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• SQLce DAL Linq to Sql or EntityFramework

  - by bretddog

  Hi, I'm learning databases, using SqlCe, and need business object to database mapping. Currently I try to decide if to use Linq to Sql, or EntityFramework. (I understand a bit L2S, but haven't familiarized with EF yet) The program will only be debeloped and used by myself, so I have good control of the priorities: I don't need to consider potential change of database type or data storage type, as I'm quite certain SQLce will stay sufficient. I DO expect continued development and changes to the data scheme while the program is in active use; change business object properties (Hence database columns), and possibly overall table scheme. So old data must be transported to new scheme. I also want to keep a decent degree of layer separation DAL/BLL, although this may not be necessary, it is good for me to learn these principles. My question is: With these priorities, would I have any benefit by choosing either Linq2Sql vs. EntityFramwork? (and please explain why) Btw, the project involves very simple table scheme with only 4-5 tables and very simple relations. Thanks!

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• Does this language feature already exists?

  - by Pindatjuh

  I'm currently developing a new language for programming in a continuous environment (compare it to electrical engineering), and I've got some ideas on a certain language construction. Let me explain the feature by explanation and then by definition; x = a | b; Where x is a variable and a and b are other variables (or static values). if(x == a) { // all references to "x" are essentially references to "a". } if(x == b) { // same but with "b" } if(x != a) { // ... } if(x == a | b) { // guaranteed that "x" is '"a" | "b"'; interacting with "x" // will interact with both "a" and "b". } // etc. In the above, all code-blocks are executed, but the "scope" changes in each block how x is interpreted. In the first block, x is guaranteed to be a: thus interacting with x inside that block will interact on a. The second and the third code-block are only equal in this situation (because not b only remains a). The last block guarantees that x is at least a or b. Further more; | is not the "bitwise or operator", but I've called it the "and/or"-operator. It's definition is: "|" = "and" | "or" (On my blog, http://cplang.wordpress.com/2009/12/19/binop-and-or/, is more (mathematical) background information on this operator. It's loosely based on sets.) I do not know if this construction already exists, so that's my question: does this language feature already exists?

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• I am trying to find how many vowels and consonants in my string in C

  - by John Walter

  #include <stdio.h> #include <string.h> int main() { int i; int counter=0, counter2=0; char *s; char name[30]; char vowel[6] = "AEIOU"; char consonants[21] = "BCDFGHJKLMNPQRSTVWXYZ"; printf ("input the string: "); scanf ("%s", name); printf ("The string is %s\n", name); for (i=0; name[i]!='\0'; i++) { if (s = strchr(vowel, name[i])) { counter++; } else if (s =strchr(consonants, name[i])) { counter2++; } printf ("First counter is %d\n", counter); printf ("The second counter is %d\n", counter2); return 0; } } And the question is, what is wrong with my code? why counter is not working? Because I tried a lot of ways, and nothing works, maybe someone can explain for me.

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• Floating Point Arithmetic - Modulo Operator on Double Type

  - by CrimsonX

  So I'm trying to figure out why the modulo operator is returning such a large unusual value. If I have the code: double result = 1.0d % 0.1d; it will give a result of 0.09999999999999995. I would expect a value of 0 Note this problem doesn't exist using the dividing operator - double result = 1.0d / 0.1d; will give a result of 10.0, meaning that the remainder should be 0. Let me be clear: I'm not surprised that an error exists, I'm surprised that the error is so darn large compared to the numbers at play. 0.0999 ~= 0.1 and 0.1 is on the same order of magnitude as 0.1d and only one order of magnitude away from 1.0d. Its not like you can compare it to a double.epsilon, or say "its equal if its < 0.00001 difference". I've read up on this topic on StackOverflow, in the following posts one two three, amongst others. Can anyone suggest explain why this error is so large? Any any suggestions to avoid running into the problems in the future (I know I could use decimal instead but I'm concerned about the performance of that).

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• xPath Groupings how?

  - by David

  OK So, I'm learning/using xpath for a basic application thats effectively ripping data off another website. I need to gain the knowledge of each persons Countryy/Suburb/area. In some instances you can get Australia/Victoria/melborne for instance. Others may just be Australia/Melbourne. Or even just Melbourne OR just AUSTRALIA. who knows. So I'm current able to view the below code and rip all of the information with the string xpath search:@" //table/tr/td/tabke/tr/td/font/a, this returns every entry, but what I really want is to group each lot separately. I hope someone out there on planet earth knows what I just tried to explain... and can help... Good day! <font face="arial" size="2"> <strong>Location:</strong> <a href="http://maps.google.com/maps?q=Australia" target="mapblast" style="text-decoration:none">Australia</a>, <a href='http://maps.google.com/maps?q=Australia%20Victoria'target="mapblast" style='text-decoration:none'>Victoria</a>, <a href='http://maps.google.com/maps?q=Australia%20Melbourne%20Victoria'target="mapblast" style='text-decoration:none'>Melbourne</a> </font> </td> </tr>

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• C# Hiding, overriding and calling function from base class.

  - by Lukasz Lysik

  I'm learning C# and I encountered the following problem. I have two classes: base and derived: class MyBase { public void MyMethod() { Console.WriteLine("MyBase::MyMethod()"); } } class MyDerived: MyBase { public void MyMethod() { Console.WriteLine("MyDerived::MyMethod()"); } } For now, without virtual and override key words. When I compile this I get the warning (which is of course expected) that I try to hide MyMethod from MyBase class. What I want to do is to call the method from the base class having an instance of derived class. I do this like this: MyDerived myDerived = new MyDerived(); ((MyBase)myDerived).MyMethod(); It works fine when I do not specify any virtual, etc. keywords in the methods. I tried to put combination of the keywords and I got the following results: | MyBase::MyMethod | MyDerived::MyMethod | Result printed on the console | | -----------------|---------------------|-------------------------------| | - | - | MyBase::MyMethod() | | - | new | MyBase::MyMethod() | | virtual | new | MyBase::MyMethod() | | virtual | override | MyDerived::MyMethod() | I hope the table is clear to you. I have two questions: Is it the correct way to call the function from the base class (((MyBase)myDerived).MyMethod();)? I know about base keyword, but it can be called only from the inside of the derived class. Is it right? Why in the last case (with virtual and override modifiers) the method which was called came from the derived class? Would you please explain that?

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• how to ignore ivy revision number?

  - by user315228

  Guys, I have certain jar files without revision number. But as rev is mandatory attribute for ivy dependency, i am providing the revision attribute. But i have something like (-[revision]) in url resolver. but its taking the module number instead of ignoring the revision attribute. I know it wont ignore the revision attribute as its not null. Following is the output that i get default-cache: no cached resolved revision for perltools#perltools;latest.integration [ivy:retrieve] tried [ivy:retrieve] listing all in [ivy:retrieve] using privateRepo to list all in [ivy:retrieve] ApacheURLLister found URL=[httP://myrepo/ivyRepository/perltools/jars/perltools.jar]. [ivy:retrieve] found 1 resources [ivy:retrieve] found revs: [perltools.jar] [ivy:retrieve] HTTP response status: 404 url=httP://myrepo/ivyRepository/perltools/jars/perltools.jar/perltools-perltools.jar.jar [ivy:retrieve] CLIENT ERROR: Not Found url=httP://myrepo/ivyRepository/perltools/jars/perltools.jar/perltools-perltools.jar.jar Can somebody please explain why its taking module.ext as revision where revision i specified is latest.integration and in myrepo, i dont have revision attribute. its just has [http://myrepo/ivyRepository/perltools/jars//perltools.jar] Can somebody please help me so that i can avoid revision attribute?

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• ASP.NET AsyncPostBackTrigger disables button's OnClick function???

  - by hahuang65

  I saw another post like this: http://stackoverflow.com/questions/1795621/asyncpostbacktrigger-disables-buttons But I don't really know what to make of it. The accepted answer was poorly typed. Basically, I have a button with an OnClick function. I also have a UpdatePanel, with is AsyncPostBackTrigger set to that same button. It seems that if I do this, my Button no longer does ANYTHING. I guess it's because I have a Page_Load() event... Can anyone explain why this is? And how should I set up my webpage if I can't use the Page_Load() function? Oh and if I put my Button in a UpdatePanel, it also won't do anything, probably because of the same reason. This is a section of my code: <asp:FileUpload id="FileUploadControl" runat="server" /> <asp:Button runat="server" id="UploadButton" text="Upload" OnClick="uploadClicked" /> <br /><br /> <asp:Label runat="server" id="StatusLabel" text="Upload status: " /> <br /> <asp:UpdatePanel ID="UpdatePanel2" runat="server" updatemode="Conditional" > <ContentTemplate> <asp:DropDownList ID="songList" runat="server" /> </ContentTemplate> <Triggers> <asp:AsyncPostBackTrigger ControlID="RefreshButton" /> </Triggers> </asp:UpdatePanel> Thanks in advance.

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• Browsers disagree about the text of a body element

  - by Charles Anderson

  My HTML looks like this: <html> <head> <title>Test</title> <script type="text/javascript" src="jQuery.js"></script> <script type="text/javascript"> function init() { var text = jQuery('body').text(); alert('length = ' + text.length); } </script> </head> <body onload="init()">0123456789</body> </html> When I load this in Firefox, the length is reported as 10. However, in Chrome it's 11 because it thinks there's a linefeed after the '9'. In IE it's also 11, but the last character is an escape. Meanwhile, Opera thinks there are 12 characters, with the last two being CR LF. If I change the body element to include a span: <body onload="init()"><span>0123456789</span></body> and the jQuery call to: var text = jQuery('body span').text(); then all the browsers agree that the length is 10. Clearly it's the body element that's causing the issue, but can anyone explain exactly why this is happening? I'm particularly surprised because the excellent jQuery is normally browser-independent.

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• Rails with passenger only runs in development

  - by Ignace

  Hey, I have a problem on one of our webservers. I'll try to explain it as clear as possible, but I'm not 100% aware of all the configuration of the server. There are 2 sites running next to eachother (blcc_preprod and blcc_prod), so in the 'sites-enabled' of apache this i have a file 'blcc' like this: <VirtualHost *:80> DocumentRoot /opt/dn/blcc/www RailsBaseURI /blcc_preprod RailsBaseURI /blcc_prod RailsEnv production </VirtualHost> My config/environments/production.log (from both) looks like this(I removed all comments, because it messes with the layout) config.cache_classes = true config.action_controller.consider_all_requests_local = false config.action_controller.perform_caching = true config.action_view.cache_template_loading = true config.log_level = :debug The weird thing is, that my production log dates from months ago, so something is really wrong. Could someone help? If you need more info, just ask. Thanks! Edit: Error.log from apache show the normal output for a event to the server (the situation here is that the webserver plugs in to another business (java) server via a framework) Access.log is empty Content from other_vhosts_access.log after we surf to ip/blcc_preprod is the following blcc.localdomain:80 192.168.21.194 - - [25/May/2010:08:33:04 +0200] "GET/ blcc_preprod HTTP/1.1" 500 594 "-" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)"

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• Accelerometer gravity components

  - by Dvd

  Hi, I know this question is definitely solved somewhere many times already, please enlighten me if you know of their existence, thanks. Quick rundown: I want to compute from a 3 axis accelerometer the gravity component on each of these 3 axes. I have used 2 axes free body diagrams to work out the accelerometer's gravity component in the world X-Z, Y-Z and X-Y axes. But the solution seems slightly off, it's acceptable for extreme cases when only 1 accelerometer axis is exposed to gravity, but for a pitch and roll of both 45 degrees, the combined total magnitude is greater than gravity (obtained by Xa^2+Ya^2+Za^2=g^2; Xa, Ya and Za are accelerometer readings in its X, Y and Z axis). More detail: The device is a Nexus One, and have a magnetic field sensor for azimuth, pitch and roll in addition to the 3-axis accelerometer. In the world's axis (with Z in the same direction as gravity, and either X or Y points to the north pole, don't think this matters much?), I assumed my device has a pitch (P) on the Y-Z axis, and a roll (R) on the X-Z axis. With that I used simple trig to get: Sin(R)=Ax/Gxz Cos(R)=Az/Gxz Tan(R)=Ax/Az There is another set for pitch, P. Now I defined gravity to have 3 components in the world's axis, a Gxz that is measurable only in the X-Z axis, a Gyz for Y-Z, and a Gxy for X-Y axis. Gxz^2+Gyz^2+Gxy^2=2*G^2 the 2G is because gravity is effectively included twice in this definition. Oh and the X-Y axis produce something more exotic... I'll explain if required later. From these equations I obtained a formula for Az, and removed the tan operations because I don't know how to handle tan90 calculations (it's infinity?). So my question is, anyone know whether I did this right/wrong or able to point me to the right direction? Thanks! Dvd

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• C# internal VS VBNET Friend

  - by Will Marcouiller

  To this SO question: What is the C# equivalent of friend?, I would personally have answered "internal", just like Ja did among the answers! However, Jon Skeet says that there is no direct equivalence of VB Friend in C#. If Jon Skeet says so, I won't be the one telling otherwise! ;P I'm wondering how can the keyword internal (C#) not be the equivalent of Friend (VBNET) when their respective definitions are: Friend VBNET The Friend (Visual Basic) keyword in the declaration statement specifies that the elements can be accessed from within the same assembly, but not from outside the assembly. [...] internal C# Internal: Access is limited to the current assembly. To my understanding, these definitions mean quite the same to me. Then, respectively, when I'm coding in VB.NET, I use the Friend keyword to specify that a class or a property shall be accessible only within the assembly where it is declared. The same in C#, I use the internal keyword to specify the same. Am I doing something or anything wrong from this perspective? What are the refinements I don't get? Might someone please explain how or in what Friend and internal are not direct equivalences? Thanks in advance for any of your answers!

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• How do I know which include path will be used in PHP?

  - by Joe Majewski

  When I run phpinfo() and look by the Configuration category under PHP Core, I see a directive titled include_path, with a local value and a master value. In this case, my local value is set to .: ./include: ../include: /usr/share/php: /usr/share/php/smarty: /usr/share/pear and my master value is set to .: /usr/share/php: /usr/share/pear: /usr/share/php/pear: /usr/share/php/smarty The reason I am trying to learn how this works is because there is a file in the system I am working on titled Smarty.class.php, which I'm sure sounds very familiar to anyone who uses Smarty Templating Engine. One of the PHP files has the following includes: require_once("Smarty.class.php"); require_once("user_info_class.inc"); The file user_info_class.inc is in the same directory as the file making the include, which makes perfect sense to me, and is the way that I've always referenced files. I decided that I wanted to open up the Smarty.class.php file and had assumed it would be in the same directory, but it was not. After doing a bit of digging, I discovered those php_ini variables, and was finally able to locate the file in the directory usr/share/php/smarty/. So it would seem that when making an include, it follows some sort of order between the Local and Master values for the include_path. Assuming that my deductions were correct thus far, can someone explain the order in which PHP searches for the files to be included?

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• When software problems reported are not really software problems

  - by AndyUK

  Hi Apologies if this has already been covered or you think it really belongs on wiki. I am a software developer at a company that manufactures microarray printing machines for the biosciences industry. I am primarily involved in interfacing with various bits of hardware (pneumatics, hydraulics, stepper motors, sensors etc) via GUI development in C++ to aspirate and print samples onto microarray slides. On joining the company I noticed that whenever there was a hardware-related problem this would cause the whole setup to freeze, with nobody being any the wiser as to what the specific problem was - hardware / software / misuse etc. Since then I have improved things somewhat by introducing software timeouts and exception handling to better identify and deal with any hardware-related problems that arise eg PLC commands not successfully completed, inappropriate FPGA response commands, and various other deadlock type conditions etc. In addition, the software will now log a summary of the specific problem, inform the user and exit the thread gracefully. This software is not embedded, just interfacing using serial ports. In spite of what has been achieved, non-software guys still do not fully appreciate that in these cases, the 'software' problem they are reporting to me is not really a software problem, rather the software is reporting a problem, but not causing it. Don't get me wrong, there is nothing I enjoy more than to come down on software bugs like a ton of bricks, and looking at ways of improving robustness in any way. I know the system well enough now that I almost have a sixth sense for these things. No matter how many times I try to explain this point to people, it does not really penetrate. They still report what are essentially hardware problems (which eventually get fixed) as software ones. I would like to hear from any others that have endured similar finger-pointing experiences and what methods they used to deal with them.

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• node.js beginner tutorials?

  - by TreyK

  Hey all, I'm working on creating my first real node.js http server, and I'm sort of drowning in it. As a good teacher of mine always said, "I'll just shove you in the water for now, and then I'll show you how to swim." Fortunately, she wasn't a swimming instructor, but it's a good analogy nonetheless. I feel like I've jumped into node.js and I've only found a ping pong ball to help, that is to say, most of the tutorials I've read stop shortly after the "Hello World" example and I've mostly been trying to make sense of copied and pasted code (or they assume I have knowledge of lower level HTTP and webserver concepts that have been done for me as an Apache/PHP developer). I have experience in both client-side Javascript and PHP, but node seems to be a beast all of its own. I don't quite have the low-level knowledge that seems necessary for creating a node server, and connect, which seems to be a nice module for simplifying things, seems quite sparsely explained, even in the docs on its Git. Where could I find some tutorials to help me in this situation? TL;DR - Are there any tutorials for node.js that go beyond "Hello World" but don't require much low-level knowledge? Or any tutorials that explain lower-level HTTP and webserver concepts that I would need to effectively create a node HTTP server? Thanks for any help. -Trey

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• Warshall Algorithm Logic - Stuck

  - by stan

  I am trying to use this logic to understand what is going on with the adjacency matrix, but i am massivley confused where it says about interspacing for a b c d ..... Could anyone explain what is going on here? Thank you (tagged as java as its the language this was demonstarted to us in, so if anyone posted any code examples they could see it was in that language) http://compprog.wordpress.com/2007/11/15/all-sources-shortest-path-the-floyd-warshall-algorithm/ Here is the code: for (k = 0; k < n; ++k) { for (i = 0; i < n; ++i) for (j = 0; j < n; ++j) /* If i and j are different nodes and if the paths between i and k and between k and j exist, do */ if ((dist[i][k] * dist[k][j] != 0) && (i != j)) /* See if you can't get a shorter path between i and j by interspacing k somewhere along the current path */ if ((dist[i][k] + dist[k][j] < dist[i][j]) || (dist[i][j] == 0)) dist[i][j] = dist[i][k] + dist[k][j];

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• When to choose which machine learning classifier?

  - by LM

  Suppose I'm working on some classification problem. (Fraud detection and comment spam are two problems I'm working on right now, but I'm curious about any classification task in general.) How do I know which classifier I should use? (Decision tree, SVM, Bayesian, logistic regression, etc.) In which cases is one of them the "natural" first choice, and what are the principles for choosing that one? Examples of the type of answers I'm looking for (from Manning et al.'s "Introduction to Information Retrieval book": http://nlp.stanford.edu/IR-book/html/htmledition/choosing-what-kind-of-classifier-to-use-1.html): a. If your data is labeled, but you only have a limited amount, you should use a classifier with high bias (for example, Naive Bayes). [I'm guessing this is because a higher-bias classifier will have lower variance, which is good because of the small amount of data.] b. If you have a ton of data, then the classifier doesn't really matter so much, so you should probably just choose a classifier with good scalability. What are other guidelines? Even answers like "if you'll have to explain your model to some upper management person, then maybe you should use a decision tree, since the decision rules are fairly transparent" are good. I care less about implementation/library issues, though. Also, for a somewhat separate question, besides standard Bayesian classifiers, are there 'standard state-of-the-art' methods for comment spam detection (as opposed to email spam)? [Not sure if stackoverflow is the best place to ask this question, since it's more machine learning than actual programming -- if not, any suggestions for where else?]

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• I need some pointers on how to implement inertia

  - by gargantaun

  Ok, so I've created a little plugin that takes a bunch of elements and creates a sort of never ending list. I'll try to explain... I have a div, and it's got about 20 elements tags in it. When the user scrolls up, the top element moves out of view and is moved to the bottom of the list. And vice-versa so that when the user scrolls down, the bottom element is moved to the top of the list. This is specifically for Mobile Safari (iPad, iPhone) web content and you can see the work in progress here... http://appliedworks.co.uk/files/times/SVGTests/drumView/drum.html You'll need an iPad or iPhone top see the scrolling in action. You can see the plugin code here... http://appliedworks.co.uk/files/times/SVGTests/drumView/drumView-0.1b.js What I would like to do is implement inertia so the scrolling slows to a halt in response to how fast or slow the user is scrolling when their finger leaves the screen. Just like the inertia commonly found in the iPhone / iPad UI. The problem is, every time an element moves to the top or the bottom of the list, the scollTop value for the parent div is adjusted to make it look like all the elements are staying in the same place. Which means the scrollTop value is never more than the top elements total height. So there's no value I can think of that I can keep on manipulating to give the illusion of inertia. I'm stumped. Does anyone have any suggestions?

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• Reading server error messages for a URLLoader

  - by Rudy

  Hello, I have an URL loader with the following code: public function getUploadURL():void { var request:URLRequest = new URLRequest(); var url:String = getPath(); // Adds time to prevent caching url += "&time=" + new Date().getTime(); request.url = url; request.method = URLRequestMethod.GET; _loader = new URLLoader(); _loader.dataFormat = URLLoaderDataFormat.TEXT; _loader.addEventListener(Event.COMPLETE, getBaseURL); _loader.addEventListener(IOErrorEvent.IO_ERROR, onGetUploadURLError); _loader.addEventListener(HTTPStatusEvent.HTTP_STATUS, getHttpStatus); _loader.load(request); } My problem is that this request might be wrong, and so the server will give me a back a 400 Bad Request, with a message to explain the error. If the Event.COMPLETE, I can see some message (a response) back from the server in the "data" field of the Event, but if onGetUploadURLError or getHttpStatus is called, it just says that the error code is 400 but does not show me the message associated with it. The "data" field is undefined in getHttpStatus and it is "" in onGetUploadURLError. On the contrary, in getBaseURL, I get: {"ResponseMetadata":{...}} I checked and I do get a similar response in my browser for a wrong request, but I cannot see it. Any idea how I can please get the message? Thank you very much, Rudy

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• Trouble with custom WPF Panel-derived class

  - by chaiguy

  I'm trying to write a custom Panel class for WPF, by overriding MeasureOverride and ArrangeOverride but, while it's mostly working I'm experiencing one strange problem I can't explain. In particular, after I call Arrange on my child items in ArrangeOverride after figuring out what their sizes should be, they aren't sizing to the size I give to them, and appear to be sizing to the size passed to their Measure method inside MeasureOverride. Am I missing something in how this system is supposed to work? My understanding is that calling Measure simply causes the child to evaluate its DesiredSize based on the supplied availableSize, and shouldn't affect its actual final size. Here is my full code (the Panel, btw, is intended to arrange children in the most space-efficient manner, giving less space to rows that don't need it and splitting remaining space up evenly among the rest--it currently only supports vertical orientation but I plan on adding horizontal once I get it working properly): protected override Size MeasureOverride( Size availableSize ) { foreach ( UIElement child in Children ) child.Measure( availableSize ); return availableSize; } protected override System.Windows.Size ArrangeOverride( System.Windows.Size finalSize ) { double extraSpace = 0.0; var sortedChildren = Children.Cast<UIElement>().OrderBy<UIElement, double>( new Func<UIElement, double>( delegate( UIElement child ) { return child.DesiredSize.Height; } ) ); double remainingSpace = finalSize.Height; double normalSpace = 0.0; int remainingChildren = Children.Count; foreach ( UIElement child in sortedChildren ) { normalSpace = remainingSpace / remainingChildren; if ( child.DesiredSize.Height < normalSpace ) // if == there would be no point continuing as there would be no remaining space remainingSpace -= child.DesiredSize.Height; else { remainingSpace = 0; break; } remainingChildren--; } extraSpace = remainingSpace / Children.Count; double offset = 0.0; foreach ( UIElement child in Children ) { //child.Measure( new Size( finalSize.Width, normalSpace ) ); double value = Math.Min( child.DesiredSize.Height, normalSpace ) + extraSpace; child.Arrange( new Rect( 0, offset, finalSize.Width, value ) ); offset += value; } return finalSize; }

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• Redirecting from an update action to the referrer of the edit

  - by Mark Westling

  My Rails 2.3 application has a User model and the usual controller actions. The edit form can be reached two ways: when a user edits his own profile from the home page, or when an admin user edits someone else's profile from users collection. What I'd like to do is have the update action redirect back to the referred of the edit action, not the update action. If I do a simple redirect_to(:back) within update, it goes back to the edit form -- not good. One solution is to forget entirely about referrers and redirect based on the current_user and the updated user: if they're the same, go back to the home page, else go to the users collection page. This will break if I ever add a third path to the edit form. It's doubtful I'll ever do this but I'd prefer a solution that's not so brittle. Another solution is to store the referrer of edit form in a hidden field and then redirect to this value from inside the update action. This doesn't feel quite right, though I can't explain why. Are there any better approaches? Or, should I stop worrying and go with one of the two I've mentioned?

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• java annotations - problem with calling a locator class from a Vaadin Project

  - by George

  Hello, I'm not sure how to explain this without writing several pages so I hope the actual code is more expressive. I've made a jar containing multiple annotation declaration similar to the following: @Target(ElementType.PACKAGE) @Retention(RetentionPolicy.RUNTIME) public @interface MarkedPackage { } then I have made a test jar containing several classes in several packages and marked just one package with the above annotation (with package-info.java) like below: @myPackage.MarkedPackage package package.test.jar; this jar had in its build path the jar containing the annotations. then I made a static class that has a method (LoadPlugins) that retrieves a list with all the jars of a directory. Then it searches through the jars for the 'package-info' class and checks if that classes package contains the MarkedPackage annotation. by calling this: if (checkPackageAnnotation(thisClass.getPackage())) where thisClass is the package-info class retrieved via a classloader. and: public static boolean checkPackageAnnotation(AnnotatedElement elem) { System.out.println(elem.getAnnotations().length); if (elem == null || !elem.isAnnotationPresent(MarkedPackage.class)) return false; return true; } the elem.getAnnotatios().length is there for debug purposes. And the problem appears when I call the method from the static class: if I call it from a main function: public class MyMain { public static void main(String[] args){ PluginUtils.LoadPlugins(); } } everything works perfectly it displays '1' from that System.out.println(elem.getAnnotations().length); But if I call it from a button from my Vaadin project: header.addComponent(new Button("CallThat", new Button.ClickListener() { public void buttonClick(ClickEvent event) { PluginUtils.LoadPlugins(); } })); It displays '0' from that System.out.println(elem.getAnnotations().length); Also I should mention that I created the main inside my Vaadin project so it would have the exact same build path and resources. Is there a problem with web applications and that "@Retention(RetentionPolicy.RUNTIME)" ? hope I was clear enough... Hope someone has a solution for me... If you need more information - let me know. Thank you.

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• Passing Derived Class Instances as void* to Generic Callbacks in C++

  - by Matthew Iselin

  This is a bit of an involved problem, so I'll do the best I can to explain what's going on. If I miss something, please tell me so I can clarify. We have a callback system where on one side a module or application provides a "Service" and clients can perform actions with this Service (A very rudimentary IPC, basically). For future reference let's say we have some definitions like so: typedef int (*callback)(void*); // This is NOT in our code, but makes explaining easier. installCallback(string serviceName, callback cb); // Really handled by a proper management system sendMessage(string serviceName, void* arg); // arg = value to pass to callback This works fine for basic types such as structs or builtins. We have an MI structure a bit like this: Device <- Disk <- MyDiskProvider class Disk : public virtual Device class MyDiskProvider : public Disk The provider may be anything from a hardware driver to a bit of glue that handles disk images. The point is that classes inherit Disk. We have a "service" which is to be notified of all new Disks in the system, and this is where things unravel: void diskHandler(void *p) { Disk *pDisk = reinterpret_cast<Disk*>(p); // Uh oh! // Remainder is not important } SomeDiskProvider::initialise() { // Probe hardware, whatever... // Tell the disk system we're here! sendMessage("disk-handler", reinterpret_cast<void*>(this)); // Uh oh! } The problem is, SomeDiskProvider inherits Disk, but the callback handler can't receive that type (as the callback function pointer must be generic). Could RTTI and templates help here? Any suggestions would be greatly appreciated.

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• NSURLConnection receives data even if no data was thrown back

  - by Anna Fortuna

  Let me explain my situation. Currently, I am experimenting long-polling using NSURLConnection. I found this and I decided to try it. What I do is send a request to the server with a timeout interval of 300 secs. (or 5 mins.) Here is a code snippet: NSURL *url = [NSURL URLWithString:urlString]; NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLCacheStorageAllowedInMemoryOnly timeoutInterval:300]; NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&resp error:&err]; Now I want to test if the connection will "hold" the request if no data was thrown back from the server, so what I did was this: if (data != nil) [self performSelectorOnMainThread:@selector(dataReceived:) withObject:data waitUntilDone:YES]; And the function dataReceived: looks like this: - (void)dataReceived:(NSData *)data { NSLog(@"DATA RECEIVED!"); NSString *string = [NSString stringWithUTF8String:[data bytes]]; NSLog(@"THE DATA: %@", string); } Server-side, I created a function that will return a data once it fits the arguments and returns none if nothing fits. Here is a snippet of the PHP function: function retrieveMessages($vardata) { if (!empty($vardata)) { $result = check_data($vardata) //check_data is the function which returns 1 if $vardata //fits the arguments, and 0 if it fails to fit if ($result == 1) { $jsonArray = array('Data' => $vardata); echo json_encode($jsonArray); } } } As you can see, the function will only return data if the $result is equal to 1. However, even if the function returns nothing, NSURLConnection will still perform the function dataReceived: meaning the NSURLConnection still receives data, albeit an empty one. So can anyone help me here? How will I perform long-polling using NSURLConnection? Basically, I want to maintain the connection as long as no data is returned. So how will I do it? NOTE: I am new to PHP, so if my code is wrong, please point it out so I can correct it.

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• Ruby on Rails bizarre behavior with ActiveRecord error handling

  - by randombits

  Can anyone explain why this happens? mybox:$ ruby script/console Loading development environment (Rails 2.3.5) >> foo = Foo.new => #<Foo id: nil, customer_id: nil, created_at: nil, updated_at: nil> >> bar = Bar.new => #<Bar id: nil, bundle_id: nil, alias: nil, real: nil, active: true, list_type: 0, body_record_active: false, created_at: nil, updated_at: nil> >> bar.save => false >> bar.errors.each_full { |msg| puts msg } Real can't be blank Real You must supply a valid email => ["Real can't be blank", "Real You must supply a valid email"] So far that is perfect, that is what i want the error message to read. Now for more: >> foo.bars << bar => [#<Bar id: nil, bundle_id: nil, alias: nil, real: nil, active: true, list_type: 0, body_record_active: false, created_at: nil, updated_at: nil>] >> foo.save => false >> foo.errors.to_xml => "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<errors>\n <error>Bars is invalid</error>\n</errors>\n" That is what I can't figure out. Why am I getting Bars is invalid versus the error messages displayed above, ["Real can't be blank", "Real you must supply a valid email"] etc. My controller simply has a respond_to method with the following in it: format.xml { render :xml => @foo.errors, :status => :unprocessable_entity } How do I have this output the real error messages so the user has some insight into what they did wrong?

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