cpp-game-engine/math/include/game/math/compare.hpp

#pragma once

#include <algorithm>
#include <cmath>

namespace math {
  template <typename T>
  bool between(T val, T min, T max) {
    return val >= min && val < max;
  }

  template <typename T>
  bool approx_equal(T lhs, T rhs, T eps) {
    T const a = std::abs(lhs);
    T const b = std::abs(rhs);
    return std::abs(lhs - rhs) <= (std::max(a, b) * eps);
  }
  
  template <typename T>
  bool essentially_equal(T lhs, T rhs, T eps) {
    T const a = std::abs(lhs);
    T const b = std::abs(rhs);
    return std::abs(lhs - rhs) <= (std::min(a, b) * eps);
  }
  
  template <typename T>
  bool definitely_greater(T lhs, T rhs, T eps) {
    T const a = std::abs(lhs);
    T const b = std::abs(rhs);
    return (lhs - rhs) > (std::max(a, b) * eps);
  }
  
  template <typename T>
  bool definitely_less(T lhs, T rhs, T eps) {
    T const a = std::abs(lhs);
    T const b = std::abs(rhs);
    return (rhs - lhs) > (std::max(a, b) * eps);
  }
}