cpp-mathematic-limit/include/math/double_equals.h

//
//  double_equals.h
//  limit
//
//  Created by Sam Jaffe on 12/9/23.
//

#pragma once

#include <algorithm>

namespace math {
inline bool approx_equal(double lhs, double rhs, double eps) {
  double const a = std::abs(lhs);
  double const b = std::abs(rhs);
  return std::abs(lhs - rhs) <= (std::max(a, b) * eps);
}

inline bool essentially_equal(double lhs, double rhs, double eps) {
  double const a = std::abs(lhs);
  double const b = std::abs(rhs);
  return std::abs(lhs - rhs) <= (std::min(a, b) * eps);
}

inline bool definitely_greater(double lhs, double rhs, double eps) {
  double const a = std::abs(lhs);
  double const b = std::abs(rhs);
  return (lhs - rhs) > (std::max(a, b) * eps);
}

inline bool definitely_less(double lhs, double rhs, double eps) {
  double const a = std::abs(lhs);
  double const b = std::abs(rhs);
  return (rhs - lhs) > (std::max(a, b) * eps);
}
}