Get index of a tuple element's type?

Question

If I have a tuple with different element types like

std::tuple

And how to get the index of a element type?

Answer 1

template 
struct Index;

template 
struct Index> {
    static const std::size_t value = 0;
};

template 
struct Index> {
    static const std::size_t value = 1 + Index>::value;
};

See it live at Coliru.

This implementation returns the index of the first occurrence of a given type. Asking for the index of a type that is not in the tuple results in a compile error (and a fairly ugly one at that).