TinyMatrix.hpp

#ifndef TINY_MATRIX_HPP
#define TINY_MATRIX_HPP

#include <utils/PugsAssert.hpp>
#include <utils/PugsMacros.hpp>

#include <utils/Types.hpp>

#include <algebra/TinyVector.hpp>

#include <iostream>

template <size_t N, typename T = double>
class [[nodiscard]] TinyMatrix
{
 public:
  using data_type = T;

 private:
  T m_values[N * N];
  static_assert((N > 0), "TinyMatrix size must be strictly positive");

  PUGS_FORCEINLINE
  constexpr size_t _index(size_t i, size_t j) const noexcept   // LCOV_EXCL_LINE (due to forced inline)
  {
    return i * N + j;
  }

  template <typename... Args>
  PUGS_FORCEINLINE constexpr void _unpackVariadicInput(const T& t, Args&&... args) noexcept
  {
    m_values[N * N - 1 - sizeof...(args)] = t;
    if constexpr (sizeof...(args) > 0) {
      this->_unpackVariadicInput(std::forward<Args>(args)...);
    }
  }

 public:
  PUGS_INLINE
  constexpr size_t dimension() const
  {
    return N * N;
  }

  PUGS_INLINE
  constexpr size_t nbRows() const
  {
    return N;
  }

  PUGS_INLINE
  constexpr size_t nbColumns() const
  {
    return N;
  }

  PUGS_INLINE
  constexpr TinyMatrix operator-() const
  {
    TinyMatrix opposite;
    for (size_t i = 0; i < N * N; ++i) {
      opposite.m_values[i] = -m_values[i];
    }
    return opposite;
  }

  PUGS_INLINE
  constexpr friend TinyMatrix operator*(const T& t, const TinyMatrix& A)
  {
    TinyMatrix B = A;