/*!
* \file use.h
* \brief Template meta-programming SFINAE helpers
*
* Copyright (C) 2018 Christos Choutouridis
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see .
*/
#ifndef __utl_meta_use_h__
#define __utl_meta_use_h__
#include
#include
/*!
* \ingroup meta
* \defgroup use
* conditional use support header. This is a SFINAE helper
*/
//! @{
namespace utl {
/*!
* void_t
* Utility meta-function that maps a sequence of any types to the type void
* \note The idea is:
* template
* using void_t = void;
*
* Until CWG 1558 (a C++14 defect), unused parameters in alias templates were not
* guaranteed to ensure SFINAE and could be ignored, so earlier compilers require
* a more complex definition of void_t, such as the following implementation
* https://en.cppreference.com
*/
//! @{
template
struct void_t_impl {
typedef void type;
};
//! The actual void_t type alias
template
using void_t = typename void_t_impl<_Ts...>::type;
//! @}
//! Alias template for if_
template
using if_t = typename if_<_Check, _Tp>::type;
//! Publicly recognized alias template for if_
template
using enable_if_t = typename if_<_Check, _Tp>::type;
//! Uniform alias template for if_
template
using use_if_t = typename if_<_Check, _Tp>::type;
//! If same type resolves to _Ret, else SFINAE
template
using use_if_same_t = typename if_::value, _Ret>::type;
//! If not same type resolves to _Ret, else SFINAE
template
using use_if_not_same_t = typename if_::value, _Ret>::type;
//! If any type (_T1 or _T2) type resolves to _Ret, else to SFINAE
template
using use_if_any_t = typename if_::value, _Ret>::type;
//! If both type (_T1 and _T2) type resolves to _Ret, else to SFINAE
template
using use_if_both_t = typename if_::value, _Ret>::type;
}
//! @}
#endif /* __utl_meta_use_h__ */