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+// This may look like C code, but it is really -*- C++ -*-
+/*
+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.
+*/
+#ifndef _HyperGeometric_h
+#ifdef __GNUG__
+#pragma interface
+#endif
+#define _HyperGeometric_h
+
+#include <Random.h>
+
+class HyperGeometric: public Random {
+protected:
+ double pMean;
+ double pVariance;
+ double pP;
+ void setState();
+
+public:
+ HyperGeometric(double mean, double variance, RNG *gen);
+
+ double mean();
+ double mean(double x);
+ double variance();
+ double variance(double x);
+
+ virtual double operator()();
+};
+
+
+inline void HyperGeometric::setState() {
+ double z = pVariance / (pMean * pMean);
+ pP = 0.5 * (1.0 - sqrt((z - 1.0) / ( z + 1.0 )));
+}
+
+inline HyperGeometric::HyperGeometric(double mean, double variance, RNG *gen)
+: Random(gen) {
+ pMean = mean; pVariance = variance;
+ setState();
+}
+
+inline double HyperGeometric::mean() { return pMean; };
+
+inline double HyperGeometric::mean(double x) {
+ double t = pMean; pMean = x;
+ setState(); return t;
+}
+
+inline double HyperGeometric::variance() { return pVariance; }
+
+inline double HyperGeometric::variance(double x) {
+ double t = pVariance; pVariance = x;
+ setState(); return t;
+}
+
+#endif
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