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  • between syntax, are there any equal function

    - by gcc
    /* char **mainp=malloc(sizeof(char *)*2); mainp[0]=malloc(sizeof(char)*300); mainp[1]=malloc(sizeof(char )*300); */ *I have some input about propositional calculus *After calculating some math funtion-removing paranthesis-changing"&" with ","-replacing "|" with"," I have >> (1) P,-Q,Q,-R is stored in mainp[0] R,A,P,B,F is stored in mainp[1] *My question is: Between comma , I have want to compare two pointer array. If there is any equal two or more functions(Q,-R is function representation) ,function which you will show me how to write must return int. According to example (1),function will return 1 (I expect like that) /*I have som thought://which function should I have use:*/ in for loop if( strspn(mainp[0][i])==1 ) increment d; continue; or in for loop srtcmp(mainp[0][i],mainp[1]);

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  • C++: Allocation of variables in a loop

    - by Rosarch
    Let's say I have a loop like this: vector<shared_ptr<someStruct>> vec; int i = 0; while (condition) { i++ shared_ptr<someStruct> sps(new someStruct()); WCHAR wchr[20]; memset(wchr, i, 20); sps->pwsz = wchr; vec.push_back(sps); } At the end of this loop, I see that for each sps element of the vector, sps->pwsz is the same. Is this because I'm passing a pointer to memory allocated in a loop, which is destructed after each iteration, and then refilling that same memory on the next iteration?

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  • [C++] Needed: A simple C++ container (stack, linked list) that is thread-safe for writing

    - by conradlee
    I am writing a multi-threaded program using OpenMP in C++. At one point my program forks into many threads, each of which need to add "jobs" to some container that keeps track of all added jobs. Each job can just be a pointer to some object. Basically, I just need the add pointers to some container from several threads at the same time. Is there a simple solution that performs well? After some googling, I found that STL containers are not thread-safe. Some stackoverflow threads address this question, but none form a consensus on a simple solution.

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  • Strange C++ thread function invocation

    - by Tony
    I have the following: class DThread { virtual void run()=0; _beginthreadex(NULL,0,tfunc,this,0,&m_UIThreadID); // class itself being passed as param to thread function... static unsigned int __stdcall tfunc(void* thisptr) { static_cast<DThread*>(thisptr)->run(); return 0; } //other stuff } The run function is implemented in a derived class. Why is the function that's being called in the thread being called through a cast this pointer? Is this good practise? Can't it just be called directly? The actual function needing to run is in the derived class. My question is

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  • Abstract class and operator!= in c++

    - by Alessandro Teruzzi
    Hi All, I have problem implementing the operator!= in a set class deriving from an abstact one. The code looks like this: class Abstract { public: //to make the syntax easier let's use a raw pointer virtual bool operator!=(const Abstract* other) = 0; }; class Implementation { SomeObject impl_; //that already implement the operator!= public: bool operator!=(const Abstract* other) { return dynamic_cast<Implementation*>(other)->impl_ != this->impl_; } }; This code works but it has the drawback to use dynamic_cast and I need to handle error in casting operation. This is a generic problem that occur when a function of a concrete class it is trying to using some internal information (not available at the abstract class level) to perform a task. Is there any better way to solve this kind of problem? Cheers

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  • C++ Iterators and inheritance

    - by jomnis
    Have a quick question about what would be the best way to implement iterators in the following: Say I have a templated base class 'List' and two subclasses "ListImpl1" and "ListImpl2". The basic requirement of the base class is to be iterable i.e. I can do: for(List<T>::iterator it = list->begin(); it != list->end(); it++){ ... } I also want to allow iterator addition e.g.: for(List<T>::iterator it = list->begin()+5; it != list->end(); it++){ ... } So the problem is that the implementation of the iterator for ListImpl1 will be different to that for ListImpl2. I got around this by using a wrapper ListIterator containing a pointer to a ListIteratorImpl with subclasses ListIteratorImpl2 and ListIteratorImpl2, but it's all getting pretty messy, especially when you need to implement operator+ in the ListIterator. Any thoughts on a better design to get around these issues?

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  • question abouut string sort

    - by davit-datuashvili
    i have question from programming pearls problem is following show how to use lomuto's partitioning scheme to sort varying length bit strings in time proportional to the sum oof their length and algorithm is following each record in x[0..n-1] has an integer length and pointer to the array bit[0..length-1] code void bsort(l,u,depth){ if (l>=u) return; for (int i=l;i<u;i++) if (x[i].length<depth) swap(i,l++); m=l; if (x[i].bit[depth] ==0) swap(i,m++); bsort(l,m-1,depth+1); bsort(m,u,depth+1); please help me i need following things 1. how this algorith works 2.how implement in java?

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  • Help with implementing a function to change size of dynamic array

    - by iRobot
    I'm trying to write a function that will change the size of a dynamic array to a new size. In my header file, I have: Image **images; //pointer to a dynamic array of image pointers int maximum; //size I want to do this by allocating a new array and copying the values over without changing their indices. If there are non-null pointers outside the range newmax, then we cant do this. So heres what I have: There are no compilation or runtime errors. However, I find that the new array isnt getting sized right. When I run the following test case: I should get an index out of bounds error, but instead the system lets it slide. Can anyone see the mistake? I've looked for hours but cant find anything.

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  • Are unspecified and undefined behavior required to be consistent between compiles?

    - by sharptooth
    Let's pretend my program contains a specific construct the C++ Standard states to be unspecified behavior. This basically means the implementation has to do something reasonable but is allowed not to document it. But is the implementation required to produce the same behavior every time it compiles a specific construct with unspecified behavior or is it allowed to produce different behavior in different compiles? What about undefined behavior? Let's pretend my program contains a construct that is UB according to the Standard. The implementation is allowed to exhibit any behavior. But can this behavior differ between compiles of the same program on the same compiler with same settings in the same environment? In other words, if I dereference a null pointer on line 78 in file X.cpp and the implementation formats the drive in such case does it mean that it will do the same after the program is recompiled?

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  • Rendering sub tools on vertical toolbar

    - by user146780
    I was wondering how ex Photoshop and Expression Design render sub tools. These show up when for example you hold your mouse down on the fill tool, a sub menu comes up to your right with the fill and gradient tools. I'm just not sure how to go about this because this sub menu would essentially have to be an extension of my toolbar, but then it would find itself on my Frame control. How is this handled? Would it be a good idea to just paint on my frame?

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  • C++ operator[] syntax.

    - by Lanissum
    Just a quick syntax question. I'm writing a map class (for school). If I define the following operator overload: template<typename Key, typename Val> class Map {... Val* operator[](Key k); What happens when a user writes: Map<int,int> myMap; map[10] = 3; Doing something like that will only overwrite a temporary copy of the [null] pointer at Key k. Is it even possible to do: map[10] = 3; printf("%i\n", map[10]); with the same operator overload?

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  • Break the limit of threading, segmentation fault

    - by user353573
    use pthread_create to create limited number of threads running concurrently Successfully compile and run However, after adding function pointer array to run the function, Segmentation fault Where is wrong? workserver number: 0 Segmentation fault void* workserver(void arg) { int status; while(true) { printf("workserver number: %d\n", (int)arg); ( job_queue[(int)arg])(); sleep(3); status = pthread_mutex_lock(&data.mutex); if(status != 0) printf("%d lock mutex", status); data.value = 1; status = pthread_cond_signal(&data.cond); if(status != 0) printf("%d signal condition", status); status = pthread_mutex_unlock(&data.mutex); if(status != 0) printf("%d unlock mutex", status); } }

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  • c++ - FIFO implementation

    - by Narek
    While implementing a FIFO I have used the following structure: struct Node { T info_; Node* link_; Node(T info, Node* link=0): info_(info), link_(link) {} }; I think this a well known trick for lots of STL containers (for example for List). Is this a good practice? What it means for compiler when you say that Node has a member with a type of it's pointer? Is this a kind of infinite loop? And finally, if this is a bad practice, how I could implement a better FIFO.

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  • lambda+for_each+delete on STL containers

    - by rubenvb
    I'm trying to get a simple delete every pointer in my vector/list/... function written with an ultra cool lambda function. Mind you, I don't know c**p about those things :) template <typename T> void delete_clear(T const& cont) { for_each(T.begin(), T.end(), [](???){ ???->delete() } ); T.clear(); } I have no clue what to fill in for the ???'s. Any help is greatly appreciated!

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  • C++ syntax of constructors " 'Object1 a (1, Object1(2))''

    - by osgx
    Hello I have a such syntax in program class Object1 : BaseClass { BaseClass *link; int i; public: Object1(int a){i=a;} Object1(int a, Object1 /*place1*/ o) {i=a; link= &o;} }; int main(){ Object1 a(1, /*place2*/ Object1(2)); ... } What do I need in place1? I want to save a link (pointer) to the second object in the first object. Should I use in place1 reference "&"? What type will have "Object1(2)" in place2? Is it a constructor of the anonymous object? Will it have a "auto" storage type?

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  • javascript code to prevent screensaver from starting

    - by gertjan
    Hi all, I am completely new to javascript programming and I have a question that I didn't manage to find an answer for anywhere. I have recently put together a simple slideshow to view the photos remotely that I host on my home computer. This by itself works fine. The problem I run into is that when I'm viewing photos I don't interact with the hardware, which after some time causes the monitor to switch off. This is particularly annoying when watching photos on my mobile phone. My question is: is there a way to prevent this from happening? I am thinking in the direction of faking a mouse or other event every time I refresh the photo, but I have no clue how to do that and if it is possible. Any help is greatly appreciated!

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  • Input Iterator for a shared_ptr

    - by Baz
    I have an iterator which contains the following functions: ... T &operator*() { return *_i; } std::shared_ptr<T> operator->() { return _i; } private: std::shared_ptr<T> _i; ... How do I get a shared pointer to the internally stored _i? std::shared_ptr<Type> item = ??? Should I do: MyInterfaceIterator<Type> i; std::shared_ptr<Type> item = i.operator->(); Or should I rewrite operator*()?

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  • How to force calling of QWidget::paintEvent() when its hovered by other window?

    - by Pie_Jesu
    Hi there. I have occured a problem: I'm writing a widget, which displays current date's day number. It's like a button, but it's not derived from QPushButton class. Just from QWidget. So I reimplemented enterEvent(), leaveEvent(), mousePressEvent(), mouseReleaseEvent(). I call update() inside these methods and widget has realistic button behavior (paintEvent() is reimplemented too). But when I change system date and hover that widget with other window, my widget doesn't calls paintEvent() and displays old date. Only when I place mouse over it, widget repaints it's contents. I guess there is an option, which paints old contents on hover event to avoid unnecessary paint events. But I need to disable it. Tried to set many attributes (Qt::WidgetAttribute enum). But it doesn't helps. Please, help me (and sorry for my bad english).

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  • C++ function call routes resolver

    - by Poni
    Hi! I'm looking for a tool that will tell/resolve for every function all the call paths (call it "routes") to it. For example: void deeper(int *pNumber) { *pNumber++; } void gateA(int *pNumber) { deeper(pNumber); } void gateB(int *pNumber) { gateA(pNumber); } void main() { int x = 123; gateA(&x); gateB(&x); } See? I need a tool that will tell me all the routes to deeper(), and more if possible. By saying "more" I mean that it will tell me if the pointer is the same as been provided to the calling function. This will greatly save me time. Thanks!

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  • Is there a Swing JPanel toolbar background that fits all OSs?

    - by Nazgulled
    I'm using a JPanel to have a toolbar on my background, but I don't like the look of it. Actually, there's basically no look, no background and the buttons are flat when the mouse is not over them. This is on Windows. How can I have a better look for this? Something that would fit better on Windows? Maybe something like the ToolStrip in Visual Studio? Or maybe something better that would look much better depending on the OS version (Windows, Mac, Linux)? Suggestions?

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  • Ubuntu 10.10, taskbar

    - by Alex
    I launched system monitor to kill one program, which didn't responded on any mouse clicks, etc. But i occasionally killed another process. so, taskbar was killed. (it was in the bottom of the screen, in the top all is good) reboot didnt help o_O. Now I use Alt-Tab and alt-controll-arrows to switch between programs and desktops (it works). How to launch taskbar again? its very strange that reboot didnt help me.

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  • Where can I find a compact programming keyboard with logical key placement?

    - by Lefler
    I recently, at the order of my chiropractor, bought a laptop stand to elevate my screen. A result of this is that I need a standalone keyboard. Normal keyboards have numeric keypads on the right side, which moves my mouse further to the right... not an optimal position chiropractically speaking. I don't use the numeric keypad, but all the compact keyboards I can find use some random placement algorithm on the arrow, page up/down, and most importantly -- the insert,delete,home and end keys. Those misplaced keys are crippling my code entry. Does anyone know of a keyboard that is minus the keypad, but places those VERY IMPORTANT keys in a more standard position?

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  • How to do hex8 encoding in c?

    - by Tech163
    I am trying to encode a string in hex8 using c. The script I have right now is: int hex8 (char str) { str = printf("%x", str); if(strlen(str) == 1) { return printf("%s", "0", str); } else { return str; } } In this function, I will need to add a 0 ahead of the string if the length is less than 1. I don't know why I'm getting: passing argument 1 of 'strlen' makes pointer from integer without a cast Does anyone know why?

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  • memcpy does not copy the data

    - by user437777
    I am caught up with a weird problem. I have one build that copies data using memcpy, while another build does not. I don't understand why, because the relevant file is still the same. I am using following code: memcpy(pxCurrentInfo, &pxInfoBuffer->axgInfoBuffer[0], sizeof(tInfo)); Data in pxInfoBuffer is fine. When I check pxCurrentInfo they are all 0s. tInfo is a structure. To give a pointer, when I put the break point and change the value pxCurrentInfo->xDL.eMethod=0 it automatically updates/copies all the correct info from pxInfoBuffer->axgInfoBuffer[0], afterwards. I don't know why.

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  • slide navigation

    - by robosot
    I'm trying to make slide navigation. Here is my code html <li> <a href="#">Services</a> <div class="subcategories"> <a href="#">Cleaning</a> </div> </li> The subcategories div is hidden. js $('li a').hover(function() { $(this).next().slideToggle('fast', function() { }); }); This code works. The problem is that when the mouse goes out of the li a the subcategories div disappears. What i want is that when the user point the li a the subcategories div to be shown so the user be able to click on some link of the sub navigation.

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