required-method.hpp

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#pragma once
 
#include <alpaqa/util/type-erasure.hpp>
#include <functional> // std::invoke
 
#define ALPAQA_TE_REQUIRED_METHOD(vtable, type, member)                        \
    do {                                                                       \
        static_assert(                                                         \
            requires { &type::member; },                                       \
            "Missing required method '" #type "::" #member "'");               \
        (vtable).member = util::type_erased_wrapped<type, &type::member>();    \
    } while (0)
#define ALPAQA_TE_OPTIONAL_METHOD(vtable, type, member, instance)              \
    do {                                                                       \
        if constexpr (requires { &type::member; }) {                           \
            using vtable_t     = std::remove_cvref_t<decltype(vtable)>;        \
            auto assign_vtable = [&] {                                         \
                (vtable).member =                                              \
                    util::type_erased_wrapped<type, &type::member,             \
                                              const vtable_t &>();             \
            };                                                                 \
            if constexpr (requires { &type::provides_##member; }) {            \
                if (std::invoke(&type::provides_##member, instance))           \
                    assign_vtable();                                           \
            } else {                                                           \
                assign_vtable();                                               \
            }                                                                  \
        }                                                                      \
    } while (0)