Question

Possible Duplicate:
template pass by value or const reference or…?

What is the good practice in the following for a function taking a function as a parameter :

template<class Function> void test1(Function f);
template<class Function> void test2(Function& f);
template<class Function> void test3(const Function& f);

where the passed function can be a functor, a std::function, a function pointer or a lambda function.

Answer 1

Use universal references and you won’t need to think about it:

template<class Function> void test(Function&& f);