our_dick/include/detail/matrix.hpp

#ifndef REXY_DETAIL_MATRIX_HPP
#define REXY_DETAIL_MATRIX_HPP

#include <cstdlib> //size_t
#include <utility> //integer_sequence

namespace math::detail{

	template<size_t SW, size_t W = SW, size_t H = SW-1, size_t... Args>
	struct gen_id_tup{
		using tup = typename gen_id_tup<SW, W-1, H, Args..., 0>::tup;
	};
	template<size_t SW, size_t H, size_t... Args>
	struct gen_id_tup<SW,SW,H,Args...>{
		using tup = typename gen_id_tup<SW, SW-1, H, Args..., 1>::tup;
	};
	template<size_t SW, size_t H, size_t... Args>
	struct gen_id_tup<SW,0,H,Args...>{
		using tup = typename gen_id_tup<SW, SW, H-1, Args..., 0>::tup;
	};
	template<size_t SW, size_t... Args>
	struct gen_id_tup<SW,SW,0,Args...>{
		using tup = std::integer_sequence<size_t,Args...,1>;
	};


	template<size_t N, size_t... Args>
	struct gen_zero_tup{
		using tup = typename gen_zero_tup<N-1,Args...,0>::tup;
	};
	template<size_t... Args>
	struct gen_zero_tup<0,Args...>{
		using tup = std::integer_sequence<size_t,Args...>;
	};

	template<size_t W>
	struct id_initialization_matrix{
		using tuple = typename gen_id_tup<W>::tup;
	};


	template<size_t W, size_t H>
	struct default_initialization_matrix{
		using tuple = typename gen_zero_tup<W>::tup;
	};
	template<size_t W>
	struct default_initialization_matrix<W,W>{
		using tuple = typename id_initialization_matrix<W>::tuple;
	};

	template<class T, size_t R>
	class mat_ref_obj
	{
	public:
		using size_type = size_t;

	protected:
		T* m_data = nullptr;
	public:
		constexpr mat_ref_obj(T* d, size_type i):
			m_data(d+i){}

		constexpr T& operator[](size_type i){
			return m_data[i*R];
		}
		constexpr const T& operator[](size_type i)const{
			return m_data[i*R];
		}
	};

	template<class T, size_t W, size_t H>
	class matrix_base
	{
		static_assert(W > 0, "Cannot have 0 columns matrix");
		static_assert(H > 0, "Cannot have 0 rows matrix");
	public:
		using value_type = T;
		using size_type = size_t;
		using pointer = value_type*;
		using const_pointer = const value_type*;
		using reference = value_type&;
		using const_reference = const value_type&;

		static constexpr size_type Columns = W;
		static constexpr size_type Rows = H;

	protected:
		value_type m_data[W*H];

	protected:
		template<size_type... Ss>
		constexpr matrix_base(std::integer_sequence<size_type,Ss...>):
			m_data{Ss...}{}

	public:
		//Default construct as identity when square, zero otherwise
		constexpr matrix_base(void):
			matrix_base(typename detail::default_initialization_matrix<Columns,Rows>::tuple{}){}

		//Range initializing constructors
		constexpr explicit matrix_base(zero_initialize_t):
			m_data{}{}
		constexpr explicit matrix_base(no_initialize_t){}
		template<class U = void>
		constexpr explicit matrix_base(id_initialize_t):
			matrix_base()
		{
			static_assert(Columns == Rows, "Identity initialization only supported on square matrices");
		}

		//Value initializing constructors
		constexpr explicit matrix_base(value_type v){
			for(size_type i = 0;i < Columns*Rows;++i)
				m_data[i] = v;
		}
		template<class... Args>
		constexpr explicit matrix_base(Args&&... args):
			m_data{std::forward<Args>(args)...}{}

		//Copying constructors
		constexpr matrix_base(const matrix_base&) = default;
		constexpr matrix_base(matrix_base&&) = default;
		template<class U>
		constexpr matrix_base(const matrix_base<U,Columns,Rows>& m){
			using mat = decltype(m);
			for(typename mat::size_type i = 0;i < mat::Columns*mat::Rows;++i)
				m_data[i] = m.get(i);
		}
		~matrix_base(void) = default;

		//Assignement
		template<class U>
		constexpr matrix_base& operator=(const matrix_base<U,Columns,Rows>& m){
			using mat = decltype(m);
			for(typename mat::size_type i = 0;i < mat::Columns*mat::Rows;++i)
				m_data[i] = m.get(i);
			return *this;
		}
		constexpr matrix_base& operator=(const matrix_base&) = default;
		constexpr matrix_base& operator=(matrix_base&&) = default;


		//Getters/Setters
		constexpr auto operator[](size_type x){
			return detail::mat_ref_obj<value_type,Rows>{m_data, x};
		}
		constexpr auto operator[](size_type x)const{
			return detail::mat_ref_obj<const value_type,Rows>{m_data, x};
		}
		constexpr reference get(size_type x, size_type y){
			return m_data[x+(y*Rows)];
		}
		constexpr const_reference get(size_type x, size_type y)const{
			return m_data[x+(y*Rows)];
		}
		constexpr reference get(size_type i){
			return m_data[i];
		}
		constexpr const_reference get(size_type i)const{
			return m_data[i];
		}

		constexpr size_type columns(void)const{
			return Columns;
		}
		constexpr size_type rows(void)const{
			return Rows;
		}
		constexpr size_type size(void)const{
			return Columns*Rows;
		}

		constexpr pointer raw(void){
			return m_data;
		}
		constexpr const_pointer raw(void)const{
			return m_data;
		}
		constexpr operator pointer(void){
			return m_data;
		}
		constexpr operator const_pointer(void)const{
			return m_data;
		}

	};

}

#endif