Poisson.cpp

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/* 
Copyright (C) 1988 Free Software Foundation
    written by Dirk Grunwald (grunwald@cs.uiuc.edu)
 
This file is part of the GNU C++ Library.  This library is free
software; you can redistribute it and/or modify it under the terms of
the GNU Library General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your
option) any later version.  This library 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 Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the Free Software
Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifdef __GNUG__
#pragma implementation
#endif
#include "Random.h"
#include "Poisson.h"
 
double Poisson::operator()()
{
    double bound = exp(-1.0 * pMean);
    int count = 0;
 
    for (double product = 1.0;
     product >= bound;
     product *= pGenerator -> asDouble()) {
         count++;
     }
    return(count - 1);
}