How to write a function that takes a functor as an argument

Question

Basically I want to do this: Can I use a lambda function or std::function object in place of a function pointer?

clearly that is impossible for now for functions that expect a function pointer. However, it will work for a function that expects a functor ( I have done it before with stl's sort() function)

However, I don't know how to write a function that takes a functor as an argument!

Anyone?

Answer 1

Just write the function to take an arbitrary type:

template <typename Func>
void foo(Func fun)
{
    fun(...);
}

This will then work with function pointers, functors and lambdas all the same.

void f() {}

struct G
{
    void operator()() {}
};

foo(&f);           // function pointer
foo(G());          // functor
foo([]() { ... }); // lambda