float_comparisons.hpp

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// Copyright 2020 Mapless AI, Inc.
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#ifndef HELPER_FUNCTIONS__FLOAT_COMPARISONS_HPP_
#define HELPER_FUNCTIONS__FLOAT_COMPARISONS_HPP_
 
#include <algorithm>
#include <cmath>
#include <limits>
 
namespace autoware
{
namespace common
{
namespace helper_functions
{
namespace comparisons
{
 
template<typename T>
bool abs_eq(const T & a, const T & b, const T & eps)
{
  static_assert(
    std::is_floating_point<T>::value,
    "Float comparisons only support floating point types.");
 
  return std::abs(a - b) <= eps;
}
 
template<typename T>
bool abs_lt(const T & a, const T & b, const T & eps)
{
  return !abs_eq(a, b, eps) && (a < b);
}
 
template<typename T>
bool abs_lte(const T & a, const T & b, const T & eps)
{
  return abs_eq(a, b, eps) || (a < b);
}
 
template<typename T>
bool abs_gte(const T & a, const T & b, const T & eps)
{
  return !abs_lt(a, b, eps);
}
 
template<typename T>
bool abs_gt(const T & a, const T & b, const T & eps)
{
  return !abs_lte(a, b, eps);
}
 
template<typename T>
bool abs_eq_zero(const T & a, const T & eps)
{
  return abs_eq(a, static_cast<T>(0), eps);
}
 
template<typename T>
bool rel_eq(const T & a, const T & b, const T & rel_eps)
{
  static_assert(
    std::is_floating_point<T>::value,
    "Float comparisons only support floating point types.");
 
  const auto delta = std::abs(a - b);
  const auto larger = std::max(std::abs(a), std::abs(b));
  const auto max_rel_delta = (larger * rel_eps);
  return delta <= max_rel_delta;
}
 
// TODO(jeff): As needed, add relative variants of <, <=, >, >=
 
template<typename T>
bool approx_eq(const T & a, const T & b, const T & abs_eps, const T & rel_eps)
{
  const auto are_absolute_eq = abs_eq(a, b, abs_eps);
  const auto are_relative_eq = rel_eq(a, b, rel_eps);
  return are_absolute_eq || are_relative_eq;
}
 
}  // namespace comparisons
}  // namespace helper_functions
}  // namespace common
}  // namespace autoware
 
#endif  // HELPER_FUNCTIONS__FLOAT_COMPARISONS_HPP_