Question

I wish to know how std::function determines the argument and parameters from the function type that you pass in.

Answer 1

It’s a partial template specialization.

template<typename T> class function;
template<typename Ret> class function<Ret()> { ... };
template<typename Ret, typename Arg1> class function<Ret(Arg1)> { ... };

As you can see, this will get old quickly, but variadic templates will handle it in C++0x.