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

You can create a trait has_const_iterator that provides a boolean value and use that in the specialization.

Something like this might do it:

template 
struct has_const_iterator {
private:
    template 
    static typename T1::const_iterator test(int);
    template 
    static void test(...);
public:
    enum { value = !std::is_void(0))>::value };
};

And then you can specialize like this:

template ::value,
          bool HasConstIterator = has_const_iterator::value>
struct Foo; // default case is invalid, so no definition!

template 
struct Foo< T, true, false>{ 
   void do_stuff(){// bla }
};

template
struct Foo {
    void do_stuff(){//bla}
};