C++11 variadic std::function parameter

Question

A function named test takes std::function<> as its parameter.

template
void test(std::functio         


        

Answer 1

This is an old one, and I can't seem to find much on the same topic, so I thought I would go ahead and put in a note.

Compiled on GCC 4.8.2, the following works:

template
R test(const std::function& func)
{
    // ...
}

However, you can't just call it by passing in your pointers, lambdas, etc. However, the following 2 examples both work with it:

test(std::function(
        [](int i, float f, std::string s)
        {
            std::cout << i << " " << f << " " << s << std::endl;
        }));

Also:

void test2(int i, float f, std::string s)
{
    std::cout << i << " " << f << " " << s << std::endl;
}

// In a function somewhere:
test(std::function(&test2));

The downside of these should stand out pretty obviously: you have to explicitly declare the std::function for them, which might look a little bit ugly.

That said, though, I threw that together with a tuple that gets expanded to call the incoming function, and it works, just requiring a little bit more of an explicitly saying what you're doing calling the test function.

Example code including the tuple thing, if you want to play with it: http://ideone.com/33mqZA