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  • Optimal way to initialize varying objects

    - by John Smith
    I have to initialize a lot of different types of objects based on an integer parameter. They all have the same overall initialization methods. At the moment I have the following code #def APPLE 1 #def PEAR 2 switch (t) { case APPLE: newobj = [[FApple alloc] init]; break; case PEAR: newobj = [[FPear] alloc] init]; break; default: retobj = nil; } I believe there must be a better way to do this. When I add FOrange I have to go and add another line here. What would be a better way?

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  • c# - best way to initialize an array of reference type object

    - by lidong
    I wonder if there is better way to initialize an array of reference type object, like this. Queue<int>[] queues = new Queue<int>[10]; for (int i = 0; i < queues.Length; i++) { queues[i] = new Queue<int>(); } I tried Enumerable.Repeat, but all elements in the array refer to same instance, Queue<int>[] queues = Enumerable.Repeat(new Queue<int>(), 10).ToArray(); I also tried Array.ForEach, but it doesn't work without ref keyword: Queue<int>[] queues = Array.ForEach(queues, queue => queue = new Queue<int>()); any other idea?

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  • unable to initialize a 512x512 array

    - by user1432196
    hey all i would just like to as why i keep getting a stack overflow error whenever i try to initialize a 512x512 array? Can anyone help? below is part of my code CImg<float> image("lena8bit.jpg"); CImgDisplay main_disp(image,"Main image"); int ImgArray [512][512]; Basically all i want to do is get the pixel values from the image and store it into this array. The image is 512x512 hence the array size. Hope to hear you answers, thanks!

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  • how-to initialize 'const std::vector<T>' like a c array

    - by vscharf
    Is there an elegant way to create and initialize a const std::vector<const T> like const T a[] = { ... } to a fixed (and small) number of values? I need to call a function frequently which expects a vector<T>, but these values will never change in my case. In principle I thought of something like namespace { const std::vector<const T> v(??); } since v won't be used outside of this compilation unit.

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  • How to initialize static const char array for ASCII codes [C++]

    - by Janney
    I want to initialize a static const char array with ASCII codes in a constructor, here's my code: class Card { public: Suit(void) { static const char *Suit[4] = {0x03, 0x04, 0x05, 0x06}; // here's the problem static const string *Rank[ 13 ] = {'A', '2', '3', '4', '5', '6', '7', '8', '9', '10', 'J', 'Q', 'K'}; // and here. } However i got a whole lot of errors stating that 'initializing' : cannot convert from 'char' to 'const std::string *' 'initializing' : cannot convert from 'int' to 'const std::string *' please help me! Thank you so much.

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  • Unknown Exception on trying to initialize the web service stub created by Axis C++

    - by Harsha Reddy
    Hi, I am trying out the sample calculator program given in the folder of axis c++. I am mainly interested in the client side. So I used the wsdl to create the stubs and my main is pretty much the same as given in the sample. However on executing the call Calculator ws (endpoint) I get an unknown exception "First-chance exception at 0x7c0024b9 in CalculatorClient.exe: 0xC0000005: Access violation reading location 0x00000000. First-chance exception at 0x7c812afb in CalculatorClient.exe: Microsoft C++ exception: [rethrow] at memory location 0x00000000.. Unhandled exception at 0x7c0024b9 in CalculatorClient.exe: 0xC0000005: Access violation reading location 0x00000000." and the exception causing code is Calculator::Calculator(const char* pchEndpointUri, AXIS_PROTOCOL_TYPE eProtocol) :Stub(pchEndpointUri, eProtocol) { } I had earlier tried to run a a webservice using Axis C++ but had received the same error. At that time my web service was a java ws on WAS. Then I later tried the calculator client (but this time I did not have any server hosting the ws as I just wanted to check if the Client could initialize). Is the problem caused due to the web service not being hosted on Apache in C++ (though I highly doubt it). Any help would be appreciated. Thanks, Harsha

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  • In .NET, What Is Fastest Way to Initialize Multi-Dimensional Array to Non-Default Value

    - by AMissico
    How do I initialize a multi-dimensional array of a primitive type as fast as possible? I am stuck with using multi-dimensional arrays. My problem is performance. The following routine initializes a 100x100 array in approx. 500 ticks. Removing the int.MaxValue initialization results in approx. 180 ticks just for the looping. Approximately 100 ticks to create the array without looping and without initializing to int.MaxValue. Routines similiar to this are called a few tens-of-thousands to several million times. I am open to suggestions on how to optimize this non-default initialization of an array. One idea I had is to use a smaller primitive type when available. For instance, using byte instead of int, saves 100 ticks. I would be happy with this, but I am hoping that I don't have to change the primitive data type. public int[,] CreateArray(Size size) { int[,] array = new int[size.Width, size.Height]; for (int x = 0; x < size.Width; x++) { for (int y = 0; y < size.Height; y++) { array[x, y] = int.MaxValue; } } return array; }

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  • How to initialize audio with Vala/SDL

    - by ioev
    I've been trying to figure this out for a few hours now. In order to start up the audio, I need to create an SDL.AudioSpec object and pass it to SDL.Audio.Open. The problem is, AudioSpec is a class with a private constructor, so when I try to create one I get: sdl.vala:18.25-18.43: error: `SDL.AudioSpec' does not have a default constructor AudioSpec audiospec = new SDL.AudioSpec(); ^^^^^^^^^^^^^^^^^^^ And if I try to just assign values to it's member vars like a struct (it's a struct in normal sdl) I get: sdl.vala:20.3-20.25: error: use of possibly unassigned local variable `audiospec' audiospec.freq = 22050; ^^^^^^^^^^^^^^^^^^^^^^^ I found the valac doc here: http://valadoc.org/sdl/SDL.AudioSpec.html But it isn't much help at all. The offending code block looks like this: // setup the audio configuration AudioSpec audiospec; AudioSpec specback; audiospec.freq = 22050; audiospec.format = SDL.AudioFormat.S16LSB; audiospec.channels = 2; audiospec.samples = 512; // try to initialize sound with these values if (SDL.Audio.open(audiospec, specback) < 0) { stdout.printf("ERROR! Check audio settings!\n"); return 1; } Any help would be greatly appreciated!

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  • Initialize Static Array of Structs in C

    - by russell_h
    I implementing a card game in C. There are lots of types of cards and each has a bunch of information, including some actions that will need to be individually scripted associated with it. Given a struct like this (and I'm not certain I have the syntax right for the function pointer) struct CARD { int value; int cost; // This is a pointer to a function that carries out actions unique // to this card int (*do_actions) (struct GAME_STATE *state, int choice1, int choice2); }; I would like to initialize a static array of these, one for each card. I'm guessing this would look something like this int do_card0(struct GAME_STATE *state, int choice1, int choice2) { // Operate on state here } int do_card1(struct GAME_STATE *state, int choice1, int choice2) { // Operate on state here } extern static struct cardDefinitions[] = { {0, 1, do_card0}, {1, 3, do_card1} }; Will this work, and am I going about this the right way at all? I'm trying to avoid huge numbers of switch statements. Do I need to define the 'do_cardN' functions ahead of time, or is there some way to define them inline in the initialization of the struct (something like a lambda function in python)? I'll need read-only access to cardDefinitions from a different file - is 'extern static' correct for that? I know this is a lot of questions rolled into one but I'm really a bit vague about how to go about this. 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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  • C++ Constructor With Parameters Won't Initialize, Errors C2059 and C2228

    - by Some Girl
    I'm a C# programmer trying to muddle through C++ to create a Windows Forms Application. I have a Windows Form that makes use of a user-created class. Basically I'm trying to use a constructor that takes parameters, but my form won't let me initialize the object with parameter. Here's the code, hopefully somebody can explain the problem to me because I'm completely baffled... Here's my header file: BankAcct.h public ref class BankAcct { private: int money; public: BankAcct(); BankAcct(int); void Deposit(int); void GetBalance(int&); }; And my definition file: BankAcct.cpp #include "StdAfx.h" #include "BankAcct.h" BankAcct::BankAcct() { money = 0; } BankAcct::BankAcct(int startAmt) { money = startAmt; } void BankAcct::Deposit(int depAmt) { money += depAmt; } void BankAcct::GetBalance(int& balance) { balance = money; } And finally my main form. Won't copy the whole thing, of course, but I'm trying to declare the new bank account object, and start it with a balance of say $50. private: BankAcct myAccount(50); //does not work! WHY?? //private: //BankAcct myAccount; //works then in the form constructor my code is this: public: frmBank(void) { InitializeComponent(); int bal; myAccount.GetBalance(bal); lblBankBalance->Text += Convert::ToString(bal); } I've included the BankAcct.h file at the top of my frmBank.h, what else am I doing wrong here? It works great if I use the default constructor (the one that starts the bank balance at zero). I get the following error messages: error C2059: syntax error: 'constant' and error C2228: left of '.GetBalance' must have class/struct/union Thank you for any and all help on this one!!

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  • How to initialize list with parent child relation

    - by user2917702
    Let's say I have the following classes. public class Parent { public string name; IList<Children> children; } public class Child { public string parentName; public int age; } As it is understandable, each parent can have multiple children, and we can have multiple parents. What is the best way to initialize these classes? Is it better to get all of the parents, and all of the children from database then use LINQ? IList<Parent> parents = GetParents()//assume this gets parents from db IList<Child> children = GetChildren() //assume this gets children from db foreach(Parent parent in parents) { parent.children = children.Where(x=>x.parentName==parent.name).ToList(); } or get all of the parents and iterate through each parent to query database by parentName to get children information? Due to requirement that I have, I cannot use datatable or dataset; I can only use datareader. IList<Parent> parents = GetParents()//assume this gets parents from db foreach(Parent parent in parents) { parent.children = GetChildrenByParentName();//assume this gets parents from db by parentName } Thank you

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  • Correct way to initialize dynamic Array in C++

    - by mef
    Hey guys, I'm currently working on a C++ project, where dynamic arrays often appear. I was wondering, what could be the correct way to initialize a dynamic array using the new-operator? A colleague of mine told me that it's a no-no to use new within the constructor, since a constructor is a construct that shouldn't be prone to errors or shouldn't fail at all, respectively. Now let's consider the following example: We have two classes, a more or less complex class State and a class StateContainer, which should be self-explained. class State { private: unsigned smth; public: State(); State( unsigned s ); }; class StateContainer { private: unsigned long nStates; State *states; public: StateContainer(); StateContainer( unsigned long n ); virtual ~StateContainer(); }; StateContainer::StateContainer() { nStates = SOME_DEFINE_N_STATES; states = new State[nStates]; if ( !states ) { // Error handling } } StateContainer::StateContainer( unsigned long n ) { nStates = n; try { states = new State[nStates] } catch ( std::bad_alloc &e ) { // Error handling } } StateContainer::~StateContainer() { if ( states ) { delete[] states; states = 0; } } Now actually, I have two questions: 1.) Is it ok, to call new within a constructor, or is it better to create an extra init()-Method for the State-Array and why? 2.) Whats the best way to check if new succeeded: if (!ptr) std::cerr << "new failed." or try { /*new*/ } catch (std::bad_alloc) { /*handling*/ } 3.) Ok its three questions ;o) Under the hood, new does some sort of ptr = (Struct *)malloc(N*sizeof(Struct)); And then call the constructor, right?

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  • Initialize a Variable Again.

    - by SoulBeaver
    That may sound a little confusing. Basically, I have a function CCard newCard() { /* Used to store the string variables intermittantly */ std::stringstream ssPIN, ssBN; int picker1, picker2; int pin, bankNum; /* Choose 5 random variables, store them in stream */ for( int loop = 0; loop < 5; ++loop ) { picker1 = rand() % 8 + 1; picker2 = rand() % 8 + 1; ssPIN << picker1; ssBN << picker2; } /* Convert them */ ssPIN >> pin; ssBN >> bankNum; CCard card( pin, bankNum ); return card; } that creates a new CCard variable and returns it to the caller CCard card = newCard(); My teacher advised me that doing this is a violation of OOP principles and has to be put in the class. He told me to use this method as a constructor. Which I did: CCard::CCard() { m_Sperre = false; m_Guthaben = rand() % 1000; /* Work */ /* Convert them */ ssPIN >> m_Geheimzahl; ssBN >> m_Nummer; } All variables with m_ are member variables. However, the constructor works when I initialize the card normally CCard card(); at the start of the program. However, I also have a function, that is supposed to create a new card and return it to the user, this function is now broken. The original command: card = newCard(); isn't available anymore, and card = new CCard(); doesn't work. What other options do I have? I have a feeling using the constructor won't work, and that I probably should just create a class method newCard, but I want to see if it is somehow at all possible to do it the way the teacher wanted. This is creating a lot of headaches for me. I told the teacher that this is a stupid idea and not everything has to be classed in OOP. He has since told me that Java or C# don't allow code outside of classes, which sounds a little incredible. Not sure that you can do this in C++, especially when templated functions exist, or generic algorithms. Is it true that this would be bad code for OOP in C++ if I didn't force it into a class?

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  • DRY'er Object Initialization in Ruby

    - by Trevoro
    Hi, Is there a more 'DRY' way to do the following in ruby? #!/usr/bin/env ruby class Volume attr_accessor :name, :size, :type, :owner, :date_created, :date_modified, :iscsi_target, :iscsi_portal SYSTEM = 0 DATA = 1 def initialize(args={:type => SYSTEM}) @name = args[:name] @size = args[:size] @type = args[:type] @owner = args[:owner] @iscsi_target = args[:iscsi_target] @iscsi_portal = args[:iscsi_portal] end def inspect return {:name => @name, :size => @size, :type => @type, :owner => @owner, :date_created => @date_created, :date_modified => @date_modified, :iscsi_target => @iscsi_target, :iscsi_portal => @iscsi_portal } end def to_json self.inspect.to_json end end

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  • How to initialize a BigInteger in C#?

    - by Akshay
    Hi, Can someone show me how to use the System.Numerics.BigInteger datatype? I tried using this as a reference - http://msdn.microsoft.com/en-us/library/system.numerics.biginteger%28VS.100%29.aspx But System.Numerics namespace isn't there on my computer. I have installed VS2010 Ultimate RC and i have .NET Framework 4.0. Can someone guide me through this? Regards, Akshay.

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  • Initialize preferences from XML in main Activity

    - by pixel
    My problem is that when I start application and user didn't open my PreferenceActivity so when I retrieve them don't get any default values defined in my preference.xml file. preference.xml file: <?xml version="1.0" encoding="utf-8"?> <PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" android:key="applicationPreference" android:title="@string/config" > <ListPreference android:key="pref1" android:defaultValue="default" android:title="Title" android:summary="Summary" android:entries="@array/entry_names" android:entryValues="@array/entry_values" android:dialogTitle="@string/dialog_title" /> </PreferenceScreen> Snippet from my main Activity (onCreate method): SharedPreferences appPreferences = PreferenceManager.getDefaultSharedPreferences(this); String pref1 = appPreferences.getString("pref1", null); In result I end up with a null value.

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  • Initialize data using memset

    - by gkid123
    memset to initilize data member- What is the benefit of initializing this way? Does it work in this example? 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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  • Initialize Pointer Through Function

    - by SoulBeaver
    I was browsing my teacher's code when I stumbled across this: Order* order1 = NULL; then order1 = order(customer1, product2); which calls Order* order(Customer* customer, Product* product) { return new Order(customer, product); } This looks like silly code. I'm not sure why, but the teacher initialized all pointers to NULL instead of declaring them right away(looking at the code it's entirely possible, but he chose not to). My question is: is this good or acceptable code? Does the function call have any benefits over calling a constructor explicitely? And how does new work in this case? Can I imagine the code now as kind of like: order1 = new Order(customer, product);

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  • Convert in memory POCO objects to c# code to initialize

    - by sidesinger
    Is there a library or code sample for converting an in memory POCO c# object to a .cs code file that creates that object. An example: object of type car in memory becomes: Car c = new Car { Name = "mazda", Id = 5, Passengers = new List<string> { "Bob", "Sally" } // etc... recursing to the bottom }; I could assume it could only set public properties.

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  • Problems using Maven to initialize a local thoughtsite (App Engine sample) project in Eclipse

    - by ovr
    This sample app ("thoughtsite") for App Engine contains a pom.xml in its trunk: http://code.google.com/p/thoughtsite/source/browse/#svn/trunk I ran mvn eclipse:eclipse and also tried using m2eclipse to import this source code into an Eclipse project. But I end up with this error despite the fact that I have the Google App Engine plugin and the Google App Engine SDK installed: Exception in thread "main" java.lang.ExceptionInInitializerError at com.google.appengine.tools.info.SdkImplInfo.<clinit>(SdkImplInfo.java:19) at com.google.appengine.tools.util.Logging.initializeLogging(Logging.java:36) at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:82) Caused by: java.lang.RuntimeException: Unable to discover the Google App Engine SDK root. This code should be loaded from the SDK directory, but was instead loaded from file:~/.m2/repository/com/google/appengine/appengine-tools-sdk/1.3.0/appengine-tools-sdk-1.3.0.jar. Specify -Dappengine.sdk.root to override the SDK location. at com.google.appengine.tools.info.SdkInfo.findSdkRoot(SdkInfo.java:106) at com.google.appengine.tools.info.SdkInfo.<clinit>(SdkInfo.java:24) ... 3 more When I go into the project settings under "Google" and try to set it to use the default App Engine SDK it always reverts to trying to use Maven's App Engine SDK instead. No idea how to get this project working.

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  • C# Initialize Subclass based on Parent object

    - by ctrlShiftBryan
    So basically I have this public class Ticket{ public TicketNumber {get; set;} ..a bunch more properties... } I want to add some properties using a subclass like this using subsumption instead of composition. public class TicketViewModel(Ticket ticket){ //set each property from value of Ticket passed in this.TicketNumber = ticket.TicketNumber; ...a bunch more lines of code.. //additional VM properties public SelectList TicketTypes {get; private set;} } How do I instantiate the properties without having to write all the lines like this this.TicketNumber = ticket.TicketNumber; Is there some kind of shortcut? Something like in the subclass constructor? this = ticket; Obviously this doesn't work but is their some way so I don't have to modify my subclass if addng/removing a property to the parent class? Or something?

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  • ASP.NET: How to initialize when *user control* is initially loaded

    - by kendor
    I have an ASP.NET user control that I'm embedding in another user control. This works fine. I need to know the best logic/method for detecting when the control is loaded. In other words, I have some display initialization logic that needs to run when the control is initially displayed. Surely there is a pattern for this. The typical method is to put (!IsPostBack) logic in the Page_Load method of the control. This works great until you end up with a state when the Parent page has already posted back many times. My user control gets added to the page but its display does not intialize properly. I'm hoping to find a way that keeps this logic inside the control, versus various hacking around in the codebehind of the parent page.

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