TinyMatrix.hpp

#ifndef TINY_MATRIX_HPP
#define TINY_MATRIX_HPP

#include <algebra/TinyVector.hpp>
#include <utils/InvalidData.hpp>
#include <utils/NaNHelper.hpp>
#include <utils/PugsAssert.hpp>
#include <utils/PugsMacros.hpp>
#include <utils/Types.hpp>

#include <iostream>

template <size_t M, size_t N = M, typename T = double>
class [[nodiscard]] TinyMatrix
{
 public:
  inline static constexpr size_t Dimension       = M * N;
  inline static constexpr size_t NumberOfRows    = M;
  inline static constexpr size_t NumberOfColumns = N;

  using data_type = T;

 private:
  static_assert((M > 0), "TinyMatrix number of rows must be strictly positive");
  static_assert((N > 0), "TinyMatrix number of columns must be strictly positive");

  T m_values[M * N];

  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[M * N - 1 - sizeof...(args)] = t;
    if constexpr (sizeof...(args) > 0) {
      this->_unpackVariadicInput(std::forward<Args>(args)...);
    }
  }

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

 public:
  [[nodiscard]] PUGS_INLINE constexpr bool
  isSquare() const noexcept
  {
    return M == N;
  }

  [[nodiscard]] PUGS_INLINE constexpr friend TinyMatrix<N, M, T>
  transpose(const TinyMatrix& A)
  {
    TinyMatrix<N, M, T> tA;
    for (size_t i = 0; i < M; ++i) {
      for (size_t j = 0; j < N; ++j) {