#pragma once

#ifndef TCG_SFINAE_H

#define TCG_SFINAE_H

/*!

  \file     sfinae.h

  \brief    Contains template metafunctions that can be used to enable or

            disable template class members.

  \details  SFINAE (Substitution Failure Is Not An Error) is a C++ \a feature

            that allows the compiler to silently discard failures in template

            function instantiations during function overload resolution.

*/

#if defined(__APPLE_CC__)

#include <type_traits>

#endif

namespace tcg {

template <typename X, typename Y>

struct type_match {

  enum { value = false };

};

template <typename X>

struct type_match<X, X> {

  enum { value = true };

};

//------------------------------------------------------------------------

template <typename X, typename Y>

struct type_mismatch {

  enum { value = true };

};

template <typename X>

struct type_mismatch<X, X> {

  enum { value = false };

};

//========================================================================

template <typename T, typename B>

struct enable_if_exists {

  typedef B type;

};

//========================================================================

template <bool, typename T = void>

struct enable_if {};

template <typename T>

struct enable_if<true, T> {

  typedef T type;

};

//========================================================================

template <bool, typename T = void>

struct disable_if {

  typedef T type;

};

template <typename T>

struct disable_if<true, T> {};

//========================================================================

template <bool, typename TrueT, typename FalseT = void>

struct choose_if;

template <typename TrueT, typename FalseT>

struct choose_if<true, TrueT, FalseT> {

  typedef TrueT type;

};

template <typename TrueT, typename FalseT>

struct choose_if<false, TrueT, FalseT> {

  typedef FalseT type;

};

//========================================================================

template <typename T, typename MatchT, typename NotMatchedT = void>

struct choose_if_match {

  typedef NotMatchedT type;

};

template <typename MatchT, typename NotMatchedT>

struct choose_if_match<MatchT, MatchT, NotMatchedT> {

  typedef MatchT type;

};

}  // namespace tcg

#endif  // TCG_SFINAE_H