I would like to copy the content of one std::map into another. Can I use std::copy for that? Obviously, the following code won't work: int main() { typedef std::map<int,double> Map; Map m1; m1[3] = 0.3; m1[5] = 0.5; Map m2; m2[1] = 0.1; std::copy(m1.begin(), m1.end(), m2.begin()); return 0; } This won't work because co...
I'm looking for some answers for a project I'm thinking of. I've searched and from what I understand (correct me if I'm wrong) the only way the program I want to make will work is through 3D application. Let me explain. I plan to make a studio production program but it's unique in the fact that I want to be able to make it fluid. Let me...
Hi, I wanted a non recursive approach to the problem of generating combination of certain set of characters or numbers. So, given a subset k of numbers n, generate all the possible combination n!/k!(n-k)! The recursive method would give a combination, given the previous one combination. A non recursive method would generate a combin...
std::vector<T> vec; // line #1 vec.reserve(100); // line #2 I am wondering if line #1 triggers a small allocation (say, memory for 10 Ts), or if the first allocation happens on line #2. Does the standard say anything about that? ...
In this small example, c++ forgets size of an array, passed to a constructor. I guess it is something simple, but I cannot see it. In classes.h, there is this code: #ifndef CLASSES_INC #define CLASSES_INC #include <iostream> class static_class { public: static_class(int array[]) { std::cout<<sizeof(array)/sizeof(int)<<"\n"; } };...
I have an std::map, and I would like to define an iterator that returns modified values. Typically, a std::map<int,double>::iterator iterates over std::pair<int,double>, and I would like the same behavior, just the double value is multiplied by a constant. I tried it with boost::transform_iterator, but it doesn't compile: #include <ma...
How do I set line spacing after a wordwrap in QTextBrowser? Ie. how dow I set line height? ...
What I want is to create a vector drawing program with layers, but to avoid using transparency / opacity, I want to draw each shape from lowest layer to highest layer onto a single bitmap. For the filling, I want to floodfill the shape. My issue is that, if I have a shape that is drawn then floodfilled, then the next shape overlaps it a ...
I remember some years ago, when I learned C using Turbo C, it had a extensive documentation on its headers... My question is: There are something like that for MingW? ...
I'm dealing with a 2D array with the following characteristics: const int cols = 500; const int rows = 100; int arr[rows][cols]; I access array arr in the following manner to do some work: for(int k = 0; k < T; ++k) { // for each trainee myscore[k] = 0; for(int i = 0; i < cols; ++i) { // for each sample for(int j = 0; j <...
int randomNumber = (double)rand() / (RAND_MAX + 1) * (10 - 0) + 0; is the code I'm using, it is getting a random number, but is getting the SAME random combination every time? Can anyone see what I'm doing wrong? ...
hello. Is there a way to define using typedef integral/float type which implies no aliasng? something equivalent to (but primitive construct): template < typename T > struct restrict { T* __restrict data; }; as related question, is it possible to ask gcc what it determines alias/no alias of pointer is? ...
(I asked a variation of this question on comp.std.c++ but didn't get an answer.) Why does the call to f(arg) in this code call the const ref overload of f? void f(const std::string &); //less efficient void f(std::string &&); //more efficient void g(const char * arg) { f(arg); } My intuition says that the f(string &&) overload ...
My Visual C++ application is compiled with /EHA option, letting me catch structured exceptions (division by zero, access violation, etc). I then translate those exceptions to my own exception class using _set_se_translator(). My goal is to improve our logging of those types of exceptions. I can get the type of exception from the EXCEP...
This is the first part of a function I have that's causing my program to crash: vector<Student> sortGPA(vector<Student> student) { vector<Student> sorted; Student test = student[0]; cout << "here\n"; sorted.insert(student.begin(), student[0]); cout << "it failed.\n"; ... It crashes right at the sorted part...
I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking a...
The following code does not compile. I get an error message: error C2039: 'Asub' : is not a member of 'C' Can someone help me to understand this? Tried VS2008 & 2010 compiler. template <class T> class B { typedef int Asub; public: void DoSomething(typename T::Asub it) { } }; class C : public B<C> { public: typedef int Asub;...
I hope this question takes a simple fix, and I am just missing something very small. I am in my second semester of C++ in college, and we are just getting into OOP. This is my first OOP program, and it is causing me a little problem. Here are the errors I am getting: Member function must be called or its address taken in function displ...
In the following code, Foo::add calls a function via a function object: struct Plus { inline int operator()(int x, int y) const { return x + y; } }; template<class Fct> struct Foo { Fct fct; Foo(Fct f) : fct(f) {} inline int add(int x, int y) { return fct(x,y); // same efficiency adding directly? } }; Is this th...
Hi, I have a class hierarchy and i am writing a virtual function in it. Say there are three classes class A { virtual A* test(); }; ( File A.h ) class B : public A { virtual C* test(); }; ( File B.h ) class C : public A {}; ( File C.h ) Now is it possible for me to avoid including C.h in B.h, by doing some kind of forward decl...