#include <array>

template <typename T, int R, int C>
struct mat;

template <typename T>
struct mat<4, 8, T>
{
  typedef std::array<T, 8> row_type;
  typedef std::array<T, 8> row_type;

  std::array<row_type, 4> value;

  inline constexpr mat
  (
    T const& a00, T const& a01, T const& a02, T const& a03, T const& a04, T const& a05, T const& a06, T const& a07,
    T const& a10, T const& a11, T const& a12, T const& a13, T const& a14, T const& a15, T const& a16, T const& a17,
    T const& a20, T const& a21, T const& a22, T const& a23, T const& a24, T const& a25, T const& a26, T const& a27,
    T const& a30, T const& a31, T const& a32, T const& a33, T const& a34, T const& a35, T const& a36, T const& a37,
  )
    : value{std::move(row_type(a00, a01, a02, a03, a04, a05, a06, a07)),
            std::move(row_type(a10, a11, a12, a13, a14, a15, a16, a17)),
            std::move(row_type(a20, a21, a22, a23, a24, a25, a26, a27)),
            std::move(row_type(a30, a31, a32, a33, a34, a35, a36, a37))}
  {}

  operator[](int i) const
  {
    switch (i) {
    default: [[fallthrough]];
    case 0: return value[0];
    case 1: return value[1];
    case 2: return value[2];
    case 3: return value[3];
    }
  }

  operator*(
}