mlNumericHelpers.h

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/*************************************************************************************
**
** Copyright 2020, MeVis Medical Solutions AG
**
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**************************************************************************************/
 
#ifndef ML_NUMERIC_HELPERS_H
#define ML_NUMERIC_HELPERS_H
 
#include <algorithm>
#include <limits>
#include <cmath>
 
namespace ml
{
  /*
   * Convert a character sequence to a corresponding integral value
   */
  template <typename T, std::size_t N> constexpr T convertTo(const char (&t)[N])
  {
    static_assert(N - 1 == sizeof(T), "Illegal character sequence for type T");
    T result{};
    for (auto index = 0u; index < N - 1; ++index)
      result = (result << 8) + t[index];
    return result;
  }
 
 
  /*
   * Helper function that checks if two floating point values are equal in within a certain epsilon
   * \param x The first value
   * \param y The second value
   * \param absoluteEpsilon If both values are close to zero, this epsilon is taken
   * \param relativeEpsilon If both values are not close to zero this relative epsilon is used
   */
  template <typename T>
  constexpr bool almostEqualRelativeAndAbs(T x, T y, T absoluteEpsilon, T relativeEpsilon = std::numeric_limits<T>::epsilon())
  {
    static_assert(std::is_floating_point_v<T>, "Deduced type T should be a floating point type");
 
    // When the values are close to zero, then the relative epsilon does not work.
    auto diff = std::fabs(x - y);
    if (diff <= absoluteEpsilon)
      return true;
 
    x = std::fabs(x);
    y = std::fabs(y);
    T largest = std::max(x, y);
 
    if (diff <= largest * relativeEpsilon)
      return true;
 
    return false;
  }
 
 
 
}
 
#endif // MEVISLAB_MLNUMERICHELPERS_H