Apply.h

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// SPDX-FileCopyrightText: Copyright (c) OpenGeoSys Community (opengeosys.org)
// SPDX-License-Identifier: BSD-3-Clause
 
#pragma once
 
#include "Get.h"
 
namespace ProcessLib::Graph
{
namespace detail
{
template <typename Function>
struct GetFunctionArgumentTypes
    : GetFunctionArgumentTypes<decltype(&Function::operator())>
{
};
 
// member function
template <typename Result, typename Class, typename... Args>
struct GetFunctionArgumentTypes<Result (Class::*)(Args...)>
{
    using type = boost::mp11::mp_list<Args...>;
};
 
// const member function
template <typename Result, typename Class, typename... Args>
struct GetFunctionArgumentTypes<Result (Class::*)(Args...) const>
{
    using type = boost::mp11::mp_list<Args...>;
};
 
// standalone function
template <typename Result, typename... Args>
struct GetFunctionArgumentTypes<Result (*)(Args...)>
{
    using type = boost::mp11::mp_list<Args...>;
};
 
// plain, i.e., without cvref
template <typename Function>
using GetFunctionArgumentTypesPlain =
    std::type_identity<boost::mp11::mp_transform<
        std::remove_cvref_t,
        typename GetFunctionArgumentTypes<Function>::type>>;
 
template <typename Function>
struct GetFunctionReturnType
    : GetFunctionReturnType<decltype(&Function::operator())>
{
};
 
// member function
template <typename Result, typename Class, typename... Args>
struct GetFunctionReturnType<Result (Class::*)(Args...)>
{
    using type = Result;
};
 
// const member function
template <typename Result, typename Class, typename... Args>
struct GetFunctionReturnType<Result (Class::*)(Args...) const>
{
    using type = Result;
};
 
// standalone function
template <typename Result, typename... Args>
struct GetFunctionReturnType<Result (*)(Args...)>
{
    using type = Result;
};
 
// Invokes the passed function object with arguments taken ("unpacked") from the
// passed tuples ts. The arguments are picked/passed according to their data
// type.
//
// overload for function objects
template <typename Object,
          typename... Tuples,
          typename... MemberFunctionArgumentTypesPlain>
auto unpackAndInvoke(
    boost::mp11::mp_list<MemberFunctionArgumentTypesPlain...> /*unused*/,
    Object&& o,
    Tuples&... ts) ->
    // std::decay_t "decays" lambdas
    typename GetFunctionReturnType<
        decltype(&std::decay_t<Object>::operator())>::type
{
    return o(
        ProcessLib::Graph::get<MemberFunctionArgumentTypesPlain>(ts...)...);
}
 
// member function
template <typename Result,
          typename Object,
          typename... Args,
          typename... Tuples,
          typename... MemberFunctionArgumentTypesPlain>
Result unpackAndInvoke(
    boost::mp11::mp_list<MemberFunctionArgumentTypesPlain...> /*unused*/,
    Result (Object::*m)(Args...),
    Object& o,
    Tuples&... ts)
{
    return (o.*m)(
        ProcessLib::Graph::get<MemberFunctionArgumentTypesPlain>(ts...)...);
}
 
// member function & temporary object
template <typename Result,
          typename Object,
          typename... Args,
          typename... Tuples,
          typename... MemberFunctionArgumentTypesPlain>
Result unpackAndInvoke(
    boost::mp11::mp_list<MemberFunctionArgumentTypesPlain...> /*unused*/,
    Result (Object::*m)(Args...),
    Object&& o,
    Tuples&... ts)
{
    return (o.*m)(
        ProcessLib::Graph::get<MemberFunctionArgumentTypesPlain>(ts...)...);
}
 
// const member function
template <typename Result,
          typename Object,
          typename... Args,
          typename... Tuples,
          typename... MemberFunctionArgumentTypesPlain>
Result unpackAndInvoke(
    boost::mp11::mp_list<MemberFunctionArgumentTypesPlain...> /*unused*/,
    Result (Object::*m)(Args...) const,
    Object const& o,
    Tuples&... ts)
{
    return (o.*m)(
        ProcessLib::Graph::get<MemberFunctionArgumentTypesPlain>(ts...)...);
}
 
// standalone function
template <typename Result,
          typename... Args,
          typename... Tuples,
          typename... FunctionArgumentTypesPlain>
Result unpackAndInvoke(
    boost::mp11::mp_list<FunctionArgumentTypesPlain...> /*unused*/,
    Result (*fct)(Args...),
    Tuples&... ts)
{
    return fct(ProcessLib::Graph::get<FunctionArgumentTypesPlain>(ts...)...);
}
 
template <typename Function, typename... PassedArgsTuples>
struct GetFlattenedTupleOfPassedArgs
    : GetFlattenedTupleOfPassedArgs<decltype(&Function::operator()),
                                    Function,
                                    PassedArgsTuples...>
{
};
 
// member function
template <typename Result,
          typename Class,
          typename... DeclaredArgs,
          typename ClassAgain,
          typename... PassedArgsTuples>
struct GetFlattenedTupleOfPassedArgs<Result (Class::*)(DeclaredArgs...),
                                     // first "argument" is the object to which
                                     // the member function belongs
                                     ClassAgain,
                                     PassedArgsTuples...>
{
    using type = typename detail::GetFlattenedTupleTypes<
        std::remove_cvref_t<PassedArgsTuples>...>::type;
};
 
// const member function
template <typename Result,
          typename Class,
          typename... DeclaredArgs,
          typename... ClassAndPassedArgsTuples>
struct GetFlattenedTupleOfPassedArgs<Result (Class::*)(DeclaredArgs...) const,
                                     ClassAndPassedArgsTuples...>
    // redirect to non-const member function implementation
    : GetFlattenedTupleOfPassedArgs<Result (Class::*)(DeclaredArgs...),
                                    ClassAndPassedArgsTuples...>
{
};
 
// standalone function
template <typename Result, typename... DeclaredArgs, typename... Tuples>
struct GetFlattenedTupleOfPassedArgs<Result (*)(DeclaredArgs...), Tuples...>
{
    using type = typename detail::GetFlattenedTupleTypes<
        std::remove_cvref_t<Tuples>...>::type;
};

template <typename Function, typename... Args>
auto applyImpl(Function&& f, Args&&... args) ->
    typename detail::GetFunctionReturnType<std::decay_t<Function>>::type
{
    using namespace boost::mp11;
 
    using FunctionPlain = std::decay_t<Function>;
    using FlattenedTuple =
        typename GetFlattenedTupleOfPassedArgs<FunctionPlain, Args...>::type;
    using FlattenedTupleOfPlainTypes =
        mp_transform<std::remove_cvref_t, FlattenedTuple>;
 
    static_assert(
        mp_is_set_v<FlattenedTupleOfPlainTypes>,
        "The types of all elements of all passed tuples must be unique.");
 
    using FunctionArgumentTypesPlain =
        typename detail::GetFunctionArgumentTypesPlain<FunctionPlain>::type;
 
    static_assert(
        mp_is_set_v<FunctionArgumentTypesPlain>,
        "The argument types of the function to be called must be unique.");
 
    return unpackAndInvoke(FunctionArgumentTypesPlain{},
                           std::forward<Function>(f),
                           std::forward<Args>(args)...);
}
}  // namespace detail

template <typename Function, typename... Tuples>
auto apply(Function& f, Tuples&... ts) ->
    typename detail::GetFunctionReturnType<std::decay_t<Function>>::type
{
    static_assert(boost::mp11::mp_similar<std::tuple<>,
                                          std::remove_cv_t<Tuples>...>::value,
                  "In the argument ts... there must be only std::tuple's.");
 
    return detail::applyImpl(f, ts...);
}

template <typename Function, typename... Tuples>
auto eval(Function& f, Tuples&... ts) ->
    typename detail::GetFunctionReturnType<decltype(&Function::eval)>::type
{
    static_assert(boost::mp11::mp_similar<std::tuple<>,
                                          std::remove_cv_t<Tuples>...>::value,
                  "In the argument ts... there must be only std::tuple's.");
 
    return detail::applyImpl(&Function::eval, f, ts...);
}

template <typename Functions, typename... Tuples>
void evalAllInOrder(Functions& fs, Tuples&... ts)
{
    boost::mp11::tuple_for_each(fs, [&ts...](auto& f) { eval(f, ts...); });
}
}  // namespace ProcessLib::Graph