calendars/mtcore_calendars/traits.hpp

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/*
 
Copyright 2025 Matthew Tolman
 
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
 
   http://www.apache.org/licenses/LICENSE-2.0
 
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
 
*/
 
#ifndef MTCORE_CALENDARS_TRAITS_HPP
#define MTCORE_CALENDARS_TRAITS_HPP
 
namespace mtcore::calendars {
  struct Fixed;
  struct Moment;
  struct UnixTimestamp;
 
  template<typename T>
  concept IsDayCalendarSystem = requires(const T &t, const Fixed &f) {
    { t.to_fixed() } -> std::same_as<Fixed>;
    { T::from_fixed(f) } -> std::same_as<T>;
    { T::EPOCH };
    { T::name };
    { t <=> t } -> std::same_as<std::strong_ordering>;
  };
 
  template<typename T>
  concept IsTimeCalendarSystem = requires(const T &t, const Moment &f) {
    { t.to_moment() } -> std::same_as<Moment>;
    { T::from_moment(f) } -> std::same_as<T>;
    { T::EPOCH };
    { T::name };
    { t <=> t } -> std::same_as<std::partial_ordering>;
  };
}  // namespace mtcore::calendars
 
#endif  // MTCORE_CALENDARS_TRAITS_HPP