ceph/src/boost/libs/hana/test/_include/support/counter.hpp

   1 // Copyright Louis Dionne 2013-2017
   2 // Copyright Jason Rice 2017
   3 // Distributed under the Boost Software License, Version 1.0.
   4 // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   5
   6 #ifndef TEST_SUPPORT_COUNTER_HPP
   7 #define TEST_SUPPORT_COUNTER_HPP
   8
   9 #include <boost/hana/fwd/at.hpp>
  10 #include <boost/hana/fwd/concept/iterable.hpp>
  11 #include <boost/hana/fwd/drop_front.hpp>
  12 #include <boost/hana/fwd/is_empty.hpp>
  13 #include <boost/hana/integral_constant.hpp>
  14
  15
  16 // Counter - an infinite iterable for the masses
  17
  18 struct Counter_tag { };
  19
  20 template <std::size_t N = 0>
  21 struct Counter {
  22     using hana_tag = Counter_tag;
  23     static constexpr std::size_t value = N;
  24 };
  25
  26
  27 namespace boost { namespace hana {
  28     //////////////////////////////////////////////////////////////////////////
  29     // Iterable
  30     //////////////////////////////////////////////////////////////////////////
  31     template <>
  32     struct at_impl<Counter_tag> {
  33         template <typename T, typename N>
  34         static constexpr decltype(auto) apply(T, N) {
  35             return hana::size_c<T::value + N::value>;
  36         }
  37     };
  38
  39     template <>
  40     struct drop_front_impl<Counter_tag> {
  41         template <typename T, typename N>
  42         static constexpr auto apply(T, N) {
  43             return Counter<T::value + N::value>{};
  44         }
  45     };
  46
  47     template <>
  48     struct is_empty_impl<Counter_tag> {
  49         template <typename Xs>
  50         static constexpr auto apply(Xs)
  51             -> hana::false_
  52         { return {}; }
  53     };
  54 }} // end namespace boost::hana
  55
  56 #endif // !TEST_SUPPORT_COUNTER_HPP