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  • IndexOf method returns 0 when it should had return -1 in C# / Java

    - by jcgarciam
    A friend of mine came to me with this strange behavior which i can't explain, any insight view would be appreciated. Im running VS 2005 (C# 2.0), the following code show the behavior int rr = "test".IndexOf(""); Console.WriteLine(rr.ToString()); the above code, print "0" which clearly show it should have return -1 This also happen in Java where the following Class show the behavior: public class Test{ public static void main(String[] args){ System.out.println("Result->"+("test".indexOf(""))); } } Im running Java 1.6.0_17

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  • virtaul function

    - by hitech
    class a { virtual void foo(void) ; }; class b : public a { public: virtual void foo(void) { cout<< "class b"; } }; int main ( ) { class a *b_ptr = new b ; b_ptr-foo(); } please guide me why the b_ptr-foo() will not call the foo() function of the class b?

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  • Undefined template methods trick ?

    - by Matthieu M.
    A colleague of mine told me about a little piece of design he has used with his team that sent my mind boiling. It's a kind of traits class that they can specialize in an extremely decoupled way. I've had a hard time understanding how it could possibly work, and I am still unsure of the idea I have, so I thought I would ask for help here. We are talking g++ here, specifically the versions 3.4.2 and 4.3.2 (it seems to work with both). The idea is quite simple: 1- Define the interface // interface.h template <class T> struct Interface { void foo(); // the method is not implemented, it could not work if it was }; // // I do not think it is necessary // but they prefer free-standing methods with templates // because of the automatic argument deduction // template <class T> void foo(Interface<T>& interface) { interface.foo(); } 2- Define a class, and in the source file specialize the interface for this class (defining its methods) // special.h class Special {}; // special.cpp #include "interface.h" #include "special.h" // // Note that this specialization is not visible outside of this translation unit // template <> struct Interface<Special> { void foo() { std::cout << "Special" << std::endl; } }; 3- To use, it's simple too: // main.cpp #include "interface.h" class Special; // yes, it only costs a forward declaration // which helps much in term of dependencies int main(int argc, char* argv[]) { Interface<Special> special; foo(special); return 0; }; It's an undefined symbol if no translation unit defined a specialization of Interface for Special. Now, I would have thought this would require the export keyword, which to my knowledge has never been implemented in g++ (and only implemented once in a C++ compiler, with its authors advising anyone not to, given the time and effort it took them). I suspect it's got something to do with the linker resolving the templates methods... Do you have ever met anything like this before ? Does it conform to the standard or do you think it's a fortunate coincidence it works ? I must admit I am quite puzzled by the construct...

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  • Call main() itself in c++?

    - by Mask
    int main() { cout << "!!!Hello World!!!" << endl; // prints !!!Hello World!!! system("pause"); return main(); } The above works,but it hardcoded the main(),is there a magic variable to get the current running function?

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  • How to store data with N columns

    - by iconiK
    I need a way to store an int for N columns. Basically what I have is this: Armies: ArmyID - UINT UnitCount1 - UINT UnitCount2 - UINT UnitCount3 - UINT UnitCount4 - UINT ... I can't possible add a column for each and every unit, so I need a fast way to store the number of each units in an army (you might have guesses it's for a game by now). Using XML is not an option as it will be dead slow.

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  • how to loop through an array of vectors in C#

    - by Robert
    Hello everyone,I now have an array of vectors: static Vector3[] axes = new Vector3[] { Vector3.UnitX, Vector3.UnitY, Vector3.UnitZ }; and I want to loop through it,the code I write is: for(int i=0;i<axes.Length;i++) { do sth. about axes[i]; } However,it doesnt work and gets into infinite loop,could anyone help? thx.

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  • Loading a entity IDs CSV column as hydrated entities in NHibernate

    - by James L
    I have a number of database table that looks like this: EntityId int : 1 Countries1: "1,2,3,4,5" Countries2: "7,9,10,22" I would like to have NHibernate load the Country entities identifed as 1,2,3,4,5,7,9 etc. whenever my EntityId is loaded. The reason for this is that we want to avoid a proliferation of joins, as there are scores of these collections.

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  • FillRect won't draw anything

    - by kaykun
    I'm trying to create a simple window in Win32 and draw a rectangle in it, but for some reason FillRect isn't working for me. Here's my source: #include <windows.h> #include "resource.h" RECT rect; LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) { static PAINTSTRUCT ps; static HDC hDC; switch(msg) { case WM_PAINT: hDC = BeginPaint(hWnd, &ps); FillRect(hDC, &rect, (HBRUSH)(COLOR_WINDOW+1)); EndPaint(hWnd, &ps); break; case WM_CLOSE: DestroyWindow(hWnd); break; case WM_DESTROY: PostQuitMessage(0); break; default: return DefWindowProc(hWnd, msg, wParam, lParam); } return 0; } int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { WNDCLASSEX wc; HWND hWnd; MSG msg; rect.left = 0; rect.right = 0; rect.top = 100; rect.bottom = 100; wc.cbSize = sizeof(WNDCLASSEX); wc.style = 0; wc.lpfnWndProc = WndProc; wc.cbClsExtra = 0; wc.cbWndExtra = 0; wc.hInstance = hInstance; wc.hIcon = LoadIcon(NULL, IDI_APPLICATION); wc.hCursor = LoadCursor(NULL, IDC_ARROW); wc.hbrBackground = (HBRUSH)(COLOR_ACTIVEBORDER+1); wc.lpszMenuName = MAKEINTRESOURCE(IDR_MAIN_MENU); wc.lpszClassName = "Main"; wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION); RegisterClassEx(&wc); hWnd = CreateWindowEx(NULL, "Main", "Main", WS_SYSMENU | WS_MINIMIZEBOX, CW_USEDEFAULT, CW_USEDEFAULT, 240, 360, NULL, NULL, hInstance, NULL); ShowWindow(hWnd, nCmdShow); UpdateWindow(hWnd); while(GetMessage(&msg, NULL, 0, 0) > 0) { TranslateMessage(&msg); DispatchMessage(&msg); } return msg.wParam; } Is there something I'm missing or doing wrong in my code? Thanks in advance

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  • [C++] FillRect won't draw anything

    - by kaykun
    I'm trying to create a simple window in Win32 and draw a rectangle in it, but for some reason FillRect isn't working for me. Here's my source: #include <windows.h> #include "resource.h" RECT rect; LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) { static PAINTSTRUCT ps; static HDC hDC; switch(msg) { case WM_PAINT: hDC = BeginPaint(hWnd, &ps); FillRect(hDC, &rect, (HBRUSH)(COLOR_WINDOW+1)); EndPaint(hWnd, &ps); break; case WM_CLOSE: DestroyWindow(hWnd); break; case WM_DESTROY: PostQuitMessage(0); break; default: return DefWindowProc(hWnd, msg, wParam, lParam); } return 0; } int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { WNDCLASSEX wc; HWND hWnd; MSG msg; rect.left = 0; rect.right = 0; rect.top = 100; rect.bottom = 100; wc.cbSize = sizeof(WNDCLASSEX); wc.style = 0; wc.lpfnWndProc = WndProc; wc.cbClsExtra = 0; wc.cbWndExtra = 0; wc.hInstance = hInstance; wc.hIcon = LoadIcon(NULL, IDI_APPLICATION); wc.hCursor = LoadCursor(NULL, IDC_ARROW); wc.hbrBackground = (HBRUSH)(COLOR_ACTIVEBORDER+1); wc.lpszMenuName = MAKEINTRESOURCE(IDR_MAIN_MENU); wc.lpszClassName = "Main"; wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION); RegisterClassEx(&wc); hWnd = CreateWindowEx(NULL, "Main", "Main", WS_SYSMENU | WS_MINIMIZEBOX, CW_USEDEFAULT, CW_USEDEFAULT, 240, 360, NULL, NULL, hInstance, NULL); ShowWindow(hWnd, nCmdShow); UpdateWindow(hWnd); while(GetMessage(&msg, NULL, 0, 0) > 0) { TranslateMessage(&msg); DispatchMessage(&msg); } return msg.wParam; } Is there something I'm missing or doing wrong in my code? Thanks in advance

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  • Java: Are these 2 codes the same?

    - by Kevin Duke
    for (Player p : players) { p.addCard(deck.dealCard()); p.addCard(deck.dealCard()); } and for (int i = 0; i < players.size() ; i++) { Player p = players.get(i); p.addCard(deck.dealCard()); p.addCard(deck.dealCard()); } The second code yeilds a null pointer exception, what can be done to make the bottom one equivalent ?

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  • Retrieve Value from NSString

    - by Taimur Hamza
    Hi, i have a NSString instance ,i want to retrieve value from it and store it into an integer. This is wat i am doing but its not working. NSString *totalcnt; char *str = totalcnt; int a = atoi(str); Help me out. Thanks Taimur

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  • Returning different data types C#

    - by user1810659
    i have create a class library (DLL) with many different methods. and the return different types of data(string string[] double double[]). Therefore i have created one class i called CustomDataType for all the methods containing different data types so each method in the Library can return object of the custom class and this way be able to return multiple data types I have done it like this: public class CustomDataType { public double Value; public string Timestamp; public string Description; public string Unit; // special for GetparamterInfo public string OpcItemUrl; public string Source; public double Gain; public double Offset; public string ParameterName; public int ParameterID; public double[] arrayOfValue; public string[] arrayOfTimestamp; // public string[] arrayOfParameterName; public string[] arrayOfUnit; public string[] arrayOfDescription; public int[] arrayOfParameterID; public string[] arrayOfItemUrl; public string[] arrayOfSource; public string[] arrayOfModBusRegister; public string[] arrayOfGain; public string[] arrayOfOffset; } The Library contains methods like these: public CustomDataType GetDeviceParameters(string deviceName) { ...................... code getDeviceParametersObj.arrayOfParameterName; return getDeviceParametersObj; } public CustomDataType GetMaxMin(string parameterName, string period, string maxMin) { .....................................code getMaxMingObj.Value = (double)reader["MaxMinValue"]; getMaxMingObj.Timestamp = reader["MeasurementDateTime"].ToString(); getMaxMingObj.Unit = reader["Unit"].ToString(); getMaxMingObj.Description = reader["Description"].ToString(); return getMaxMingObj; } public CustomDataType GetSelectedMaxMinData(string[] parameterName, string period, string mode) {................................code selectedMaxMinObj.arrayOfValue = MaxMinvalueList.ToArray(); selectedMaxMinObj.arrayOfTimestamp = MaxMintimeStampList.ToArray(); selectedMaxMinObj.arrayOfDescription = MaxMindescriptionList.ToArray(); selectedMaxMinObj.arrayOfUnit = MaxMinunitList.ToArray(); return selectedMaxMinObj; } As illustrated thi different methods returns different data types,and it works fine for me but when i import the DLL and want to use the methods Visual studio shwos all the data types in the CustomDataType class as suggestion for all the methods even though the return different data.This is illusrtated in the picture below. As we can see from the picture with the suggestion of all the different return data the user can get confused and choose wrong return data for some of the methods. So my question is how can i improve this. so Visual studio suggest just the belonging return data type for each method.

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  • Naming guidelines with C#.

    - by VansFannel
    Hello! I have this class: class DoSomething { private int timesDone; ... } Which is the right way to named variable 'timesDone'? Sometimes I see named as m_timesDone. Is this correct? Where I can find information about naming guidelines? Thank you!

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  • memset for initialization in C++

    - by skydoor
    memset is sometimes used to initialize data in a constructor like the example below. Does it work in general ? Is it a good idea in general? class A { public: A(); private: int a; float f; char str[35]; long *lp; }; A::A() { memset(this, 0, sizeof(*this)); }

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  • C++ error message output format

    - by sub
    If I want to trigger an error in my interpreter I call this function: Error( ErrorType type, ErrorSeverity severity, const char* msg, int line ); However, with that I can only output Name error: Undefined variable in line 1 instead of Name error: Undefined variable 'someVariableName' in line 1 I'm working entirely with strings (except for the error messages as they all are constant at the moment), so sprintf won't work. What is the best way to create an efficient error function that can output a constant message combined with a string that describes which object, e.g.: a non-existing variable, triggered the error?

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  • 'Good' programming form in maintaining / updating / accessing files by entry

    - by zhermes
    Basic Question: If I'm storying/modifying data, should I access elements of a file by index hard-coded index, i.e. targetFile.getElement(5); via a hardcoded identifier (internally translated into index), i.e. target.getElementWithID("Desired Element"), or with some intermediate DESIRED_ELEMENT = 5; ... target.getElement(DESIRED_ELEMENT), etc. Background: My program (c++) stores data in lots of different 'dataFile's. I also keep a list of all of the data-files in another file---a 'listFile'---which also stores some of each one's properties (see below, but i.e. what it's name is, how many lines of information it has etc.). There is an object which manages the data files and the list file, call it a 'fileKeeper'. The entries of a listFile look something like: filename , contents name , number of lines , some more numbers ... Its definitely possible that I may add / remove fields from this list --- but in general, they'll stay static. Right now, I have a constant string array which holds the identification of each element in each entry, something like: const string fileKeeper::idKeys[] = { "FileName" , "Contents" , "NumLines" ... }; const int fileKeeper::idKeysNum = 6; // 6 - for example I'm trying to manage this stuff in 'good' programatic form. Thus, when I want to retrieve the number of lines in a file (for example), instead of having a method which just retrieves the '3'rd element... Instead I do something like: string desiredID = "NumLines"; int desiredIndex = indexForID(desiredID); string desiredElement = elementForIndex(desiredIndex); where the function indexForID() goes through the entries of idKeys until it finds desiredID then returns the index it corresponds to. And elementForIndex(index) actually goes into the listFile to retrieve the index'th element of the comma-delimited string. Problem: This still seems pretty ugly / poor-form. Is there a way I should be doing this? If not, what are some general ways in which this is usually done? Thanks!

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  • doubt regarding sequence points

    - by tushar
    i recently came across a question about sequence points in c++ at this site what the code will output: int c=0; cout<<c++<<c; it was answered that the output is undefined and << is not a sequence point but still i want to know why does it that even if i compile it 25 times it still prints 01

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  • Initializing a C++ vector to random values... fast

    - by Flamewires
    Hey, id like to make this as fast as possible because it gets called A LOT in a program i'm writing, so is there any faster way to initialize a C++ vector to random values than: double range;//set to the range of a particular function i want to evaluate. std::vector<double> x(30, 0.0); for (int i=0;i<x.size();i++) { x.at(i) = (rand()/(double)RAND_MAX)*range; } EDIT:Fixed x's initializer.

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  • Graph Tour with Uniform Cost Search in Java

    - by user324817
    Hi. I'm new to this site, so hopefully you guys don't mind helping a nub. Anyway, I've been asked to write code to find the shortest cost of a graph tour on a particular graph, whose details are read in from file. The graph is shown below: http://img339.imageshack.us/img339/8907/graphr.jpg This is for an Artificial Intelligence class, so I'm expected to use a decent enough search method (brute force has been allowed, but not for full marks). I've been reading, and I think that what I'm looking for is an A* search with constant heuristic value, which I believe is a uniform cost search. I'm having trouble wrapping my head around how to apply this in Java. Basically, here's what I have: Vertex class - ArrayList<Edge> adjacencies; String name; int costToThis; Edge class - final Vertex target; public final int weight; Now at the moment, I'm struggling to work out how to apply the uniform cost notion to my desired goal path. Basically I have to start on a particular node, visit all other nodes, and end on that same node, with the lowest cost. As I understand it, I could use a PriorityQueue to store all of my travelled paths, but I can't wrap my head around how I show the goal state as the starting node with all other nodes visited. Here's what I have so far, which is pretty far off the mark: public static void visitNode(Vertex vertex) { ArrayList<Edge> firstEdges = vertex.getAdjacencies(); for(Edge e : firstEdges) { e.target.costToThis = e.weight + vertex.costToThis; queue.add(e.target); } Vertex next = queue.remove(); visitNode(next); } Initially this takes the starting node, then recursively visits the first node in the PriorityQueue (the path with the next lowest cost). My problem is basically, how do I stop my program from following a path specified in the queue if that path is at the goal state? The queue currently stores Vertex objects, but in my mind this isn't going to work as I can't store whether other vertices have been visited inside a Vertex object. Help is much appreciated! Josh

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  • rename keys in a dictionary

    - by user366660
    i want to rename the keys of a dictionary are which are ints, and i need them to be ints with leading zeros's so that they sort correctly. for example my keys are like: '1','101','11' and i need them to be: '001','101','011' this is what im doing now, but i know there is a better way tmpDict = {} for oldKey in aDict: tmpDict['%04d'%int(oldKey)] = aDict[oldKey] newDict = tmpDict

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  • Typcast a null pointer to char*

    - by user326253
    Suppose I have a char* elem that is supposed to hold a char*, s.t. elem[0] = char*, elem[1...m]= more chars. Is there a way I can put a null ptr within char* elem? When I try to set elem = NULL, it gives me a type error because NULL is an int. Any help would be greatly appreciated!

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  • Scala return type for tuple-functions

    - by Felix
    Hello Guys, I want to make a scala function which returns a scala tuple. I can do a function like this: def foo = (1,"hello","world") and this will work fine, but now I want to tell the compiler what I expect to be returned from the function instead of using the built in type inference (after all, I have no idea what a (1,"hello","world") is) I thought I remembered the classname being something like Tuple3[Int,String,String] but that doesnt work for me. Suggestions? :D (ps: I love stack overflow!)

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