Line data    Source code

       1           0 : // Distributed under the MIT License.
       2             : // See LICENSE.txt for details.
       3             : 
       4             : #pragma once
       5             : 
       6             : #include <type_traits>
       7             : 
       8             : #include "Utilities/ProtocolHelpers.hpp"
       9             : 
      10             : /// \brief Protocols for the DataBox
      11           1 : namespace db::protocols {
      12             : 
      13             : /// \brief A DataBox mutator
      14             : ///
      15             : /// A class conforming to this protocol can be used as the template argument for
      16             : /// a call to db::mutate_apply(const gsl::not_null<DataBox<BoxTags>*> box,
      17             : /// Args&&... args).  The conforming class must provide the following:
      18             : ///
      19             : /// - `return_tags`: A type list of tags corresponding to mutable items in the
      20             : ///   DataBox passed to `db::mutate_apply` that may be modified.
      21             : /// - `argument_tags`: A type list of tags corresponding to items in the DataBox
      22             : ///   passed to `db::mutate_apply` that may not be modified.
      23             : /// - `apply`: A static function whose return value is returned by
      24             : ///   `db::mutate_apply`, and that takes as arguments:
      25             : ///      - A `const gsl::not_null<Tag::type*>` for each `Tag` in `return_tags`
      26             : ///      - A `const db::const_item_type<Tag, BoxTags>` for each `Tag` in
      27             : ///        `argument_tags`
      28             : ///      - The additional arguments passed to `db::mutate_apply`
      29             : ///
      30             : ///   Note: use the explicit type whenever possible, not the type aliases.
      31             : ///   `db::const_item_type` will usually be `Tag::type` unless that is a
      32             : ///   `std::unique_ptr<T>`, in which case it will be `T`
      33             : ///
      34             : /// Here is an example for a class conforming to this protocol:
      35             : ///
      36             : /// \snippet DataBox/Examples.hpp mutator_protocol
      37           1 : struct Mutator {
      38             :   template <typename ConformingType>
      39           0 :   struct test {
      40           0 :     using argument_tags = typename ConformingType::argument_tags;
      41           0 :     using return_tags = typename ConformingType::return_tags;
      42             :   };
      43             : };
      44             : }  // namespace db::protocols