matrix.hxx

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#pragma once
#include <ice/math/constants.hxx>
 
namespace ice::math
{
 
    template<u32 Rows, u32 Cols, typename T>
    struct mat
    {
        using value_type = T;
        static constexpr u32 count_rows = Rows;
        static constexpr u32 count_columns = Cols;
 
        T v[count_columns][count_rows];
    };
 
    template<typename T>
    struct mat<2, 2, T>
    {
        using value_type = T;
        static constexpr u32 count_rows = 3;
        static constexpr u32 count_columns = 3;
 
        T v[count_columns][count_rows];
 
        template<typename U>
        constexpr operator mat<3, 3, U>() noexcept;
    };
 
 
    template<typename Mat>
    constexpr auto identity() noexcept;
 
 
    using mat2x2 = mat<2, 2, f32>;
    using mat2 = mat2x2;
 
    using mat3x3 = mat<3, 3, f32>;
    using mat3 = mat3x3;
 
    using mat4x4 = mat<4, 4, f32>;
    using mat4 = mat4x4;
 
    template<typename T>
    template<typename U>
    constexpr mat<2, 2, T>::operator mat<3, 3, U>() noexcept
    {
        mat<3, 3, U> result;
        result.v[0][0] = v[0][0];
        result.v[0][1] = v[0][1];
        result.v[1][0] = v[1][0];
        result.v[1][1] = v[1][1];
        result.v[2][2] = 1;
        return result;
    }
 
    template<typename Mat>
    constexpr auto identity() noexcept
    {
        static_assert(
            Mat::count_columns == Mat::count_rows,
            "Only even martices can be used with 'core::math::identity()'"
        );
 
        Mat result{ };
        for (u32 col = 0; col < Mat::count_columns; ++col)
        {
            result.v[col][col] = typename Mat::value_type{ 1 };
        }
        return result;
    }
 
 
    static constexpr auto mat2x2_identity = identity<mat<2, 2, f32>>();
    static constexpr auto mat3x3_identity = identity<mat<3, 3, f32>>();
    static constexpr auto mat4x4_identity = identity<mat<4, 4, f32>>();
 
} // namespace ice::math