69 lines
1.8 KiB
C++
69 lines
1.8 KiB
C++
// This may look like C code, but it is really -*- C++ -*-
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/*
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Copyright (C) 1988 Free Software Foundation
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written by Dirk Grunwald (grunwald@cs.uiuc.edu)
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This file is part of the GNU C++ Library. This library is free
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software; you can redistribute it and/or modify it under the terms of
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the GNU Library General Public License as published by the Free
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Software Foundation; either version 2 of the License, or (at your
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option) any later version. This library is distributed in the hope
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that it will be useful, but WITHOUT ANY WARRANTY; without even the
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implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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PURPOSE. See the GNU Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with this library; if not, write to the Free Software
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Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#ifndef _Erlang_h
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#ifdef __GNUG__
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#pragma interface
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#endif
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#define _Erlang_h 1
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#include <Random.h>
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class Erlang: public Random {
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protected:
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double pMean;
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double pVariance;
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int k;
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double a;
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void setState();
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public:
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Erlang(double mean, double variance, RNG *gen);
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double mean();
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double mean(double x);
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double variance();
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double variance(double x);
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virtual double operator()();
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};
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inline void Erlang::setState() {
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k = int( (pMean * pMean ) / pVariance + 0.5 );
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k = (k > 0) ? k : 1;
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a = k / pMean;
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}
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inline Erlang::Erlang(double mean, double variance, RNG *gen) : Random(gen)
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{
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pMean = mean; pVariance = variance;
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setState();
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}
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inline double Erlang::mean() { return pMean; }
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inline double Erlang::mean(double x) {
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double tmp = pMean; pMean = x; setState(); return tmp;
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};
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inline double Erlang::variance() { return pVariance; }
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inline double Erlang::variance(double x) {
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double tmp = pVariance; pVariance = x; setState(); return tmp;
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}
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#endif
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