Condition in Template Definition

Question

I want to change the return type of a template function depending on a property of the given type. Is there a possibility to do something like this, maybe with partial specialization (one for the cool T and one for not cool ones)?

template<typename T, typename ret = T::IsCool ? int : float>
inline ret get() {}

(It is always guaranteed, that T has the bool property IsCool.)

Answer 1

You can use std::conditional to achieve this.

See http://en.cppreference.com/w/cpp/types/conditional

You can use it like so:

C++11

template<typename T, typename ret = std::conditional<T::IsCool, int, float>::type>
inline ret get() {}

C++14

template<typename T, typename ret = std::conditional_t<T::IsCool, int, float>>
inline ret get() {}