Question

I have a simple function that uses a callback and I want use functor instead of normal function to be used as callback. But I get compilation error. It seems I missing smth.

Here is the code

#include <iostream>
#include <functional>

void some_func( void (*f)() ) 
{
    f(); 
}

class Functor
{
public:
    void g() { std::cout << "world"; }
    void operator() () { std::cout << "hello"; }
};

void g()
{
    std::cout << "beautiful";
}

int main(int c, char**v)
{
    Functor f;
    f();
    some_func(g);
    some_func(f);//line 26
    some_func(std::bind(&Functor::g, f));//line 27
    return 0;
}

Results:

g++ 1.cpp std=c++0x
1.cpp: In function 'int main(int, char**)':
1.cpp:26:16: error: cannot convert 'Functor' to 'void (*)()' for argument '1' to 'void some_func(void (*)())'
1.cpp:27:37: error: cannot convert 'std::_Bind<std::_Mem_fn<void (Functor::*)()>(Functor)>' to 'void (*)()' for argument '1' to 'void some_func(void (*)())'

Same story for cl

Answer 1

some_func takes only real function pointers as arguments, not functor classes. Try using:

template <class Functor>
void some_func( Functor f ) 
{
    f();
}