formula_base.h

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/*
 * Copyright 2021 MusicScience37 (Kenta Kabashima)
 *
 * 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.
 */
#pragma once
 
#include "num_collect/ode/concepts/problem.h"
 
namespace num_collect::ode {
 
template <typename Derived, concepts::problem Problem>
class formula_base {
public:
    using problem_type = Problem;
 
    using variable_type = typename problem_type::variable_type;
 
    using scalar_type = typename problem_type::scalar_type;
 
    explicit formula_base(const problem_type& problem = problem_type())
        : problem_(problem) {}
 
    void step(scalar_type time, scalar_type step_size,
        const variable_type& current, variable_type& estimate) {
        derived().step(time, step_size, current, estimate);
    }
 
    [[nodiscard]] auto problem() -> problem_type& { return problem_; }
 
    [[nodiscard]] auto problem() const -> const problem_type& {
        return problem_;
    }
 
protected:
    [[nodiscard]] auto derived() noexcept -> Derived& {
        return *static_cast<Derived*>(this);
    }
 
    [[nodiscard]] auto derived() const noexcept -> const Derived& {
        return *static_cast<const Derived*>(this);
    }
 
    template <typename T>
    static constexpr auto coeff(T val) -> scalar_type {
        return static_cast<scalar_type>(val);
    }
 
    template <typename T1, typename T2>
    static constexpr auto coeff(T1 num, T2 den) -> scalar_type {
        return static_cast<scalar_type>(num) / static_cast<scalar_type>(den);
    }
 
private:
    problem_type problem_;
};
 
}  // namespace num_collect::ode