comparison DEPENDENCIES/generic/include/boost/random/beta_distribution.hpp @ 102:f46d142149f5

Whoops, finish that update

+/* boost random/beta_distribution.hpp header file
+ *
+ * Copyright Steven Watanabe 2014
+ * Distributed under the Boost Software License, Version 1.0. (See
+ * accompanying file LICENSE_1_0.txt or copy at
+ * http://www.boost.org/LICENSE_1_0.txt)
+ *
+ * See http://www.boost.org for most recent version including documentation.
+ *
+ * $Id$
+ */
+
+#ifndef BOOST_RANDOM_BETA_DISTRIBUTION_HPP
+#define BOOST_RANDOM_BETA_DISTRIBUTION_HPP
+
+#include <cassert>
+#include <istream>
+#include <iosfwd>
+#include <boost/random/detail/operators.hpp>
+#include <boost/random/gamma_distribution.hpp>
+
+namespace boost {
+namespace random {
+
+/**
+ * The beta distribution is a real-valued distribution which produces
+ * values in the range [0, 1].  It has two parameters, alpha and beta.
+ *
+ * It has \f$\displaystyle p(x) = \frac{x^{\alpha-1}(1-x)^{\beta-1}}{B(\alpha, \beta)}\f$.
+ */
+template<class RealType = double>
+class beta_distribution {
+public:
+    typedef RealType result_type;
+    typedef RealType input_type;
+
+    class param_type {
+    public:
+        typedef beta_distribution distribution_type;
+
+        /**
+         * Constructs a @c param_type from the "alpha" and "beta" parameters
+         * of the distribution.
+         *
+         * Requires: alpha > 0, beta > 0
+         */
+        explicit param_type(RealType alpha_arg = RealType(1.0),
+                            RealType beta_arg = RealType(1.0))
+          : _alpha(alpha_arg), _beta(beta_arg)
+        {
+            assert(alpha_arg > 0);
+            assert(beta_arg > 0);
+        }
+
+        /** Returns the "alpha" parameter of the distribtuion. */
+        RealType alpha() const { return _alpha; }
+        /** Returns the "beta" parameter of the distribution. */
+        RealType beta() const { return _beta; }
+
+        /** Writes a @c param_type to a @c std::ostream. */
+        BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm)
+        { os << parm._alpha << ' ' << parm._beta; return os; }
+
+        /** Reads a @c param_type from a @c std::istream. */
+        BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm)
+        { is >> parm._alpha >> std::ws >> parm._beta; return is; }
+
+        /** Returns true if the two sets of parameters are the same. */
+        BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs)
+        { return lhs._alpha == rhs._alpha && lhs._beta == rhs._beta; }
+        
+        /** Returns true if the two sets of parameters are the different. */
+        BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type)
+
+    private:
+        RealType _alpha;
+        RealType _beta;
+    };
+
+    /**
+     * Constructs an @c beta_distribution from its "alpha" and "beta" parameters.
+     *
+     * Requires: alpha > 0, beta > 0
+     */
+    explicit beta_distribution(RealType alpha_arg = RealType(1.0),
+                               RealType beta_arg = RealType(1.0))
+      : _alpha(alpha_arg), _beta(beta_arg)
+    {
+        assert(alpha_arg > 0);
+        assert(beta_arg > 0);
+    }
+    /** Constructs an @c beta_distribution from its parameters. */
+    explicit beta_distribution(const param_type& parm)
+      : _alpha(parm.alpha()), _beta(parm.beta())
+    {}
+
+    /**
+     * Returns a random variate distributed according to the
+     * beta distribution.
+     */
+    template<class URNG>
+    RealType operator()(URNG& urng) const
+    {
+        RealType a = gamma_distribution<RealType>(_alpha, RealType(1.0))(urng);
+        RealType b = gamma_distribution<RealType>(_beta, RealType(1.0))(urng);
+        return a / (a + b);
+    }
+
+    /**
+     * Returns a random variate distributed accordint to the beta
+     * distribution with parameters specified by @c param.
+     */
+    template<class URNG>
+    RealType operator()(URNG& urng, const param_type& parm) const
+    {
+        return beta_distribution(parm)(urng);
+    }
+
+    /** Returns the "alpha" parameter of the distribution. */
+    RealType alpha() const { return _alpha; }
+    /** Returns the "beta" parameter of the distribution. */
+    RealType beta() const { return _beta; }
+
+    /** Returns the smallest value that the distribution can produce. */
+    RealType min BOOST_PREVENT_MACRO_SUBSTITUTION () const
+    { return RealType(0.0); }
+    /** Returns the largest value that the distribution can produce. */
+    RealType max BOOST_PREVENT_MACRO_SUBSTITUTION () const
+    { return RealType(1.0); }
+
+    /** Returns the parameters of the distribution. */
+    param_type param() const { return param_type(_alpha, _beta); }
+    /** Sets the parameters of the distribution. */
+    void param(const param_type& parm)
+    {
+        _alpha = parm.alpha();
+        _beta = parm.beta();
+    }
+
+    /**
+     * Effects: Subsequent uses of the distribution do not depend
+     * on values produced by any engine prior to invoking reset.
+     */
+    void reset() { }
+
+    /** Writes an @c beta_distribution to a @c std::ostream. */
+    BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, beta_distribution, wd)
+    {
+        os << wd.param();
+        return os;
+    }
+
+    /** Reads an @c beta_distribution from a @c std::istream. */
+    BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, beta_distribution, wd)
+    {
+        param_type parm;
+        if(is >> parm) {
+            wd.param(parm);
+        }
+        return is;
+    }
+
+    /**
+     * Returns true if the two instances of @c beta_distribution will
+     * return identical sequences of values given equal generators.
+     */
+    BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(beta_distribution, lhs, rhs)
+    { return lhs._alpha == rhs._alpha && lhs._beta == rhs._beta; }
+    
+    /**
+     * Returns true if the two instances of @c beta_distribution will
+     * return different sequences of values given equal generators.
+     */
+    BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(beta_distribution)
+
+private:
+    RealType _alpha;
+    RealType _beta;
+};
+
+} // namespace random
+} // namespace boost
+
+#endif // BOOST_RANDOM_BETA_DISTRIBUTION_HPP