#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