ceph/src/boost/libs/fusion/include/boost/fusion/support/detail/and.hpp

   1 /*=============================================================================
   2     Copyright (c) 2016 Lee Clagett
   3
   4     Distributed under the Boost Software License, Version 1.0. (See accompanying
   5     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 ==============================================================================*/
   7 #ifndef FUSION_AND_07152016_1625
   8 #define FUSION_AND_07152016_1625
   9
  10 #include <boost/config.hpp>
  11 #include <boost/type_traits/integral_constant.hpp>
  12
  13 #if defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
  14 #error fusion::detail::and_ requires variadic templates
  15 #endif
  16
  17 namespace boost { namespace fusion { namespace detail {
  18     template<typename ...Cond>
  19     struct and_impl : false_type {};
  20
  21     template<typename ...T>
  22     struct and_impl<integral_constant<T, true>...> : true_type {};
  23
  24     // This specialization is necessary to avoid MSVC-12 variadics bug.
  25     template<bool ...Cond>
  26     struct and_impl1 : and_impl<integral_constant<bool, Cond>...> {};
  27
  28     /* fusion::detail::and_ differs from mpl::and_ in the following ways:
  29        - The empty set is valid and returns true
  30        - A single element set is valid and returns the identity
  31        - There is no upper bound on the set size
  32        - The conditions are evaluated at once, and are not short-circuited. This
  33          reduces instantations when returning true; the implementation is not
  34          recursive. */
  35     template<typename ...Cond>
  36     struct and_ : and_impl1<Cond::value...> {};
  37 }}}
  38
  39 #endif // FUSION_AND_07152016_1625