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• C# Multidimensional Array Definition

  - by Blaenk

  Can someone help me convert this to C#. I've already spent more time than I would have liked trying to do it myself and it's preventing me from actually getting any work done. I guess it seems like C# has a limitation regarding how one can define arrays. I think somewhere inside I have to keep doing new int[] but I'm not sure exactly where. You don't have to convert the whole thing, just enough so I can understand how to do it. I would really appreciate it. I would like to use integers instead of characters, by the way. Thanks again // Pieces definition char mArray [7][4][5][5] = { // Square { { {0, 0, 0, 0, 0}, {0, 0, 0, 0, 0}, {0, 0, 2, 1, 0}, {0, 0, 1, 1, 0}, {0, 0, 0, 0, 0} }, { {0, 0, 0, 0, 0}, {0, 0, 0, 0, 0}, {0, 0, 2, 1, 0}, {0, 0, 1, 1, 0}, {0, 0, 0, 0, 0} }, { {0, 0, 0, 0, 0}, {0, 0, 0, 0, 0}, {0, 0, 2, 1, 0}, {0, 0, 1, 1, 0}, {0, 0, 0, 0, 0} }, { {0, 0, 0, 0, 0}, {0, 0, 0, 0, 0}, {0, 0, 2, 1, 0}, {0, 0, 1, 1, 0}, {0, 0, 0, 0, 0} } }, // and so on and so forth, for 6 more };

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• Strange Access Denied warning when running the simplest C++ program.

  - by DaveJohnston

  I am just starting to learn C++ (coming from a Java background) and I have come across something that I can't explain. I am working through the C++ Primer book and doing the exercises. Every time I get to a new exercise I create a new .cpp file and set it up with the main method (and any includes I think I will need) e.g.: #include <list> #include <vector> int main(int argc, char **args) { } and just to make sure I go to the command prompt and compile and run: g++ whatever.cpp a.exe Normally this works just fine and I start working on the exercise, but I just did it and got a strange error. It compiles fine, but when I run it it says Access Denied and AVG pops up telling me that a threat has been detected 'Trojan Horse Generic 17.CKZT'. I tried compiling again using the Microsoft Compiler (cl.exe) and it runs fines. So I went back, and added: #include <iostream> compiled using g++ and ran. This time it worked fine. So can anyone tell me why AVG would report an empty main method as a trojan horse but if the iostream header is included it doesn't?

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• reading a file of unknown length with a function

  - by Faken

  I'm trying to write a short function that will let me quickly read in a file of unknown size and return pointer to the array of data and the length of that array but it seems my code isn't working. What am i doing wrong? int readIn(int* pointer, param parameters, string description) { string fileName = parameters.fileName + " " + description + ".bin"; ifstream readFile; readFile.open(fileName.c_str(), ios::in|ios::binary|ios::ate); int size = readFile.tellg(); int length = size / 4; int* output = new int [length]; readFile.seekg (0, ios::beg); readFile.read(reinterpret_cast<char*>(output), (size)); readFile.close(); pointer = output; // link new array with the pointer return length; } and in the main function: int* testList; int numEntries = readIn(testList, parameters, "test"); I end up with an error saying that my testList variable was used and not initialized. What am i doing wrong?

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• C#: socket closing if user user exists

  - by corvallo

  Hi to everyone I'm trying to create a server/client application for a school project. This is the scenario: a server on a given port, multiple user connected, each user has it's own username. Now I want to check if a user that try to connect to the user use a valid username, for example if a user with username A it's already connected a new user that want to connect cannot use the username A. If this happen the server answer to the new client with an error code. This is the code for this part private void Receive() { while (true) { byte[] buffer = new byte[64]; socket.Receive(buffer); string received = Encoding.Default.GetString(buffer); if (received.IndexOf("!error") != -1) { string[] mySplit = received.Split(':'); string errorCode = mySplit[1].Trim((char)0); if (errorCode == "user exists") { richTextBox1.AppendText("Your connection was refused by server, because there's already another user connected with the username you choose"); socket.Disconnect(true); connectBtn.Enabled = true; } } } } But when I try to do this the program crash and visual studio said that there's an invalid cross-thread operation on richTextBox1. Any ideas. Thank you in advance.

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• ISO C90 forbids mixed declarations and code sscanf

  - by Need4Sleep

  I'm getting a strange error attempting to compile my unit test code,. For some reason the compiler treats my sscanf call as a mixed declaration? I don't quite understand, here is the entire error: cc1: warnings being treated as errors /home/brlcad/brlcad/src/libbn/tests/bn_complex.c: In function 'main': /home/brlcad/brlcad/src/libbn/tests/bn_complex.c:53: error: ISO C90 forbids mixed declarations and code make[2]: *** [src/libbn/tests/CMakeFiles/tester_bn_complex.dir/bn_complex.c.o] Error 1 make[1]: *** [src/libbn/tests/CMakeFiles/tester_bn_complex.dir/all] Error 2 make: *** [all] Error 2 int main(int argc, char *argv[]) { double expRe1, expIm2, expSqRe1, expSqIm2; double actRe1, actIm2, actSqRe1, actSqIm2; actRe1 = actIm2 = actSqRe1 = actSqIm2 = expRe1 = expIm2 = expSqRe1 = expSqIm2 = 0.0; bn_complex_t com1,com2; //a struct that holds two doubles if(argc < 5) bu_exit(1, "ERROR: Invalid parameters[%s]\n", argv[0]); sscanf(argv[1], "%lf,%lf", &com1.re, &com1.im); /* Error is HERE */ sscanf(argv[2], "%lf,%lf", &com2.re, &com2.im); sscanf(argv[3], "%lf,%lf", &expRe1, &expIm2); sscanf(argv[4], "%lf,%lf", &expSqRe1, &expSqIm2); test_div(com1, com2, &actRe1, &actIm2); test_sqrt(com1,com2, &actSqRe1, &actSqIm2); if((fabs(actRe1 - expRe1) < 0.00001) || (fabs(actIm2 - expIm2) < 0.00001)){ printf("Division failed...\n"); return 1; } if((fabs(actSqRe1 - expSqRe1) < 0.00001) || (fabs(actSqIm2 - expSqIm2) < 0.00001)){ printf("Square roots failed...\n"); return 1; } return 0; }

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• Objective-C ref count and autorelease

  - by turbovince

  Hey guys, suppose the following code: int main (int argc, const char * argv[]) { //[...] Rectangle* myRect = [[Rectangle alloc] init]; Vector2* newOrigin = [[[Vector2 alloc] init] autorelease]; // ref count 1 [newOrigin setX: 50.0f]; [myRect setOrigin: newOrigin]; // ref count 2 [myRect.origin setXY: 25.0f :100.0f]; // ref count goes to 3... why ? [myRect release]; [pool drain]; return 0; } Rectangle's origin is declared as a (retain) synthesized property. Just wondering 2 things: Why does ref count goes to 3 when using the getter accessor of Rectangle's origin? Am I doing something wrong ? With a ref count of 3, I don't understand how this snippet of code cannot leak. Calling release on myRect will make it go down to 2 since I call release on the origin in dealloc(). But then, when does autorelease take effect? Thanks!

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• c# winforms events restore textbox contents on escape

  - by aj3jr

  Using c# in 2008 Express. I have a textbox containing a path. I append a "\" at the end on Leave Event. If the user presses 'Escape' key I want the old contents to be restored. When I type over all the text and press 'Escape' I hear a thump and the old text isn't restored. Here what I have so far ... public string _path; public string _oldPath; this.txtPath.KeyPress += new System.Windows.Forms.KeyPressEventHandler(txtPath_CheckKeys); this.txtPath.Enter +=new EventHandler(txtPath_Enter); this.txtPath.LostFocus += new EventHandler(txtPath_LostFocus); public void txtPath_CheckKeys(object sender, KeyPressEventArgs kpe) { if (kpe.KeyChar == (char)27) { _path = _oldPath; } } public void txtPath_Enter(object sender, EventArgs e) { //AppendSlash(sender, e); _oldPath = _path; } void txtPath_LostFocus(object sender, EventArgs e) { //throw new NotImplementedException(); AppendSlash(sender, e); } public void AppendSlash(object sender, EventArgs e) { //add a slash to the end of the txtPath string on ANY change except a restore this.txtPath.Text += @"\"; } Thanks in advance,

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• C++ MACRO that will execute a block of code and a certain command after that block.

  - by Poni

  void main() { int xyz = 123; // original value { // code block starts xyz++; if(xyz < 1000) xyz = 1; } // code block ends int original_value = xyz; // should be 123 } void main() { int xyz = 123; // original value MACRO_NAME(xyz = 123) // the macro takes the code code that should be executed at the end of the block. { // code block starts xyz++; if(xyz < 1000) xyz = 1; } // code block ends << how to make the macro execute the "xyz = 123" statement? int original_value = xyz; // should be 123 } Only the first main() works. I think the comments explain the issue. It doesn't need to be a macro but to me it just sounds like a classical "macro-needed" case. By the way, there's the BOOST_FOREACH macro/library and I think it does the exact same thing I'm trying to achieve but it's too complex for me to find the essence of what I need. From its introductory manual page, an example: #include <string> #include <iostream> #include <boost/foreach.hpp> int main() { std::string hello( "Hello, world!" ); BOOST_FOREACH( char ch, hello ) { std::cout << ch; } return 0; }

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• c++ connect() keeps returning WSATIMEDOUT over internet but not localy

  - by KaiserJohaan

  Hello, For some reason, my chat application always gets WSATIMEDOUT when trying to connect to another person over the internet. int len_ip = GetWindowTextLength(GetDlgItem(hWnd,ID_EDIT_IP)); char ipBuffer[16]; SendMessage(GetDlgItem(hWnd,ID_EDIT_IP),WM_GETTEXT,16,(LPARAM)ipBuffer); long host_ip = inet_addr(ipBuffer); int initializeConnection(long host_ip, HWND hWnd) { // initialize winsock WSADATA wdata; int result = WSAStartup(MAKEWORD(2,2),&wdata); if (result != 0) { return 0; } // setup socket tcp_sock = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP); if (tcp_sock == INVALID_SOCKET) { return 0; } // setup socket address SOCKADDR_IN tcp_sock_addr; tcp_sock_addr.sin_family = AF_INET; tcp_sock_addr.sin_port = SERVER_TCP_PORT; tcp_sock_addr.sin_addr.s_addr = host_ip; // connect to server if (connect(tcp_sock,(SOCKADDR*)&tcp_sock_addr,sizeof(tcp_sock_addr)) == SOCKET_ERROR) { return 0; } HRESULT hr = WSAGetLastError(); // set socket in asynchronous mode if (WSAAsyncSelect(tcp_sock,hWnd,SOCKET_TCP, FD_READ | FD_WRITE | FD_CONNECT | FD_CLOSE) == SOCKET_ERROR) { return 0; } return 1; } For some reason it works perfectly fine on local network between computers, but totally screws up over the internet. WSATIMEDOUT is always returned (not connection refused, so its not a port problem). It makes me believe something is wrong with the IP but why on earth can it work on local addresses (like 192.168.2.4) Any ideas? Cheers

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• Using Relative Paths to Load Resources in Cocoa/C++

  - by moka

  I am currently working directly with Cocoa for the first time to built a screen saver. Now I came across a problem when trying to load resources from within the .saver bundle. I basically have a small C++ wrapper class to load .exr files using freeImage. This works as long as I use absoulte paths, but that's not very useful, is it? So, basically, I tried everything: putting the .exr file at the level of the .saver bundle itself, inside the bundles Resources folder, and so on. Then I simply tried to load the .exr like this, but without success: particleTex = [self loadExrTexture:@"ball.exr"]; I also tried making it go to the .saver bundles location like this: particleTex = [self loadExrTexture:@"../../../ball.exr"]; ...to maybe load the .exr from that location, but without success. I then came across this: NSString * path = [[NSBundle mainBundle] pathForResource:@"ball" ofType:@"exr"]; const char * pChar = [path UTF8String]; ...which seems to be a common way to find resources in Cocoa, but for some reason it's empty in my case. Any ideas about that? I really tried out anything that came to my mind without success so I would be glad about some input!

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• How to make command-line options mandatory with GLib?

  - by ahe

  I use GLib to parse some command-line options. The problem is that I want to make two of those options mandatory so that the program terminates with the help screen if the user omits them. My code looks like this: static gint line = -1; static gint column = -1; static GOptionEntry options[] = { {"line", 'l', 0, G_OPTION_ARG_INT, &line, "The line", "L"}, {"column", 'c', 0, G_OPTION_ARG_INT, &column, "The column", "C"}, {NULL} }; ... int main(int argc, char** argv) { GError *error = NULL; GOptionContext *context; context = g_option_context_new ("- test"); g_option_context_add_main_entries (context, options, NULL); if (!g_option_context_parse(context, &argc, &argv, &error)) { usage(error->message, context); } ... return 0; } If I omit one of those parameters or both on the command-line g_option_context_parse() still succeeds and the values in question (line and or column) are still -1. How can I tell GLib to fail parsing if the user doesn't pass both options on the command-line? Maybe I'm just blind but I couldn't find a flag I can put into my GOptionEntry data structure to tell it to make those fields mandatory. Of course I could check if one of those variables is still -1 but then the user could just have passed this value on the command-line and I want to print a separate error message if the values are out of range.

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• How to wrap a C function whose parameters are pointer to structs, so that it can be called from Lua?

  - by pierr

  I have the follwing C function. How should I wrap it so it can be called from a Lua script? typedef struct tagT{ int a ; int b ; } type_t; int lib_a_f_4(type_t *t) { return t->a * t->b ; } I know how to wrapr it if the function parameter type were int or char *. Should I use table type for a C structure? EDIT: I am using SWIG for the wraping , according to this doc, It seems that I should automatically have this funtion new_type_t(2,3) , but it is not the case. If you wrap a C structure, it is also mapped to a Lua userdata. By adding a metatable to the userdata, this provides a very natural interface. For example, struct Point{ int x,y; }; is used as follows: p=example.new_Point() p.x=3 p.y=5 print(p.x,p.y) 3 5 Similar access is provided for unions and the data members of C++ classes. C structures are created using a function new_Point(), but for C++ classes are created using just the name Point().

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• Proper QUuid usage in Qt ? (7-Zip DLL usage problems (QLibrary, QUuid GUID conversion, interfaces))

  - by whipsnap

  Hi, I'm trying to write a program that would use 7-Zip DLL for reading files from inside archive files (7z, zip etc). Here's where I'm so far: #include QtCore/QCoreApplication #include QLibrary #include QUuid #include iostream using namespace std; #include "7z910/CPP/7zip/Archive/IArchive.h" #include "7z910/CPP/7zip/IStream.h" #include "MyCom.h" // {23170F69-40C1-278A-1000-000110070000} QUuid CLSID_CFormat7z(0x23170F69, 0x40C1, 0x278A, 0x10, 0x00, 0x00, 0x01, 0x10, 0x07, 0x00, 0x00); typedef int (*CreateObjectFunc)( const GUID *clsID, const GUID *interfaceID, void **outObject); void readFileInArchive() { QLibrary myLib("7z.dll"); CreateObjectFunc myFunction = (CreateObjectFunc)myLib.resolve("CreateObject"); if (myFunction == 0) { cout outArchive; myFunction(&CLSID_CFormat7z, &IID_IOutArchive, (void **)&outArchive); } int main(int argc, char *argv[]) { QCoreApplication a(argc, argv); readFileInArchive(); return a.exec(); } Trying to build that in Qt Creator will lead to following error: cannot convert 'QUuid*' to 'const GUID*' in argument passing How should QUuid be correctly used in this context? Also, being a C++ and Qt newbie I haven't yet quite grasped templates or interfaces, so overall I'm having trouble getting through these first steps. If someone could give tips or even example code on how for example an image file could be extracted from ZIP file (to be shown in Qt GUI later on*), I would highly appreciate that. My main goal at the moment is to write a program with GUI for selecting archive files containing image files (PNG, JPG etc) and displaying those files one at a time in the GUI. A Qt based CDisplayEx in short.

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• Converting "A* Search" code from C++ to Java [on hold]

  - by mr5

  Updated! I get this code from this site It's A* Search Algorithm(finding shortest path with heuristics) I modify most of variable names and some if conditions from the original version to satisfy my syntactic taste. It works in C++ (as I can't see any trouble with it) but fails in Java version. Java Code: String findPath(int startX, int startY, int finishX, int finishY) { @SuppressWarnings("unchecked") LinkedList<Node>[] nodeList = (LinkedList<Node>[]) new LinkedList<?>[2]; nodeList[0] = new LinkedList<Node>(); nodeList[1] = new LinkedList<Node>(); Node n0; Node m0; int nlIndex = 0; // queueList index // reset the node maps for(int y = 0;y < ROW_COUNT; ++y) { for(int x = 0;x < COL_COUNT; ++x) { close_nodes_map[y][x] = 0; open_nodes_map[y][x] = 0; } } // create the start node and push into list of open nodes n0 = new Node( startX, startY, 0, 0 ); n0.updatePriority( finishX, finishY ); nodeList[nlIndex].push( n0 ); open_nodes_map[startY][startX] = n0.getPriority(); // mark it on the open nodes map // A* search while( !nodeList[nlIndex].isEmpty() ) { LinkedList<Node> pq = nodeList[nlIndex]; // get the current node w/ the highest priority // from the list of open nodes n0 = new Node( pq.peek().getX(), pq.peek().getY(), pq.peek().getIterCount(), pq.peek().getPriority()); int x = n0.getX(); int y = n0.getY(); nodeList[nlIndex].pop(); // remove the node from the open list open_nodes_map[y][x] = 0; // mark it on the closed nodes map close_nodes_map[y][x] = 1; // quit searching when the goal state is reached //if((*n0).estimate(finishX, finishY) == 0) if( x == finishX && y == finishY ) { // generate the path from finish to start // by following the directions String path = ""; while( !( x == startX && y == startY) ) { int j = dir_map[y][x]; int c = '0' + ( j + Node.DIRECTION_COUNT / 2 ) % Node.DIRECTION_COUNT; path = (char)c + path; x += DIR_X[j]; y += DIR_Y[j]; } return path; } // generate moves (child nodes) in all possible directions for(int i = 0; i < Node.DIRECTION_COUNT; ++i) { int xdx = x + DIR_X[i]; int ydy = y + DIR_Y[i]; // boundary check if (!(xdx >= 0 && xdx < COL_COUNT && ydy >= 0 && ydy < ROW_COUNT)) continue; if ( ( gridMap.getData( ydy, xdx ) == GridMap.WALKABLE || gridMap.getData( ydy, xdx ) == GridMap.FINISH) && close_nodes_map[ydy][xdx] != 1 ) { // generate a child node m0 = new Node( xdx, ydy, n0.getIterCount(), n0.getPriority() ); m0.nextLevel( i ); m0.updatePriority( finishX, finishY ); // if it is not in the open list then add into that if( open_nodes_map[ydy][xdx] == 0 ) { open_nodes_map[ydy][xdx] = m0.getPriority(); nodeList[nlIndex].push( m0 ); // mark its parent node direction dir_map[ydy][xdx] = ( i + Node.DIRECTION_COUNT / 2 ) % Node.DIRECTION_COUNT; } else if( open_nodes_map[ydy][xdx] > m0.getPriority() ) { // update the priority info open_nodes_map[ydy][xdx] = m0.getPriority(); // update the parent direction info dir_map[ydy][xdx] = ( i + Node.DIRECTION_COUNT / 2 ) % Node.DIRECTION_COUNT; // replace the node // by emptying one queueList to the other one // except the node to be replaced will be ignored // and the new node will be pushed in instead while( !(nodeList[nlIndex].peek().getX() == xdx && nodeList[nlIndex].peek().getY() == ydy ) ) { nodeList[1 - nlIndex].push( nodeList[nlIndex].pop() ); } nodeList[nlIndex].pop(); // remove the wanted node // empty the larger size queueList to the smaller one if( nodeList[nlIndex].size() > nodeList[ 1 - nlIndex ].size() ) nlIndex = 1 - nlIndex; while( !nodeList[nlIndex].isEmpty() ) { nodeList[1 - nlIndex].push( nodeList[nlIndex].pop() ); } nlIndex = 1 - nlIndex; nodeList[nlIndex].push( m0 ); // add the better node instead } } } } return ""; // no route found } Output1: Legends . = PATH ? = START X = FINISH 3,2,1 = OBSTACLES (Misleading path) Output2: Changing these lines: n0 = new Node( a, b, c, d ); m0 = new Node( e, f, g, h ); to n0.set( a, b, c, d ); m0.set( e, f, g, h ); I get (I'm really confused) C++ Code: std::string A_Star::findPath(int startX, int startY, int finishX, int finishY) { typedef std::queue<Node> List_Container; List_Container nodeList[2]; // list of open (not-yet-tried) nodes Node n0; Node m0; int pqIndex = 0; // nodeList index // reset the node maps for(int y = 0;y < ROW_COUNT; ++y) { for(int x = 0;x < COL_COUNT; ++x) { close_nodes_map[y][x] = 0; open_nodes_map[y][x] = 0; } } // create the start node and push into list of open nodes n0 = Node( startX, startY, 0, 0 ); n0.updatePriority( finishX, finishY ); nodeList[pqIndex].push( n0 ); open_nodes_map[startY][startX] = n0.getPriority(); // mark it on the open nodes map // A* search while( !nodeList[pqIndex].empty() ) { List_Container &pq = nodeList[pqIndex]; // get the current node w/ the highest priority // from the list of open nodes n0 = Node( pq.front().getX(), pq.front().getY(), pq.front().getIterCount(), pq.front().getPriority()); int x = n0.getX(); int y = n0.getY(); nodeList[pqIndex].pop(); // remove the node from the open list open_nodes_map[y][x] = 0; // mark it on the closed nodes map close_nodes_map[y][x] = 1; // quit searching when the goal state is reached //if((*n0).estimate(finishX, finishY) == 0) if( x == finishX && y == finishY ) { // generate the path from finish to start // by following the directions std::string path = ""; while( !( x == startX && y == startY) ) { int j = dir_map[y][x]; char c = '0' + ( j + DIRECTION_COUNT / 2 ) % DIRECTION_COUNT; path = c + path; x += DIR_X[j]; y += DIR_Y[j]; } return path; } // generate moves (child nodes) in all possible directions for(int i = 0; i < DIRECTION_COUNT; ++i) { int xdx = x + DIR_X[i]; int ydy = y + DIR_Y[i]; // boundary check if (!( xdx >= 0 && xdx < COL_COUNT && ydy >= 0 && ydy < ROW_COUNT)) continue; if ( ( pGrid->getData(ydy,xdx) == WALKABLE || pGrid->getData(ydy, xdx) == FINISH) && close_nodes_map[ydy][xdx] != 1 ) { // generate a child node m0 = Node( xdx, ydy, n0.getIterCount(), n0.getPriority() ); m0.nextLevel( i ); m0.updatePriority( finishX, finishY ); // if it is not in the open list then add into that if( open_nodes_map[ydy][xdx] == 0 ) { open_nodes_map[ydy][xdx] = m0.getPriority(); nodeList[pqIndex].push( m0 ); // mark its parent node direction dir_map[ydy][xdx] = ( i + DIRECTION_COUNT / 2 ) % DIRECTION_COUNT; } else if( open_nodes_map[ydy][xdx] > m0.getPriority() ) { // update the priority info open_nodes_map[ydy][xdx] = m0.getPriority(); // update the parent direction info dir_map[ydy][xdx] = ( i + DIRECTION_COUNT / 2 ) % DIRECTION_COUNT; // replace the node // by emptying one nodeList to the other one // except the node to be replaced will be ignored // and the new node will be pushed in instead while ( !( nodeList[pqIndex].front().getX() == xdx && nodeList[pqIndex].front().getY() == ydy ) ) { nodeList[1 - pqIndex].push( nodeList[pqIndex].front() ); nodeList[pqIndex].pop(); } nodeList[pqIndex].pop(); // remove the wanted node // empty the larger size nodeList to the smaller one if( nodeList[pqIndex].size() > nodeList[ 1 - pqIndex ].size() ) pqIndex = 1 - pqIndex; while( !nodeList[pqIndex].empty() ) { nodeList[1-pqIndex].push(nodeList[pqIndex].front()); nodeList[pqIndex].pop(); } pqIndex = 1 - pqIndex; nodeList[pqIndex].push( m0 ); // add the better node instead } } } } return ""; // no route found } Output: Legends . = PATH ? = START X = FINISH 3,2,1 = OBSTACLES (Just right) From what I read about Java's documentation, I came up with the conclusion: C++'s std::queue<T>::front() == Java's LinkedList<T>.peek() Java's LinkedList<T>.pop() == C++'s std::queue<T>::front() + std::queue<T>::pop() What might I be missing in my Java version? In what way does it became different algorithmically from the C++ version?

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• Getting functions of inherited functions to be called

  - by wrongusername

  Let's say I have a base class Animal from which a class Cow inherits, and a Barn class containing an Animal vector, and let's say the Animal class has a virtual function scream(), which Cow overrides. With the following code: Animal.h #ifndef _ANIMAL_H #define _ANIMAL_H #include <iostream> using namespace std; class Animal { public: Animal() {}; virtual void scream() {cout << "aaaAAAAAAAAAAGHHHHHHHHHH!!! ahhh..." << endl;} }; #endif /* _ANIMAL_H */ Cow.h #ifndef _COW_H #define _COW_H #include "Animal.h" class Cow: public Animal { public: Cow() {} void scream() {cout << "MOOooooOOOOOOOO!!!" << endl;} }; #endif /* _COW_H */ Barn.h #ifndef _BARN_H #define _BARN_H #include "Animal.h" #include <vector> class Barn { std::vector<Animal> animals; public: Barn() {} void insertAnimal(Animal animal) {animals.push_back(animal);} void tortureAnimals() { for(int a = 0; a < animals.size(); a++) animals[a].scream(); } }; #endif /* _BARN_H */ and finally main.cpp #include <stdlib.h> #include "Barn.h" #include "Cow.h" #include "Chicken.h" /* * */ int main(int argc, char** argv) { Barn barn; barn.insertAnimal(Cow()); barn.tortureAnimals(); return (EXIT_SUCCESS); } I get this output: aaaAAAAAAAAAAGHHHHHHHHHH!!! ahhh... How should I code this to get MOOooooOOOOOOOO!!! (and whatever other classes inheriting Animal wants scream() to be) instead?

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• What goes into main function?

  - by Woltan

  I am looking for a best practice tip of what goes into the main function of a program using c++. Currently I think two approaches are possible. (Although the "margins" of those approaches can be arbitrarily close to each other) 1: Write a "Master"-class that receives the parameters passed to the main function and handle the complete program in that "Master"-class (Of course you also make use of other classes). Therefore the main function would be reduced to a minimum of lines. #include "MasterClass.h" int main(int args, char* argv[]) { MasterClass MC(args, argv); } 2: Write the "complete" program in the main function making use of user defined objects of course! However there are also global functions involved and the main function can get somewhat large. I am looking for some general guidelines of how to write the main function of a program in c++. I came across this issue by trying to write some unit test for the first approach, which is a little difficult since most of the methods are private. Thx in advance for any help, suggestion, link, ...

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• How do you safely wrap a JS string variable in double quote chars?

  - by incombinative

  Obviously when you're creating an actual string literal yourself, you backslash escape the double quote characters yourself. var foo = "baz\"bat"; Just as you would with the handful of other control characters, like linebreaks and backslashes. var bar = "baz\\bat"; but when you already have a variable, and you're wrapping that existing variable in quote characters, there's some confusion. Obviously you have to escape any potential double quote characters that are in the string. (Assuming whatever system you're giving the explicitly quoted string to, needs to be able to parse them correctly. =) var doubleQuoteRe = /\"/g; var quoted = unquoted.replace(escaper, '\\\"'); However from there opinions diverge a little. In particular, according to some you also have to worry about escaping literal backslash characters in the variable. // now say i have a string bar, that has both single backslash character in it, // as well as a double-quote character in it. // the following code ONLY worries about escaping the double quote char. var quoted = bar.replace(doubleQuoteRe, '\\\"'); The above seems fine to me. But is there a problem im not seeing?

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• Template Child Class Overriding a Parent Class's Virtual Function

  - by user334066

  The below code compiles with gcc v4.3.3 and the templated child class seems to be overriding a virtual function in the parent, but doesn't that break the rule that you cannot have a virtual template function? Or is something else happening that I don't understand? class BaseClass { public: virtual void Func(int var) { std::cout<<"Base int "<<var<<std::endl; } virtual void Func(double var) { std::cout<<"Base double "<<var<<std::endl; } }; template <class TT> class TemplateClass : public BaseClass { public: using BaseClass::Func; virtual void Func(TT var) { std::cout<<"Child TT "<<var<<std::endl; } }; int main(int argc, char **argv) { BaseClass a; TemplateClass<int> b; BaseClass *c = new TemplateClass<int>; int intVar = 3; double doubleVar = 5.5; a.Func(intVar); a.Func(doubleVar); b.Func(intVar); b.Func(doubleVar); c->Func(intVar); c->Func(doubleVar); delete c; } This then outputs: Base int 3 Base double 5.5 Child TT 3 Base double 5.5 Child TT 3 Base double 5.5 as I hoped, but I'm not sure why it works.

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• How can I hardcode input with the "select" system call in C?

  - by Archer

  If I understand this system call "select" correctly, it will loop waiting for user input from the keyboard or from an outside server. Every time I call "message_loop", I'm going to type in the same few lines of input each time. Is there a way to hard code this in so I don't have to type it in each time? void message_loop(FILE* fpin, FILE* fpout, Socket sock) { fd_set readfds, readfds_bak ; int in, max_fd, n, ret ; char buf[MAXMESG]; in = fileno(fpin) ; FD_ZERO(&readfds) ; FD_SET(in, &readfds) ; FD_SET(sock.socketfd, &readfds) ; readfds_bak = readfds ; max_fd = ((in > sock.socketfd) ? in : sock.socketfd) + 1 ; while(1){ readfds = readfds_bak ; /* select function */ if((ret = select(max_fd, &readfds, NULL, NULL, NULL)) < 0){ perror("select") ; break ; } else if (ret != 0) { if(FD_ISSET(in, &readfds)){ /* keyboard input */ fgets(buf, MAXMESG, fpin) ; if(send_message(buf, sock) == -1) break ; } if(FD_ISSET(sock.socketfd, &readfds)){ /* messages from server */ n = receive_message(buf, MAXMESG, &sock) ; if(n == -1) break ; else if(n > 0){ fputs(buf, fpout) ; fputc('\n', fpout) ; } fflush(stdout) ; } } } }

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• Sending data in a GTK Callback

  - by snostorm

  How can I send data through a GTK callback? I've Googled, and with the information I found created this: #include <gtk/gtk.h> #include <stdio.h> void button_clicked( GtkWidget *widget, GdkEvent *event, gchar *data); int main( int argc, char *argv[]){ GtkWidget *window; GtkWidget *button; gtk_init (&argc, &argv); window = gtk_window_new(GTK_WINDOW_TOPLEVEL); button = gtk_button_new_with_label("Go!"); gtk_container_add(GTK_CONTAINER(window), button); g_signal_connect_swapped(G_OBJECT(window), "destroy", G_CALLBACK(gtk_main_quit), NULL); g_signal_connect(G_OBJECT(button), "clicked", G_CALLBACK(button_clicked),"test" ); gtk_widget_show(window); gtk_widget_show(button); gtk_main(); return 0; } void button_clicked( GtkWidget *widget, GdkEvent *event, gchar *data){ printf("%s \n", (gchar *) data); return; } But it just Segfaults when I press the button. What is the right way to do this?

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• F# ref-mutable vars vs object fields

  - by rwallace

  I'm writing a parser in F#, and it needs to be as fast as possible (I'm hoping to parse a 100 MB file in less than a minute). As normal, it uses mutable variables to store the next available character and the next available token (i.e. both the lexer and the parser proper use one unit of lookahead). My current partial implementation uses local variables for these. Since closure variables can't be mutable (anyone know the reason for this?) I've declared them as ref: let rec read file includepath = let c = ref ' ' let k = ref NONE let sb = new StringBuilder() use stream = File.OpenText file let readc() = c := stream.Read() |> char // etc I assume this has some overhead (not much, I know, but I'm trying for maximum speed here), and it's a little inelegant. The most obvious alternative would be to create a parser class object and have the mutable variables be fields in it. Does anyone know which is likely to be faster? Is there any consensus on which is considered better/more idiomatic style? Is there another option I'm missing?

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• How is an AppDelegate instanciated?

  - by pwny

  I have an iOS application for which I want to create a ViewController programmatically. I started an empty XCode project and modified the main method so it looks like this int main(int argc, char *argv[]) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; int retVal = UIApplicationMain(argc, argv, nil, @"MyAppDelegate_iPad"); [pool release]; return retVal; } The app is a Universal Application, MyAppDelegate_iPad is a subclass of MyAppDelegate, which is a subclass of NSObject <UIApplicationDelegate>. My problem is that the applicationDidFinishLoading method I've overridden in MyAppDelegate_iPad is never called (break point on the first line never hits). The method looks like this -(void) applicationDidFinishLaunching:(UIApplication *)application { window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]]; if(!window) { [self release]; return; } window.backgroundColor = [UIColor whiteColor]; rootController = [[MyViewController alloc] init]; [window addSubview:rootController.view]; [window makeKeyAndVisible]; [window layoutSubviews]; } I removed the line to link to a nib file from my plist file (I used to get the default "My Universal app on iPad" white screen) and now all that is displayed is a black screen. applicationDidFinishLoading is still not being called. Am I doing something wrong? How should I properly create my AppDelegate instance?

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• How can several different datatypes be saved in one table

  - by poseidon

  This is my situation: I am constructing an ad-like application in Django and Mysql. I am using a flexible-ad approach where we have: a table with ad categories (several categories such as home, furniture, cars, etc.) id_category name a table with details for the ad categories (home: area, squared meters. car: seats, color.) id_detail id_category (the categ the detail describes) name type (boolean, char, int, long, etc.) the ad table (i am selling a house. i am selling a car.) id_ad id_category text date a table where i plan to consolidate the details of the ads (home: A-area, 500 sq-meters. car: 5 seats, red.) id_detail_ad id_ad id_detail value Is this possible? Can I have a table of details for all the ads, even if details include numbers, texts, booleans, etc? Or would I have to save them all as text and then interpret them via code accordingly? Please express your opinions. Thank you.

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• Function calculating the probability of a letter in an sentence

  - by Mike

  I have a function that is supposed to calculate the number of times a letter occurs in a sentence, and based on that, calculate the probability of it occurring in the sentence. To accomplish this, I have a sentence: The Washington Metropolitan Area is the most educated and affluent metropolitan area in the United States. An array of structures, containing the letter, the number of times it occurs, and the probability of it occurring, with one structure for each letter character and an additional structure for punctuation and spaces: struct letters { char letter; int occur; double prob; }box[53]; This is the function itself: void probability(letters box[53], int sum { cout<<sum<<endl<<endl; for(int c8=0;c8<26;c8++) { box[c8].prob = (box[c8].occur/sum); cout<<box[c8].letter<<endl; cout<<box[c8].occur<<endl; cout<<box[c8].prob<<endl<<endl; } } It correctly identifies that there are 90 letters in the sentence in the first line, prints out the uppercase letter as per the structure in the second line of the for loop, and prints out the number of times it occurs. It continually prints 0 for the probability. What am I doing wrong?

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• Classes and Objects in C++

  - by anurag18294

  class anurag { private: int rollno; char name[50]; int marks; float percen; void percentage(int num) { percen=(num/500)*100; } public: void getdata(void) { cout<<"\n\nEnter the name of the student:"; gets(name); cout<<"\n\nEnter the roll no: and the marks:"; cin>>rollno>>marks; percentage(marks); } void display(void) { cout<<"\n\nThe name of the student is:"; cout.write(name,50); cout<<"\n\nThe roll no: of the student is:"; cout<<rollno; cout<<"\n\n The marks obtained is:"<<marks; cout<<"\n\nThe percentage is:"<<percen; }}; void main() { clrscr(); anurag F; F.getdata(); F.display(); getch(); } why the following code is not giving the desired output?

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