interpolation_set.h

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// SPDX-License-Identifier: GPL-2.0-only
//
// Copyright (c) 2007-2008 Marc Brooker and Michael Inggs
// Copyright (c) 2008-present FERS Contributors (see AUTHORS.md).
//
// See the GNU GPLv2 LICENSE file in the FERS project root for more information.
 
/**
 * @file interpolation_set.h
 * @brief Header file for the interpolation of sets of data.
 */
 
#pragma once
 
#include <map>
#include <memory>
#include <optional>
 
#include "core/config.h"
 
namespace interp
{
    /// Concept constraining interpolation inputs to arithmetic values.
    template <typename T>
    concept RealConcept = std::is_arithmetic_v<T>;
 
    /**
     * @class InterpSetData
     * @brief Class for managing a set of data and performing interpolation.
     */
    class InterpSetData
    {
    public:
        /**
         * @brief Inserts a sample point into the interpolation set.
         *
         * @tparam T The type of the x and y coordinates (must be an arithmetic type).
         * @param x The x-coordinate of the sample point.
         * @param y The y-coordinate of the sample point.
         */
        template <RealConcept T>
        void insertSample(T x, T y) noexcept
        {
            _data.insert({x, y});
        }
 
        /**
         * @brief Retrieves the interpolated value at a given point.
         *
         * @tparam T The type of the x-coordinate (must be an arithmetic type).
         * @param x The x-coordinate at which to interpolate the value.
         * @return The interpolated value at the given x-coordinate, or std::nullopt if the dataset is empty.
         */
        template <RealConcept T>
        [[nodiscard]] std::optional<T> value(T x) const noexcept;
 
        /**
         * @brief Retrieves the maximum absolute value in the interpolation set.
         *
         * @return The maximum absolute y-value in the dataset, or 0.0 if the set is empty.
         */
        [[nodiscard]] double max() const noexcept;
 
        /**
         * @brief Divides all y-values in the dataset by a given number.
         *
         * @tparam T The type of the divisor (must be an arithmetic type).
         * @param a The divisor to divide all y-values by.
         * @throws std::invalid_argument Thrown if the divisor is zero.
         */
        template <RealConcept T>
        void divide(T a);
 
    private:
        std::map<RealType, RealType> _data; ///< The set of data points
    };
 
    /**
     * @class InterpSet
     * @brief Wrapper class for managing interpolation sets using smart pointers.
     */
    class InterpSet
    {
    public:
        /**
         * @brief Constructs a new InterpSet object.
         */
        constexpr InterpSet() : _data(std::make_unique<InterpSetData>()) {}
 
        constexpr ~InterpSet() = default;
 
        InterpSet(const InterpSet&) = delete;
        InterpSet& operator=(const InterpSet&) = delete;
        InterpSet(InterpSet&&) = delete;
        InterpSet& operator=(InterpSet&&) = delete;
 
        /**
         * @brief Inserts a sample point into the interpolation set.
         *
         * @tparam T The type of the x and y coordinates (must be an arithmetic type).
         * @param x The x-coordinate of the sample point.
         * @param y The y-coordinate of the sample point.
         */
        template <RealConcept T>
        void insertSample(T x, T y) const noexcept
        {
            _data->insertSample(x, y);
        }
 
        /**
         * @brief Retrieves the interpolated value at a given point.
         *
         * @tparam T The type of the x-coordinate (must be an arithmetic type).
         * @param x The x-coordinate at which to interpolate the value.
         * @return The interpolated value at the given x-coordinate, or std::nullopt if the dataset is empty.
         */
        template <RealConcept T>
        [[nodiscard]] std::optional<T> getValueAt(T x) const noexcept
        {
            return _data->value(x);
        }
 
        /**
         * @brief Retrieves the maximum absolute value in the interpolation set.
         *
         * @return The maximum absolute y-value in the dataset, or 0.0 if the set is empty.
         */
        [[nodiscard]] double getMax() const noexcept { return _data->max(); }
 
        /**
         * @brief Divides all y-values in the dataset by a given number.
         *
         * @tparam T The type of the divisor (must be an arithmetic type).
         * @param a The divisor to divide all y-values by.
         * @throws std::invalid_argument Thrown if the divisor is zero.
         */
        template <RealConcept T>
        void divide(T a) const
        {
            _data->divide(a);
        }
 
    private:
        std::unique_ptr<InterpSetData> _data; ///< The internal InterpSetData object
    };
}