Line data    Source code

       1            0 : // Distributed under the MIT License.
       2              : // See LICENSE.txt for details.
       3              : 
       4              : #pragma once
       5              : 
       6              : #include "Utilities/TMPL.hpp"
       7              : 
       8              : /// \ingroup UtilitiesGroup
       9              : /// \brief Helpers for derived class registration
      10              : ///
      11              : /// SpECTRE's factory mechanism requires that the base class contain a
      12              : /// list of all derived classes (in the special nested type alias
      13              : /// `creatable_classes`).  This can be problematic when the desired
      14              : /// list of derived classes can vary with use of the base class.
      15              : /// These helpers provide a method to simplify handling these
      16              : /// compile-time registrations.
      17              : ///
      18              : /// Each optional derived class defines a registrar helper and both
      19              : /// the base class and derived classes are templated on the list of
      20              : /// registrars.  The typical structure of these classes is:
      21              : /// \snippet Test_Registration.cpp registrar_structure
      22              : /// A concrete base class type with a specific set of derived classes
      23              : /// is constructed like
      24              : /// \snippet Test_Registration.cpp registrar_use
      25              : ///
      26              : /// It is frequently useful to default the registrar list in a derived
      27              : /// class to the registrar for that class.  This ensures that any
      28              : /// methods in the base class using the registrar list (such as those
      29              : /// using `call_with_dynamic_type()`) work
      30              : /// as expected on an explicitly constructed derived class with the
      31              : /// list omitted.
      32            1 : namespace Registration {
      33              : /// A template for defining a registrar.
      34              : ///
      35              : /// A registrar for a class can be defined by making a type alias to
      36              : /// this struct, filling in the registrant.
      37              : /// \snippet Test_Registration.cpp registrar
      38              : /// In more complex cases (such as with non-type template
      39              : /// parameters) defining a registrar manually may be necessary.
      40              : /// \snippet Test_Registration.cpp custom_registrar
      41              : template <template <typename...> class Registrant, typename... Args>
      42            1 : struct Registrar {
      43              :   // Final registrant type, specialized with input Args... and the
      44              :   // RegistrarList it was extracted from.  This will be a full
      45              :   // specialization of a derived class that uses the registration
      46              :   // framework.
      47              :   template <typename RegistrarList>
      48            0 :   using f = Registrant<Args..., RegistrarList>;
      49              : };
      50              : 
      51              : namespace detail {
      52              : template <typename RegistrarList, typename Registrar>
      53              : struct registrant {
      54              :   using type = typename Registrar::template f<RegistrarList>;
      55              : };
      56              : }  // namespace detail
      57              : 
      58              : /// Transform a list of registrars into the list of associated
      59              : /// registrants.  This is usually used to define the
      60              : /// `creatable_classes` type list.
      61              : template <typename RegistrarList>
      62            1 : using registrants = tmpl::transform<
      63              :     tmpl::remove_duplicates<RegistrarList>,
      64              :     detail::registrant<tmpl::pin<tmpl::remove_duplicates<RegistrarList>>,
      65              :                        tmpl::_1>>;
      66              : }  // namespace Registration