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  • Question of using static_cast on "this" pointer in a derived object to base class

    - by Johnyy
    Hi, this is an example taken from Effective C++ 3ed, it says that if the static_cast is used this way, the base part of the object is copied, and the call is invoked from that part. I wanted to understand what is happening under the hood, will anyone help? class Window { // base class public: virtual void onResize() { } // base onResize impl }; class SpecialWindow: public Window { // derived class public: virtual void onResize() { // derived onResize impl; static_cast<Window>(*this).onResize(); // cast *this to Window, // then call its onResize; // this doesn't work! // do SpecialWindow- } // specific stuff };

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  • PHP: Extending static member arrays

    - by tstenner
    I'm having the following scenario: class A { public static $arr=array(1,2); } class B extends A { public static $arr=array(3,4); } Is there any way to combine these 2 arrays so B::$arr is 1,2,3,4? I don't need to alter these arrays, but I can't declare them als const, as PHP doesn't allow const arrays.http://stackoverflow.com/questions/ask The PHP manual states, that I can only assign strings and constants, so parent::$arr + array(1,2) won't work, but I think it should be possible to do this.

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  • Pointer to local variable

    - by Radek Šimko
    May I have any acces to local variable in different function? If may, how? void replaceNumberAndPrint(int array[3]) { printf("%i\n", array[1]); printf("%i\n", array[1]); } int * getArray() { int myArray[3] = {4, 65, 23}; return myArray; } int main() { replaceNumberAndPrint(getArray()); } The output of the piece of code above: 65 4202656 What am i doing wrong? What the "4202656" means?? Do I have to copy the whole array in the replaceNumberAndPrint() function to be able to access to it more than first times?

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  • saving a records containing a member of type string to a file (Delphi, Windows)

    - by wonderer
    I have a record that looks similar to: type TNote = record Title : string; Note : string; Index : integer; end; Simple. The reason I chose to set the variables as string (as opposed to an array of chars) is that I have no idea how long those strings are going to be. They can be 1 char long, 200 or 2000. Of course when I try to save the record to a type file (file of...) the compiler complains that I have to give a size to string. Is there a way to overcome this? or a way to save those records to an untyped file and still maintain a sort of searchable way? Please do not point me to possible solutions, if you know the solution please post code. Thank you

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  • Is this pointer initialization necessary?

    - by bstullkid
    Lets say I have the following: CHARLINK * _init_link(CHARLINK **link) { short i; (*link)->cl = (CHARLINK **) calloc(NUM_CHARS, sizeof(CHARLINK *)); for (i = 0; i < NUM_CHARS; i++) (*link)->cl[i] = NULL; return (*link); } Is the loop to initialize each element to NULL necessary or are they automatically NULL from calloc?

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  • Write pointer to file in C

    - by Sergey
    I have a stucture: typedef structure student { char *name; char *surname; int age; } Student; I need to write it to binary file. Student *s = malloc(sizeof(*s)); I fill my structure with data and then i write in to the file: fwrite(s, sizeof(*s), 1, fp); In my file doesnt exist a name and surname, it have an adresses of char*. How can i write to file a word, not an adresses?

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  • Struct sockaddr, sin_family is not a member

    - by leon22
    According to this article from msdn ( http://msdn.microsoft.com/en-us/library/windows/desktop/ms740496(v=vs.85).aspx) the struct varies depending on which protocol is selected! Now I want to use this code from http://www.intelliproject.net/articles/showArticle/index/check_tcp_udp_port to check if a port is open or not! Now I have the struct sockaddr as follows: struct sockaddr { ushort sa_family; char sa_data[14]; }; but need this strcuture: struct sockaddr { short sin_family; u_short sin_port; struct in_addr sin_addr; char sin_zero[8]; }; Which changes are necessary? (Ws2_32.lib is linked and following includes #define WIN32_LEAN_AND_MEAN // sockets #include "windows.h" #include <winsock2.h> #include <ws2tcpip.h> Thx

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  • Calling member method on unmanaged C++ pointer from C# (I think)

    - by Jacob G
    I apologize in advance if this is a trivial question... I'm pretty C++ / unmanaged dumb. Here's a simplified analog to my setup: --In myUnmanagedObject.h in DLL: class myUnmanagedObject { public: virtual void myMethod(){} } --In MyControl.h in Assembly #1: #pragma make_public(myUnmanagedObject) [event_source(managed)] public ref class MyControl : public System::Windows::Forms::UserControl { public: myUnmanagedObject* GetMyUnmanagedObject(); } --in C# in Assembly #2: unsafe { MyControl temp = new MyControl(); myUnmanagedObject* obj = temp.GetMyUnmanagedObject(); obj-myMethod(); } I get a compile error saying that myUnmanagedObject does not contain a definition for myMethod. Assembly #2 references Assembly #1. Assembly #1 references DLL. If I compile the DLL with /clr and reference it directly from Assembly #2, it makes no difference. How, from C#, do I execute myMethod ?

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  • Android Add Icon to homescreen to set member variable in broadcast receiver

    - by JonF
    I would like to add some sort of icon that a user can press in order to flip a variable in a broadcast receiver my app uses. Basically I just can a icon that they can press which will flip the value of a boolean in the broadcast receiver, and change the icon to indicate something happened. I think I need to do something with a widget? Could anyone point me in the direction of some tutorial I could check out?

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  • Getting a file pointer from file descriptor

    - by Naga Kiran
    In PHP 5.2.3, "fdopen" was used to read/write to a file descriptor that's opened by another application. fdopen(<fileDescriptorId>,"rw"); //It worked fine with PHP 5.2.3 After upgrading PHP to 5.3.2, it's throwing "undefined reference to 'fdopen' function". Please suggest whats the replacement for this in PHP 5.3.2 or any workaround.

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  • Warning: pointer of type 'void *' used in subtraction

    - by idealistikz
    Although it runs correctly, the following results in the aforementioned compiler warning: return ((item - (my->items))/(my->itemSize)); 'item' is a 'void *'; 'my-items' is a 'void *'; 'my-itemSize' is an 'int' Casting 'item' and 'my-items' as an 'int *' caused the program to run improperly. What is the best way to remove the warning?

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  • Pointer arithmetic.

    - by Knowing me knowing you
    Having code: int** a = new int*[2]; a[0] = new int(1); a[1] = new int(2); cout << "a[0] " << a[0] << '\n'; cout << "a[1] " << a[1] << '\n'; cout << "a[2] " << a[2] << '\n'; cout << "a[0] + 1 " << a[0] + 1 << '\n';//WHY THIS ISN'T == a[1] ? cout << "*(a + 1): " << *(a + 1) << '\n'; //WHY THIS IS == a[1] ? cout << "a[0] - a[1] " << static_cast<int>(a[0] - a[1])<< '\n';//WHY THIS IS == 16 not 4? cout << sizeof(int**); Questions are included right next to relevant lines in code.

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  • null pointer exception comparing two strings in java.

    - by David
    I got this error message and I'm not quite sure whats wrong: Exception in thread "main" java.lang.NullPointerException at Risk.runTeams(Risk.java:384) at Risk.blobRunner(Risk.java:220) at Risk.genRunner(Risk.java:207) at Risk.main(Risk.java:176) Here is the relevant bits of code (i will draw attention to the line numbers within the error message via comments in the code as well as inputs i put into the program while its running where relevant) public class Risk { ... public static void main (String[]arg) { String CPUcolor = CPUcolor () ; genRunner (CPUcolor) ; //line 176 ... } ... public static void genRunner (String CPUcolor) // when this method runs i select 0 and run blob since its my only option. Theres nothing wrong with this method so long as i know, this is only significant because it takes me to blob runner and because another one of our relelvent line numbers apears. { String[] strats = new String[1] ; strats[0] = "0 - Blob" ; int s = chooseStrat (strats) ; if (s == 0) blobRunner (CPUcolor) ; // this is line 207 } ... public static void blobRunner (String CPUcolor) { System.out.println ("blob Runner") ; int turn = 0 ; boolean gameOver = false ; Dice other = new Dice ("other") ; Dice a1 = new Dice ("a1") ; Dice a2 = new Dice ("a2") ; Dice a3 = new Dice ("a3") ; Dice d1 = new Dice ("d1") ; Dice d2 = new Dice ("d2") ; space (5) ; Territory[] board = makeBoard() ; IdiceRoll (other) ; String[] colors = runTeams(CPUcolor) ; //this is line 220 Card[] deck = Card.createDeck () ; System.out.println (StratUtil.canTurnIn (deck)) ; while (gameOver == false) { idler (deck) ; board = assignTerri (board, colors) ; checkBoard (board, colors) ; } } ... public static String[] runTeams (String CPUcolor) { boolean z = false ; String[] a = new String[6] ; while (z == false) { a = assignTeams () ; printOrder (a) ; boolean CPU = false ; for (int i = 0; i<a.length; i++) { if (a[i].equals(CPUcolor)) CPU = true ; //this is line 384 } if (CPU==false) { System.out.println ("ERROR YOU NEED TO INCLUDE THE COLOR OF THE CPU IN THE TURN ORDER") ; runTeams (CPUcolor) ; } System.out.println ("is this turn order correct? (Y/N)") ; String s = getIns () ; while (!((s.equals ("y")) || (s.equals ("Y")) || (s.equals ("n")) || (s.equals ("N")))) { System.out.println ("try again") ; s = getIns () ; } if (s.equals ("y") || s.equals ("Y") ) z = true ; } return a ; } ... } // This } closes the class The reason i don't think i should be getting a Null:pointerException is because in this line: a[i].equals(CPUcolor) a at index i holds a string and CPUcolor is a string. Both at this point definatly have a value neither is null. Can anyone please tell me whats going wrong?

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  • pass by pointer is not working

    - by user323422
    #include"iostream" class CMessage { public:int a; CMessage(){} ~CMessage(){} }; void Testing(CMessage *f_pMessage)//l_pMessage is output parameter { f_pMessage = new CMessage(); f_pMessage->a = 1; } int main() { CMessage *l_pMessage =NULL; Testing(l_pMessage); std::cout<<l_pMessage->a;//getting l_pMessage = NULL; return 0; } when i called testing then inside testing f_pMessage is getting intialize but as ssoon as i after excuting testing function it should be store in l_Pmessage but it is showing NULL.confussed.....

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  • Add a new member to a Twitter List

    - by yc10
    I'm trying to add a user (by variable $id) to a Twitter List using PHP CURL, and I can't get it to work. $curl_handle = curl_init(); curl_setopt($curl_handle, CURLOPT_URL, "http://twitter.com/username/list/members.xml"); curl_setopt($curl_handle, CURLOPT_POST, 1); curl_setopt($curl_handle, CURLOPT_POSTFIELDS, "id=$id"); curl_setopt($curl_handle, CURLOPT_CONNECTTIMEOUT, 2); curl_setopt($curl_handle, CURLOPT_RETURNTRANSFER, 1); curl_setopt($curl_handle, CURLOPT_USERPWD, "username:password"); curl_setopt($curl_handle, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1); curl_setopt($curl_handle, CURLOPT_VERBOSE, 1); $result = curl_exec($curl_handle); // Look at the returned header $resultArray = curl_getinfo($curl_handle); curl_close($curl_handle); if($resultArray['http_code'] == "200"){ echo 'Success'; } else { echo var_dump($resultArray); } The var_dump reveals that the http_code of the return is 403.

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  • accessing private variable from member function in PHP

    - by Carson Myers
    I have derived a class from Exception, basically like so: class MyException extends Exception { private $_type; public function type() { return $this->_type; //line 74 } public function __toString() { include "sometemplate.php"; return ""; } } Then, I derived from MyException like so: class SpecialException extends MyException { private $_type = "superspecial"; } If I throw new SpecialException("bla") from a function, catch it, and go echo $e, then the __toString function should load a template, display that, and then not actually return anything to echo. This is basically what's in the template file <div class="<?php echo $this->type(); ?>class"> <p> <?php echo $this->message; ?> </p> </div> in my mind, this should definitely work. However, I get the following error when an exception is thrown and I try to display it: Fatal error: Cannot access private property SpecialException::$_type in C:\path\to\exceptions.php on line 74 Can anyone explain why I am breaking the rules here? Am I doing something horribly witty with this code? Is there a much more idiomatic way to handle this situation? The point of the $_type variable is (as shown) that I want a different div class to be used depending on the type of exception caught.

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  • Pass temporary object to function that takes pointer

    - by Happy Mittal
    I tried following code : #include<iostream> #include<string> using namespace std; string f1(string s) { return s="f1 called"; } void f2(string *s) { cout<<*s<<endl; } int main() { string str; f2(&f1(str)); } But this code doesn't compile. What I think is : f1 returns by value so it creates temporary, of which I am taking address and passing to f2. Now Please explain me where I am thinking wrong?

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  • C++: Reference and Pointer question (example regarding OpenGL)

    - by Jay
    I would like to load textures, and then have them be used by multiple objects. Would this work? class Sprite { GLuint* mTextures; // do I need this to also be a reference? Sprite( GLuint* textures ) // do I need this to also be a reference? { mTextures = textures; } void Draw( textureNumber ) { glBindTexture( GL_TEXTURE_2D, mTextures[ textureNumber ] ); // drawing code } }; // normally these variables would be inputed, but I did this for simplicity. const int NUMBER_OF_TEXTURES = 40; const int WHICH_TEXTURE = 10; void main() { std::vector<GLuint> the_textures; the_textures.resize( NUMBER_OF_TEXTURES ); glGenTextures( NUMBER_OF_TEXTURES, &the_textures[0] ); // texture loading code Sprite the_sprite( &the_textures[0] ); the_sprite.Draw( WHICH_TEXTURE ); } And is there a different way I should do this, even if it would work? Thanks.

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  • python multiprocessing member variable not set

    - by Jake
    In the following script, I get the "stop message received" output but the process never ends. Why is that? Is there another way to end a process besides terminate or os.kill that is along these lines? from multiprocessing import Process from time import sleep class Test(Process): def __init__(self): Process.__init__(self) self.stop = False def run(self): while self.stop == False: print "running" sleep(1.0) def end(self): print "stop message received" self.stop = True if __name__ == "__main__": test = Test() test.start() sleep(1.0) test.end() test.join()

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  • Call to a member function query() on a non-object

    - by Randy Gonzalez
    Ok, this is so weird!!! I am running PHP Version 5.1.6 when I try and run the code below it gives a fatal error of an object that has not been instantiated. As soon as I un-comment this line of code //$cb_db = new cb_db(USER, PASSWORD, NAME, HOST); everything works. Even though I have declared the $cb_db object as global within in the method. Any help would be greatly appreciated. require_once ( ROOT_CB_CLASSES . 'db.php'); $cb_db = new cb_db(USER, PASSWORD, NAME, HOST); class cb_user { protected function find_by_sql( $sql ) { global $cb_db; //$cb_db = new cb_db(USER, PASSWORD, NAME, HOST); $result_set = $cb_db->query( $sql ); $object_array = array(); while( $row = $cb_db->fetch_array( $result_set ) ) { $object_array[] = self::instantiate( $row ); } return $object_array; } }

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  • How to treat Base* pointer as Derived<T>* pointer?

    - by dehmann
    I would like to store pointers to a Base class in a vector, but then use them as function arguments where they act as a specific class, see here: #include <iostream> #include <vector> class Base {}; template<class T> class Derived : public Base {}; void Foo(Derived<int>* d) { std::cerr << "Processing int" << std::endl; } void Foo(Derived<double>* d) { std::cerr << "Processing double" << std::endl; } int main() { std::vector<Base*> vec; vec.push_back(new Derived<int>()); vec.push_back(new Derived<double>()); Foo(vec[0]); Foo(vec[1]); delete vec[0]; delete vec[1]; return 0; } This doesn't compile: error: call of overloaded 'Foo(Base*&)' is ambiguous Is it possible to make it work? I need to process the elements of the vector differently, according to their int, double, etc. types.

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  • C++ arrays as parameters, subscript vs. pointer

    - by awshepard
    Alright, I'm guessing this is an easy question, so I'll take the knocks, but I'm not finding what I need on google or SO. I'd like to create an array in one place, and populate it inside a different function. I define a function: void someFunction(double results[]) { for (int i = 0; i<100; ++i) { for (int n = 0; n<16; ++n) //note this iteration limit { results[n] += i * n; } } } That's an approximation to what my code is doing, but regardless, shouldn't be running into any overflow or out of bounds issues or anything. I generate an array: double result[16]; for(int i = 0; i<16; i++) { result[i] = -1; } then I want to pass it to someFunction someFunction(result); When I set breakpoints and step through the code, upon entering someFunction, results is set to the same address as result, and the value there is -1.000000 as expected. However, when I start iterating through the loop, results[n] doesn't seem to resolve to *(results+n) or *(results+n*sizeof(double)), it just seems to resolve to *(results). What I end up with is that instead of populating my result array, I just get one value. What am I doing wrong?

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