vtkMathUtilities.h

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// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-License-Identifier: BSD-3-Clause
 
#ifndef vtkMathUtilities_h
#define vtkMathUtilities_h
 
#include "vtkABINamespace.h"
 
#include <cmath>
#include <limits>
#include <tuple>
#include <type_traits>
 
namespace vtkMathUtilities
{
VTK_ABI_NAMESPACE_BEGIN
 
template <class A>
bool FuzzyCompare(A a, A b, A epsilon = std::numeric_limits<A>::epsilon())
{
  return fabs(a - b) < epsilon;
}
 
template <class A>
A SafeDivision(A a, A b)
{
  // Avoid overflow
  if ((b < static_cast<A>(1)) && (a > b * std::numeric_limits<A>::max()))
  {
    return std::numeric_limits<A>::max();
  }
 
  // Avoid underflow
  if ((a == static_cast<A>(0)) ||
    ((b > static_cast<A>(1)) && (a < b * std::numeric_limits<A>::min())))
  {
    return static_cast<A>(0);
  }
 
  // safe to do the division
  return (a / b);
}
 
template <class A>
bool NearlyEqual(A a, A b, A tol = std::numeric_limits<A>::epsilon())
{
  A absdiff = fabs(a - b);
  A d1 = vtkMathUtilities::SafeDivision<A>(absdiff, fabs(a));
  A d2 = vtkMathUtilities::SafeDivision<A>(absdiff, fabs(b));
 
  return ((d1 <= tol) || (d2 <= tol));
}
 
template <class A>
void UpdateRangeImpl(A& min0, A& max0, const A& value)
{
  // need temporaries to handle const/non const ref mismatch
  if (value < min0)
  {
    min0 = value;
    max0 = max0 < value ? value : max0;
  }
  else if (value > max0)
  {
    min0 = min0 > value ? value : min0;
    max0 = value;
  }
}
 
template <class A> // Non floating point implementation not caring about NaN
void UpdateRange(A& min0, A& max0, const A& value,
  typename std::enable_if<!std::is_floating_point<A>::value>::type* = nullptr)
{
  UpdateRangeImpl<A>(min0, max0, value);
}
 
template <class A> // Floating point implementation specifically considering NaN
void UpdateRange(A& min0, A& max0, const A& value,
  typename std::enable_if<std::is_floating_point<A>::value>::type* = nullptr)
{
  if (!std::isnan(value))
  {
    UpdateRangeImpl<A>(min0, max0, value);
  }
}
 
VTK_ABI_NAMESPACE_END
} // End vtkMathUtilities namespace.
 
#endif // vtkMathUtilities_h
// VTK-HeaderTest-Exclude: vtkMathUtilities.h