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  • Pointers to structures

    - by blacktooth
    typedef struct queue { int q[max]; int qhead; int qrear; } queue; void init_queue(queue *QUEUE) { QUEUE.qhead = 0; QUEUE.qrear = -1; } void enqueue(queue *QUEUE,int data) { QUEUE.qrear++; QUEUE.q[QUEUE.qrear] = data; } int process_queue(queue *QUEUE) { if(QUEUE.qhead > QUEUE.qrear) return -1; else return QUEUE.q[QUEUE.qhead++]; } I am implementing queues using arrays just to keep it simple. Wats the error with the above code?

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  • Convert Pen to IntPtr

    - by Bevin
    Is there a simple way to convert a System.Drawing.Pen into its unmanaged counterpart? Like, if you had a Pen like this: Pen p = new Pen(Color.Blue, 1f); IntPtr ptr = p.ToPtr(); I know this code doesn't work, but is there a way to do it similarly?

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  • Xlib mouse events and ButtonPressMask

    - by Trilly Campanelino
    I have written a simple program which will report key press and release events for a particular window. In my case, it is mostly the terminal since I invoke the program from the terminal. I am able to get the key press and release events taking place in the terminal window (I have used XSelectInput() with KeyPressMask and KeyReleaseMask on the terminal) but the same is not working with ButtonPress and ButtonRelease. Not just these, but any events related to the mouse are not being reported. Any idea why this is happening? #include #include #include #include #include #include int main() { Display *display = XOpenDisplay(NULL); KeySym k; int revert_to; Window window; XEvent event; XGetInputFocus(display, &window, &revert_to); XSelectInput(display, window, KeyPressMask | KeyReleaseMask | ButtonPressMask | ButtonReleaseMask); while(1) { XNextEvent(display,&event); switch (event.type) { case KeyPress : printf("Key Pressed\n"); break; case KeyRelease : printf("Key Released\n"); break; case ButtonPress : printf("Button Pressed\n"); break; case ButtonRelease : printf("Button Released\n"); break; case EnterNotify : printf("Enter\n"); break; } } XCloseDisplay(display); return 0; }

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  • Refcounted pointers on iPhone

    - by anon
    1) Refcounted pointers need stack variables to have constructors / destructors called at predictable places. 2) Objective-C, afaik, does not support the above. 3) The cocoa libraries are bound in Objective-C, not C++. Thus, my question: is there a easy way to use the Cocoa libraries, yet still have most of my app in C++ (and thus use my refcounted pointers)? Thanks! (iPhone in the title since this is mainly targeted at the iPhone)

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  • question/problem regarding assigning an array of char *

    - by Fantastic Fourier
    Hi I'm working with C and I have a question about assigning pointers. struct foo { int _bar; char * _car[MAXINT]; // this is meant to be an array of char * so that it can hold pointers to names of cars } int foofunc (void * arg) { int bar; char * car[MAXINT]; struct foo thing = (struct foo *) arg; bar = arg->_bar; // this works fine car = arg->_car; // this gives compiler errors of incompatible types in assignment } car and _car have same declaration so why am I getting an error about incompatible types? My guess is that it has something to do with them being pointers (because they are pointers to arrays of char *, right?) but I don't see why that is a problem. when i declared char * car; instead of char * car[MAXINT]; it compiles fine. but I don't see how that would be useful to me later when I need to access certain info using index, it would be very annoying to access that info later. in fact, I'm not even sure if I am going about the right way, maybe there is a better way to store a bunch of strings instead of using array of char *?

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  • c incompatible types in assignment, problem with pointers?

    - by Fantastic Fourier
    Hi I'm working with C and I have a question about assigning pointers. struct foo { int _bar; char * _car[MAXINT]; // this is meant to be an array of char * so that it can hold pointers to names of cars } int foofunc (void * arg) { int bar; char * car[MAXINT]; struct foo thing = (struct foo *) arg; bar = arg->_bar; // this works fine car = arg->_car; // this gives compiler errors of incompatible types in assignment } car and _car have same declaration so why am I getting an error about incompatible types? My guess is that it has something to do with them being pointers (because they are pointers to arrays of char *, right?) but I don't see why that is a problem. when i declared char * car; instead of char * car[MAXINT]; it compiles fine. but I don't see how that would be useful to me later when I need to access certain info using index, it would be very annoying to access that info later. in fact, I'm not even sure if I am going about the right way, maybe there is a better way to store a bunch of strings instead of using array of char *?

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  • Programatically change cursor speed in windows

    - by Juan Manuel Formoso
    Since getting a satisfactory answer on SuperUser is very difficult, I want to rephrase this question and ask: Is there any way to programatically detect a mouse was plugged in the usb port, and change the cursor speed in windows (perhaps through an API)? I'd like to use C#, but I'm open to any language that can run on a windows 7 machine.

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  • how to use char* as char[]

    - by phunehehe
    Hello, I have a struck like this typedef struct bookStruct { char title[80]; char author[80]; } BookType; And I have two strings like this char *title = "A Book on C"; char *author = "A. Kelly"; Now I can't create a BookType like this BookType book = {title, author}; Can anyone tell me what is wrong? How can I do that?

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  • Declaring pointers; asterisk on the left or right of the space between the type and name?

    - by GenTiradentes
    I've seen mixed versions of this in a lot of code. (This applies to C and C++, by the way.) People seem to declare pointers in one of two ways, and I have no idea which one is correct, of if it even matters. The first way it to put the asterisk adjacent the type name, like so: someType* somePtr; The second way is to put the asterisk adjacent the name of the variable, like so: someType *somePtr; This has been driving me nuts for some time now. Is there any standard way of declaring pointers? Does it even matter how pointers are declared? I've used both declarations before, and I know that the compiler doesn't care which way it is. However, the fact that I've seen pointers declared in two different ways leads me to believe that there's a reason behind it. I'm curious if either method is more readable or logical in some way that I'm missing.

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  • How to change the value of value in BASH ??

    - by debugger
    Hello All, Let's say i have the Following, Vegetable=Potato ( Kind of vegetable that i have ) Potato=3 ( quantity available ) If i wanna know how many vegetables i have (from a script where i have access only to variable Vegetable), i do the following: Quantity=${!Vegetable} But let's say i take one Potato then i want to update the quantity, i should be able to do the following: ${Vegetable}=$(expr ${!Vegetable} - 1) It does not work !! Any clues to realize this Thanks

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  • Where can I get the CUR files for the Firefox cursor values?

    - by harpo
    I'm using some of Firefox's specially-defined values for cursor, in particular -moz-zoom-in -moz-zoom-out -moz-grab -moz-grabbing In order to display these on other browsers, I'd like to deploy the equivalent CUR files — but I can't seem to find these online, or in my copy of Firefox. Anyone know where these are available?

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  • how to write a constructor...

    - by Nima
    is that correct to write a constructor like this? class A { A::A(const A& a) { .... } }; if yes, then is it correct to invoke it like this: A* other; ... A* instance = new A(*(other)); if not, what do you suggest? Thanks

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  • Using a ref Parameter with the this Keyword?

    - by grefly
    Is there a way to force the this keyword to act as a ref argument? I would like to pass in a visitor that modifies multiple properties on the object, but this only wants to act like a value parameter. Code in Object: public void Accept(Visitor<MyObject> visitor) { visitor.Visit(this); } Code in Visitor: public void Visit(ref Visitor<MyObject> receiver) { receiver.Property = new PropertyValue(); receiver.Property2 = new PropertyValue(); }

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  • how to use iterator in c++?

    - by tsubasa
    I'm trying to calculate distance between 2 points. The 2 points I stored in a vector in c++: (0,0) and (1,1). I'm supposed to get results as 0 1.4 1.4 0 but the actual result that I got is 0 1 -1 0 I think there's something wrong with the way I use iterator in vector. Could somebody help? I posted the code below. typedef struct point { float x; float y; } point; float distance(point *p1, point *p2) { return sqrt((p1->x - p2->x)*(p1->x - p2->x) + (p1->y - p2->y)*(p1->y - p2->y)); } int main() { vector <point> po; point p1; p1.x=0; p1.y=0; point p2; p2.x=1; p2.y=1; po.push_back(p1); po.push_back(p2); vector <point>::iterator ii; vector <point>::iterator jj; for (ii=po.begin(); ii!=po.end(); ii++) { for (jj=po.begin(); jj!=po.end(); jj++) { cout<<distance(ii,jj)<<" "; } } return 0; }

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  • Silverlight: Is it possible to use custom mouse cursors/pointers?

    - by Mark Redman
    I have just found this page indicating the support for Silverlight mouse cursors: http://msdn.microsoft.com/en-us/library/system.windows.input.cursor(VS.95).aspx Is that it!!! :-| what are they thinking, at least there is stylish looking Eraser! Is there aany other way to use custom cursors? How efficient/usable would it be to hide the cursor and show a png instead?

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  • C++ using cdb_read returns extra characters on some reads

    - by Moe Be
    Hi All, I am using the following function to loop through a couple of open CDB hash tables. Sometimes the value for a given key is returned along with an additional character (specifically a CTRL-P (a DLE character/0x16/0o020)). I have checked the cdb key/value pairs with a couple of different utilities and none of them show any additional characters appended to the values. I get the character if I use cdb_read() or cdb_getdata() (the commented out code below). If I had to guess I would say I am doing something wrong with the buffer I create to get the result from the cdb functions. Any advice or assistance is greatly appreciated. char* HashReducer::getValueFromDb(const string &id, vector <struct cdb *> &myHashFiles) { unsigned char hex_value[BUFSIZ]; size_t hex_len; //construct a real hex (not ascii-hex) value to use for database lookups atoh(id,hex_value,&hex_len); char *value = NULL; vector <struct cdb *>::iterator my_iter = myHashFiles.begin(); vector <struct cdb *>::iterator my_end = myHashFiles.end(); try { //while there are more databases to search and we have not found a match for(; my_iter != my_end && !value ; my_iter++) { //cerr << "\n looking for this MD5:" << id << " hex(" << hex_value << ") \n"; if (cdb_find(*my_iter, hex_value, hex_len)){ //cerr << "\n\nI found the key " << id << " and it is " << cdb_datalen(*my_iter) << " long\n\n"; value = (char *)malloc(cdb_datalen(*my_iter)); cdb_read(*my_iter,value,cdb_datalen(*my_iter),cdb_datapos(*my_iter)); //value = (char *)cdb_getdata(*my_iter); //cerr << "\n\nThe value is:" << value << " len is:" << strlen(value)<< "\n\n"; }; } } catch (...){} return value; }

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  • JNA problem with char** (in dll)

    - by underline
    Hi, ok it is 'easy' to make jna wrapper solution for mapping exported functions within dll using jna: long f1(int x), just int long f2(char* y), just char[] but how to deal with long f3(char** z) ? I need f3's result(long) as well as z value on java side. Please don't say cpp code should be rewritten to avoid this:-)

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  • Reusing a NSString variable - does it cause a memory leak?

    - by Chris S
    Coming from a .NET background I'm use to reusing string variables for storage, so is the code below likely to cause a memory leak? The code is targeting OS X on the iphone/itouch so no automatic GC. -(NSString*) stringExample { NSString *result = @"example"; result = [result stringByAppendingString:@" test"]; // where does "example" go? return result; } What confuses me is an NSStrings are immutable, but you can reuse an 'immutable' variable with no problem.

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  • C++: ptr->hello(); /* VERSUS */ (*ptr).hello();

    - by Joey
    i was learning about c++ pointers... so the "-" operator seemed strange to me... instead of ptr-hello(); one could write (*ptr).hello(); because it also seems to work, so i thought the former is just a more convenient way is that the case or is there any difference?

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  • C++: Cannot convert from foo& to foo*

    - by Rosarch
    I have a method: odp(foo& bar); I'm trying to call it: foo baz; odp(&baz); I get a compiler error: error C2664: "odp" cannot convert parameter 1 from 'foo *' to 'foo &' What am I doing wrong? Aren't I passing in a reference to baz? UPDATE: Perhaps I have a misconception about the relationship between pointers and references. I thought that they were the same, except references couldn't be null. Is that incorrect?

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  • Basic help needed with pointers

    - by sbsp
    Hi, i asked some time ago on an account i cant remember how to manipulate basic pointers and someone gave me a really good demo for example char *ptr = hello (hello = a char array) so now *ptr is pointing at h ptr++ = moves the ptr to point at the next element, to get its value i do *ptr and that gives me e ok so far i hope :D but now i need to manipulate a char **ptr and was wondering how i do this in a way that mimmicks the effects of a 2d array? some basic tips would be much appreciated as i need to do an assignment that has a **ptr to immitate a 2d array and without knowing how it does this first means i cant even solve it on paper (for example, how do you dereference a **ptr, how do you get [x][y] values etc) thanks

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  • Building 16 bit os - character array not working

    - by brainbarshan
    Hi. I am building a 16 bit operating system. But character array does not seem to work. Here is my example kernel code: asm(".code16gcc\n"); void putchar(char); int main() { char *str = "hello"; putchar('A'); if(str[0]== 'h') putchar('h'); return 0; } void putchar(char val) { asm("movb %0, %%al\n" "movb $0x0E, %%ah\n" "int $0x10\n" : :"m"(val) ) ; } It prints: A that means putchar function is working properly but if(str[0]== 'h') putchar('h'); is not working. I am compiling it by: gcc -fno-toplevel-reorder -nostdinc -fno-builtin -I./include -c -o ./bin/kernel.o ./source/kernel.c ld -Ttext=0x9000 -o ./bin/kernel.bin ./bin/kernel.o -e 0x0 What should I do?

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