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• Using Visual Studio 2010 Express to create a surface I can draw to

  - by Joel

  I'm coming from a Java background and trying to port a simple version of Conway's Game of Life that I wrote to C# in order to learn the language. In Java, I drew my output by inheriting from JComponent and overriding paint(). My new canvas class then had an instance of the simulation's backend which it could read/manipulate. I was then able to get the WYSIWYG GUI editor (Matisse, from NetBeans) to allow me to visually place the canvas. In C#, I've gathered that I need to override OnPaint() to draw things, which (as far as I know) requires me to inherit from something (I chose Panel). I can't figure out how to get the Windows forms editor to let me place my custom class. I'm also uncertain about where in the generated code I need to place my class. How can I do this, and is putting all my drawing code into a subclass really how I should be going about this? The lack of easy answers on Google suggests I'm missing something important here. If anyone wants to suggest a method for doing this in WPF as well, I'm curious to hear it. Thanks

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• Javascript function with PHP throwing a "Illegally Formed XML Syntax" error

  - by Joe

  I'm trying to learn some javascript and i'm having trouble figuring out why my code is incorrect (i'm sure i'm doing something wrong lol), but anyways I am trying to create a login page so that when the form is submitted javascript will call a function that checks if the login is in a mysql database and then checks the validity of the password for the user if they exist. however I am getting an error (Illegally Formed XML Syntax) i cannot resolve. I'm really confused, mostly because netbeans is saying it is a xml syntax error and i'm not using xml. here is the code in question: function validateLogin(login){ login.addEventListener("input", function() { $value = login.value; if (<?php //connect to mysql mysql_connect(host, user, pass) or die(mysql_error()); echo("<script type='text/javascript'>"); echo("alert('MYSQL Connected.');"); echo("</script>"); //select db mysql_select_db() or die(mysql_error()); echo("<script type='text/javascript'>"); echo("alert('MYSQL Database Selected.');"); echo("</script>"); //query $result = mysql_query("SELECT * FROM logins") or die(mysql_error()); //check results against given login while($row = mysql_fetch_array($result)){ if($row[login] == $value){ echo("true"); exit(0); } } echo("false"); exit(0); ?>) { login.setCustomValidity("Invalid Login. Please Click 'Register' Below.") } else { login.setCustomValidity("") } }); } the code is in an external js file and the error throws on the last line. Also from reading i understand best practices is to not mix js and php so how would i got about separating them but maintaining the functionality i need? thanks!

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• Why initialize an object to empty

  - by ProgEnthu

  I am learning windows programming with the help of MSDN.Why would somebody initialize an object like the following? WNDCLASS wc = { }; Will this zero all the memory of the object? Whole source code is following: #ifndef UNICODE #define UNICODE #endif #include <windows.h> LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam); int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE, PWSTR pCmdLine, int nCmdShow) { // Register the window class. const wchar_t CLASS_NAME[] = L"Sample Window Class"; WNDCLASS wc = { }; wc.lpfnWndProc = WindowProc; wc.hInstance = hInstance; wc.lpszClassName = CLASS_NAME; RegisterClass(&wc); // Create the window. HWND hwnd = CreateWindowEx( 0, // Optional window styles. CLASS_NAME, // Window class L"Learn to Program Windows", // Window text WS_OVERLAPPEDWINDOW, // Window style // Size and position CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, // Parent window NULL, // Menu hInstance, // Instance handle NULL // Additional application data ); if (hwnd == NULL) { return 0; } ShowWindow(hwnd, nCmdShow); // Run the message loop. MSG msg = { }; while (GetMessage(&msg, NULL, 0, 0)) { TranslateMessage(&msg); DispatchMessage(&msg); } return 0; } LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) { switch (uMsg) { case WM_DESTROY: PostQuitMessage(0); return 0; case WM_PAINT: { PAINTSTRUCT ps; HDC hdc = BeginPaint(hwnd, &ps); FillRect(hdc, &ps.rcPaint, (HBRUSH) (COLOR_WINDOW+1)); EndPaint(hwnd, &ps); } return 0; } return DefWindowProc(hwnd, uMsg, wParam, lParam); }

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• Why do people keep parsing HTML using regex? [closed]

  - by polygenelubricants

  As much as I love regular expressions, it's obvious to me that it's not the best tool for parsing HTML, especially given the numerous good HTML parsers out there. And yet there are numerous questions on stackoverflow that attempts to parse HTML using regex. And people would always point out what a bad idea that is in the comments. And the accepted answer would often have a disclaimer how this isn't really the ideal way of doing things. But based on the constant flow of questions, it still seems that people keep parsing HTML using regex, despite the perceived difficulty in reading and maintaining it (and that's putting correctness aside for now). So my question is: why? Is it because it's easy to learn? Is it because it's faster? Is it because it's the industry standard? Is it because there are already so many reusable regexes to build from? Is it because 100% correctness is never really the objective? (90% good enough?) etc... I'd also like to hear from the downvoters why they did so. Is it because: There's absolutely nothing wrong with using regex to parse HTML and asking "Why?" is just dumb? The premise of the question is flawed because the people who are using regex to parse HTML is such a small minority?

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• Delphi: EInvalidOp in neural network class (TD-lambda)

  - by user89818

  I have the following draft for a neural network class. This neural network should learn with TD-lambda. It is started by calling the getRating() function. But unfortunately, there is an EInvalidOp (invalid floading point operation) error after about 1000 iterations in the following lines: neuronsHidden[j] := neuronsHidden[j]+neuronsInput[t][i]*weightsInput[i][j]; // input -> hidden weightsHidden[j][k] := weightsHidden[j][k]+LEARNING_RATE_HIDDEN*tdError[k]*eligibilityTraceOutput[j][k]; // adjust hidden->output weights according to TD-lambda Why is this error? I can't find the mistake in my code :( Can you help me? Thank you very much in advance! unit uNeuronalesNetz; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, ExtCtrls, StdCtrls, Grids, Menus, Math; const NEURONS_INPUT = 43; // number of neurons in the input layer NEURONS_HIDDEN = 60; // number of neurons in the hidden layer NEURONS_OUTPUT = 1; // number of neurons in the output layer NEURONS_TOTAL = NEURONS_INPUT+NEURONS_HIDDEN+NEURONS_OUTPUT; // total number of neurons in the network MAX_TIMESTEPS = 42; // maximum number of timesteps possible (after 42 moves: board is full) LEARNING_RATE_INPUT = 0.25; // in ideal case: decrease gradually in course of training LEARNING_RATE_HIDDEN = 0.15; // in ideal case: decrease gradually in course of training GAMMA = 0.9; LAMBDA = 0.7; // decay parameter for eligibility traces type TFeatureVector = Array[1..43] of SmallInt; // definition of the array type TFeatureVector TArtificialNeuralNetwork = class // definition of the class TArtificialNeuralNetwork private // GENERAL SETTINGS START learningMode: Boolean; // does the network learn and change its weights? // GENERAL SETTINGS END // NETWORK CONFIGURATION START neuronsInput: Array[1..MAX_TIMESTEPS] of Array[1..NEURONS_INPUT] of Extended; // array of all input neurons (their values) for every timestep neuronsHidden: Array[1..NEURONS_HIDDEN] of Extended; // array of all hidden neurons (their values) neuronsOutput: Array[1..NEURONS_OUTPUT] of Extended; // array of output neurons (their values) weightsInput: Array[1..NEURONS_INPUT] of Array[1..NEURONS_HIDDEN] of Extended; // array of weights: input->hidden weightsHidden: Array[1..NEURONS_HIDDEN] of Array[1..NEURONS_OUTPUT] of Extended; // array of weights: hidden->output // NETWORK CONFIGURATION END // LEARNING SETTINGS START outputBefore: Array[1..NEURONS_OUTPUT] of Extended; // the network's output value in the last timestep (the one before) eligibilityTraceHidden: Array[1..NEURONS_INPUT] of Array[1..NEURONS_HIDDEN] of Array[1..NEURONS_OUTPUT] of Extended; // array of eligibility traces: hidden layer eligibilityTraceOutput: Array[1..NEURONS_TOTAL] of Array[1..NEURONS_TOTAL] of Extended; // array of eligibility traces: output layer reward: Array[1..MAX_TIMESTEPS] of Array[1..NEURONS_OUTPUT] of Extended; // the reward value for all output neurons in every timestep tdError: Array[1..NEURONS_OUTPUT] of Extended; // the network's error value for every single output neuron t: Byte; // current timestep cyclesTrained: Integer; // number of cycles trained so far (learning rates could be decreased accordingly) last50errors: Array[1..50] of Extended; // LEARNING SETTINGS END public constructor Create; // create the network object and do the initialization procedure UpdateEligibilityTraces; // update the eligibility traces for the hidden and output layer procedure tdLearning; // learning algorithm: adjust the network's weights procedure ForwardPropagation; // propagate the input values through the network to the output layer function getRating(state: TFeatureVector; explorative: Boolean): Extended; // get the rating for a given state (feature vector) function HyperbolicTangent(x: Extended): Extended; // calculate the hyperbolic tangent [-1;1] procedure StartNewCycle; // start a new cycle with everything set to default except for the weights procedure setLearningMode(activated: Boolean=TRUE); // switch the learning mode on/off procedure setInputs(state: TFeatureVector); // transfer the given feature vector to the input layer (set input neurons' values) procedure setReward(currentReward: SmallInt); // set the reward for the current timestep (with learning then or without) procedure nextTimeStep; // increase timestep t function getCyclesTrained(): Integer; // get the number of cycles trained so far procedure Visualize(imgHidden: Pointer); // visualize the neural network's hidden layer end; implementation procedure TArtificialNeuralNetwork.UpdateEligibilityTraces; var i, j, k: Integer; begin // how worthy is a weight to be adjusted? for j := 1 to NEURONS_HIDDEN do begin for k := 1 to NEURONS_OUTPUT do begin eligibilityTraceOutput[j][k] := LAMBDA*eligibilityTraceOutput[j][k]+(neuronsOutput[k]*(1-neuronsOutput[k]))*neuronsHidden[j]; for i := 1 to NEURONS_INPUT do begin eligibilityTraceHidden[i][j][k] := LAMBDA*eligibilityTraceHidden[i][j][k]+(neuronsOutput[k]*(1-neuronsOutput[k]))*weightsHidden[j][k]*neuronsHidden[j]*(1-neuronsHidden[j])*neuronsInput[t][i]; end; end; end; end; procedure TArtificialNeuralNetwork.setReward; VAR i: Integer; begin for i := 1 to NEURONS_OUTPUT do begin // +1 = player A wins // 0 = draw // -1 = player B wins reward[t][i] := currentReward; end; end; procedure TArtificialNeuralNetwork.tdLearning; var i, j, k: Integer; begin if learningMode then begin for k := 1 to NEURONS_OUTPUT do begin if reward[t][k] = 0 then begin tdError[k] := GAMMA*neuronsOutput[k]-outputBefore[k]; // network's error value when reward is 0 end else begin tdError[k] := reward[t][k]-outputBefore[k]; // network's error value in the final state (reward received) end; for j := 1 to NEURONS_HIDDEN do begin weightsHidden[j][k] := weightsHidden[j][k]+LEARNING_RATE_HIDDEN*tdError[k]*eligibilityTraceOutput[j][k]; // adjust hidden->output weights according to TD-lambda for i := 1 to NEURONS_INPUT do begin weightsInput[i][j] := weightsInput[i][j]+LEARNING_RATE_INPUT*tdError[k]*eligibilityTraceHidden[i][j][k]; // adjust input->hidden weights according to TD-lambda end; end; end; end; end; procedure TArtificialNeuralNetwork.ForwardPropagation; var i, j, k: Integer; begin for j := 1 to NEURONS_HIDDEN do begin neuronsHidden[j] := 0; for i := 1 to NEURONS_INPUT do begin neuronsHidden[j] := neuronsHidden[j]+neuronsInput[t][i]*weightsInput[i][j]; // input -> hidden end; neuronsHidden[j] := HyperbolicTangent(neuronsHidden[j]); // activation of hidden neuron j end; for k := 1 to NEURONS_OUTPUT do begin neuronsOutput[k] := 0; for j := 1 to NEURONS_HIDDEN do begin neuronsOutput[k] := neuronsOutput[k]+neuronsHidden[j]*weightsHidden[j][k]; // hidden -> output end; neuronsOutput[k] := HyperbolicTangent(neuronsOutput[k]); // activation of output neuron k end; end; procedure TArtificialNeuralNetwork.setLearningMode; begin learningMode := activated; end; constructor TArtificialNeuralNetwork.Create; var i, j, k: Integer; begin inherited Create; Randomize; // initialize random numbers generator learningMode := TRUE; cyclesTrained := -2; // only set to -2 because it will be increased twice in the beginning StartNewCycle; for j := 1 to NEURONS_HIDDEN do begin for k := 1 to NEURONS_OUTPUT do begin weightsHidden[j][k] := abs(Random-0.5); // initialize weights: 0 <= random < 0.5 end; for i := 1 to NEURONS_INPUT do begin weightsInput[i][j] := abs(Random-0.5); // initialize weights: 0 <= random < 0.5 end; end; for i := 1 to 50 do begin last50errors[i] := 0; end; end; procedure TArtificialNeuralNetwork.nextTimeStep; begin t := t+1; end; procedure TArtificialNeuralNetwork.StartNewCycle; var i, j, k, m: Integer; begin t := 1; // start in timestep 1 cyclesTrained := cyclesTrained+1; // increase the number of cycles trained so far for j := 1 to NEURONS_HIDDEN do begin neuronsHidden[j] := 0; for k := 1 to NEURONS_OUTPUT do begin eligibilityTraceOutput[j][k] := 0; outputBefore[k] := 0; neuronsOutput[k] := 0; for m := 1 to MAX_TIMESTEPS do begin reward[m][k] := 0; end; end; for i := 1 to NEURONS_INPUT do begin for k := 1 to NEURONS_OUTPUT do begin eligibilityTraceHidden[i][j][k] := 0; end; end; end; end; function TArtificialNeuralNetwork.getCyclesTrained; begin result := cyclesTrained; end; procedure TArtificialNeuralNetwork.setInputs; var k: Integer; begin for k := 1 to NEURONS_INPUT do begin neuronsInput[t][k] := state[k]; end; end; function TArtificialNeuralNetwork.getRating; begin setInputs(state); ForwardPropagation; result := neuronsOutput[1]; if not explorative then begin tdLearning; // adjust the weights according to TD-lambda ForwardPropagation; // calculate the network's output again outputBefore[1] := neuronsOutput[1]; // set outputBefore which will then be used in the next timestep UpdateEligibilityTraces; // update the eligibility traces for the next timestep nextTimeStep; // go to the next timestep end; end; function TArtificialNeuralNetwork.HyperbolicTangent; begin if x > 5500 then // prevent overflow result := 1 else result := (Exp(2*x)-1)/(Exp(2*x)+1); end; end.

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• Should I go to school and get my degree in computer science?

  - by ryan

  I'll try and keep this short and simple. I've always enjoyed programming and I've been doing it since high school. Right after I graduated from high school (2002), I opted to skip college because I was offered a software engineer position. I quit after a couple of years later to team up on various startup companies. However, most of them did not launch as well as expected. But it honestly did not matter to me because I've learned so much from that experience. So fast forwarding to today, now turned 25, I need a job due to this tough economic climate. Looking on Craigslist, a lot of the listings require computer science degrees. It's evident now that programming is what I want to do because I seem to never get enough of it. But just the thought of having to push 2 years without attending any real computer class for an Associates at age 25 is very, very discouraging. And the thought of having to learn from basic (Hello WOOOOORRLLLD) just does not seem exciting. I guess I have 3 questions to wrap this up: Should I just suck it up and go back to school while working at McDonalds at age 25? Is there a way where I can just skip all the boring stuff and just get tested with what I know? From your experience, how many jobs use computer science degrees as prerequisites? Or am I screwed and better pray that my next startup will be the next big thing?

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• Expressionengine 2 and git (version control)

  - by Danny

  Hey guys I’m looking to move over to using git to make my EE development a lot easier and more manageable. I’m already aware of the guides posted on devotee and a few othersites but after scanning over them they seem a little old and seem to be specifically for ee 1.x, I was wondering if anyone had been successful with ee 2. I’ve only recently made the transition from svn to git, previously I found that using ee via svn was a ballache, so many confit conflicts, wrong urls, and all versions of the site were using the same database. I’m basically looking for the best or should I say the ideal way to setup both git and ee to work in harmony together. I’d like to also learn how to branch other sites I develop with ee from this too, if anyone has experience with this that’d be great! Also if it’s any use I’m hosted by dreamhost, As far as I understand they support git, I’ve looked over their knowledge base on how best to set things up, would anyone reccomend their way of doing things? And has anyone had a successful experience whilst doing so?  I look forward to hearing your responses! Thanks Sent from my iPhone, whilst falling asleep so excuse the possible typos!a

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• Best way to build an application based on R?

  - by Prasad Chalasani

  I'm looking for suggestions on how to go about building an application that uses R for analytics, table generation, and plotting. What I have in mind is an application that: displays various data tables in different tabs, somewhat like in Excel, and the columns should be sortable by clicking. takes user input parameters in some dialog windows. displays plots dynamically (i.e. user-input-dependent) either in a tab or in a new pop-up window/frame Note that I am not talking about a general-purpose fron-end/GUI for exploring data with R (like say Rattle), but a specific application. Some questions I'd like to see addressed are: Is an entirely R-based approach even possible ( on Windows ) ? The following passage from the Rattle article in R-Journal intrigues me: It is interesting to note that the first implementation of Rattle actually used Python for implementing the callbacks and R for the statistics, using rpy. The release of RGtk2 allowed the interface el- ements of Rattle to be written directly in R so that Rattle is a fully R-based application If it's better to use another language for the GUI part, which language is best suited for this? I'm looking for a language where it's relatively "painless" to build the GUI, and that also integrates very well with R. From this StackOverflow question How should I do rapid GUI development for R and Octave methods (possibly with Python)? I see that Python + PyQt4 + QtDesigner + RPy2 seems to be the best combo. Is that the consensus ? Anyone have pointers to specific (open source) applications of the type I describe, as examples that I can learn from?

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• Java SOAP - Need help on Body and ChildElement manipulation

  - by techventure

  Hi guys I'm trying to write some code in java to learn more about coding with WSDL and SOAP. I've been able to build up a BodyElement for a given namespace. But when i come to adding the childElements I'm runnig intp problems. For example given :'<'to:checkAccount xmlns:to="http://foo" '<'to:id test' <'/to:id '<'to:password test '<'/to:password '<'to:checkAccount " I'm able to set the bodyElement(to:checkAccount), but when i try to add the childElements (to:id, to:password) , the childElement needs to have the "to" prefix otherwise it won't work. ie. sf = SOAPFactory.newInstance(); Name childName = sf.createName("id"); SOAPElement symbol = bodyElement.addChildElement(childName); this doesn't work since it doesn't have the "to" prefix to id and password. I cannot do Name childName = sf.createName("id","to",null); as it gives me an error saying wrong namespace... can someone tell me how i can add to:id and to:password to to:checkAccount ?

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• transforming 1d (1column) into 5d(5column) matrix through copy paste or other

  - by Curious

  Ex. I want to take the column with 12345..... and order 5 columns across as seen. next 5 numbers in column will be next row. However my code creates a 4 row gap in between each successive row. I dont know what additional logic (possibly if then statement) I can embed into do loop to may make it cleaner. I am new to this, so showing as much sample code to learn the syntax would be most beneficial. thanks in advance. Below is the Result of my code. VBA code is below result. 1 1 2 3 4 5 2 3 4 5 6 6 7 8 9 10 7 8 9 10 11 11 12 13 14 15 12 13 14 15 16 16 17 17 Sub Working_Code() ' Working_Code Macro Do ActiveCell.Select Selection.Copy ActiveCell.Offset(0, 5).Select ActiveSheet.Paste ActiveCell.Offset(1, -5).Select Selection.Copy ActiveCell.Offset(-1, 6).Select ActiveSheet.Paste ActiveCell.Offset(2, -6).Select Selection.Copy ActiveCell.Offset(-2, 7).Select ActiveSheet.Paste ActiveCell.Offset(3, -7).Select Selection.Copy ActiveCell.Offset(-3, 8).Select ActiveSheet.Paste ActiveCell.Offset(4, -8).Select Selection.Copy ActiveCell.Offset(-4, 9).Select ActiveSheet.Paste ActiveCell.Offset(5, -9).Select Loop Until IsEmpty(ActiveCell.Offset(0, -1)) End Sub

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• C#: How to get all public (both get and set) string properties of a type

  - by Svish

  I am trying to make a method that will go through a list of generic objects and replace all their properties of type string which is either null or empty with a replacement. How is a good way to do this? I have this kind of... shell... so far: public static void ReplaceEmptyStrings<T>(List<T> list, string replacement) { var properties = typeof(T).GetProperties( -- What BindingFlags? -- ); foreach(var p in properties) { foreach(var item in list) { if(string.IsNullOrEmpty((string) p.GetValue(item, null))) p.SetValue(item, replacement, null); } } } So, how do I find all the properties of a type that are: Of type string Has public get Has public set ? I made this test class: class TestSubject { public string Public; private string Private; public string PublicPublic { get; set; } public string PublicPrivate { get; private set; } public string PrivatePublic { private get; set; } private string PrivatePrivate { get; set; } } The following does not work: var properties = typeof(TestSubject) .GetProperties(BindingFlags.Instance|BindingFlags.Public) .Where(ø => ø.CanRead && ø.CanWrite) .Where(ø => ø.PropertyType == typeof(string)); If I print out the Name of those properties I get there, I get: PublicPublic PublicPrivate PrivatePublic In other words, I get two properties too much. Note: This could probably be done in a better way... using nested foreach and reflection and all here... but if you have any great alternative ideas, please let me know cause I want to learn!

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• where to store temporary data in MVC 2.0 project

  - by StuffHappens

  Hello! I'm starting to learn MVC 2.0 and I'm trying to create a site with a quiz: user is asked a question and given several options of answer. If he chooses the right answer he gets some points, if he doesn't, he looses them. I tried to do this the following way public class HomeController : Controller { private ITaskGenerator taskGenerator = new TaskGenerator(); private string correctAnswer; public ActionResult Index() { var task = taskGenerator .GenerateTask(); ViewData["Task"] = task.Task; ViewData["Options"] = task.Options; correctAnswer= task.CorrectAnswer; return View(); } public ActionResult Answer(string id) { if (id == correctAnswer) return View("Correct") return View("Incorrect"); } } But I have a problem: when user answers the cotroller class is recreated and I loose correct answer. So what is the best place to store correct answer? Should I create a static class for this purpose? Thanks for your help!

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• How do you make use of the provider independency in the Entity Framework?

  - by Anders Svensson

  I'm trying to learn more about data access and the Entity Framework. My goal is to have a "provider independent" data access layer (to be able to switch easily e.g. from SQL Server to MySQL or vice versa), and since the EF is supposed to be provider independent it seems like a good way to go. But how do you use this provider independence? I mean, I was expecting to be able to sort of "program to an interface", and then just be able to switch database provider. But as far as I can tell I'm only getting a concrete type to program against, an "Entities" class, e.g. in my case it is: UserDBEntities _context = new UserDBEntities(); What I would have expected to be able to switch provider easily was to have an interface e.g. like IEntities _context = new UserDBEntities(); Sort of like I can do with datasets... But maybe that isn't how it works at all with EF? Or do you just switch provider in the connectionstring, and the model stays the same?? Please remember that I'm a complete newbie at this EF, and rather inexperienced with databases in general, so I would really appreciate if you could be as clear as possible :-)

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• Which way to go in Linux 3D programming?

  - by Tek

  I'm looking for some answers for a project I'm thinking of. I've searched and from what I understand (correct me if I'm wrong) the only way the program I want to make will work is through 3D application. Let me explain. I plan to make a studio production program but it's unique in the fact that I want to be able to make it fluid. Let me explain. Imagine Microsoft's Surface program where you're able to touch and drag pictures across the screen. Instead of pictures I want them to be sound samples (wavs,mp3,etc). Of course instead the input will be with the mouse but if I ever do finish the project I would totally add touch screen input compatibility! Anyway, I'm guessing there's "physics" to do with it which is why I'm thinking that even though it'll be a 2D application I'll need to code it in a 3D environment. Assuming that I'm correct in how I want to approach my project, where can I start learning about 3D programming? I actually come from PHP programming which will make C++ easier for me to learn. But I don't even know where to start. If I'm not wrong OpenGL is the most up to date API as far as I know. Anyway, please give me your insights guys. I could really use some guidance here since I could totally be wrong in everything that I wrote :)

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• Best (Java) book for understanding 'under the bonnet' for programming?

  - by Ben

  What would you say is the best book to buy to understand exactly how programming works under the hood in order to increase performance? I've coded in assembly at university, I studied computer architecture and I obviously did high level programming, but what I really dont understand is things like: -what is happening when I perform a cast -whats the difference in performance if I declare something global as opposed to local? -How does the memory layout for an ArrayList compare with a Vector or LinkedList? -Whats the overhead with pointers? -Are locks more efficient than using synchronized? -Would creating my own array using int[] be faster than using ArrayList -Advantages/disadvantages of declaring a variable volatile I have got a copy of Java Performance Tuning but it doesnt go down very low and it contains rather obvious things like suggesting a hashmap instead of using an ArrayList as you can map the keys to memory addresses etc. I want something a bit more Computer Sciencey, linking the programming language to what happens with the assembler/hardware. The reason im asking is that I have an interview coming up for a job in High Frequency Trading and everything has to be as efficient as possible, yet I cant remember every single possible efficiency saving so i'd just like to learn the fundamentals. Thanks in advance

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• Filtering string in Python

  - by Ecce_Homo

  I am making algorithm for checking the string (e-mail) - like "E-mail addres is valid" but their are rules. First part of e-mail has to be string that has 1-8 characters (can contain alphabet, numbers, underscore [ _ ]...all the parts that e-mail contains) and after @ the second part of e-mail has to have string that has 1-12 characters (also containing all legal expressions) and it has to end with top level domain .com EDIT email = raw_input ("Enter the e-mail address:") length = len (email) if length > 20 print "Address is too long" elif lenght < 5: print "Address is too short" if not email.endswith (".com"): print "Address doesn't contain correct domain ending" first_part = len (splitting[0]) second_part = len(splitting[1]) account = splitting[0] domain = splitting[1] for c in account: if c not in "abcdefghijklmopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_.": print "Invalid char", "->", c,"<-", "in account name of e-mail" for c in domain: if c not in "abcdefghijklmopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_.": print "Invalid char", "->", c,"<-", "in domain of e-mail" if first_part == 0: print "You need at least 1 character before the @" elif first_part> 8: print "The first part is too long" if second_part == 4: print "You need at least 1 character after the @" elif second_part> 16: print "The second part is too long" else: # if everything is fine return this print "E-mail addres is valid" EDIT: After reproting what is wrong with our input, now I need to make Python recognize valid address and return ("E-mail adress is valid") This is the best i can do with my knowledge....and we cant use regular expressions, teacher said we are going to learn them later.

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• Scala always returning true....WHY?

  - by jhamm

  I am trying to learn Scala and am a newbie. I know that this is not optimal functional code and welcome any advice that anyone can give me, but I want to understand why I keep getting true for this function. def balance(chars: List[Char]): Boolean = { val newList = chars.filter(x => x.equals('(') || x.equals(')')); return countParams(newList, 0) } def countParams(xs: List[Char], y: Int): Boolean = { println(y + " right Here") if (y < 0) { println(y + " Here") return false } else { println(y + " Greater than 0") if (xs.size > 0) { println(xs.size + " this is the size") xs match { case xs if (xs.head.equals('(')) => countParams(xs.tail, y + 1) case xs if (xs.head.equals(')')) => countParams(xs.tail, y - 1) case xs => 0 } } } return true; } balance("()())))".toList) I know that I am hitting the false branch of my if statement, but it still returns true at the end of my function. Please help me understand. Thanks.

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• Fundamentals of Deserialization in .NET?

  - by Codehelp

  I have been working with XML for past couple of months with .NET Basically all the work I do involve XML in oneway of another so I thought it would be good to learn the serialization and deserialization part of the game. My work mostly involves the 'Deserialization' part of it. Almost every time I have an XML file which has to be used by the application that I write. An object form of the XML is the best way to use. Now initially the XML was very straight forward, just a couple of tags which would translate into a class very easily using XSD.exe tool. Things grew a bit complex with nesting of tags and I found Xsd2Code gen tool work fine. During this whole process I have been able to do my work with a lot of help from Stackoverflow community, thanks for that, but I think I have missed the forest for the trees. I need to know how Deserialization works in .NET Fundamentally, I would like to know what happens behind the scenes in taking a XML and converting it into a usable object. Code samples have helped me in the past, and as mentioned earlier the problem get's solved but the learning does not happen. So, if anyone can guide to resources that can get me started on the Deserialization part of the game, I would be thankful to them. Regards.

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• Is it still true, to make cross broswer layouts for desktop browsers using table+css is easier then

  - by metal-gear-solid

  My one of web designer friend still making sites with table but he use css very nicely and I also use css nicely but with <div> and i face cross browser problem in layout more than my friend. and i given some reason to my friend about cons of <table>. read my whole discussion with friend? I - you site will be problematic with screen reader My friend - OK, but i never got any call from any client regarding this. I - you will devote more time to make any changes in layout, if changes comes from client My friend - I don't think so, but if it is then show me how can i save time with <div>? I - your sites will not work well with search engine. My friend - it's not true. I've made many site and no problem with any site or client regarding this I - layout is old way, non w3c and non standard way. My friend - what is old and what is new, Who is W3C i don't know, What is standard? Whatever i make works in all browsers, it's enough for me and my client will not pay for standard and W3C guidelines rules I - Your site will not work in mobile browsers My friend - No problem for me, my client don't care about mobile phone I - Your sites are not accessible? My Friend - What do u mean not accessible? Whatever i make works in all browsers. my any client never asked about accessibility I - You will not get more work in future, with table? My friend - OK, no problem when clients will not accept site with table then i will learn about div based layouts in future. My questions? Is it still true, to make cross browser layouts for desktop browsers using table+css is easier then div+css? What is the benefit for developer to use DIV+CSS layout in place of <table> layouts if client would not mind if i use ?

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• Stopping at my Front-End abilities... good career move?

  - by R. H.

  Just curious about what other front-end and back-end people think, career wise. Here's the details: I'm a 30 yr old mom who is pretty good at front end development - that's my day job at an interactive agency. Don't have the money or time to go back to school or lots of high priced training sessions. I started out as a graphic designer ten years ago or so, then moved into database-backed web stuff, like CMS. I'm great at transforming PSD to a working html and css structure, especially for Wordpress themes. I enjoy this part of the process, probably because it's easy and fun, and as I learn a little more about jQuery and PHP, I can make it even better if I want or need. I'm not sure where I should stop though, as far as my career goes. I don't know that I'll ever get to the point that I'm a great PHP developer or jQuery master. Is it lame to just be a front-end designer/developer? Can that be a successful career all its own? Or, should I obligate myself to learning the harder programming, if I'm capable? Any advice or points any of you may have is appreciated!

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• OpenSceneGraph C++ Access Violation reading location 0x00421000

  - by Kobojunkie

  Working with OpenSceneGraph, and I keep running into this violation issue that I would appreciate some help with. The problem is with the particular line below which happens to be the first in my main function. osg::ref_ptr<osg::Node> bench = osgDB::readNodeFile("Models/test.IVE"); I have my models folder right in my directory. The error is as below. Unhandled exception at 0x68630A6C (msvcr100.dll) in OSG3D.exe: 0xC0000005: Access violation reading location 0x00421000. And this is where the problem seems to be coming up. /** Read an osg::Node from file. * Return valid osg::Node on success, * return NULL on failure. * The osgDB::Registry is used to load the appropriate ReaderWriter plugin * for the filename extension, and this plugin then handles the request * to read the specified file.*/ inline osg::Node* readNodeFile(const std::string& filename) { return readNodeFile(filename,Registry::instance()->getOptions()); } I would appreciate details on how best to tackle this kind of exception message in the future. Are there tools that make this easy to debug or are there ways to capture the exact issues and fix them? I would appreciate any help with this. My ultimate goal is to learn how to better debug C++ related issues please. With this, it means reading through the compiler error list http://msdn.microsoft.com/en-us/library/850cstw1(v=vs.71).aspx is not enough

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• C#: Thread.CurrentThread.CurrentUICulture not working consistently

  - by xTRUMANx

  I've been working on a pet project on the weekends to learn more about C# and have encountered an odd problem when working with localization. To be more specific, the problem I have is with System.Threading.Thread.CurrentThread.CurrentUICulture. I've set up my app so that the user can quickly change the language of the app by clicking a menu item. The menu item in turn, saves the two-letter code for the language (e.g. "en", "fr", etc.) in a user setting called 'Language' and then restarts the application. Properties.Settings.Default.Language = "en"; Properties.Settings.Default.Save(); Application.Restart(); When the application is started up, the first line of code in the Form's constructor (even before InitializeComponent()) fetches the Language string from the settings and sets the CurrentUICulture like so: public Form1() { Thread.CurrentThread.CurrentUICulture = new CultureInfo(Properties.Settings.Default.Language); InitializeComponent(); } The thing is, this doesn't work consistently. Sometimes, all works well and the application loads the correct language based on the string saved in the settings file. Other times, it doesn't, and the language remains the same after the application is restarted. At first I thought that I didn't save the language before restarting the application but that is definitely not the case. When the correct language fails to load, if I were to close the application and run it again, the correct language would come up correctly. So this implies that the Language string has been saved but the CurrentUICulture assignment in my form constructor is having no effect sometimes. Any help? Is there something I'm missing of how threading works in C#? This could be machine-specific, so if it makes any difference I'm using Pentium Dual-Core CPU.

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• Is long long in C++ known to be very nasty in terms of precision?

  - by Kevin

  The Given Problem: Given a theater with n rows, m seats, and a list of seats that are reserved. Given these values, determine how many ways two friends can sit together in the same row. So, if the theater was a size of 2x3 and the very first seat in the first row was reserved, there would be 3 different seatings that these two guys can take. The Problem That I'm Dealing With The function itself is supposed to return the number of seatings that there are based on these constraints. The return value is a long long. I've gone through my code many many times...and I'm pretty sure that it's right. All I'm doing is incrementing this one value. However, ALL of the values that my function return differ from the actual solution by 1 or 2. Any ideas? And if you think that it's just something wrong with my code, please tell me. I don't mind being called an idiot just as long as I learn something.

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• The Purpose of a Service Layer and ASP.NET MVC 2

  - by user332022

  In an effort to understand MVC 2 and attempt to get my company to adopt it as a viable platform for future development, I have been doing a lot of reading lately. Having worked with ASP.NET pretty exclusively for the past few years, I had some catching up to do. Currently, I understand the repository pattern, models, controllers, data annotations, etc. But there is one thing that is keeping me from completely understanding enough to start work on a reference application. The first is the Service Layer Pattern. I have read many blog posts and questions here on Stack Overflow, but I still don't completely understand the purpose of this pattern. I watched the entire video series at MVCCentral on the Golf Tracker Application and also looked at the demo code he posted and it looks to me like the service layer is just another wrapper around the repository pattern that doesn't perform any work at all. I also read this post: http://www.asp.net/Learn/mvc/tutorial-38-cs.aspx and it seemed to somewhat answer my question, however, if you are using data annotations to perform your validation, this seems unnecessary. I have looked for demonstrations, posts, etc. but I can't seem to find anything that simply explains the pattern and gives me compelling evidence to use it. Can someone please provide me with a 2nd grade (ok, maybe 5th grade) reason to use this pattern, what I would lose if I don't, and what I gain if I do?a

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• C -- Basic Struct questions

  - by Ryan Yu

  So I'm trying to learn C right now, and I have some basic struct questions I'd like to clear up: Basically, everything centers around this snippet of code: #include <stdio.h> #include <stdlib.h> #define MAX_NAME_LEN 127 typedef struct { char name[MAX_NAME_LEN + 1]; unsigned long sid; } Student; /* return the name of student s */ const char* getName (const Student* s) { // the parameter 's' is a pointer to a Student struct return s->name; // returns the 'name' member of a Student struct } /* set the name of student s If name is too long, cut off characters after the maximum number of characters allowed. */ void setName(Student* s, const char* name) { // 's' is a pointer to a Student struct | 'name' is a pointer to the first element of a char array (repres. a string) s->name = name; } /* return the SID of student s */ unsigned long getStudentID(const Student* s) { // 's' is a pointer to a Student struct return s->sid; } /* set the SID of student s */ void setStudentID(Student* s, unsigned long sid) { // 's' is a pointer to a Student struct | 'sid' is a 'long' representing the desired SID s->sid = sid; } I've commented up the code in an attempt to solidify my understanding of pointers; I hope they're all accurate. So anyway, I have a feeling that setName and setStudentID aren't correct, but I'm not exactly sure why. Can someone explain? Thanks!

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