Re: SFINAE question 2

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

On 22 August 2012 22:15, Onay Urfalioglu wrote:
>
> I wonder whether it is possible to overload the operator*() to have two
> versions:
>   - one for all T_VECTOR - types having operator[]
>   - one for all T_VECTOR - types not having operator[] but providing say a
> forward iterator, like std::list
>
> (This is just a toy requirement, I am aware that one can implement this in
> other ways too...)
>
> You see I am painfully missing some C++11 concepts functionality here...

Instead of your TransformationTrait (which defines a nested type)
define a UnaryTypeTrait (which defines a boolean constant) for "has
operator[]" and another UnaryTypeTrait for "has forward iterator" then
selectively enable one overload with
enable_if<has_index_operator<T>::value>::type and the other with
enable_if<!has_index_operator<T>::value &&
has_forward_iterator<T>::value>::type.

This is not the right list to learn how to do that though.