Question

Here’s the declaration:

#include <functional>    

class A { ... };

double fA( std::function<double((A::*)(double))> fp) { ... }

which gives me error

In function ‘double fA(std::function)’:
tb.cpp:32:8: error: ‘fp’ has incomplete type

Though there is no problem with

double fA( double ((A::*fp)(double)) ) { ... }

What’s the right way to supply this type as a template parameter to std::function?

Answer 1

Ended up doing something very similar to @chris’s suggestion, the code from his example is the following:

#include <functional>
#include <iostream>

struct S {
   void foo() {std::cout << i;};
   int i;
};

void bar(std::function<void()> func) {
    func();
}

int main() {
   S s1, s2;
   s1.i = 5;
   s2.i = 6;

   bar(std::bind(&S::foo, s1));
   bar(std::bind(&S::foo, s2));
}