ame_Math.hpp

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#pragma once
 
#if __has_include("arm_math.h")
    #ifdef __cplusplus
extern "C"
{
    #endif
 
    #include "arm_math.h"
 
    #ifdef __cplusplus
}
    #endif
 
    #ifndef USE_CMSIS_DSP
        #define USE_CMSIS_DSP
        #pragma message("CMSIS-DSP is used.")
    #endif
#else
    #include <cmath>
    #pragma message("CMSIS-DSP is NOT used. cmath is used instead.")
#endif
 
#include <concepts>
#include <limits>
#include <numbers>
 
namespace ame
{
template <std::floating_point FloatType>
inline constexpr FloatType pi = std::numbers::pi_v<FloatType>; 
 
template <std::floating_point FloatType>
inline constexpr FloatType twoPi = 2.0 * std::numbers::pi_v<FloatType>; 
 
template <std::floating_point FloatType>
inline constexpr FloatType halfPi = std::numbers::pi_v<FloatType> / 2.0; 
 
template <std::floating_point FloatType>
inline constexpr FloatType sqrt2 = std::numbers::sqrt2_v<FloatType>; 
 
template <std::floating_point FloatType>
inline constexpr FloatType invSqrt2 = 1.0 / std::numbers::sqrt2_v<FloatType>; 
 
constexpr inline float sin (float x)
{
    if (std::is_constant_evaluated())
    {
        //コンパイル時
        auto fabs = [] (float v) -> float
        { return (v < 0.0f) ? (-v) : (v); };
 
        float xSq = -(x * x);
        float series = x;
        float tmp = x;
        float fact = 2.0f;
 
        //マクローリン級数の計算
        do
        {
            tmp *= xSq / (fact * (fact + 1.0f));
            series += tmp;
            fact += 2.0f;
        } while (fabs (tmp) >= std::numeric_limits<float>::epsilon());
 
        return series;
    }
    else
    {
        //実行時
#ifdef USE_CMSIS_DSP
        return arm_sin_f32 (x);
#else
        return std::sin (x);
#endif
    }
}
 
constexpr inline double sin (double x)
{
    if (std::is_constant_evaluated())
    {
        //コンパイル時
        auto fabs = [] (double v) -> double
        { return (v < 0.0) ? (-v) : (v); };
 
        double xSq = -(x * x);
        double series = x;
        double tmp = x;
        double fact = 2.0;
 
        //マクローリン級数の計算
        do
        {
            tmp *= xSq / (fact * (fact + 1.0));
            series += tmp;
            fact += 2.0;
        } while (fabs (tmp) >= std::numeric_limits<double>::epsilon());
 
        return series;
    }
    else
    {
        //実行時
        return std::sin (x);
    }
}
 
constexpr inline float cos (float x)
{
    if (std::is_constant_evaluated())
    {
        //コンパイル時
        auto fabs = [] (float v) -> float
        { return (v < float (0.0)) ? (-v) : (v); };
        float xSq = -(x * x);
        float series = float (1.0);
        float tmp = float (1.0);
        float fact = float (1.0);
 
        //マクローリン級数の計算
        do
        {
            tmp *= xSq / (fact * (fact + float (1.0)));
            series += tmp;
            fact += float (2.0);
        } while (fabs (tmp) >= std::numeric_limits<float>::epsilon());
 
        return series;
    }
    else
    {
//実行時
#ifdef USE_CMSIS_DSP
        return arm_cos_f32 (x);
#else
        return std::cos (x);
#endif
    }
}
 
constexpr inline double cos (double x)
{
    if (std::is_constant_evaluated())
    {
        //コンパイル時
        auto fabs = [] (double v) -> double
        { return (v < 0.0) ? (-v) : (v); };
        double xSq = -(x * x);
        double series = 1.0;
        double tmp = 1.0;
        double fact = 1.0;
 
        //マクローリン級数の計算
        do
        {
            tmp *= xSq / (fact * (fact + 1.0));
            series += tmp;
            fact += 2.0;
        } while (fabs (tmp) >= std::numeric_limits<double>::epsilon());
 
        return series;
    }
    else
    {
        //実行時
        return std::cos (x); //libstdc++だとstd:cosf()は未定義なので、std::cos()にしている
    }
}
} // namespace ame