detecting typedef at compile time (template metaprogramming)

Question

I am currently doing some template metaprogramming. In my case I can handle any \"iteratable\" type, i.e. any type for which a typedef foo const_iterator exists in

Answer 1

Here's another version of a member type trait check:

template
struct has_const_iterator
{
private:
    typedef char                      yes;
    typedef struct { char array[2]; } no;

    template static yes test(typename C::const_iterator*);
    template static no  test(...);
public:
    static const bool value = sizeof(test(0)) == sizeof(yes);
};