vtkMathUtilities.h

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/*=========================================================================
 
  Program:   Visualization Toolkit
  Module:    vtkMathUtilities.h
 
  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
 
     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.
 
=========================================================================*/
 
#ifndef vtkMathUtilities_h
#define vtkMathUtilities_h
 
#include <cmath>
#include <limits>
 
namespace vtkMathUtilities
{
 
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));
}
 
} // End vtkMathUtilities namespace.
 
#endif // vtkMathUtilities_h
// VTK-HeaderTest-Exclude: vtkMathUtilities.h