utility/numutil.h

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/*******************************************************************
 * File:            numutil.h
 * Description:      
 * Author:          Subhasis Ray
 * E-mail:          ray dot subhasis at gmail dot com
 * Created:         2007-11-02 11:47:21
 ********************************************************************/
/**********************************************************************
** This program is part of 'MOOSE', the
** Messaging Object Oriented Simulation Environment,
** also known as GENESIS 3 base code.
**           copyright (C) 2003-2005 Upinder S. Bhalla. and NCBS
** It is made available under the terms of the
** GNU General Public License version 2
** See the file COPYING.LIB for the full notice.
**********************************************************************/

#ifndef _NUMUTIL_H
#define _NUMUTIL_H

#include <cmath>
#include <cfloat>
#include <limits>

const int WORD_LENGTH = 32; // number of bits in a word - check for portability
const double LN2 = 0.69314718055994528622676;
const unsigned long LN2BYTES = 0xB1721814;
const double NATURAL_E = 2.718281828459045;

//extern const double getMachineEpsilon();
//extern const double EPSILON;
#ifndef M_PI
#define M_PI 3.14159265358979323846             
#endif

#ifndef M_E
#define M_E  2.7182818284590452353
#endif


template<class T>
bool isNaN( T value )
{
    return value != value;
}

template< typename T >
bool isInfinity( T value )
{
    return value == std::numeric_limits< T >::infinity();
}

template< class T >
bool isClose( T a, T b, T tolerance )
{
    T epsilon = std::numeric_limits< T >::epsilon();
    
    if ( a == b )
        return true;
    
    if ( a == 0 || b == 0 )
        return ( fabs( a - b ) < tolerance * epsilon );
    
    return (
        fabs( ( a - b ) / a ) < tolerance * epsilon
        &&
        fabs( ( a - b ) / b ) < tolerance * epsilon
    );
}

bool almostEqual(float x, float y, float epsilon = FLT_EPSILON);
bool almostEqual(double x, double y, double epsilon = DBL_EPSILON);
bool almostEqual(long double x, long double y, long double epsilon = LDBL_EPSILON);

// round, isinf and isnan are not defined in VC++ or Borland C++
#if defined(__TURBOC__) || defined(__BORLANDC__) || defined(_MSC_VER)
#define isinf(param) !_finite(param)
#define isnan(param) _isnan(param)
#define round(param) floor(param+0.5)
#endif
#endif

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