stablecomparison.h

/**********************************************************************
  StableComp - Functions for comparing numbers with a tolerance

  Copyright (C) 2011 by David C. Lonie

  This file is part of the Avogadro molecular editor project.
  For more information, see <http://avogadro.openmolecules.net/>

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation version 2 of the License.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
 ***********************************************************************/

#ifndef STABLECOMPARISON
#define STABLECOMPARISON

#include <cmath>

#define STABLE_COMP_TOL 1e-5

namespace StableComp {

  inline bool lt(double v1,
                 double v2,
                 double prec =
                 STABLE_COMP_TOL)
  {
    return ( v1 < (v2 - prec) );
  }

  inline bool gt(double v1,
                 double v2,
                 double prec =
                 STABLE_COMP_TOL)
  {
    return ( v2 < (v1 - prec) );
  }

  inline bool eq(double v1,
                 double v2,
                 double prec =
                 STABLE_COMP_TOL)
  {
    return (!(lt(v1,v2,prec) ||
              gt(v1,v2,prec) ) );
  }

  inline bool neq(double v1,
                  double v2,
                  double prec =
                  STABLE_COMP_TOL)
  {
    return (!(eq(v1,v2,prec)));
  }

  inline bool leq(double v1,
                  double v2,
                  double prec =
                  STABLE_COMP_TOL)
  {
    return (!gt(v1, v2, prec));
  }

  inline bool geq(double v1,
                  double v2,
                  double prec =
                  STABLE_COMP_TOL)
  {
    return (!lt(v1, v2, prec));
  }

  inline double sign(double v)
  {
    // consider 0 to be positive
    if (v >= 0) return 1.0;
    else return -1.0;
  }

  inline double round(double v,
                      int dec)
  {
    const double shift = pow(10.0,dec);
    const double shifted = v * shift;
    return floor(shifted+0.5) / shift;
  }
}

#endif