llvm-project/libcxx/include/experimental/tuple

// -*- C++ -*-
//===----------------------------- tuple ----------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_EXPERIMENTAL_TUPLE
#define _LIBCPP_EXPERIMENTAL_TUPLE

/*
    experimental/tuple synopsis

// C++1y

#include <tuple>

namespace std {
namespace experimental {
inline namespace fundamentals_v1 {

  // See C++14 20.4.2.5, tuple helper classes
  template <class T> constexpr size_t tuple_size_v
    = tuple_size<T>::value;

  // 3.2.2, Calling a function with a tuple of arguments
  template <class F, class Tuple>
  constexpr decltype(auto) apply(F&& f, Tuple&& t);

} // namespace fundamentals_v1
} // namespace experimental
} // namespace std

 */

# include <experimental/__config>

#if _LIBCPP_STD_VER > 11

# include <tuple>
# include <utility>
# include <__functional_base>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_LFTS

#ifndef _LIBCPP_HAS_NO_VARIABLE_TEMPLATES
template <class _Tp>
_LIBCPP_CONSTEXPR size_t tuple_size_v = tuple_size<_Tp>::value;
#endif

template <class _Fn, class _Tuple, size_t ..._Id>
inline _LIBCPP_INLINE_VISIBILITY
decltype(auto) __apply_tuple_impl(_Fn && __f, _Tuple && __t,
                                  integer_sequence<size_t, _Id...>) {
    return _VSTD::__invoke(
        _VSTD::forward<_Fn>(__f),
        _VSTD::get<_Id>(_VSTD::forward<_Tuple>(__t))...
    );
}

template <class _Fn, class _Tuple>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
decltype(auto) apply(_Fn && __f, _Tuple && __t) {
    return _VSTD_LFTS::__apply_tuple_impl(
        _VSTD::forward<_Fn>(__f), _VSTD::forward<_Tuple>(__t),
        make_index_sequence<tuple_size<typename decay<_Tuple>::type>::value>()
    );
}

_LIBCPP_END_NAMESPACE_LFTS

#endif /* _LIBCPP_STD_VER > 11 */

#endif /* _LIBCPP_EXPERIMENTAL_TUPLE */