ceph/src/boost/boost/mp11/utility.hpp

   1 #ifndef BOOST_MP11_UTILITY_HPP_INCLUDED
   2 #define BOOST_MP11_UTILITY_HPP_INCLUDED
   3
   4 //  Copyright 2015, 2017 Peter Dimov.
   5 //
   6 //  Distributed under the Boost Software License, Version 1.0.
   7 //
   8 //  See accompanying file LICENSE_1_0.txt or copy at
   9 //  http://www.boost.org/LICENSE_1_0.txt
  10
  11 #include <boost/mp11/integral.hpp>
  12 #include <boost/config.hpp>
  13 #include <boost/detail/workaround.hpp>
  14
  15 namespace boost
  16 {
  17 namespace mp11
  18 {
  19
  20 // mp_identity
  21 template<class T> struct mp_identity
  22 {
  23     using type = T;
  24 };
  25
  26 // mp_identity_t
  27 template<class T> using mp_identity_t = typename mp_identity<T>::type;
  28
  29 // mp_inherit
  30 template<class... T> struct mp_inherit: T... {};
  31
  32 // mp_if, mp_if_c
  33 namespace detail
  34 {
  35
  36 template<bool C, class T, class... E> struct mp_if_c_impl
  37 {
  38 };
  39
  40 template<class T, class... E> struct mp_if_c_impl<true, T, E...>
  41 {
  42     using type = T;
  43 };
  44
  45 template<class T, class E> struct mp_if_c_impl<false, T, E>
  46 {
  47     using type = E;
  48 };
  49
  50 } // namespace detail
  51
  52 template<bool C, class T, class... E> using mp_if_c = typename detail::mp_if_c_impl<C, T, E...>::type;
  53 template<class C, class T, class... E> using mp_if = typename detail::mp_if_c_impl<static_cast<bool>(C::value), T, E...>::type;
  54
  55 // mp_valid
  56 // implementation by Bruno Dutra (by the name is_evaluable)
  57 namespace detail
  58 {
  59
  60 template<template<class...> class F, class... T> struct mp_valid_impl
  61 {
  62     template<template<class...> class G, class = G<T...>> static mp_true check(int);
  63     template<template<class...> class> static mp_false check(...);
  64
  65     using type = decltype(check<F>(0));
  66 };
  67
  68 } // namespace detail
  69
  70 template<template<class...> class F, class... T> using mp_valid = typename detail::mp_valid_impl<F, T...>::type;
  71
  72 // mp_defer
  73 namespace detail
  74 {
  75
  76 template<template<class...> class F, class... T> struct mp_defer_impl
  77 {
  78     using type = F<T...>;
  79 };
  80
  81 struct mp_no_type
  82 {
  83 };
  84
  85 } // namespace detail
  86
  87 template<template<class...> class F, class... T> using mp_defer = mp_if<mp_valid<F, T...>, detail::mp_defer_impl<F, T...>, detail::mp_no_type>;
  88
  89 // mp_eval_if, mp_eval_if_c
  90 namespace detail
  91 {
  92
  93 template<bool C, class T, template<class...> class F, class... U> struct mp_eval_if_c_impl;
  94
  95 template<class T, template<class...> class F, class... U> struct mp_eval_if_c_impl<true, T, F, U...>
  96 {
  97     using type = T;
  98 };
  99
 100 template<class T, template<class...> class F, class... U> struct mp_eval_if_c_impl<false, T, F, U...>: mp_defer<F, U...>
 101 {
 102 };
 103
 104 } // namespace detail
 105
 106 template<bool C, class T, template<class...> class F, class... U> using mp_eval_if_c = typename detail::mp_eval_if_c_impl<C, T, F, U...>::type;
 107 template<class C, class T, template<class...> class F, class... U> using mp_eval_if = typename detail::mp_eval_if_c_impl<static_cast<bool>(C::value), T, F, U...>::type;
 108 template<class C, class T, class Q, class... U> using mp_eval_if_q = typename detail::mp_eval_if_c_impl<static_cast<bool>(C::value), T, Q::template fn, U...>::type;
 109
 110 // mp_cond
 111
 112 // so elegant; so doesn't work
 113 // template<class C, class T, class... E> using mp_cond = mp_eval_if<C, T, mp_cond, E...>;
 114
 115 namespace detail
 116 {
 117
 118 template<class C, class T, class... E> struct mp_cond_impl;
 119
 120 } // namespace detail
 121
 122 template<class C, class T, class... E> using mp_cond = typename detail::mp_cond_impl<C, T, E...>::type;
 123
 124 namespace detail
 125 {
 126
 127 template<class C, class T, class... E> using mp_cond_ = mp_eval_if<C, T, mp_cond, E...>;
 128
 129 template<class C, class T, class... E> struct mp_cond_impl: mp_defer<mp_cond_, C, T, E...>
 130 {
 131 };
 132
 133 } // namespace detail
 134
 135 // mp_quote
 136 template<template<class...> class F> struct mp_quote
 137 {
 138     // the indirection through mp_defer works around the language inability
 139     // to expand T... into a fixed parameter list of an alias template
 140
 141     template<class... T> using fn = typename mp_defer<F, T...>::type;
 142 };
 143
 144 // mp_quote_trait
 145 template<template<class...> class F> struct mp_quote_trait
 146 {
 147     template<class... T> using fn = typename F<T...>::type;
 148 };
 149
 150 // mp_invoke
 151 #if BOOST_WORKAROUND( BOOST_MSVC, < 1900 )
 152
 153 namespace detail
 154 {
 155
 156 template<class Q, class... T> struct mp_invoke_impl: mp_defer<Q::template fn, T...> {};
 157
 158 } // namespace detail
 159
 160 template<class Q, class... T> using mp_invoke = typename detail::mp_invoke_impl<Q, T...>::type;
 161
 162 #elif BOOST_WORKAROUND( BOOST_GCC, < 50000 )
 163
 164 template<class Q, class... T> using mp_invoke = typename mp_defer<Q::template fn, T...>::type;
 165
 166 #else
 167
 168 template<class Q, class... T> using mp_invoke = typename Q::template fn<T...>;
 169
 170 #endif
 171
 172 } // namespace mp11
 173 } // namespace boost
 174
 175 #endif // #ifndef BOOST_MP11_UTILITY_HPP_INCLUDED