Function almostEqual

app/src/DSP.h:1314–1328

 */
template<Concepts::Numeric T>
[[nodiscard]] inline bool almostEqual(T a, T b, T relEps = T(1e-12), T absEps = T(1e-12)) noexcept
{
  if constexpr (std::floating_point<T>) {
    if (!std::isfinite(a) || !std::isfinite(b))
      return a == b;
  }

  const T diff = std::abs(a - b);

  if (diff <= absEps)
    return true;

  const T scale = std::max(std::abs(a), std::abs(b));
  return diff <= relEps * scale;
}

/**
 * @brief Explicit "not equal" companion to almostEqual().