I did come across the other Rails test fixture question http://stackoverflow.com/questions/1547634/rails-unit-testing-doesnt-load-fixtures, but that leads to a plugin issue (something to do with the order of loading fixtures). BTW, I am developing on Mac OS X 10.6 with Rail 2.3.5 and Ruby 1.8.7, no additional plugins (beyond the base install). Any pointers on how to debug, why the magic of Rails appears to be failing here? Is it a version problem? Can I trace code into the libraries and find the answer? There are so many "mixin" modules I can't find where the fixtures method really lives.

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  • How can I use Web Services Core to send a complex type as a parameter to a SOAP API method

    - by Matthew Brindley
    I don't do much Cocoa programming, so I'm probably missing something obvious, so please excuse the basic question. I have a SOAP method that expects a complex type as a paramater. Here's some WSDL: <s:element name="SaveTestResult"> <s:complexType> <s:sequence> <s:element minOccurs="0" maxOccurs="1" name="result" type="tns:TestItemResponse" /> </s:sequence> </s:complexType> </s:element> Here's the definition of the complex type "TestItemResponse": <s:complexType name="TestItemResponse"> <s:sequence> <s:element minOccurs="1" maxOccurs="1" name="TestItemRequestId" type="s:int" /> <s:element minOccurs="1" maxOccurs="1" name="ExternalId" type="s:int" /> <s:element minOccurs="0" maxOccurs="1" name="ApiId" type="s:string" /> <s:element minOccurs="0" maxOccurs="1" name="InboxGuid" type="s:string" /> <s:element minOccurs="0" maxOccurs="1" name="SpamResult" type="tns:SpamResult" /> <s:element minOccurs="0" maxOccurs="1" name="ResultImageSet" type="tns:ResultImageSet" /> <s:element minOccurs="1" maxOccurs="1" name="ExclusiveUseMailAccountId" type="s:int" /> <s:element minOccurs="1" maxOccurs="1" name="State" type="tns:TestItemResponseState" /> <s:element minOccurs="0" maxOccurs="1" name="ErrorShortDescription" type="s:string" /> <s:element minOccurs="0" maxOccurs="1" name="ErrorFullDescription" type="s:string" /> </s:sequence> </s:complexType> I've been using Web Services Core to call a SOAP API method that requires a simple string param, that works great. That same method returns a complex type which WSC converted into nested NSDictionaries, so no problems there. So I assumed I'd be able to convert my local TestItemResponse class into an NSDictionary and then use that as the complex type param. It almost worked, but unfortunately WSC set the object's type as "Dictionary", instead of "TestItemResponse", and the server complained. <TestItemResponse xsi:type=\"SOAP-ENC:Dictionary\"> <ErrorFullDescription xsi:type=\"xsd:string\">foo</ErrorFullDescription> ... I can't seem to find anything that allows you to override the type WSC assigns to the element in the SOAP XML. I've been using code adapted from here, I'm happy to list it, it's just quite long and this is already the longest SO question I've ever posted.

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  • Soon to be PhD in Computer Science - Which Path to Follow?

    - by mttr
    I am going to submit my PhD thesis within the next six months. My PhD is on managing the availabiity of large-scale distributed systems, so I have some experience actually building non-trivial systems (+ I have four years experience working as a programmer). I am now trying to figure out what I should do following the PhD. I enjoy research (a quick definition: identify problem, come up with solution, ask interesting questions, find ways to answer them, build system, experiment, contribute some new knowledge and publish). I also like teaching and supervising students. It would seem that a career in academia is the ideal thing to do (can work on non-trivial problems and contribute something of use to some or more people). However, a career in academia has two significant drawbacks. First, it can be difficult to gain access to real systems with real users which then display real problems. This creates the danger that you do work that seems important (to you and maybe to some of your colleagues), but is not really relevant to anything or anyone. Second, the pay is pretty sad. Apparently, you have to sacrifice this for the privilege of doing research. I enjoy programming, but don't just want to hack some web-based system for the rest of my life. That is, working in IT for a bank is not a future I see myself enjoying. I want to work on interesting problms (that's difficult to define clearly): things where you don't know how to start, that take some time to figure out and attack, that require a rigorous approach to demonstrate that the problem has been solved, and problems that need a solution in the real world. Give the experience of people on stackoverflow, what do you think suitable options are and why (or alternatively, what gaps in my thinking does the above reveal)? Is industrial research (aka IBM Research, Microsoft Research) the only alternative avenue to a career in academia? What other areas, companies, occupations, etc. could provide me with stimulating, inspiring work? Which regions, countries am I most likely to find such work? Please share your experience.

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  • Is it possible to change HANDLE that has been opened for synchronous I/O to be opened for asynchrono

    - by Martin Dobšík
    Dear all, Most of my daily programming work in Windows is nowadays around I/O operations of all kind (pipes, consoles, files, sockets, ...). I am well aware of different methods of reading and writing from/to different kinds of handles (Synchronous, asynchronous waiting for completion on events, waiting on file HANDLEs, I/O completion ports, and alertable I/O). We use many of those. For some of our applications it would be very useful to have only one way to treat all handles. I mean, the program may not know, what kind of handle it has received and we would like to use, let's say, I/O completion ports for all. So first I would ask: Let's assume I have a handle: HANDLE h; which has been received by my process for I/O from somewhere. Is there any easy and reliable way to find out what flags it has been created with? The main flag in question is FILE_FLAG_OVERLAPPED. The only way known to me so far, is to try to register such handle into I/O completion port (using CreateIoCompletionPort()). If that succeeds the handle has been created with FILE_FLAG_OVERLAPPED. But then only I/O completion port must be used, as the handle can not be unregistered from it without closing the HANDLE h itself. Providing there is an easy a way to determine presence of FILE_FLAG_OVERLAPPED, there would come my second question: Is there any way how to add such flag to already existing handle? That would make a handle that has been originally open for synchronous operations to be open for asynchronous. Would there be a way how to create opposite (remove the FILE_FLAG_OVERLAPPED to create synchronous handle from asynchronous)? I have not found any direct way after reading through MSDN and googling a lot. Would there be at least some trick that could do the same? Like re-creating the handle in same way using CreateFile() function or something similar? Something even partly documented or not documented at all? The main place where I would need this, is to determine the the way (or change the way) process should read/write from handles sent to it by third party applications. We can not control how third party products create their handles. Dear Windows gurus: help please! With regards Martin

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  • Offline backup synchronization

    - by Pavan Kumar
    There is a Central Server running Windows Server 2003 and SQL Server 2005 and there are 7 client machines situated in various places and has XP Pro & SQL Server 2005 installed in all of them. They are not interconnected so they are physically seperate. One person goes to each of these centers maybe twice a month and takes the backup (Full database consisting of mdf and ldf files) with a pen drive and brings it to the Central server which contains the central database holding same schema as all the other client databases. I need to synchronize each backup database (belonging to different centers) one by one to update the existing data or inserting new data in the central database . The solution i got was Replication. The pendrive is brought to central server consisting of 7 instances of the databases and then the databases is attached to the central server one by one to the same SQL Server where the central database exists. Then my idea was to replicate the backup database one by one i.e using single subscription (Central Database) and multiple publication ( i.e 7 instances of databases in my case) toplogy by performing replication locally (i.e in the same machine). So i tried to develop a UI in C# .Net to programatically run the Transactional Replication with push subscription using RMO Programming (which is incomplete as of now because there is no point in developing when you already know it is not the solution). Transactional Replication can either be set to initialize with a snapshot or without a snapshot. If i go for the first option i.e with a snapshot , the data whatever is present in Central Database is overwritten by the new data . So the data present initially in the central database is lost. If i try to initialize without snapshot , no data (the data already has the updated and new data) will be sent from the backup database to server. The replication will work in a scenario where any incremental changes is done only after you set the replication . So the initial data whatever was present in the backup database when setting up the replication will not be replicated when running the snapshot agent for the first time to synchronize. Only changes in the backup database thereafter will be reflected to the central database .(Remember I am not going to insert new data or make any changes to the backup database after i attach it to the Central Server. ) So this solution is not feasible. I want a solution for synchronizing from one client database to central database present in the same machine using C#.NET. If you can provide me small example maybe with two databases(with same schema) DB1(Client) to DB2(Server) consisting of one or two tables it will be very helpful. The synchronization is not bidirectional.I want to only update existing data or insert new data from DB1 to DB2 (DB2 may contain some data initially). Thanks and Regards Pavan

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  • Calculating multiple column average in SQLite3

    - by Benjamin Oakes
    I need to average some values in a row-wise fashion, rather than a column-wise fashion. (If I were doing a column-wise average, I could just use avg()). My specific application of this requires me ignore NULLs in averaging. It's pretty straightforward logic, but seems awfully difficult to do in SQL. Is there an elegant way of doing my calculation? I'm using SQLite3, for what it's worth. Details If you need more details, here's an illustration: I have a a table with a survey: | q1 | q2 | q3 | ... | q144 | |----|-------|-------|-----|------| | 1 | 3 | 7 | ... | 2 | | 4 | 2 | NULL | ... | 1 | | 5 | NULL | 2 | ... | 3 | (Those are just some example values and simple column names. The valid values are 1 through 7 and NULL.) I need to calculate some averages like so: q7 + q33 + q38 + q40 + ... + q119 / 11 as domain_score_1 q10 + q11 + q34 + q35 + ... + q140 / 13 as domain_score_2 ... q2 + q5 + q13 + q25 + ... + q122 / 12 as domain_score_14 ...but i need to pull out the nulls and average based on the non-nulls. So, for domain_score_1 (which has 11 items), I would need to do: Input: 3, 5, NULL, 7, 2, NULL, 3, 1, 5, NULL, 1 (3 + 5 + 7 + 2 + 3 + 1 + 5 + 1) / (11 - 3) 27 / 8 3.375 A simple algorithm I'm considering is: Input: 3, 5, NULL, 7, 2, NULL, 3, 1, 5, NULL, 1 Coalesce each value to 0 if NULL: 3, 5, 0, 7, 2, 0, 3, 1, 5, 0, 1 Sum: 27 Get the number of non-zeros by converting values 0 to 1 and sum: 3, 5, 0, 7, 2, 0, 3, 1, 5, 0, 1 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1 8 Divide those two numbers 27 / 8 3.375 But that seems like a lot more programming than this should take. Is there an elegant way of doing this that I'm not aware of? Update: Unless I'm misunderstanding something, avg() won't work for this. Example of what I would want to do: select avg(q7, q33, q38, ..., q119) from survey; Output: SQL error near line 3: wrong number of arguments to function avg()

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  • Do you still limit line length in code?

    - by Noldorin
    This is a matter on which I would like to gauge the opinion of the community: Do you still limit the length of lines of code to a fixed maximum? This was certainly a convention of the past for many languages; one would typically cap the number of characters per line to a value such as 80 (and more recnetly 100 or 120 I believe). As far as I understand, the primary reasons for limiting line length are: Readability - You don't have to scroll over horizontally when you want to see the end of some lines. Printing - Admittedly (at least in my experience), most code that you are working on does not get printed out on paper, but by limiting the number of characters you can insure that formatting doesn't get messed up when printed. Past editors (?) - Not sure about this one, but I suspect that at some point in the distant past of programming, (at least some) text editors may have been based on a fixed-width buffer. I'm sure there are points that I am still missing out, so feel free to add to these... Now, when I tend to observe C or C# code nowadays, I often see a number of different styles, the main ones being: Line length capped to 80, 100, or even 120 characters. As far as I understand, 80 is the traditional length, but the longer ones of 100 and 120 have appeared because of the widespread use of high resolutions and widescreen monitors nowadays. No line length capping at all. This tends to be pretty horrible to read, and I don't see it too often, though it's certainly not too rare either. Inconsistent capping of line length. The length of some lines are limited to a fixed maximum (or even a maximum that changes depending on the file/location in code), while others (possibly comments) are not at all. My personal preference here (at least recently) has been to cap the line length to 100 in the Visual Studio editor. This means that in a decently sized window (on a non-widescreen monitor), the ends of lines are still fully visible. I can however see a few disadvantages in this, especially when you end up writing code that's indented 3 or 4 levels and then having to include a long string literal - though I often take this as a sign to refactor my code! In particular, I am curious what the C and C# coders (or anyone who uses Visual Studio for that matter) think about this point, though I would be interested in hearing anyone's thoughts on the subject. Edit Thanks for the all answers - I appreciate the variety of opinions here, all presenting sound reasons. Consensus does seem to be tipping in the direction of always (or almost always) limit the line length. Interestingly, it seems to be in various coding standards to limit the line length. Judging by some of the answers, both the Python and Google CPP guidelines set the limit at 80 chars. I haven't seen anything similar regarding C# or VB.NET, but I would be curious to see if there are ones anywhere.

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  • How to write this Linq SQL as a Dynamic Query (using strings)?

    - by Dr. Zim
    Skip to the "specific question" as needed. Some background: The scenario: I have a set of products with a "drill down" filter (Query Object) populated with DDLs. Each progressive DDL selection will further limit the product list as well as what options are left for the DDLs. For example, selecting a hammer out of tools limits the Product Sizes to only show hammer sizes. Current setup: I created a query object, sent it to a repository, and fed each option to a SQL "table valued function" where null values represent "get all products". I consider this a good effort, but far from DDD acceptable. I want to avoid any "programming" in SQL, hopefully doing everything with a repository. Comments on this topic would be appreciated. Specific question: How would I rewrite this query as a Dynamic Query? A link to something like 101 Linq Examples would be fantastic, but with a Dynamic Query scope. I really want to pass to this method the field in quotes "" for which I want a list of options and how many products have that option. from p in db.Products group p by p.ProductSize into g select new Category { PropertyType = g.Key, Count = g.Count() } Each DDL option will have "The selection (21)" where the (21) is the quantity of products that have that attribute. Upon selecting an option, all other remaining DDLs will update with the remaining options and counts. Edit: Additional notes: .OrderBy("it.City") // "it" refers to the entire record .GroupBy("City", "new(City)") // This produces a unique list of City .Select("it.Count()") //This gives a list of counts... getting closer .Select("key") // Selects a list of unique City .Select("new (key, count() as string)") // +1 to me LOL. key is a row of group .GroupBy("new (City, Manufacturer)", "City") // New = list of fields to group by .GroupBy("City", "new (Manufacturer, Size)") // Second parameter is a projection Product .Where("ProductType == @0", "Maps") .GroupBy("new(City)", "new ( null as string)")// Projection not available later? .Select("new (key.City, it.count() as string)")// GroupBy new makes key an object Product .Where("ProductType == @0", "Maps") .GroupBy("new(City)", "new ( null as string)")// Projection not available later? .Select("new (key.City, it as object)")// the it object is the result of GroupBy var a = Product .Where("ProductType == @0", "Maps") .GroupBy("@0", "it", "City") // This fails to group Product at all .Select("new ( Key, it as Product )"); // "it" is property cast though What I have learned so far is LinqPad is fantastic, but still looking for an answer. Eventually, completely random research like this will prevail I guess. LOL. Edit:

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  • Java - How to make a set of JInternalFrame independant of each other?

    - by Amokrane
    Hello, I'm programming a short Paint program like and I'm trying to make an MDI architecture for it. To make that happen, I used JInternalFrame inside a JDesktopPane. Although I kind of obtain multiple frames, there are not really working properly. Basically, if I have 2 JInternalFrame I can draw only on the last one. The other one seems to be disabled. Here is a short video illustrating the problem. http://bit.ly/9ydiwM Here are some part of the code. Panneau.java public class Panneau extends JDesktopPane { /** La liste de fenêtres ouvertes */ private static ArrayList<Cadre> cadres; /** Le pannel comportant la liste des formes à dessiner*/ private Pannel pannel; /** La barre d'outils */ private ToolBox toolBox; public Panneau() { this.setLayout(new BorderLayout()); // Initialisations des listes de cadres cadres = new ArrayList<Cadre>(); // En haut ToolBox toolBox = new ToolBox(); this.add(toolBox, BorderLayout.NORTH); **// Intialisation de la première internal frame Cadre cadre = new Cadre(); this.add(cadre, BorderLayout.CENTER);** cadres.add(cadre); // Ajout du pannel à gauche pannel = new Pannel(); this.add(pannel, BorderLayout.WEST); } /** * Crée une nouvelle fenêtre de dessin * */ **public void createNewInternalFrame() { Cadre cadre = new Cadre(); this.add(cadre, BorderLayout.CENTER); cadres.add(cadre); }** } public class Cadre extends JInternalFrame { /** Largeur par d'une fenêtre interne */ private int width; /** Hauteur d'une fenêtre interne */ private int height; /** Titre d'une fenêtre interne */ private String title; /** Toile associée à la fenêtre interne */ private Toile toile; public Cadre() { width = 400; height = 400; title = "Form"; toile = new Toile(); this.setTitle(title); this.setSize(width, height); this.setEnabled(true); this.setResizable(true); this.setAutoscrolls(true); this.setClosable(true); this.setIconifiable(true); this.setDoubleBuffered(true); this.setContentPane(toile); this.setVisible(true); this.pack(); } } Basically, Panneau is the main Window that contains all the differents parts of the GUI. I can create as much JInternalFrame that I want, using : Panneau.createNewInternalFrame(). Toile is basically where I draw my shapes. Any idea ? Thanks

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  • What are the Tags Around Default iPhone Address Book People Phone Number Labels?

    - by rnistuk
    My question concerns markup that surrounds some of the default phone number labels in the Person entries of the Contact list on the iPhone. I have created an iPhone contact list address book entry for a person, "John Smith" with the following phone number entries: Mobile (604) 123-4567 iPhone (778) 123-4567 Home (604) 789-4561 Work (604) 456-7891 Main (604) 789-1234 megaphone (234) 567-8990 Note that the first five labels are default labels provided by the Contacts application and the last label, "megaphone", is a custom label. I wrote the following method to retrieve and display the labels and phone numbers for each person in the address book: -(void)displayPhoneNumbersForAddressBook { ABAddressBookRef book = ABAddressBookCreate(); CFArrayRef people = ABAddressBookCopyArrayOfAllPeople(book); ABRecordRef record = CFArrayGetValueAtIndex(people, 0); ABMultiValueRef multi = ABRecordCopyValue(record, kABPersonPhoneProperty); NSLog(@"---------" ); NSLog(@"displayPhoneNumbersForAddressBook" ); CFStringRef label, phone; for (CFIndex i = 0; i < ABMultiValueGetCount(multi); ++i) { label = ABMultiValueCopyLabelAtIndex(multi, i); phone = ABMultiValueCopyValueAtIndex(multi, i); NSLog(@"label: \"%@\" number: \"%@\"", (NSString*)label, (NSString*)phone); CFRelease(label); CFRelease(phone); } NSLog(@"---------" ); CFRelease(multi); CFRelease(people); CFRelease(book); } and here is the output for the address book entry that I entered: 2010-03-08 13:24:28.789 test2m[2479:207] --------- 2010-03-08 13:24:28.789 test2m[2479:207] displayPhoneNumbersForAddressBook 2010-03-08 13:24:28.790 test2m[2479:207] label: "_$!<Mobile>!$_" number: "(604) 123-4567" 2010-03-08 13:24:28.790 test2m[2479:207] label: "iPhone" number: "(778) 123-4567" 2010-03-08 13:24:28.791 test2m[2479:207] label: "_$!<Home>!$_" number: "(604) 789-4561" 2010-03-08 13:24:28.791 test2m[2479:207] label: "_$!<Work>!$_" number: "(604) 456-7891" 2010-03-08 13:24:28.792 test2m[2479:207] label: "_$!<Main>!$_" number: "(604) 789-1234" 2010-03-08 13:24:28.792 test2m[2479:207] label: "megaphone" number: "(234) 567-8990" 2010-03-08 13:24:28.793 test2m[2479:207] --------- What are the markup characters _$!< and >!$_ surrounding most, save for iPhone, of the default labels for? Can you point me to where in the "Address Book Programming Guide for iPhone OS" I can find the information? Thank you for your help.

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  • Scared of Calculus - Required to pass Differential Calculus as part of my Computer science major

    - by ke3pup
    Hi guys I'm finishing my Computer science degree in university but my fear of maths (lack of background knowledge) made me to leave all my maths units til' the very end which is now. i either take them on and pass or have to give up. I've passed all my programming units easily but knowing my poor maths skills won't do i've been staying clear of the maths units. I have to pass Differential Calculus and Linear Algebra first. With a help of book named "Linear Algebra: A Modern Introduction" i'm finding myself on track and i think i can pass the Linear Algebra unit. But with differential calculus i can't find a book to help me. They're either too advanced or just too simple for what i have to learn. The things i'm required to know for this units are: Set notation, the real number line, Complex numbers in cartesian form. Complex plane, modulus. Complex numbers in polar form. De Moivre’s Theorem. Complex powers and nth roots. Definition of ei? and ez for z complex. Applications to trigonometry. Revision of domain and range of a function Working in R3. Curves and surfaces. Functions of 2 variables. Level curves.Partial derivatives and tangent planes. The derivative as a difference quotient. Geometric significance of the derivative. Discussion of limit. Higher order partial derivatives. Limits of f(x,y). Continuity. Maxima and minima of f(x,y). The chain rule. Implicit differentiation. Directional derivatives and the gradient. Limit laws, l’Hoˆpital’s rule, composition law. Definition of sinh and cosh and their inverses. Taylor polynomials. The remainder term. Taylor series. Is there a book to help me get on track with the above? Being a student i can't buy too many books hence why i'm looking for a book that covers topics I need to know. The University library has a fairly limited collection which i took as loan but didn't find useful as it was too complex.

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