cpp-d1064d
[cross.git] / i686-linux-gnu-4.7 / usr / include / c++ / 4.7 / bits / random.h
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+// random number generation -*- C++ -*-
+
+// Copyright (C) 2009-2012 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, 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 General Public License for more details.
+
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+// <http://www.gnu.org/licenses/>.
+
+/**
+ * @file bits/random.h
+ *  This is an internal header file, included by other library headers.
+ *  Do not attempt to use it directly. @headername{random}
+ */
+
+#ifndef _RANDOM_H
+#define _RANDOM_H 1
+
+#include <vector>
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+  // [26.4] Random number generation
+
+  /**
+   * @defgroup random Random Number Generation
+   * @ingroup numerics
+   *
+   * A facility for generating random numbers on selected distributions.
+   * @{
+   */
+
+  /**
+   * @brief A function template for converting the output of a (integral)
+   * uniform random number generator to a floatng point result in the range
+   * [0-1).
+   */
+  template<typename _RealType, size_t __bits,
+          typename _UniformRandomNumberGenerator>
+    _RealType
+    generate_canonical(_UniformRandomNumberGenerator& __g);
+
+_GLIBCXX_END_NAMESPACE_VERSION
+
+  /*
+   * Implementation-space details.
+   */
+  namespace __detail
+  {
+  _GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+    template<typename _UIntType, size_t __w,
+            bool = __w < static_cast<size_t>
+                         (std::numeric_limits<_UIntType>::digits)>
+      struct _Shift
+      { static const _UIntType __value = 0; };
+
+    template<typename _UIntType, size_t __w>
+      struct _Shift<_UIntType, __w, true>
+      { static const _UIntType __value = _UIntType(1) << __w; };
+
+    template<typename _Tp, _Tp __m, _Tp __a, _Tp __c, bool>
+      struct _Mod;
+
+    // Dispatch based on modulus value to prevent divide-by-zero compile-time
+    // errors when m == 0.
+    template<typename _Tp, _Tp __m, _Tp __a = 1, _Tp __c = 0>
+      inline _Tp
+      __mod(_Tp __x)
+      { return _Mod<_Tp, __m, __a, __c, __m == 0>::__calc(__x); }
+
+    /*
+     * An adaptor class for converting the output of any Generator into
+     * the input for a specific Distribution.
+     */
+    template<typename _Engine, typename _DInputType>
+      struct _Adaptor
+      {
+
+      public:
+       _Adaptor(_Engine& __g)
+       : _M_g(__g) { }
+
+       _DInputType
+       min() const
+       { return _DInputType(0); }
+
+       _DInputType
+       max() const
+       { return _DInputType(1); }
+
+       /*
+        * Converts a value generated by the adapted random number generator
+        * into a value in the input domain for the dependent random number
+        * distribution.
+        */
+       _DInputType
+       operator()()
+       {
+         return std::generate_canonical<_DInputType,
+                                   std::numeric_limits<_DInputType>::digits,
+                                   _Engine>(_M_g);
+       }
+
+      private:
+       _Engine& _M_g;
+      };
+
+  _GLIBCXX_END_NAMESPACE_VERSION
+  } // namespace __detail
+
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+  /**
+   * @addtogroup random_generators Random Number Generators
+   * @ingroup random
+   *
+   * These classes define objects which provide random or pseudorandom
+   * numbers, either from a discrete or a continuous interval.  The
+   * random number generator supplied as a part of this library are
+   * all uniform random number generators which provide a sequence of
+   * random number uniformly distributed over their range.
+   *
+   * A number generator is a function object with an operator() that
+   * takes zero arguments and returns a number.
+   *
+   * A compliant random number generator must satisfy the following
+   * requirements.  <table border=1 cellpadding=10 cellspacing=0>
+   * <caption align=top>Random Number Generator Requirements</caption>
+   * <tr><td>To be documented.</td></tr> </table>
+   *
+   * @{
+   */
+
+  /**
+   * @brief A model of a linear congruential random number generator.
+   *
+   * A random number generator that produces pseudorandom numbers via
+   * linear function:
+   * @f[
+   *     x_{i+1}\leftarrow(ax_{i} + c) \bmod m 
+   * @f]
+   *
+   * The template parameter @p _UIntType must be an unsigned integral type
+   * large enough to store values up to (__m-1). If the template parameter
+   * @p __m is 0, the modulus @p __m used is
+   * std::numeric_limits<_UIntType>::max() plus 1. Otherwise, the template
+   * parameters @p __a and @p __c must be less than @p __m.
+   *
+   * The size of the state is @f$1@f$.
+   */
+  template<typename _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
+    class linear_congruential_engine
+    {
+      static_assert(std::is_unsigned<_UIntType>::value, "template argument "
+                   "substituting _UIntType not an unsigned integral type");
+      static_assert(__m == 0u || (__a < __m && __c < __m),
+                   "template argument substituting __m out of bounds");
+
+      // XXX FIXME:
+      // _Mod::__calc should handle correctly __m % __a >= __m / __a too.
+      static_assert(__m % __a < __m / __a,
+                   "sorry, not implemented yet: try a smaller 'a' constant");
+
+    public:
+      /** The type of the generated random value. */
+      typedef _UIntType result_type;
+
+      /** The multiplier. */
+      static constexpr result_type multiplier   = __a;
+      /** An increment. */
+      static constexpr result_type increment    = __c;
+      /** The modulus. */
+      static constexpr result_type modulus      = __m;
+      static constexpr result_type default_seed = 1u;
+
+      /**
+       * @brief Constructs a %linear_congruential_engine random number
+       *        generator engine with seed @p __s.  The default seed value
+       *        is 1.
+       *
+       * @param __s The initial seed value.
+       */
+      explicit
+      linear_congruential_engine(result_type __s = default_seed)
+      { seed(__s); }
+
+      /**
+       * @brief Constructs a %linear_congruential_engine random number
+       *        generator engine seeded from the seed sequence @p __q.
+       *
+       * @param __q the seed sequence.
+       */
+      template<typename _Sseq, typename = typename
+       std::enable_if<!std::is_same<_Sseq, linear_congruential_engine>::value>
+              ::type>
+        explicit
+        linear_congruential_engine(_Sseq& __q)
+        { seed(__q); }
+
+      /**
+       * @brief Reseeds the %linear_congruential_engine random number generator
+       *        engine sequence to the seed @p __s.
+       *
+       * @param __s The new seed.
+       */
+      void
+      seed(result_type __s = default_seed);
+
+      /**
+       * @brief Reseeds the %linear_congruential_engine random number generator
+       *        engine
+       * sequence using values from the seed sequence @p __q.
+       *
+       * @param __q the seed sequence.
+       */
+      template<typename _Sseq>
+        typename std::enable_if<std::is_class<_Sseq>::value>::type
+        seed(_Sseq& __q);
+
+      /**
+       * @brief Gets the smallest possible value in the output range.
+       *
+       * The minimum depends on the @p __c parameter: if it is zero, the
+       * minimum generated must be > 0, otherwise 0 is allowed.
+       */
+      static constexpr result_type
+      min()
+      { return __c == 0u ? 1u : 0u; }
+
+      /**
+       * @brief Gets the largest possible value in the output range.
+       */
+      static constexpr result_type
+      max()
+      { return __m - 1u; }
+
+      /**
+       * @brief Discard a sequence of random numbers.
+       */
+      void
+      discard(unsigned long long __z)
+      {
+       for (; __z != 0ULL; --__z)
+         (*this)();
+      }
+
+      /**
+       * @brief Gets the next random number in the sequence.
+       */
+      result_type
+      operator()()
+      {
+       _M_x = __detail::__mod<_UIntType, __m, __a, __c>(_M_x);
+       return _M_x;
+      }
+
+      /**
+       * @brief Compares two linear congruential random number generator
+       * objects of the same type for equality.
+       *
+       * @param __lhs A linear congruential random number generator object.
+       * @param __rhs Another linear congruential random number generator
+       *              object.
+       *
+       * @returns true if the infinite sequences of generated values
+       *          would be equal, false otherwise.
+       */
+      friend bool
+      operator==(const linear_congruential_engine& __lhs,
+                const linear_congruential_engine& __rhs)
+      { return __lhs._M_x == __rhs._M_x; }
+
+      /**
+       * @brief Writes the textual representation of the state x(i) of x to
+       *        @p __os.
+       *
+       * @param __os  The output stream.
+       * @param __lcr A % linear_congruential_engine random number generator.
+       * @returns __os.
+       */
+      template<typename _UIntType1, _UIntType1 __a1, _UIntType1 __c1,
+              _UIntType1 __m1, typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::linear_congruential_engine<_UIntType1,
+                  __a1, __c1, __m1>& __lcr);
+
+      /**
+       * @brief Sets the state of the engine by reading its textual
+       *        representation from @p __is.
+       *
+       * The textual representation must have been previously written using
+       * an output stream whose imbued locale and whose type's template
+       * specialization arguments _CharT and _Traits were the same as those
+       * of @p __is.
+       *
+       * @param __is  The input stream.
+       * @param __lcr A % linear_congruential_engine random number generator.
+       * @returns __is.
+       */
+      template<typename _UIntType1, _UIntType1 __a1, _UIntType1 __c1,
+              _UIntType1 __m1, typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::linear_congruential_engine<_UIntType1, __a1,
+                  __c1, __m1>& __lcr);
+
+    private:
+      _UIntType _M_x;
+    };
+
+  /**
+   * @brief Compares two linear congruential random number generator
+   * objects of the same type for inequality.
+   *
+   * @param __lhs A linear congruential random number generator object.
+   * @param __rhs Another linear congruential random number generator
+   *              object.
+   *
+   * @returns true if the infinite sequences of generated values
+   *          would be different, false otherwise.
+   */
+  template<typename _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
+    inline bool
+    operator!=(const std::linear_congruential_engine<_UIntType, __a,
+              __c, __m>& __lhs,
+              const std::linear_congruential_engine<_UIntType, __a,
+              __c, __m>& __rhs)
+    { return !(__lhs == __rhs); }
+
+
+  /**
+   * A generalized feedback shift register discrete random number generator.
+   *
+   * This algorithm avoids multiplication and division and is designed to be
+   * friendly to a pipelined architecture.  If the parameters are chosen
+   * correctly, this generator will produce numbers with a very long period and
+   * fairly good apparent entropy, although still not cryptographically strong.
+   *
+   * The best way to use this generator is with the predefined mt19937 class.
+   *
+   * This algorithm was originally invented by Makoto Matsumoto and
+   * Takuji Nishimura.
+   *
+   * @tparam __w  Word size, the number of bits in each element of 
+   *              the state vector.
+   * @tparam __n  The degree of recursion.
+   * @tparam __m  The period parameter.
+   * @tparam __r  The separation point bit index.
+   * @tparam __a  The last row of the twist matrix.
+   * @tparam __u  The first right-shift tempering matrix parameter.
+   * @tparam __d  The first right-shift tempering matrix mask.
+   * @tparam __s  The first left-shift tempering matrix parameter.
+   * @tparam __b  The first left-shift tempering matrix mask.
+   * @tparam __t  The second left-shift tempering matrix parameter.
+   * @tparam __c  The second left-shift tempering matrix mask.
+   * @tparam __l  The second right-shift tempering matrix parameter.
+   * @tparam __f  Initialization multiplier.
+   */
+  template<typename _UIntType, size_t __w,
+          size_t __n, size_t __m, size_t __r,
+          _UIntType __a, size_t __u, _UIntType __d, size_t __s,
+          _UIntType __b, size_t __t,
+          _UIntType __c, size_t __l, _UIntType __f>
+    class mersenne_twister_engine
+    {
+      static_assert(std::is_unsigned<_UIntType>::value, "template argument "
+                   "substituting _UIntType not an unsigned integral type");
+      static_assert(1u <= __m && __m <= __n,
+                   "template argument substituting __m out of bounds");
+      static_assert(__r <= __w, "template argument substituting "
+                   "__r out of bound");
+      static_assert(__u <= __w, "template argument substituting "
+                   "__u out of bound");
+      static_assert(__s <= __w, "template argument substituting "
+                   "__s out of bound");
+      static_assert(__t <= __w, "template argument substituting "
+                   "__t out of bound");
+      static_assert(__l <= __w, "template argument substituting "
+                   "__l out of bound");
+      static_assert(__w <= std::numeric_limits<_UIntType>::digits,
+                   "template argument substituting __w out of bound");
+      static_assert(__a <= (__detail::_Shift<_UIntType, __w>::__value - 1),
+                   "template argument substituting __a out of bound");
+      static_assert(__b <= (__detail::_Shift<_UIntType, __w>::__value - 1),
+                   "template argument substituting __b out of bound");
+      static_assert(__c <= (__detail::_Shift<_UIntType, __w>::__value - 1),
+                   "template argument substituting __c out of bound");
+      static_assert(__d <= (__detail::_Shift<_UIntType, __w>::__value - 1),
+                   "template argument substituting __d out of bound");
+      static_assert(__f <= (__detail::_Shift<_UIntType, __w>::__value - 1),
+                   "template argument substituting __f out of bound");
+
+    public:
+      /** The type of the generated random value. */
+      typedef _UIntType result_type;
+
+      // parameter values
+      static constexpr size_t      word_size                 = __w;
+      static constexpr size_t      state_size                = __n;
+      static constexpr size_t      shift_size                = __m;
+      static constexpr size_t      mask_bits                 = __r;
+      static constexpr result_type xor_mask                  = __a;
+      static constexpr size_t      tempering_u               = __u;
+      static constexpr result_type tempering_d               = __d;
+      static constexpr size_t      tempering_s               = __s;
+      static constexpr result_type tempering_b               = __b;
+      static constexpr size_t      tempering_t               = __t;
+      static constexpr result_type tempering_c               = __c;
+      static constexpr size_t      tempering_l               = __l;
+      static constexpr result_type initialization_multiplier = __f;
+      static constexpr result_type default_seed = 5489u;
+
+      // constructors and member function
+      explicit
+      mersenne_twister_engine(result_type __sd = default_seed)
+      { seed(__sd); }
+
+      /**
+       * @brief Constructs a %mersenne_twister_engine random number generator
+       *        engine seeded from the seed sequence @p __q.
+       *
+       * @param __q the seed sequence.
+       */
+      template<typename _Sseq, typename = typename
+        std::enable_if<!std::is_same<_Sseq, mersenne_twister_engine>::value>
+              ::type>
+        explicit
+        mersenne_twister_engine(_Sseq& __q)
+        { seed(__q); }
+
+      void
+      seed(result_type __sd = default_seed);
+
+      template<typename _Sseq>
+       typename std::enable_if<std::is_class<_Sseq>::value>::type
+        seed(_Sseq& __q);
+
+      /**
+       * @brief Gets the smallest possible value in the output range.
+       */
+      static constexpr result_type
+      min()
+      { return 0; };
+
+      /**
+       * @brief Gets the largest possible value in the output range.
+       */
+      static constexpr result_type
+      max()
+      { return __detail::_Shift<_UIntType, __w>::__value - 1; }
+
+      /**
+       * @brief Discard a sequence of random numbers.
+       */
+      void
+      discard(unsigned long long __z)
+      {
+       for (; __z != 0ULL; --__z)
+         (*this)();
+      }
+
+      result_type
+      operator()();
+
+      /**
+       * @brief Compares two % mersenne_twister_engine random number generator
+       *        objects of the same type for equality.
+       *
+       * @param __lhs A % mersenne_twister_engine random number generator
+       *              object.
+       * @param __rhs Another % mersenne_twister_engine random number
+       *              generator object.
+       *
+       * @returns true if the infinite sequences of generated values
+       *          would be equal, false otherwise.
+       */
+      friend bool
+      operator==(const mersenne_twister_engine& __lhs,
+                const mersenne_twister_engine& __rhs)
+      { return (std::equal(__lhs._M_x, __lhs._M_x + state_size, __rhs._M_x)
+               && __lhs._M_p == __rhs._M_p); }
+
+      /**
+       * @brief Inserts the current state of a % mersenne_twister_engine
+       *        random number generator engine @p __x into the output stream
+       *        @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A % mersenne_twister_engine random number generator
+       *             engine.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _UIntType1,
+              size_t __w1, size_t __n1,
+              size_t __m1, size_t __r1,
+              _UIntType1 __a1, size_t __u1,
+              _UIntType1 __d1, size_t __s1,
+              _UIntType1 __b1, size_t __t1,
+              _UIntType1 __c1, size_t __l1, _UIntType1 __f1,
+              typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::mersenne_twister_engine<_UIntType1, __w1, __n1,
+                  __m1, __r1, __a1, __u1, __d1, __s1, __b1, __t1, __c1,
+                  __l1, __f1>& __x);
+
+      /**
+       * @brief Extracts the current state of a % mersenne_twister_engine
+       *        random number generator engine @p __x from the input stream
+       *        @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x  A % mersenne_twister_engine random number generator
+       *             engine.
+       *
+       * @returns The input stream with the state of @p __x extracted or in
+       * an error state.
+       */
+      template<typename _UIntType1,
+              size_t __w1, size_t __n1,
+              size_t __m1, size_t __r1,
+              _UIntType1 __a1, size_t __u1,
+              _UIntType1 __d1, size_t __s1,
+              _UIntType1 __b1, size_t __t1,
+              _UIntType1 __c1, size_t __l1, _UIntType1 __f1,
+              typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::mersenne_twister_engine<_UIntType1, __w1, __n1, __m1,
+                  __r1, __a1, __u1, __d1, __s1, __b1, __t1, __c1,
+                  __l1, __f1>& __x);
+
+    private:
+      _UIntType _M_x[state_size];
+      size_t    _M_p;
+    };
+
+  /**
+   * @brief Compares two % mersenne_twister_engine random number generator
+   *        objects of the same type for inequality.
+   *
+   * @param __lhs A % mersenne_twister_engine random number generator
+   *              object.
+   * @param __rhs Another % mersenne_twister_engine random number
+   *              generator object.
+   *
+   * @returns true if the infinite sequences of generated values
+   *          would be different, false otherwise.
+   */
+  template<typename _UIntType, size_t __w,
+          size_t __n, size_t __m, size_t __r,
+          _UIntType __a, size_t __u, _UIntType __d, size_t __s,
+          _UIntType __b, size_t __t,
+          _UIntType __c, size_t __l, _UIntType __f>
+    inline bool
+    operator!=(const std::mersenne_twister_engine<_UIntType, __w, __n, __m,
+              __r, __a, __u, __d, __s, __b, __t, __c, __l, __f>& __lhs,
+              const std::mersenne_twister_engine<_UIntType, __w, __n, __m,
+              __r, __a, __u, __d, __s, __b, __t, __c, __l, __f>& __rhs)
+    { return !(__lhs == __rhs); }
+
+
+  /**
+   * @brief The Marsaglia-Zaman generator.
+   *
+   * This is a model of a Generalized Fibonacci discrete random number
+   * generator, sometimes referred to as the SWC generator.
+   *
+   * A discrete random number generator that produces pseudorandom
+   * numbers using:
+   * @f[
+   *     x_{i}\leftarrow(x_{i - s} - x_{i - r} - carry_{i-1}) \bmod m 
+   * @f]
+   *
+   * The size of the state is @f$r@f$
+   * and the maximum period of the generator is @f$(m^r - m^s - 1)@f$.
+   *
+   * @var _M_x     The state of the generator.  This is a ring buffer.
+   * @var _M_carry The carry.
+   * @var _M_p     Current index of x(i - r).
+   */
+  template<typename _UIntType, size_t __w, size_t __s, size_t __r>
+    class subtract_with_carry_engine
+    {
+      static_assert(std::is_unsigned<_UIntType>::value, "template argument "
+                   "substituting _UIntType not an unsigned integral type");
+      static_assert(0u < __s && __s < __r,
+                   "template argument substituting __s out of bounds");
+      static_assert(0u < __w && __w <= std::numeric_limits<_UIntType>::digits,
+                   "template argument substituting __w out of bounds");
+
+    public:
+      /** The type of the generated random value. */
+      typedef _UIntType result_type;
+
+      // parameter values
+      static constexpr size_t      word_size    = __w;
+      static constexpr size_t      short_lag    = __s;
+      static constexpr size_t      long_lag     = __r;
+      static constexpr result_type default_seed = 19780503u;
+
+      /**
+       * @brief Constructs an explicitly seeded % subtract_with_carry_engine
+       *        random number generator.
+       */
+      explicit
+      subtract_with_carry_engine(result_type __sd = default_seed)
+      { seed(__sd); }
+
+      /**
+       * @brief Constructs a %subtract_with_carry_engine random number engine
+       *        seeded from the seed sequence @p __q.
+       *
+       * @param __q the seed sequence.
+       */
+      template<typename _Sseq, typename = typename
+        std::enable_if<!std::is_same<_Sseq, subtract_with_carry_engine>::value>
+              ::type>
+        explicit
+        subtract_with_carry_engine(_Sseq& __q)
+        { seed(__q); }
+
+      /**
+       * @brief Seeds the initial state @f$x_0@f$ of the random number
+       *        generator.
+       *
+       * N1688[4.19] modifies this as follows.  If @p __value == 0,
+       * sets value to 19780503.  In any case, with a linear
+       * congruential generator lcg(i) having parameters @f$ m_{lcg} =
+       * 2147483563, a_{lcg} = 40014, c_{lcg} = 0, and lcg(0) = value
+       * @f$, sets @f$ x_{-r} \dots x_{-1} @f$ to @f$ lcg(1) \bmod m
+       * \dots lcg(r) \bmod m @f$ respectively.  If @f$ x_{-1} = 0 @f$
+       * set carry to 1, otherwise sets carry to 0.
+       */
+      void
+      seed(result_type __sd = default_seed);
+
+      /**
+       * @brief Seeds the initial state @f$x_0@f$ of the
+       * % subtract_with_carry_engine random number generator.
+       */
+      template<typename _Sseq>
+       typename std::enable_if<std::is_class<_Sseq>::value>::type
+        seed(_Sseq& __q);
+
+      /**
+       * @brief Gets the inclusive minimum value of the range of random
+       * integers returned by this generator.
+       */
+      static constexpr result_type
+      min()
+      { return 0; }
+
+      /**
+       * @brief Gets the inclusive maximum value of the range of random
+       * integers returned by this generator.
+       */
+      static constexpr result_type
+      max()
+      { return __detail::_Shift<_UIntType, __w>::__value - 1; }
+
+      /**
+       * @brief Discard a sequence of random numbers.
+       */
+      void
+      discard(unsigned long long __z)
+      {
+       for (; __z != 0ULL; --__z)
+         (*this)();
+      }
+
+      /**
+       * @brief Gets the next random number in the sequence.
+       */
+      result_type
+      operator()();
+
+      /**
+       * @brief Compares two % subtract_with_carry_engine random number
+       *        generator objects of the same type for equality.
+       *
+       * @param __lhs A % subtract_with_carry_engine random number generator
+       *              object.
+       * @param __rhs Another % subtract_with_carry_engine random number
+       *              generator object.
+       *
+       * @returns true if the infinite sequences of generated values
+       *          would be equal, false otherwise.
+      */
+      friend bool
+      operator==(const subtract_with_carry_engine& __lhs,
+                const subtract_with_carry_engine& __rhs)
+      { return (std::equal(__lhs._M_x, __lhs._M_x + long_lag, __rhs._M_x)
+               && __lhs._M_carry == __rhs._M_carry
+               && __lhs._M_p == __rhs._M_p); }
+
+      /**
+       * @brief Inserts the current state of a % subtract_with_carry_engine
+       *        random number generator engine @p __x into the output stream
+       *        @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A % subtract_with_carry_engine random number generator
+       *             engine.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _UIntType1, size_t __w1, size_t __s1, size_t __r1,
+              typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>&,
+                  const std::subtract_with_carry_engine<_UIntType1, __w1,
+                  __s1, __r1>&);
+
+      /**
+       * @brief Extracts the current state of a % subtract_with_carry_engine
+       *        random number generator engine @p __x from the input stream
+       *        @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x  A % subtract_with_carry_engine random number generator
+       *             engine.
+       *
+       * @returns The input stream with the state of @p __x extracted or in
+       * an error state.
+       */
+      template<typename _UIntType1, size_t __w1, size_t __s1, size_t __r1,
+              typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>&,
+                  std::subtract_with_carry_engine<_UIntType1, __w1,
+                  __s1, __r1>&);
+
+    private:
+      _UIntType  _M_x[long_lag];
+      _UIntType  _M_carry;
+      size_t     _M_p;
+    };
+
+  /**
+   * @brief Compares two % subtract_with_carry_engine random number
+   *        generator objects of the same type for inequality.
+   *
+   * @param __lhs A % subtract_with_carry_engine random number generator
+   *              object.
+   * @param __rhs Another % subtract_with_carry_engine random number
+   *              generator object.
+   *
+   * @returns true if the infinite sequences of generated values
+   *          would be different, false otherwise.
+   */
+  template<typename _UIntType, size_t __w, size_t __s, size_t __r>
+    inline bool
+    operator!=(const std::subtract_with_carry_engine<_UIntType, __w,
+              __s, __r>& __lhs,
+              const std::subtract_with_carry_engine<_UIntType, __w,
+              __s, __r>& __rhs)
+    { return !(__lhs == __rhs); }
+
+
+  /**
+   * Produces random numbers from some base engine by discarding blocks of
+   * data.
+   *
+   * 0 <= @p __r <= @p __p
+   */
+  template<typename _RandomNumberEngine, size_t __p, size_t __r>
+    class discard_block_engine
+    {
+      static_assert(1 <= __r && __r <= __p,
+                   "template argument substituting __r out of bounds");
+
+    public:
+      /** The type of the generated random value. */
+      typedef typename _RandomNumberEngine::result_type result_type;
+
+      // parameter values
+      static constexpr size_t block_size = __p;
+      static constexpr size_t used_block = __r;
+
+      /**
+       * @brief Constructs a default %discard_block_engine engine.
+       *
+       * The underlying engine is default constructed as well.
+       */
+      discard_block_engine()
+      : _M_b(), _M_n(0) { }
+
+      /**
+       * @brief Copy constructs a %discard_block_engine engine.
+       *
+       * Copies an existing base class random number generator.
+       * @param __rng An existing (base class) engine object.
+       */
+      explicit
+      discard_block_engine(const _RandomNumberEngine& __rng)
+      : _M_b(__rng), _M_n(0) { }
+
+      /**
+       * @brief Move constructs a %discard_block_engine engine.
+       *
+       * Copies an existing base class random number generator.
+       * @param __rng An existing (base class) engine object.
+       */
+      explicit
+      discard_block_engine(_RandomNumberEngine&& __rng)
+      : _M_b(std::move(__rng)), _M_n(0) { }
+
+      /**
+       * @brief Seed constructs a %discard_block_engine engine.
+       *
+       * Constructs the underlying generator engine seeded with @p __s.
+       * @param __s A seed value for the base class engine.
+       */
+      explicit
+      discard_block_engine(result_type __s)
+      : _M_b(__s), _M_n(0) { }
+
+      /**
+       * @brief Generator construct a %discard_block_engine engine.
+       *
+       * @param __q A seed sequence.
+       */
+      template<typename _Sseq, typename = typename
+       std::enable_if<!std::is_same<_Sseq, discard_block_engine>::value
+                      && !std::is_same<_Sseq, _RandomNumberEngine>::value>
+              ::type>
+        explicit
+        discard_block_engine(_Sseq& __q)
+       : _M_b(__q), _M_n(0)
+        { }
+
+      /**
+       * @brief Reseeds the %discard_block_engine object with the default
+       *        seed for the underlying base class generator engine.
+       */
+      void
+      seed()
+      {
+       _M_b.seed();
+       _M_n = 0;
+      }
+
+      /**
+       * @brief Reseeds the %discard_block_engine object with the default
+       *        seed for the underlying base class generator engine.
+       */
+      void
+      seed(result_type __s)
+      {
+       _M_b.seed(__s);
+       _M_n = 0;
+      }
+
+      /**
+       * @brief Reseeds the %discard_block_engine object with the given seed
+       *        sequence.
+       * @param __q A seed generator function.
+       */
+      template<typename _Sseq>
+        void
+        seed(_Sseq& __q)
+        {
+         _M_b.seed(__q);
+         _M_n = 0;
+       }
+
+      /**
+       * @brief Gets a const reference to the underlying generator engine
+       *        object.
+       */
+      const _RandomNumberEngine&
+      base() const noexcept
+      { return _M_b; }
+
+      /**
+       * @brief Gets the minimum value in the generated random number range.
+       */
+      static constexpr result_type
+      min()
+      { return _RandomNumberEngine::min(); }
+
+      /**
+       * @brief Gets the maximum value in the generated random number range.
+       */
+      static constexpr result_type
+      max()
+      { return _RandomNumberEngine::max(); }
+
+      /**
+       * @brief Discard a sequence of random numbers.
+       */
+      void
+      discard(unsigned long long __z)
+      {
+       for (; __z != 0ULL; --__z)
+         (*this)();
+      }
+
+      /**
+       * @brief Gets the next value in the generated random number sequence.
+       */
+      result_type
+      operator()();
+
+      /**
+       * @brief Compares two %discard_block_engine random number generator
+       *        objects of the same type for equality.
+       *
+       * @param __lhs A %discard_block_engine random number generator object.
+       * @param __rhs Another %discard_block_engine random number generator
+       *              object.
+       *
+       * @returns true if the infinite sequences of generated values
+       *          would be equal, false otherwise.
+       */
+      friend bool
+      operator==(const discard_block_engine& __lhs,
+                const discard_block_engine& __rhs)
+      { return __lhs._M_b == __rhs._M_b && __lhs._M_n == __rhs._M_n; }
+
+      /**
+       * @brief Inserts the current state of a %discard_block_engine random
+       *        number generator engine @p __x into the output stream
+       *        @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %discard_block_engine random number generator engine.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _RandomNumberEngine1, size_t __p1, size_t __r1,
+              typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::discard_block_engine<_RandomNumberEngine1,
+                  __p1, __r1>& __x);
+
+      /**
+       * @brief Extracts the current state of a % subtract_with_carry_engine
+       *        random number generator engine @p __x from the input stream
+       *        @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x  A %discard_block_engine random number generator engine.
+       *
+       * @returns The input stream with the state of @p __x extracted or in
+       * an error state.
+       */
+      template<typename _RandomNumberEngine1, size_t __p1, size_t __r1,
+              typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::discard_block_engine<_RandomNumberEngine1,
+                  __p1, __r1>& __x);
+
+    private:
+      _RandomNumberEngine _M_b;
+      size_t _M_n;
+    };
+
+  /**
+   * @brief Compares two %discard_block_engine random number generator
+   *        objects of the same type for inequality.
+   *
+   * @param __lhs A %discard_block_engine random number generator object.
+   * @param __rhs Another %discard_block_engine random number generator
+   *              object.
+   *
+   * @returns true if the infinite sequences of generated values
+   *          would be different, false otherwise.
+   */
+  template<typename _RandomNumberEngine, size_t __p, size_t __r>
+    inline bool
+    operator!=(const std::discard_block_engine<_RandomNumberEngine, __p,
+              __r>& __lhs,
+              const std::discard_block_engine<_RandomNumberEngine, __p,
+              __r>& __rhs)
+    { return !(__lhs == __rhs); }
+
+
+  /**
+   * Produces random numbers by combining random numbers from some base
+   * engine to produce random numbers with a specifies number of bits @p __w.
+   */
+  template<typename _RandomNumberEngine, size_t __w, typename _UIntType>
+    class independent_bits_engine
+    {
+      static_assert(std::is_unsigned<_UIntType>::value, "template argument "
+                   "substituting _UIntType not an unsigned integral type");
+      static_assert(0u < __w && __w <= std::numeric_limits<_UIntType>::digits,
+                   "template argument substituting __w out of bounds");
+
+    public:
+      /** The type of the generated random value. */
+      typedef _UIntType result_type;
+
+      /**
+       * @brief Constructs a default %independent_bits_engine engine.
+       *
+       * The underlying engine is default constructed as well.
+       */
+      independent_bits_engine()
+      : _M_b() { }
+
+      /**
+       * @brief Copy constructs a %independent_bits_engine engine.
+       *
+       * Copies an existing base class random number generator.
+       * @param __rng An existing (base class) engine object.
+       */
+      explicit
+      independent_bits_engine(const _RandomNumberEngine& __rng)
+      : _M_b(__rng) { }
+
+      /**
+       * @brief Move constructs a %independent_bits_engine engine.
+       *
+       * Copies an existing base class random number generator.
+       * @param __rng An existing (base class) engine object.
+       */
+      explicit
+      independent_bits_engine(_RandomNumberEngine&& __rng)
+      : _M_b(std::move(__rng)) { }
+
+      /**
+       * @brief Seed constructs a %independent_bits_engine engine.
+       *
+       * Constructs the underlying generator engine seeded with @p __s.
+       * @param __s A seed value for the base class engine.
+       */
+      explicit
+      independent_bits_engine(result_type __s)
+      : _M_b(__s) { }
+
+      /**
+       * @brief Generator construct a %independent_bits_engine engine.
+       *
+       * @param __q A seed sequence.
+       */
+      template<typename _Sseq, typename = typename
+       std::enable_if<!std::is_same<_Sseq, independent_bits_engine>::value
+                      && !std::is_same<_Sseq, _RandomNumberEngine>::value>
+               ::type>
+        explicit
+        independent_bits_engine(_Sseq& __q)
+        : _M_b(__q)
+        { }
+
+      /**
+       * @brief Reseeds the %independent_bits_engine object with the default
+       *        seed for the underlying base class generator engine.
+       */
+      void
+      seed()
+      { _M_b.seed(); }
+
+      /**
+       * @brief Reseeds the %independent_bits_engine object with the default
+       *        seed for the underlying base class generator engine.
+       */
+      void
+      seed(result_type __s)
+      { _M_b.seed(__s); }
+
+      /**
+       * @brief Reseeds the %independent_bits_engine object with the given
+       *        seed sequence.
+       * @param __q A seed generator function.
+       */
+      template<typename _Sseq>
+        void
+        seed(_Sseq& __q)
+        { _M_b.seed(__q); }
+
+      /**
+       * @brief Gets a const reference to the underlying generator engine
+       *        object.
+       */
+      const _RandomNumberEngine&
+      base() const noexcept
+      { return _M_b; }
+
+      /**
+       * @brief Gets the minimum value in the generated random number range.
+       */
+      static constexpr result_type
+      min()
+      { return 0U; }
+
+      /**
+       * @brief Gets the maximum value in the generated random number range.
+       */
+      static constexpr result_type
+      max()
+      { return __detail::_Shift<_UIntType, __w>::__value - 1; }
+
+      /**
+       * @brief Discard a sequence of random numbers.
+       */
+      void
+      discard(unsigned long long __z)
+      {
+       for (; __z != 0ULL; --__z)
+         (*this)();
+      }
+
+      /**
+       * @brief Gets the next value in the generated random number sequence.
+       */
+      result_type
+      operator()();
+
+      /**
+       * @brief Compares two %independent_bits_engine random number generator
+       * objects of the same type for equality.
+       *
+       * @param __lhs A %independent_bits_engine random number generator
+       *              object.
+       * @param __rhs Another %independent_bits_engine random number generator
+       *              object.
+       *
+       * @returns true if the infinite sequences of generated values
+       *          would be equal, false otherwise.
+       */
+      friend bool
+      operator==(const independent_bits_engine& __lhs,
+                const independent_bits_engine& __rhs)
+      { return __lhs._M_b == __rhs._M_b; }
+
+      /**
+       * @brief Extracts the current state of a % subtract_with_carry_engine
+       *        random number generator engine @p __x from the input stream
+       *        @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x  A %independent_bits_engine random number generator
+       *             engine.
+       *
+       * @returns The input stream with the state of @p __x extracted or in
+       *          an error state.
+       */
+      template<typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::independent_bits_engine<_RandomNumberEngine,
+                  __w, _UIntType>& __x)
+       {
+         __is >> __x._M_b;
+         return __is;
+       }
+
+    private:
+      _RandomNumberEngine _M_b;
+    };
+
+  /**
+   * @brief Compares two %independent_bits_engine random number generator
+   * objects of the same type for inequality.
+   *
+   * @param __lhs A %independent_bits_engine random number generator
+   *              object.
+   * @param __rhs Another %independent_bits_engine random number generator
+   *              object.
+   *
+   * @returns true if the infinite sequences of generated values
+   *          would be different, false otherwise.
+   */
+  template<typename _RandomNumberEngine, size_t __w, typename _UIntType>
+    inline bool
+    operator!=(const std::independent_bits_engine<_RandomNumberEngine, __w,
+              _UIntType>& __lhs,
+              const std::independent_bits_engine<_RandomNumberEngine, __w,
+              _UIntType>& __rhs)
+    { return !(__lhs == __rhs); }
+
+  /**
+   * @brief Inserts the current state of a %independent_bits_engine random
+   *        number generator engine @p __x into the output stream @p __os.
+   *
+   * @param __os An output stream.
+   * @param __x  A %independent_bits_engine random number generator engine.
+   *
+   * @returns The output stream with the state of @p __x inserted or in
+   *          an error state.
+   */
+  template<typename _RandomNumberEngine, size_t __w, typename _UIntType,
+          typename _CharT, typename _Traits>
+    std::basic_ostream<_CharT, _Traits>&
+    operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+              const std::independent_bits_engine<_RandomNumberEngine,
+              __w, _UIntType>& __x)
+    {
+      __os << __x.base();
+      return __os;
+    }
+
+
+  /**
+   * @brief Produces random numbers by combining random numbers from some
+   * base engine to produce random numbers with a specifies number of bits
+   * @p __w.
+   */
+  template<typename _RandomNumberEngine, size_t __k>
+    class shuffle_order_engine
+    {
+      static_assert(1u <= __k, "template argument substituting "
+                   "__k out of bound");
+
+    public:
+      /** The type of the generated random value. */
+      typedef typename _RandomNumberEngine::result_type result_type;
+
+      static constexpr size_t table_size = __k;
+
+      /**
+       * @brief Constructs a default %shuffle_order_engine engine.
+       *
+       * The underlying engine is default constructed as well.
+       */
+      shuffle_order_engine()
+      : _M_b()
+      { _M_initialize(); }
+
+      /**
+       * @brief Copy constructs a %shuffle_order_engine engine.
+       *
+       * Copies an existing base class random number generator.
+       * @param __rng An existing (base class) engine object.
+       */
+      explicit
+      shuffle_order_engine(const _RandomNumberEngine& __rng)
+      : _M_b(__rng)
+      { _M_initialize(); }
+
+      /**
+       * @brief Move constructs a %shuffle_order_engine engine.
+       *
+       * Copies an existing base class random number generator.
+       * @param __rng An existing (base class) engine object.
+       */
+      explicit
+      shuffle_order_engine(_RandomNumberEngine&& __rng)
+      : _M_b(std::move(__rng))
+      { _M_initialize(); }
+
+      /**
+       * @brief Seed constructs a %shuffle_order_engine engine.
+       *
+       * Constructs the underlying generator engine seeded with @p __s.
+       * @param __s A seed value for the base class engine.
+       */
+      explicit
+      shuffle_order_engine(result_type __s)
+      : _M_b(__s)
+      { _M_initialize(); }
+
+      /**
+       * @brief Generator construct a %shuffle_order_engine engine.
+       *
+       * @param __q A seed sequence.
+       */
+      template<typename _Sseq, typename = typename
+       std::enable_if<!std::is_same<_Sseq, shuffle_order_engine>::value
+                      && !std::is_same<_Sseq, _RandomNumberEngine>::value>
+              ::type>
+        explicit
+        shuffle_order_engine(_Sseq& __q)
+        : _M_b(__q)
+        { _M_initialize(); }
+
+      /**
+       * @brief Reseeds the %shuffle_order_engine object with the default seed
+                for the underlying base class generator engine.
+       */
+      void
+      seed()
+      {
+       _M_b.seed();
+       _M_initialize();
+      }
+
+      /**
+       * @brief Reseeds the %shuffle_order_engine object with the default seed
+       *        for the underlying base class generator engine.
+       */
+      void
+      seed(result_type __s)
+      {
+       _M_b.seed(__s);
+       _M_initialize();
+      }
+
+      /**
+       * @brief Reseeds the %shuffle_order_engine object with the given seed
+       *        sequence.
+       * @param __q A seed generator function.
+       */
+      template<typename _Sseq>
+        void
+        seed(_Sseq& __q)
+        {
+         _M_b.seed(__q);
+         _M_initialize();
+       }
+
+      /**
+       * Gets a const reference to the underlying generator engine object.
+       */
+      const _RandomNumberEngine&
+      base() const noexcept
+      { return _M_b; }
+
+      /**
+       * Gets the minimum value in the generated random number range.
+       */
+      static constexpr result_type
+      min()
+      { return _RandomNumberEngine::min(); }
+
+      /**
+       * Gets the maximum value in the generated random number range.
+       */
+      static constexpr result_type
+      max()
+      { return _RandomNumberEngine::max(); }
+
+      /**
+       * Discard a sequence of random numbers.
+       */
+      void
+      discard(unsigned long long __z)
+      {
+       for (; __z != 0ULL; --__z)
+         (*this)();
+      }
+
+      /**
+       * Gets the next value in the generated random number sequence.
+       */
+      result_type
+      operator()();
+
+      /**
+       * Compares two %shuffle_order_engine random number generator objects
+       * of the same type for equality.
+       *
+       * @param __lhs A %shuffle_order_engine random number generator object.
+       * @param __rhs Another %shuffle_order_engine random number generator
+       *              object.
+       *
+       * @returns true if the infinite sequences of generated values
+       *          would be equal, false otherwise.
+      */
+      friend bool
+      operator==(const shuffle_order_engine& __lhs,
+                const shuffle_order_engine& __rhs)
+      { return (__lhs._M_b == __rhs._M_b
+               && std::equal(__lhs._M_v, __lhs._M_v + __k, __rhs._M_v)
+               && __lhs._M_y == __rhs._M_y); }
+
+      /**
+       * @brief Inserts the current state of a %shuffle_order_engine random
+       *        number generator engine @p __x into the output stream
+       @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %shuffle_order_engine random number generator engine.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _RandomNumberEngine1, size_t __k1,
+              typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::shuffle_order_engine<_RandomNumberEngine1,
+                  __k1>& __x);
+
+      /**
+       * @brief Extracts the current state of a % subtract_with_carry_engine
+       *        random number generator engine @p __x from the input stream
+       *        @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x  A %shuffle_order_engine random number generator engine.
+       *
+       * @returns The input stream with the state of @p __x extracted or in
+       * an error state.
+       */
+      template<typename _RandomNumberEngine1, size_t __k1,
+              typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::shuffle_order_engine<_RandomNumberEngine1, __k1>& __x);
+
+    private:
+      void _M_initialize()
+      {
+       for (size_t __i = 0; __i < __k; ++__i)
+         _M_v[__i] = _M_b();
+       _M_y = _M_b();
+      }
+
+      _RandomNumberEngine _M_b;
+      result_type _M_v[__k];
+      result_type _M_y;
+    };
+
+  /**
+   * Compares two %shuffle_order_engine random number generator objects
+   * of the same type for inequality.
+   *
+   * @param __lhs A %shuffle_order_engine random number generator object.
+   * @param __rhs Another %shuffle_order_engine random number generator
+   *              object.
+   *
+   * @returns true if the infinite sequences of generated values
+   *          would be different, false otherwise.
+   */
+  template<typename _RandomNumberEngine, size_t __k>
+    inline bool
+    operator!=(const std::shuffle_order_engine<_RandomNumberEngine,
+              __k>& __lhs,
+              const std::shuffle_order_engine<_RandomNumberEngine,
+              __k>& __rhs)
+    { return !(__lhs == __rhs); }
+
+
+  /**
+   * The classic Minimum Standard rand0 of Lewis, Goodman, and Miller.
+   */
+  typedef linear_congruential_engine<uint_fast32_t, 16807UL, 0UL, 2147483647UL>
+  minstd_rand0;
+
+  /**
+   * An alternative LCR (Lehmer Generator function).
+   */
+  typedef linear_congruential_engine<uint_fast32_t, 48271UL, 0UL, 2147483647UL>
+  minstd_rand;
+
+  /**
+   * The classic Mersenne Twister.
+   *
+   * Reference:
+   * M. Matsumoto and T. Nishimura, Mersenne Twister: A 623-Dimensionally
+   * Equidistributed Uniform Pseudo-Random Number Generator, ACM Transactions
+   * on Modeling and Computer Simulation, Vol. 8, No. 1, January 1998, pp 3-30.
+   */
+  typedef mersenne_twister_engine<
+    uint_fast32_t,
+    32, 624, 397, 31,
+    0x9908b0dfUL, 11,
+    0xffffffffUL, 7,
+    0x9d2c5680UL, 15,
+    0xefc60000UL, 18, 1812433253UL> mt19937;
+
+  /**
+   * An alternative Mersenne Twister.
+   */
+  typedef mersenne_twister_engine<
+    uint_fast64_t,
+    64, 312, 156, 31,
+    0xb5026f5aa96619e9ULL, 29,
+    0x5555555555555555ULL, 17,
+    0x71d67fffeda60000ULL, 37,
+    0xfff7eee000000000ULL, 43,
+    6364136223846793005ULL> mt19937_64;
+
+  typedef subtract_with_carry_engine<uint_fast32_t, 24, 10, 24>
+    ranlux24_base;
+
+  typedef subtract_with_carry_engine<uint_fast64_t, 48, 5, 12>
+    ranlux48_base;
+
+  typedef discard_block_engine<ranlux24_base, 223, 23> ranlux24;
+
+  typedef discard_block_engine<ranlux48_base, 389, 11> ranlux48;
+
+  typedef shuffle_order_engine<minstd_rand0, 256> knuth_b;
+
+  typedef minstd_rand0 default_random_engine;
+
+  /**
+   * A standard interface to a platform-specific non-deterministic
+   * random number generator (if any are available).
+   */
+  class random_device
+  {
+  public:
+    /** The type of the generated random value. */
+    typedef unsigned int result_type;
+
+    // constructors, destructors and member functions
+
+#ifdef _GLIBCXX_USE_RANDOM_TR1
+
+    explicit
+    random_device(const std::string& __token = "/dev/urandom")
+    {
+      if ((__token != "/dev/urandom" && __token != "/dev/random")
+         || !(_M_file = std::fopen(__token.c_str(), "rb")))
+       std::__throw_runtime_error(__N("random_device::"
+                                      "random_device(const std::string&)"));
+    }
+
+    ~random_device()
+    { std::fclose(_M_file); }
+
+#else
+
+    explicit
+    random_device(const std::string& __token = "mt19937")
+    : _M_mt(_M_strtoul(__token)) { }
+
+  private:
+    static unsigned long
+    _M_strtoul(const std::string& __str)
+    {
+      unsigned long __ret = 5489UL;
+      if (__str != "mt19937")
+       {
+         const char* __nptr = __str.c_str();
+         char* __endptr;
+         __ret = std::strtoul(__nptr, &__endptr, 0);
+         if (*__nptr == '\0' || *__endptr != '\0')
+           std::__throw_runtime_error(__N("random_device::_M_strtoul"
+                                          "(const std::string&)"));
+       }
+      return __ret;
+    }
+
+  public:
+
+#endif
+
+    static constexpr result_type
+    min()
+    { return std::numeric_limits<result_type>::min(); }
+
+    static constexpr result_type
+    max()
+    { return std::numeric_limits<result_type>::max(); }
+
+    double
+    entropy() const noexcept
+    { return 0.0; }
+
+    result_type
+    operator()()
+    {
+#ifdef _GLIBCXX_USE_RANDOM_TR1
+      result_type __ret;
+      std::fread(reinterpret_cast<void*>(&__ret), sizeof(result_type),
+                1, _M_file);
+      return __ret;
+#else
+      return _M_mt();
+#endif
+    }
+
+    // No copy functions.
+    random_device(const random_device&) = delete;
+    void operator=(const random_device&) = delete;
+
+  private:
+
+#ifdef _GLIBCXX_USE_RANDOM_TR1
+    FILE*        _M_file;
+#else
+    mt19937      _M_mt;
+#endif
+  };
+
+  /* @} */ // group random_generators
+
+  /**
+   * @addtogroup random_distributions Random Number Distributions
+   * @ingroup random
+   * @{
+   */
+
+  /**
+   * @addtogroup random_distributions_uniform Uniform Distributions
+   * @ingroup random_distributions
+   * @{
+   */
+
+  /**
+   * @brief Uniform discrete distribution for random numbers.
+   * A discrete random distribution on the range @f$[min, max]@f$ with equal
+   * probability throughout the range.
+   */
+  template<typename _IntType = int>
+    class uniform_int_distribution
+    {
+      static_assert(std::is_integral<_IntType>::value,
+                   "template argument not an integral type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _IntType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef uniform_int_distribution<_IntType> distribution_type;
+
+       explicit
+       param_type(_IntType __a = 0,
+                  _IntType __b = std::numeric_limits<_IntType>::max())
+       : _M_a(__a), _M_b(__b)
+       {
+         _GLIBCXX_DEBUG_ASSERT(_M_a <= _M_b);
+       }
+
+       result_type
+       a() const
+       { return _M_a; }
+
+       result_type
+       b() const
+       { return _M_b; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_a == __p2._M_a && __p1._M_b == __p2._M_b; }
+
+      private:
+       _IntType _M_a;
+       _IntType _M_b;
+      };
+
+    public:
+      /**
+       * @brief Constructs a uniform distribution object.
+       */
+      explicit
+      uniform_int_distribution(_IntType __a = 0,
+                          _IntType __b = std::numeric_limits<_IntType>::max())
+      : _M_param(__a, __b)
+      { }
+
+      explicit
+      uniform_int_distribution(const param_type& __p)
+      : _M_param(__p)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       *
+       * Does nothing for the uniform integer distribution.
+       */
+      void
+      reset() { }
+
+      result_type
+      a() const
+      { return _M_param.a(); }
+
+      result_type
+      b() const
+      { return _M_param.b(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the inclusive lower bound of the distribution range.
+       */
+      result_type
+      min() const
+      { return this->a(); }
+
+      /**
+       * @brief Returns the inclusive upper bound of the distribution range.
+       */
+      result_type
+      max() const
+      { return this->b(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+        { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+      /**
+       * @brief Return true if two uniform integer distributions have
+       *        the same parameters.
+       */
+      friend bool
+      operator==(const uniform_int_distribution& __d1,
+                const uniform_int_distribution& __d2)
+      { return __d1._M_param == __d2._M_param; }
+
+    private:
+      param_type _M_param;
+    };
+
+  /**
+   * @brief Return true if two uniform integer distributions have
+   *        different parameters.
+   */
+  template<typename _IntType>
+    inline bool
+    operator!=(const std::uniform_int_distribution<_IntType>& __d1,
+              const std::uniform_int_distribution<_IntType>& __d2)
+    { return !(__d1 == __d2); }
+
+  /**
+   * @brief Inserts a %uniform_int_distribution random number
+   *        distribution @p __x into the output stream @p os.
+   *
+   * @param __os An output stream.
+   * @param __x  A %uniform_int_distribution random number distribution.
+   *
+   * @returns The output stream with the state of @p __x inserted or in
+   * an error state.
+   */
+  template<typename _IntType, typename _CharT, typename _Traits>
+    std::basic_ostream<_CharT, _Traits>&
+    operator<<(std::basic_ostream<_CharT, _Traits>&,
+              const std::uniform_int_distribution<_IntType>&);
+
+  /**
+   * @brief Extracts a %uniform_int_distribution random number distribution
+   * @p __x from the input stream @p __is.
+   *
+   * @param __is An input stream.
+   * @param __x  A %uniform_int_distribution random number generator engine.
+   *
+   * @returns The input stream with @p __x extracted or in an error state.
+   */
+  template<typename _IntType, typename _CharT, typename _Traits>
+    std::basic_istream<_CharT, _Traits>&
+    operator>>(std::basic_istream<_CharT, _Traits>&,
+              std::uniform_int_distribution<_IntType>&);
+
+
+  /**
+   * @brief Uniform continuous distribution for random numbers.
+   *
+   * A continuous random distribution on the range [min, max) with equal
+   * probability throughout the range.  The URNG should be real-valued and
+   * deliver number in the range [0, 1).
+   */
+  template<typename _RealType = double>
+    class uniform_real_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef uniform_real_distribution<_RealType> distribution_type;
+
+       explicit
+       param_type(_RealType __a = _RealType(0),
+                  _RealType __b = _RealType(1))
+       : _M_a(__a), _M_b(__b)
+       {
+         _GLIBCXX_DEBUG_ASSERT(_M_a <= _M_b);
+       }
+
+       result_type
+       a() const
+       { return _M_a; }
+
+       result_type
+       b() const
+       { return _M_b; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_a == __p2._M_a && __p1._M_b == __p2._M_b; }
+
+      private:
+       _RealType _M_a;
+       _RealType _M_b;
+      };
+
+    public:
+      /**
+       * @brief Constructs a uniform_real_distribution object.
+       *
+       * @param __a [IN]  The lower bound of the distribution.
+       * @param __b [IN]  The upper bound of the distribution.
+       */
+      explicit
+      uniform_real_distribution(_RealType __a = _RealType(0),
+                               _RealType __b = _RealType(1))
+      : _M_param(__a, __b)
+      { }
+
+      explicit
+      uniform_real_distribution(const param_type& __p)
+      : _M_param(__p)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       *
+       * Does nothing for the uniform real distribution.
+       */
+      void
+      reset() { }
+
+      result_type
+      a() const
+      { return _M_param.a(); }
+
+      result_type
+      b() const
+      { return _M_param.b(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the inclusive lower bound of the distribution range.
+       */
+      result_type
+      min() const
+      { return this->a(); }
+
+      /**
+       * @brief Returns the inclusive upper bound of the distribution range.
+       */
+      result_type
+      max() const
+      { return this->b(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+        { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p)
+       {
+         __detail::_Adaptor<_UniformRandomNumberGenerator, result_type>
+           __aurng(__urng);
+         return (__aurng() * (__p.b() - __p.a())) + __p.a();
+       }
+
+      /**
+       * @brief Return true if two uniform real distributions have
+       *        the same parameters.
+       */
+      friend bool
+      operator==(const uniform_real_distribution& __d1,
+                const uniform_real_distribution& __d2)
+      { return __d1._M_param == __d2._M_param; }
+
+    private:
+      param_type _M_param;
+    };
+
+  /**
+   * @brief Return true if two uniform real distributions have
+   *        different parameters.
+   */
+  template<typename _IntType>
+    inline bool
+    operator!=(const std::uniform_real_distribution<_IntType>& __d1,
+              const std::uniform_real_distribution<_IntType>& __d2)
+    { return !(__d1 == __d2); }
+
+  /**
+   * @brief Inserts a %uniform_real_distribution random number
+   *        distribution @p __x into the output stream @p __os.
+   *
+   * @param __os An output stream.
+   * @param __x  A %uniform_real_distribution random number distribution.
+   *
+   * @returns The output stream with the state of @p __x inserted or in
+   *          an error state.
+   */
+  template<typename _RealType, typename _CharT, typename _Traits>
+    std::basic_ostream<_CharT, _Traits>&
+    operator<<(std::basic_ostream<_CharT, _Traits>&,
+              const std::uniform_real_distribution<_RealType>&);
+
+  /**
+   * @brief Extracts a %uniform_real_distribution random number distribution
+   * @p __x from the input stream @p __is.
+   *
+   * @param __is An input stream.
+   * @param __x  A %uniform_real_distribution random number generator engine.
+   *
+   * @returns The input stream with @p __x extracted or in an error state.
+   */
+  template<typename _RealType, typename _CharT, typename _Traits>
+    std::basic_istream<_CharT, _Traits>&
+    operator>>(std::basic_istream<_CharT, _Traits>&,
+              std::uniform_real_distribution<_RealType>&);
+
+  /* @} */ // group random_distributions_uniform
+
+  /**
+   * @addtogroup random_distributions_normal Normal Distributions
+   * @ingroup random_distributions
+   * @{
+   */
+
+  /**
+   * @brief A normal continuous distribution for random numbers.
+   *
+   * The formula for the normal probability density function is
+   * @f[
+   *     p(x|\mu,\sigma) = \frac{1}{\sigma \sqrt{2 \pi}}
+   *            e^{- \frac{{x - \mu}^ {2}}{2 \sigma ^ {2}} } 
+   * @f]
+   */
+  template<typename _RealType = double>
+    class normal_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef normal_distribution<_RealType> distribution_type;
+
+       explicit
+       param_type(_RealType __mean = _RealType(0),
+                  _RealType __stddev = _RealType(1))
+       : _M_mean(__mean), _M_stddev(__stddev)
+       {
+         _GLIBCXX_DEBUG_ASSERT(_M_stddev > _RealType(0));
+       }
+
+       _RealType
+       mean() const
+       { return _M_mean; }
+
+       _RealType
+       stddev() const
+       { return _M_stddev; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return (__p1._M_mean == __p2._M_mean
+                 && __p1._M_stddev == __p2._M_stddev); }
+
+      private:
+       _RealType _M_mean;
+       _RealType _M_stddev;
+      };
+
+    public:
+      /**
+       * Constructs a normal distribution with parameters @f$mean@f$ and
+       * standard deviation.
+       */
+      explicit
+      normal_distribution(result_type __mean = result_type(0),
+                         result_type __stddev = result_type(1))
+      : _M_param(__mean, __stddev), _M_saved_available(false)
+      { }
+
+      explicit
+      normal_distribution(const param_type& __p)
+      : _M_param(__p), _M_saved_available(false)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      { _M_saved_available = false; }
+
+      /**
+       * @brief Returns the mean of the distribution.
+       */
+      _RealType
+      mean() const
+      { return _M_param.mean(); }
+
+      /**
+       * @brief Returns the standard deviation of the distribution.
+       */
+      _RealType
+      stddev() const
+      { return _M_param.stddev(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return std::numeric_limits<result_type>::min(); }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+      /**
+       * @brief Return true if two normal distributions have
+       *        the same parameters and the sequences that would
+       *        be generated are equal.
+       */
+      template<typename _RealType1>
+       friend bool
+        operator==(const std::normal_distribution<_RealType1>& __d1,
+                  const std::normal_distribution<_RealType1>& __d2);
+
+      /**
+       * @brief Inserts a %normal_distribution random number distribution
+       * @p __x into the output stream @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %normal_distribution random number distribution.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::normal_distribution<_RealType1>& __x);
+
+      /**
+       * @brief Extracts a %normal_distribution random number distribution
+       * @p __x from the input stream @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x  A %normal_distribution random number generator engine.
+       *
+       * @returns The input stream with @p __x extracted or in an error
+       *          state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::normal_distribution<_RealType1>& __x);
+
+    private:
+      param_type  _M_param;
+      result_type _M_saved;
+      bool        _M_saved_available;
+    };
+
+  /**
+   * @brief Return true if two normal distributions are different.
+   */
+  template<typename _RealType>
+    inline bool
+    operator!=(const std::normal_distribution<_RealType>& __d1,
+              const std::normal_distribution<_RealType>& __d2)
+    { return !(__d1 == __d2); }
+
+
+  /**
+   * @brief A lognormal_distribution random number distribution.
+   *
+   * The formula for the normal probability mass function is
+   * @f[
+   *     p(x|m,s) = \frac{1}{sx\sqrt{2\pi}}
+   *                \exp{-\frac{(\ln{x} - m)^2}{2s^2}} 
+   * @f]
+   */
+  template<typename _RealType = double>
+    class lognormal_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef lognormal_distribution<_RealType> distribution_type;
+
+       explicit
+       param_type(_RealType __m = _RealType(0),
+                  _RealType __s = _RealType(1))
+       : _M_m(__m), _M_s(__s)
+       { }
+
+       _RealType
+       m() const
+       { return _M_m; }
+
+       _RealType
+       s() const
+       { return _M_s; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_m == __p2._M_m && __p1._M_s == __p2._M_s; }
+
+      private:
+       _RealType _M_m;
+       _RealType _M_s;
+      };
+
+      explicit
+      lognormal_distribution(_RealType __m = _RealType(0),
+                            _RealType __s = _RealType(1))
+      : _M_param(__m, __s), _M_nd()
+      { }
+
+      explicit
+      lognormal_distribution(const param_type& __p)
+      : _M_param(__p), _M_nd()
+      { }
+
+      /**
+       * Resets the distribution state.
+       */
+      void
+      reset()
+      { _M_nd.reset(); }
+
+      /**
+       *
+       */
+      _RealType
+      m() const
+      { return _M_param.m(); }
+
+      _RealType
+      s() const
+      { return _M_param.s(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return result_type(0); }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p)
+        { return std::exp(__p.s() * _M_nd(__urng) + __p.m()); }
+
+      /**
+       * @brief Return true if two lognormal distributions have
+       *        the same parameters and the sequences that would
+       *        be generated are equal.
+       */
+      friend bool
+      operator==(const lognormal_distribution& __d1,
+                const lognormal_distribution& __d2)
+      { return (__d1._M_param == __d2._M_param
+               && __d1._M_nd == __d2._M_nd); }
+
+      /**
+       * @brief Inserts a %lognormal_distribution random number distribution
+       * @p __x into the output stream @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %lognormal_distribution random number distribution.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::lognormal_distribution<_RealType1>& __x);
+
+      /**
+       * @brief Extracts a %lognormal_distribution random number distribution
+       * @p __x from the input stream @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x A %lognormal_distribution random number
+       *            generator engine.
+       *
+       * @returns The input stream with @p __x extracted or in an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::lognormal_distribution<_RealType1>& __x);
+
+    private:
+      param_type _M_param;
+
+      std::normal_distribution<result_type> _M_nd;
+    };
+
+  /**
+   * @brief Return true if two lognormal distributions are different.
+   */
+  template<typename _RealType>
+    inline bool
+    operator!=(const std::lognormal_distribution<_RealType>& __d1,
+              const std::lognormal_distribution<_RealType>& __d2)
+    { return !(__d1 == __d2); }
+
+
+  /**
+   * @brief A gamma continuous distribution for random numbers.
+   *
+   * The formula for the gamma probability density function is:
+   * @f[
+   *     p(x|\alpha,\beta) = \frac{1}{\beta\Gamma(\alpha)}
+   *                         (x/\beta)^{\alpha - 1} e^{-x/\beta} 
+   * @f]
+   */
+  template<typename _RealType = double>
+    class gamma_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef gamma_distribution<_RealType> distribution_type;
+       friend class gamma_distribution<_RealType>;
+
+       explicit
+       param_type(_RealType __alpha_val = _RealType(1),
+                  _RealType __beta_val = _RealType(1))
+       : _M_alpha(__alpha_val), _M_beta(__beta_val)
+       {
+         _GLIBCXX_DEBUG_ASSERT(_M_alpha > _RealType(0));
+         _M_initialize();
+       }
+
+       _RealType
+       alpha() const
+       { return _M_alpha; }
+
+       _RealType
+       beta() const
+       { return _M_beta; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return (__p1._M_alpha == __p2._M_alpha
+                 && __p1._M_beta == __p2._M_beta); }
+
+      private:
+       void
+       _M_initialize();
+
+       _RealType _M_alpha;
+       _RealType _M_beta;
+
+       _RealType _M_malpha, _M_a2;
+      };
+
+    public:
+      /**
+       * @brief Constructs a gamma distribution with parameters
+       * @f$\alpha@f$ and @f$\beta@f$.
+       */
+      explicit
+      gamma_distribution(_RealType __alpha_val = _RealType(1),
+                        _RealType __beta_val = _RealType(1))
+      : _M_param(__alpha_val, __beta_val), _M_nd()
+      { }
+
+      explicit
+      gamma_distribution(const param_type& __p)
+      : _M_param(__p), _M_nd()
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      { _M_nd.reset(); }
+
+      /**
+       * @brief Returns the @f$\alpha@f$ of the distribution.
+       */
+      _RealType
+      alpha() const
+      { return _M_param.alpha(); }
+
+      /**
+       * @brief Returns the @f$\beta@f$ of the distribution.
+       */
+      _RealType
+      beta() const
+      { return _M_param.beta(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return result_type(0); }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+      /**
+       * @brief Return true if two gamma distributions have the same
+       *        parameters and the sequences that would be generated
+       *        are equal.
+       */
+      friend bool
+      operator==(const gamma_distribution& __d1,
+                const gamma_distribution& __d2)
+      { return (__d1._M_param == __d2._M_param
+               && __d1._M_nd == __d2._M_nd); }
+
+      /**
+       * @brief Inserts a %gamma_distribution random number distribution
+       * @p __x into the output stream @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %gamma_distribution random number distribution.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::gamma_distribution<_RealType1>& __x);
+
+      /**
+       * @brief Extracts a %gamma_distribution random number distribution
+       * @p __x from the input stream @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x  A %gamma_distribution random number generator engine.
+       *
+       * @returns The input stream with @p __x extracted or in an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::gamma_distribution<_RealType1>& __x);
+
+    private:
+      param_type _M_param;
+
+      std::normal_distribution<result_type> _M_nd;
+    };
+
+  /**
+   * @brief Return true if two gamma distributions are different.
+   */
+   template<typename _RealType>
+    inline bool
+     operator!=(const std::gamma_distribution<_RealType>& __d1,
+               const std::gamma_distribution<_RealType>& __d2)
+    { return !(__d1 == __d2); }
+
+
+  /**
+   * @brief A chi_squared_distribution random number distribution.
+   *
+   * The formula for the normal probability mass function is
+   * @f$p(x|n) = \frac{x^{(n/2) - 1}e^{-x/2}}{\Gamma(n/2) 2^{n/2}}@f$
+   */
+  template<typename _RealType = double>
+    class chi_squared_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef chi_squared_distribution<_RealType> distribution_type;
+
+       explicit
+       param_type(_RealType __n = _RealType(1))
+       : _M_n(__n)
+       { }
+
+       _RealType
+       n() const
+       { return _M_n; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_n == __p2._M_n; }
+
+      private:
+       _RealType _M_n;
+      };
+
+      explicit
+      chi_squared_distribution(_RealType __n = _RealType(1))
+      : _M_param(__n), _M_gd(__n / 2)
+      { }
+
+      explicit
+      chi_squared_distribution(const param_type& __p)
+      : _M_param(__p), _M_gd(__p.n() / 2)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      { _M_gd.reset(); }
+
+      /**
+       *
+       */
+      _RealType
+      n() const
+      { return _M_param.n(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return result_type(0); }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return 2 * _M_gd(__urng); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p)
+        {
+         typedef typename std::gamma_distribution<result_type>::param_type
+           param_type;
+         return 2 * _M_gd(__urng, param_type(__p.n() / 2));
+       }
+
+      /**
+       * @brief Return true if two Chi-squared distributions have
+       *        the same parameters and the sequences that would be
+       *        generated are equal.
+       */
+      friend bool
+      operator==(const chi_squared_distribution& __d1,
+                const chi_squared_distribution& __d2)
+      { return __d1._M_param == __d2._M_param && __d1._M_gd == __d2._M_gd; }
+
+      /**
+       * @brief Inserts a %chi_squared_distribution random number distribution
+       * @p __x into the output stream @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %chi_squared_distribution random number distribution.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::chi_squared_distribution<_RealType1>& __x);
+
+      /**
+       * @brief Extracts a %chi_squared_distribution random number distribution
+       * @p __x from the input stream @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x A %chi_squared_distribution random number
+       *            generator engine.
+       *
+       * @returns The input stream with @p __x extracted or in an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::chi_squared_distribution<_RealType1>& __x);
+
+    private:
+      param_type _M_param;
+
+      std::gamma_distribution<result_type> _M_gd;
+    };
+
+  /**
+   * @brief Return true if two Chi-squared distributions are different.
+   */
+  template<typename _RealType>
+    inline bool
+    operator!=(const std::chi_squared_distribution<_RealType>& __d1,
+              const std::chi_squared_distribution<_RealType>& __d2)
+    { return !(__d1 == __d2); }
+
+
+  /**
+   * @brief A cauchy_distribution random number distribution.
+   *
+   * The formula for the normal probability mass function is
+   * @f$p(x|a,b) = (\pi b (1 + (\frac{x-a}{b})^2))^{-1}@f$
+   */
+  template<typename _RealType = double>
+    class cauchy_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef cauchy_distribution<_RealType> distribution_type;
+
+       explicit
+       param_type(_RealType __a = _RealType(0),
+                  _RealType __b = _RealType(1))
+       : _M_a(__a), _M_b(__b)
+       { }
+
+       _RealType
+       a() const
+       { return _M_a; }
+
+       _RealType
+       b() const
+       { return _M_b; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_a == __p2._M_a && __p1._M_b == __p2._M_b; }
+
+      private:
+       _RealType _M_a;
+       _RealType _M_b;
+      };
+
+      explicit
+      cauchy_distribution(_RealType __a = _RealType(0),
+                         _RealType __b = _RealType(1))
+      : _M_param(__a, __b)
+      { }
+
+      explicit
+      cauchy_distribution(const param_type& __p)
+      : _M_param(__p)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      { }
+
+      /**
+       *
+       */
+      _RealType
+      a() const
+      { return _M_param.a(); }
+
+      _RealType
+      b() const
+      { return _M_param.b(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return std::numeric_limits<result_type>::min(); }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+      /**
+       * @brief Return true if two Cauchy distributions have
+       *        the same parameters.
+       */
+      friend bool
+      operator==(const cauchy_distribution& __d1,
+                const cauchy_distribution& __d2)
+      { return __d1._M_param == __d2._M_param; }
+
+    private:
+      param_type _M_param;
+    };
+
+  /**
+   * @brief Return true if two Cauchy distributions have
+   *        different parameters.
+   */
+  template<typename _RealType>
+    inline bool
+    operator!=(const std::cauchy_distribution<_RealType>& __d1,
+              const std::cauchy_distribution<_RealType>& __d2)
+    { return !(__d1 == __d2); }
+
+  /**
+   * @brief Inserts a %cauchy_distribution random number distribution
+   * @p __x into the output stream @p __os.
+   *
+   * @param __os An output stream.
+   * @param __x  A %cauchy_distribution random number distribution.
+   *
+   * @returns The output stream with the state of @p __x inserted or in
+   * an error state.
+   */
+  template<typename _RealType, typename _CharT, typename _Traits>
+    std::basic_ostream<_CharT, _Traits>&
+    operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+              const std::cauchy_distribution<_RealType>& __x);
+
+  /**
+   * @brief Extracts a %cauchy_distribution random number distribution
+   * @p __x from the input stream @p __is.
+   *
+   * @param __is An input stream.
+   * @param __x A %cauchy_distribution random number
+   *            generator engine.
+   *
+   * @returns The input stream with @p __x extracted or in an error state.
+   */
+  template<typename _RealType, typename _CharT, typename _Traits>
+    std::basic_istream<_CharT, _Traits>&
+    operator>>(std::basic_istream<_CharT, _Traits>& __is,
+              std::cauchy_distribution<_RealType>& __x);
+
+
+  /**
+   * @brief A fisher_f_distribution random number distribution.
+   *
+   * The formula for the normal probability mass function is
+   * @f[
+   *     p(x|m,n) = \frac{\Gamma((m+n)/2)}{\Gamma(m/2)\Gamma(n/2)}
+   *                (\frac{m}{n})^{m/2} x^{(m/2)-1}
+   *                (1 + \frac{mx}{n})^{-(m+n)/2} 
+   * @f]
+   */
+  template<typename _RealType = double>
+    class fisher_f_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef fisher_f_distribution<_RealType> distribution_type;
+
+       explicit
+       param_type(_RealType __m = _RealType(1),
+                  _RealType __n = _RealType(1))
+       : _M_m(__m), _M_n(__n)
+       { }
+
+       _RealType
+       m() const
+       { return _M_m; }
+
+       _RealType
+       n() const
+       { return _M_n; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_m == __p2._M_m && __p1._M_n == __p2._M_n; }
+
+      private:
+       _RealType _M_m;
+       _RealType _M_n;
+      };
+
+      explicit
+      fisher_f_distribution(_RealType __m = _RealType(1),
+                           _RealType __n = _RealType(1))
+      : _M_param(__m, __n), _M_gd_x(__m / 2), _M_gd_y(__n / 2)
+      { }
+
+      explicit
+      fisher_f_distribution(const param_type& __p)
+      : _M_param(__p), _M_gd_x(__p.m() / 2), _M_gd_y(__p.n() / 2)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      {
+       _M_gd_x.reset();
+       _M_gd_y.reset();
+      }
+
+      /**
+       *
+       */
+      _RealType
+      m() const
+      { return _M_param.m(); }
+
+      _RealType
+      n() const
+      { return _M_param.n(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return result_type(0); }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return (_M_gd_x(__urng) * n()) / (_M_gd_y(__urng) * m()); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p)
+        {
+         typedef typename std::gamma_distribution<result_type>::param_type
+           param_type;
+         return ((_M_gd_x(__urng, param_type(__p.m() / 2)) * n())
+                 / (_M_gd_y(__urng, param_type(__p.n() / 2)) * m()));
+       }
+
+      /**
+       * @brief Return true if two Fisher f distributions have
+       *        the same parameters and the sequences that would
+       *        be generated are equal.
+       */
+      friend bool
+      operator==(const fisher_f_distribution& __d1,
+                const fisher_f_distribution& __d2)
+      { return (__d1._M_param == __d2._M_param
+               && __d1._M_gd_x == __d2._M_gd_x
+               && __d1._M_gd_y == __d2._M_gd_y); }
+
+      /**
+       * @brief Inserts a %fisher_f_distribution random number distribution
+       * @p __x into the output stream @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %fisher_f_distribution random number distribution.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::fisher_f_distribution<_RealType1>& __x);
+
+      /**
+       * @brief Extracts a %fisher_f_distribution random number distribution
+       * @p __x from the input stream @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x A %fisher_f_distribution random number
+       *            generator engine.
+       *
+       * @returns The input stream with @p __x extracted or in an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::fisher_f_distribution<_RealType1>& __x);
+
+    private:
+      param_type _M_param;
+
+      std::gamma_distribution<result_type> _M_gd_x, _M_gd_y;
+    };
+
+  /**
+   * @brief Return true if two Fisher f distributions are diferent.
+   */
+  template<typename _RealType>
+    inline bool
+    operator!=(const std::fisher_f_distribution<_RealType>& __d1,
+              const std::fisher_f_distribution<_RealType>& __d2)
+    { return !(__d1 == __d2); }
+
+  /**
+   * @brief A student_t_distribution random number distribution.
+   *
+   * The formula for the normal probability mass function is:
+   * @f[
+   *     p(x|n) = \frac{1}{\sqrt(n\pi)} \frac{\Gamma((n+1)/2)}{\Gamma(n/2)}
+   *              (1 + \frac{x^2}{n}) ^{-(n+1)/2} 
+   * @f]
+   */
+  template<typename _RealType = double>
+    class student_t_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef student_t_distribution<_RealType> distribution_type;
+
+       explicit
+       param_type(_RealType __n = _RealType(1))
+       : _M_n(__n)
+       { }
+
+       _RealType
+       n() const
+       { return _M_n; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_n == __p2._M_n; }
+
+      private:
+       _RealType _M_n;
+      };
+
+      explicit
+      student_t_distribution(_RealType __n = _RealType(1))
+      : _M_param(__n), _M_nd(), _M_gd(__n / 2, 2)
+      { }
+
+      explicit
+      student_t_distribution(const param_type& __p)
+      : _M_param(__p), _M_nd(), _M_gd(__p.n() / 2, 2)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      {
+       _M_nd.reset();
+       _M_gd.reset();
+      }
+
+      /**
+       *
+       */
+      _RealType
+      n() const
+      { return _M_param.n(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return std::numeric_limits<result_type>::min(); }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+        operator()(_UniformRandomNumberGenerator& __urng)
+        { return _M_nd(__urng) * std::sqrt(n() / _M_gd(__urng)); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p)
+        {
+         typedef typename std::gamma_distribution<result_type>::param_type
+           param_type;
+       
+         const result_type __g = _M_gd(__urng, param_type(__p.n() / 2, 2));
+         return _M_nd(__urng) * std::sqrt(__p.n() / __g);
+        }
+
+      /**
+       * @brief Return true if two Student t distributions have
+       *        the same parameters and the sequences that would
+       *        be generated are equal.
+       */
+      friend bool
+      operator==(const student_t_distribution& __d1,
+                const student_t_distribution& __d2)
+      { return (__d1._M_param == __d2._M_param
+               && __d1._M_nd == __d2._M_nd && __d1._M_gd == __d2._M_gd); }
+
+      /**
+       * @brief Inserts a %student_t_distribution random number distribution
+       * @p __x into the output stream @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %student_t_distribution random number distribution.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::student_t_distribution<_RealType1>& __x);
+
+      /**
+       * @brief Extracts a %student_t_distribution random number distribution
+       * @p __x from the input stream @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x A %student_t_distribution random number
+       *            generator engine.
+       *
+       * @returns The input stream with @p __x extracted or in an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::student_t_distribution<_RealType1>& __x);
+
+    private:
+      param_type _M_param;
+
+      std::normal_distribution<result_type> _M_nd;
+      std::gamma_distribution<result_type> _M_gd;
+    };
+
+  /**
+   * @brief Return true if two Student t distributions are different.
+   */
+  template<typename _RealType>
+    inline bool
+    operator!=(const std::student_t_distribution<_RealType>& __d1,
+              const std::student_t_distribution<_RealType>& __d2)
+    { return !(__d1 == __d2); }
+
+
+  /* @} */ // group random_distributions_normal
+
+  /**
+   * @addtogroup random_distributions_bernoulli Bernoulli Distributions
+   * @ingroup random_distributions
+   * @{
+   */
+
+  /**
+   * @brief A Bernoulli random number distribution.
+   *
+   * Generates a sequence of true and false values with likelihood @f$p@f$
+   * that true will come up and @f$(1 - p)@f$ that false will appear.
+   */
+  class bernoulli_distribution
+  {
+  public:
+    /** The type of the range of the distribution. */
+    typedef bool result_type;
+    /** Parameter type. */
+    struct param_type
+    {
+      typedef bernoulli_distribution distribution_type;
+
+      explicit
+      param_type(double __p = 0.5)
+      : _M_p(__p)
+      {
+       _GLIBCXX_DEBUG_ASSERT((_M_p >= 0.0) && (_M_p <= 1.0));
+      }
+
+      double
+      p() const
+      { return _M_p; }
+
+      friend bool
+      operator==(const param_type& __p1, const param_type& __p2)
+      { return __p1._M_p == __p2._M_p; }
+
+    private:
+      double _M_p;
+    };
+
+  public:
+    /**
+     * @brief Constructs a Bernoulli distribution with likelihood @p p.
+     *
+     * @param __p  [IN]  The likelihood of a true result being returned.
+     *                   Must be in the interval @f$[0, 1]@f$.
+     */
+    explicit
+    bernoulli_distribution(double __p = 0.5)
+    : _M_param(__p)
+    { }
+
+    explicit
+    bernoulli_distribution(const param_type& __p)
+    : _M_param(__p)
+    { }
+
+    /**
+     * @brief Resets the distribution state.
+     *
+     * Does nothing for a Bernoulli distribution.
+     */
+    void
+    reset() { }
+
+    /**
+     * @brief Returns the @p p parameter of the distribution.
+     */
+    double
+    p() const
+    { return _M_param.p(); }
+
+    /**
+     * @brief Returns the parameter set of the distribution.
+     */
+    param_type
+    param() const
+    { return _M_param; }
+
+    /**
+     * @brief Sets the parameter set of the distribution.
+     * @param __param The new parameter set of the distribution.
+     */
+    void
+    param(const param_type& __param)
+    { _M_param = __param; }
+
+    /**
+     * @brief Returns the greatest lower bound value of the distribution.
+     */
+    result_type
+    min() const
+    { return std::numeric_limits<result_type>::min(); }
+
+    /**
+     * @brief Returns the least upper bound value of the distribution.
+     */
+    result_type
+    max() const
+    { return std::numeric_limits<result_type>::max(); }
+
+    /**
+     * @brief Generating functions.
+     */
+    template<typename _UniformRandomNumberGenerator>
+      result_type
+      operator()(_UniformRandomNumberGenerator& __urng)
+      { return this->operator()(__urng, _M_param); }
+
+    template<typename _UniformRandomNumberGenerator>
+      result_type
+      operator()(_UniformRandomNumberGenerator& __urng,
+                const param_type& __p)
+      {
+       __detail::_Adaptor<_UniformRandomNumberGenerator, double>
+         __aurng(__urng);
+       if ((__aurng() - __aurng.min())
+            < __p.p() * (__aurng.max() - __aurng.min()))
+         return true;
+       return false;
+      }
+
+    /**
+     * @brief Return true if two Bernoulli distributions have
+     *        the same parameters.
+     */
+    friend bool
+    operator==(const bernoulli_distribution& __d1,
+              const bernoulli_distribution& __d2)
+    { return __d1._M_param == __d2._M_param; }
+
+  private:
+    param_type _M_param;
+  };
+
+  /**
+   * @brief Return true if two Bernoulli distributions have
+   *        different parameters.
+   */
+  inline bool
+  operator!=(const std::bernoulli_distribution& __d1,
+            const std::bernoulli_distribution& __d2)
+  { return !(__d1 == __d2); }
+
+  /**
+   * @brief Inserts a %bernoulli_distribution random number distribution
+   * @p __x into the output stream @p __os.
+   *
+   * @param __os An output stream.
+   * @param __x  A %bernoulli_distribution random number distribution.
+   *
+   * @returns The output stream with the state of @p __x inserted or in
+   * an error state.
+   */
+  template<typename _CharT, typename _Traits>
+    std::basic_ostream<_CharT, _Traits>&
+    operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+              const std::bernoulli_distribution& __x);
+
+  /**
+   * @brief Extracts a %bernoulli_distribution random number distribution
+   * @p __x from the input stream @p __is.
+   *
+   * @param __is An input stream.
+   * @param __x  A %bernoulli_distribution random number generator engine.
+   *
+   * @returns The input stream with @p __x extracted or in an error state.
+   */
+  template<typename _CharT, typename _Traits>
+    std::basic_istream<_CharT, _Traits>&
+    operator>>(std::basic_istream<_CharT, _Traits>& __is,
+              std::bernoulli_distribution& __x)
+    {
+      double __p;
+      __is >> __p;
+      __x.param(bernoulli_distribution::param_type(__p));
+      return __is;
+    }
+
+
+  /**
+   * @brief A discrete binomial random number distribution.
+   *
+   * The formula for the binomial probability density function is
+   * @f$p(i|t,p) = \binom{n}{i} p^i (1 - p)^{t - i}@f$ where @f$t@f$
+   * and @f$p@f$ are the parameters of the distribution.
+   */
+  template<typename _IntType = int>
+    class binomial_distribution
+    {
+      static_assert(std::is_integral<_IntType>::value,
+                   "template argument not an integral type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _IntType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef binomial_distribution<_IntType> distribution_type;
+       friend class binomial_distribution<_IntType>;
+
+       explicit
+       param_type(_IntType __t = _IntType(1), double __p = 0.5)
+       : _M_t(__t), _M_p(__p)
+       {
+         _GLIBCXX_DEBUG_ASSERT((_M_t >= _IntType(0))
+                               && (_M_p >= 0.0)
+                               && (_M_p <= 1.0));
+         _M_initialize();
+       }
+
+       _IntType
+       t() const
+       { return _M_t; }
+
+       double
+       p() const
+       { return _M_p; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_t == __p2._M_t && __p1._M_p == __p2._M_p; }
+
+      private:
+       void
+       _M_initialize();
+
+       _IntType _M_t;
+       double _M_p;
+
+       double _M_q;
+#if _GLIBCXX_USE_C99_MATH_TR1
+       double _M_d1, _M_d2, _M_s1, _M_s2, _M_c,
+              _M_a1, _M_a123, _M_s, _M_lf, _M_lp1p;
+#endif
+       bool   _M_easy;
+      };
+
+      // constructors and member function
+      explicit
+      binomial_distribution(_IntType __t = _IntType(1),
+                           double __p = 0.5)
+      : _M_param(__t, __p), _M_nd()
+      { }
+
+      explicit
+      binomial_distribution(const param_type& __p)
+      : _M_param(__p), _M_nd()
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      { _M_nd.reset(); }
+
+      /**
+       * @brief Returns the distribution @p t parameter.
+       */
+      _IntType
+      t() const
+      { return _M_param.t(); }
+
+      /**
+       * @brief Returns the distribution @p p parameter.
+       */
+      double
+      p() const
+      { return _M_param.p(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return 0; }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return _M_param.t(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+      /**
+       * @brief Return true if two binomial distributions have
+       *        the same parameters and the sequences that would
+       *        be generated are equal.
+       */
+       friend bool
+        operator==(const binomial_distribution& __d1,
+                  const binomial_distribution& __d2)
+#ifdef _GLIBCXX_USE_C99_MATH_TR1
+       { return __d1._M_param == __d2._M_param && __d1._M_nd == __d2._M_nd; }
+#else
+        { return __d1._M_param == __d2._M_param; }
+#endif
+
+      /**
+       * @brief Inserts a %binomial_distribution random number distribution
+       * @p __x into the output stream @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %binomial_distribution random number distribution.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _IntType1,
+              typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::binomial_distribution<_IntType1>& __x);
+
+      /**
+       * @brief Extracts a %binomial_distribution random number distribution
+       * @p __x from the input stream @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x  A %binomial_distribution random number generator engine.
+       *
+       * @returns The input stream with @p __x extracted or in an error
+       *          state.
+       */
+      template<typename _IntType1,
+              typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::binomial_distribution<_IntType1>& __x);
+
+    private:
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       _M_waiting(_UniformRandomNumberGenerator& __urng, _IntType __t);
+
+      param_type _M_param;
+
+      // NB: Unused when _GLIBCXX_USE_C99_MATH_TR1 is undefined.
+      std::normal_distribution<double> _M_nd;
+    };
+
+  /**
+   * @brief Return true if two binomial distributions are different.
+   */
+  template<typename _IntType>
+    inline bool
+    operator!=(const std::binomial_distribution<_IntType>& __d1,
+              const std::binomial_distribution<_IntType>& __d2)
+    { return !(__d1 == __d2); }
+
+
+  /**
+   * @brief A discrete geometric random number distribution.
+   *
+   * The formula for the geometric probability density function is
+   * @f$p(i|p) = p(1 - p)^{i}@f$ where @f$p@f$ is the parameter of the
+   * distribution.
+   */
+  template<typename _IntType = int>
+    class geometric_distribution
+    {
+      static_assert(std::is_integral<_IntType>::value,
+                   "template argument not an integral type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _IntType  result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef geometric_distribution<_IntType> distribution_type;
+       friend class geometric_distribution<_IntType>;
+
+       explicit
+       param_type(double __p = 0.5)
+       : _M_p(__p)
+       {
+         _GLIBCXX_DEBUG_ASSERT((_M_p > 0.0) && (_M_p < 1.0));
+         _M_initialize();
+       }
+
+       double
+       p() const
+       { return _M_p; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_p == __p2._M_p; }
+
+      private:
+       void
+       _M_initialize()
+       { _M_log_1_p = std::log(1.0 - _M_p); }
+
+       double _M_p;
+
+       double _M_log_1_p;
+      };
+
+      // constructors and member function
+      explicit
+      geometric_distribution(double __p = 0.5)
+      : _M_param(__p)
+      { }
+
+      explicit
+      geometric_distribution(const param_type& __p)
+      : _M_param(__p)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       *
+       * Does nothing for the geometric distribution.
+       */
+      void
+      reset() { }
+
+      /**
+       * @brief Returns the distribution parameter @p p.
+       */
+      double
+      p() const
+      { return _M_param.p(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return 0; }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+      /**
+       * @brief Return true if two geometric distributions have
+       *        the same parameters.
+       */
+      friend bool
+      operator==(const geometric_distribution& __d1,
+                const geometric_distribution& __d2)
+      { return __d1._M_param == __d2._M_param; }
+
+    private:
+      param_type _M_param;
+    };
+
+  /**
+   * @brief Return true if two geometric distributions have
+   *        different parameters.
+   */
+  template<typename _IntType>
+    inline bool
+    operator!=(const std::geometric_distribution<_IntType>& __d1,
+              const std::geometric_distribution<_IntType>& __d2)
+    { return !(__d1 == __d2); }
+
+  /**
+   * @brief Inserts a %geometric_distribution random number distribution
+   * @p __x into the output stream @p __os.
+   *
+   * @param __os An output stream.
+   * @param __x  A %geometric_distribution random number distribution.
+   *
+   * @returns The output stream with the state of @p __x inserted or in
+   * an error state.
+   */
+  template<typename _IntType,
+          typename _CharT, typename _Traits>
+    std::basic_ostream<_CharT, _Traits>&
+    operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+              const std::geometric_distribution<_IntType>& __x);
+
+  /**
+   * @brief Extracts a %geometric_distribution random number distribution
+   * @p __x from the input stream @p __is.
+   *
+   * @param __is An input stream.
+   * @param __x  A %geometric_distribution random number generator engine.
+   *
+   * @returns The input stream with @p __x extracted or in an error state.
+   */
+  template<typename _IntType,
+          typename _CharT, typename _Traits>
+    std::basic_istream<_CharT, _Traits>&
+    operator>>(std::basic_istream<_CharT, _Traits>& __is,
+              std::geometric_distribution<_IntType>& __x);
+
+
+  /**
+   * @brief A negative_binomial_distribution random number distribution.
+   *
+   * The formula for the negative binomial probability mass function is
+   * @f$p(i) = \binom{n}{i} p^i (1 - p)^{t - i}@f$ where @f$t@f$
+   * and @f$p@f$ are the parameters of the distribution.
+   */
+  template<typename _IntType = int>
+    class negative_binomial_distribution
+    {
+      static_assert(std::is_integral<_IntType>::value,
+                   "template argument not an integral type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _IntType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef negative_binomial_distribution<_IntType> distribution_type;
+
+       explicit
+       param_type(_IntType __k = 1, double __p = 0.5)
+       : _M_k(__k), _M_p(__p)
+       {
+         _GLIBCXX_DEBUG_ASSERT((_M_k > 0) && (_M_p > 0.0) && (_M_p <= 1.0));
+       }
+
+       _IntType
+       k() const
+       { return _M_k; }
+
+       double
+       p() const
+       { return _M_p; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_k == __p2._M_k && __p1._M_p == __p2._M_p; }
+
+      private:
+       _IntType _M_k;
+       double _M_p;
+      };
+
+      explicit
+      negative_binomial_distribution(_IntType __k = 1, double __p = 0.5)
+      : _M_param(__k, __p), _M_gd(__k, (1.0 - __p) / __p)
+      { }
+
+      explicit
+      negative_binomial_distribution(const param_type& __p)
+      : _M_param(__p), _M_gd(__p.k(), (1.0 - __p.p()) / __p.p())
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      { _M_gd.reset(); }
+
+      /**
+       * @brief Return the @f$k@f$ parameter of the distribution.
+       */
+      _IntType
+      k() const
+      { return _M_param.k(); }
+
+      /**
+       * @brief Return the @f$p@f$ parameter of the distribution.
+       */
+      double
+      p() const
+      { return _M_param.p(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return result_type(0); }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+        operator()(_UniformRandomNumberGenerator& __urng);
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+      /**
+       * @brief Return true if two negative binomial distributions have
+       *        the same parameters and the sequences that would be
+       *        generated are equal.
+       */
+      friend bool
+      operator==(const negative_binomial_distribution& __d1,
+                const negative_binomial_distribution& __d2)
+      { return __d1._M_param == __d2._M_param && __d1._M_gd == __d2._M_gd; }
+
+      /**
+       * @brief Inserts a %negative_binomial_distribution random
+       *        number distribution @p __x into the output stream @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %negative_binomial_distribution random number
+       *             distribution.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       *          an error state.
+       */
+      template<typename _IntType1, typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::negative_binomial_distribution<_IntType1>& __x);
+
+      /**
+       * @brief Extracts a %negative_binomial_distribution random number
+       *        distribution @p __x from the input stream @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x A %negative_binomial_distribution random number
+       *            generator engine.
+       *
+       * @returns The input stream with @p __x extracted or in an error state.
+       */
+      template<typename _IntType1, typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::negative_binomial_distribution<_IntType1>& __x);
+
+    private:
+      param_type _M_param;
+
+      std::gamma_distribution<double> _M_gd;
+    };
+
+  /**
+   * @brief Return true if two negative binomial distributions are different.
+   */
+  template<typename _IntType>
+    inline bool
+    operator!=(const std::negative_binomial_distribution<_IntType>& __d1,
+              const std::negative_binomial_distribution<_IntType>& __d2)
+    { return !(__d1 == __d2); }
+
+
+  /* @} */ // group random_distributions_bernoulli
+
+  /**
+   * @addtogroup random_distributions_poisson Poisson Distributions
+   * @ingroup random_distributions
+   * @{
+   */
+
+  /**
+   * @brief A discrete Poisson random number distribution.
+   *
+   * The formula for the Poisson probability density function is
+   * @f$p(i|\mu) = \frac{\mu^i}{i!} e^{-\mu}@f$ where @f$\mu@f$ is the
+   * parameter of the distribution.
+   */
+  template<typename _IntType = int>
+    class poisson_distribution
+    {
+      static_assert(std::is_integral<_IntType>::value,
+                   "template argument not an integral type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _IntType  result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef poisson_distribution<_IntType> distribution_type;
+       friend class poisson_distribution<_IntType>;
+
+       explicit
+       param_type(double __mean = 1.0)
+       : _M_mean(__mean)
+       {
+         _GLIBCXX_DEBUG_ASSERT(_M_mean > 0.0);
+         _M_initialize();
+       }
+
+       double
+       mean() const
+       { return _M_mean; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_mean == __p2._M_mean; }
+
+      private:
+       // Hosts either log(mean) or the threshold of the simple method.
+       void
+       _M_initialize();
+
+       double _M_mean;
+
+       double _M_lm_thr;
+#if _GLIBCXX_USE_C99_MATH_TR1
+       double _M_lfm, _M_sm, _M_d, _M_scx, _M_1cx, _M_c2b, _M_cb;
+#endif
+      };
+
+      // constructors and member function
+      explicit
+      poisson_distribution(double __mean = 1.0)
+      : _M_param(__mean), _M_nd()
+      { }
+
+      explicit
+      poisson_distribution(const param_type& __p)
+      : _M_param(__p), _M_nd()
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      { _M_nd.reset(); }
+
+      /**
+       * @brief Returns the distribution parameter @p mean.
+       */
+      double
+      mean() const
+      { return _M_param.mean(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return 0; }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+       /**
+       * @brief Return true if two Poisson distributions have the same
+       *        parameters and the sequences that would be generated
+       *        are equal.
+       */
+      friend bool
+      operator==(const poisson_distribution& __d1,
+                const poisson_distribution& __d2)
+#ifdef _GLIBCXX_USE_C99_MATH_TR1
+      { return __d1._M_param == __d2._M_param && __d1._M_nd == __d2._M_nd; }
+#else
+      { return __d1._M_param == __d2._M_param; }
+#endif
+
+      /**
+       * @brief Inserts a %poisson_distribution random number distribution
+       * @p __x into the output stream @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %poisson_distribution random number distribution.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _IntType1, typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::poisson_distribution<_IntType1>& __x);
+
+      /**
+       * @brief Extracts a %poisson_distribution random number distribution
+       * @p __x from the input stream @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x  A %poisson_distribution random number generator engine.
+       *
+       * @returns The input stream with @p __x extracted or in an error
+       *          state.
+       */
+      template<typename _IntType1, typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::poisson_distribution<_IntType1>& __x);
+
+    private:
+      param_type _M_param;
+
+      // NB: Unused when _GLIBCXX_USE_C99_MATH_TR1 is undefined.
+      std::normal_distribution<double> _M_nd;
+    };
+
+  /**
+   * @brief Return true if two Poisson distributions are different.
+   */
+  template<typename _IntType>
+    inline bool
+    operator!=(const std::poisson_distribution<_IntType>& __d1,
+              const std::poisson_distribution<_IntType>& __d2)
+    { return !(__d1 == __d2); }
+
+
+  /**
+   * @brief An exponential continuous distribution for random numbers.
+   *
+   * The formula for the exponential probability density function is
+   * @f$p(x|\lambda) = \lambda e^{-\lambda x}@f$.
+   *
+   * <table border=1 cellpadding=10 cellspacing=0>
+   * <caption align=top>Distribution Statistics</caption>
+   * <tr><td>Mean</td><td>@f$\frac{1}{\lambda}@f$</td></tr>
+   * <tr><td>Median</td><td>@f$\frac{\ln 2}{\lambda}@f$</td></tr>
+   * <tr><td>Mode</td><td>@f$zero@f$</td></tr>
+   * <tr><td>Range</td><td>@f$[0, \infty]@f$</td></tr>
+   * <tr><td>Standard Deviation</td><td>@f$\frac{1}{\lambda}@f$</td></tr>
+   * </table>
+   */
+  template<typename _RealType = double>
+    class exponential_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef exponential_distribution<_RealType> distribution_type;
+
+       explicit
+       param_type(_RealType __lambda = _RealType(1))
+       : _M_lambda(__lambda)
+       {
+         _GLIBCXX_DEBUG_ASSERT(_M_lambda > _RealType(0));
+       }
+
+       _RealType
+       lambda() const
+       { return _M_lambda; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_lambda == __p2._M_lambda; }
+
+      private:
+       _RealType _M_lambda;
+      };
+
+    public:
+      /**
+       * @brief Constructs an exponential distribution with inverse scale
+       *        parameter @f$\lambda@f$.
+       */
+      explicit
+      exponential_distribution(const result_type& __lambda = result_type(1))
+      : _M_param(__lambda)
+      { }
+
+      explicit
+      exponential_distribution(const param_type& __p)
+      : _M_param(__p)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       *
+       * Has no effect on exponential distributions.
+       */
+      void
+      reset() { }
+
+      /**
+       * @brief Returns the inverse scale parameter of the distribution.
+       */
+      _RealType
+      lambda() const
+      { return _M_param.lambda(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return result_type(0); }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+        { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p)
+       {
+         __detail::_Adaptor<_UniformRandomNumberGenerator, result_type>
+           __aurng(__urng);
+         return -std::log(result_type(1) - __aurng()) / __p.lambda();
+       }
+
+      /**
+       * @brief Return true if two exponential distributions have the same
+       *        parameters.
+       */
+      friend bool
+      operator==(const exponential_distribution& __d1,
+                const exponential_distribution& __d2)
+      { return __d1._M_param == __d2._M_param; }
+
+    private:
+      param_type _M_param;
+    };
+
+  /**
+   * @brief Return true if two exponential distributions have different
+   *        parameters.
+   */
+  template<typename _RealType>
+    inline bool
+    operator!=(const std::exponential_distribution<_RealType>& __d1,
+              const std::exponential_distribution<_RealType>& __d2)
+    { return !(__d1 == __d2); }
+
+  /**
+   * @brief Inserts a %exponential_distribution random number distribution
+   * @p __x into the output stream @p __os.
+   *
+   * @param __os An output stream.
+   * @param __x  A %exponential_distribution random number distribution.
+   *
+   * @returns The output stream with the state of @p __x inserted or in
+   * an error state.
+   */
+  template<typename _RealType, typename _CharT, typename _Traits>
+    std::basic_ostream<_CharT, _Traits>&
+    operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+              const std::exponential_distribution<_RealType>& __x);
+
+  /**
+   * @brief Extracts a %exponential_distribution random number distribution
+   * @p __x from the input stream @p __is.
+   *
+   * @param __is An input stream.
+   * @param __x A %exponential_distribution random number
+   *            generator engine.
+   *
+   * @returns The input stream with @p __x extracted or in an error state.
+   */
+  template<typename _RealType, typename _CharT, typename _Traits>
+    std::basic_istream<_CharT, _Traits>&
+    operator>>(std::basic_istream<_CharT, _Traits>& __is,
+              std::exponential_distribution<_RealType>& __x);
+
+
+  /**
+   * @brief A weibull_distribution random number distribution.
+   *
+   * The formula for the normal probability density function is:
+   * @f[
+   *     p(x|\alpha,\beta) = \frac{\alpha}{\beta} (\frac{x}{\beta})^{\alpha-1}
+   *                         \exp{(-(\frac{x}{\beta})^\alpha)} 
+   * @f]
+   */
+  template<typename _RealType = double>
+    class weibull_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef weibull_distribution<_RealType> distribution_type;
+
+       explicit
+       param_type(_RealType __a = _RealType(1),
+                  _RealType __b = _RealType(1))
+       : _M_a(__a), _M_b(__b)
+       { }
+
+       _RealType
+       a() const
+       { return _M_a; }
+
+       _RealType
+       b() const
+       { return _M_b; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_a == __p2._M_a && __p1._M_b == __p2._M_b; }
+
+      private:
+       _RealType _M_a;
+       _RealType _M_b;
+      };
+
+      explicit
+      weibull_distribution(_RealType __a = _RealType(1),
+                          _RealType __b = _RealType(1))
+      : _M_param(__a, __b)
+      { }
+
+      explicit
+      weibull_distribution(const param_type& __p)
+      : _M_param(__p)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      { }
+
+      /**
+       * @brief Return the @f$a@f$ parameter of the distribution.
+       */
+      _RealType
+      a() const
+      { return _M_param.a(); }
+
+      /**
+       * @brief Return the @f$b@f$ parameter of the distribution.
+       */
+      _RealType
+      b() const
+      { return _M_param.b(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return result_type(0); }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+      /**
+       * @brief Return true if two Weibull distributions have the same
+       *        parameters.
+       */
+      friend bool
+      operator==(const weibull_distribution& __d1,
+                const weibull_distribution& __d2)
+      { return __d1._M_param == __d2._M_param; }
+
+    private:
+      param_type _M_param;
+    };
+
+   /**
+    * @brief Return true if two Weibull distributions have different
+    *        parameters.
+    */
+  template<typename _RealType>
+    inline bool
+    operator!=(const std::weibull_distribution<_RealType>& __d1,
+              const std::weibull_distribution<_RealType>& __d2)
+    { return !(__d1 == __d2); }
+
+  /**
+   * @brief Inserts a %weibull_distribution random number distribution
+   * @p __x into the output stream @p __os.
+   *
+   * @param __os An output stream.
+   * @param __x  A %weibull_distribution random number distribution.
+   *
+   * @returns The output stream with the state of @p __x inserted or in
+   * an error state.
+   */
+  template<typename _RealType, typename _CharT, typename _Traits>
+    std::basic_ostream<_CharT, _Traits>&
+    operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+              const std::weibull_distribution<_RealType>& __x);
+
+  /**
+   * @brief Extracts a %weibull_distribution random number distribution
+   * @p __x from the input stream @p __is.
+   *
+   * @param __is An input stream.
+   * @param __x A %weibull_distribution random number
+   *            generator engine.
+   *
+   * @returns The input stream with @p __x extracted or in an error state.
+   */
+  template<typename _RealType, typename _CharT, typename _Traits>
+    std::basic_istream<_CharT, _Traits>&
+    operator>>(std::basic_istream<_CharT, _Traits>& __is,
+              std::weibull_distribution<_RealType>& __x);
+
+
+  /**
+   * @brief A extreme_value_distribution random number distribution.
+   *
+   * The formula for the normal probability mass function is
+   * @f[
+   *     p(x|a,b) = \frac{1}{b}
+   *                \exp( \frac{a-x}{b} - \exp(\frac{a-x}{b})) 
+   * @f]
+   */
+  template<typename _RealType = double>
+    class extreme_value_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef extreme_value_distribution<_RealType> distribution_type;
+
+       explicit
+       param_type(_RealType __a = _RealType(0),
+                  _RealType __b = _RealType(1))
+       : _M_a(__a), _M_b(__b)
+       { }
+
+       _RealType
+       a() const
+       { return _M_a; }
+
+       _RealType
+       b() const
+       { return _M_b; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_a == __p2._M_a && __p1._M_b == __p2._M_b; }
+
+      private:
+       _RealType _M_a;
+       _RealType _M_b;
+      };
+
+      explicit
+      extreme_value_distribution(_RealType __a = _RealType(0),
+                                _RealType __b = _RealType(1))
+      : _M_param(__a, __b)
+      { }
+
+      explicit
+      extreme_value_distribution(const param_type& __p)
+      : _M_param(__p)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      { }
+
+      /**
+       * @brief Return the @f$a@f$ parameter of the distribution.
+       */
+      _RealType
+      a() const
+      { return _M_param.a(); }
+
+      /**
+       * @brief Return the @f$b@f$ parameter of the distribution.
+       */
+      _RealType
+      b() const
+      { return _M_param.b(); }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return std::numeric_limits<result_type>::min(); }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      { return std::numeric_limits<result_type>::max(); }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+      /**
+       * @brief Return true if two extreme value distributions have the same
+       *        parameters.
+       */
+      friend bool
+      operator==(const extreme_value_distribution& __d1,
+                const extreme_value_distribution& __d2)
+      { return __d1._M_param == __d2._M_param; }
+
+    private:
+      param_type _M_param;
+    };
+
+  /**
+    * @brief Return true if two extreme value distributions have different
+    *        parameters.
+   */
+  template<typename _RealType>
+    inline bool
+    operator!=(const std::extreme_value_distribution<_RealType>& __d1,
+              const std::extreme_value_distribution<_RealType>& __d2)
+    { return !(__d1 == __d2); }
+
+  /**
+   * @brief Inserts a %extreme_value_distribution random number distribution
+   * @p __x into the output stream @p __os.
+   *
+   * @param __os An output stream.
+   * @param __x  A %extreme_value_distribution random number distribution.
+   *
+   * @returns The output stream with the state of @p __x inserted or in
+   * an error state.
+   */
+  template<typename _RealType, typename _CharT, typename _Traits>
+    std::basic_ostream<_CharT, _Traits>&
+    operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+              const std::extreme_value_distribution<_RealType>& __x);
+
+  /**
+   * @brief Extracts a %extreme_value_distribution random number
+   *        distribution @p __x from the input stream @p __is.
+   *
+   * @param __is An input stream.
+   * @param __x A %extreme_value_distribution random number
+   *            generator engine.
+   *
+   * @returns The input stream with @p __x extracted or in an error state.
+   */
+  template<typename _RealType, typename _CharT, typename _Traits>
+    std::basic_istream<_CharT, _Traits>&
+    operator>>(std::basic_istream<_CharT, _Traits>& __is,
+              std::extreme_value_distribution<_RealType>& __x);
+
+
+  /**
+   * @brief A discrete_distribution random number distribution.
+   *
+   * The formula for the discrete probability mass function is
+   *
+   */
+  template<typename _IntType = int>
+    class discrete_distribution
+    {
+      static_assert(std::is_integral<_IntType>::value,
+                   "template argument not an integral type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _IntType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef discrete_distribution<_IntType> distribution_type;
+       friend class discrete_distribution<_IntType>;
+
+       param_type()
+       : _M_prob(), _M_cp()
+       { }
+
+       template<typename _InputIterator>
+         param_type(_InputIterator __wbegin,
+                    _InputIterator __wend)
+         : _M_prob(__wbegin, __wend), _M_cp()
+         { _M_initialize(); }
+
+       param_type(initializer_list<double> __wil)
+       : _M_prob(__wil.begin(), __wil.end()), _M_cp()
+       { _M_initialize(); }
+
+       template<typename _Func>
+         param_type(size_t __nw, double __xmin, double __xmax,
+                    _Func __fw);
+
+       // See: http://cpp-next.com/archive/2010/10/implicit-move-must-go/
+       param_type(const param_type&) = default;
+       param_type& operator=(const param_type&) = default;
+
+       std::vector<double>
+       probabilities() const
+       { return _M_prob.empty() ? std::vector<double>(1, 1.0) : _M_prob; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_prob == __p2._M_prob; }
+
+      private:
+       void
+       _M_initialize();
+
+       std::vector<double> _M_prob;
+       std::vector<double> _M_cp;
+      };
+
+      discrete_distribution()
+      : _M_param()
+      { }
+
+      template<typename _InputIterator>
+       discrete_distribution(_InputIterator __wbegin,
+                             _InputIterator __wend)
+       : _M_param(__wbegin, __wend)
+       { }
+
+      discrete_distribution(initializer_list<double> __wl)
+      : _M_param(__wl)
+      { }
+
+      template<typename _Func>
+       discrete_distribution(size_t __nw, double __xmin, double __xmax,
+                             _Func __fw)
+       : _M_param(__nw, __xmin, __xmax, __fw)
+       { }
+
+      explicit
+      discrete_distribution(const param_type& __p)
+      : _M_param(__p)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      { }
+
+      /**
+       * @brief Returns the probabilities of the distribution.
+       */
+      std::vector<double>
+      probabilities() const
+      {
+       return _M_param._M_prob.empty()
+         ? std::vector<double>(1, 1.0) : _M_param._M_prob;
+      }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      { return result_type(0); }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      {
+       return _M_param._M_prob.empty()
+         ? result_type(0) : result_type(_M_param._M_prob.size() - 1);
+      }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+      /**
+       * @brief Return true if two discrete distributions have the same
+       *        parameters.
+       */
+      friend bool
+      operator==(const discrete_distribution& __d1,
+                const discrete_distribution& __d2)
+      { return __d1._M_param == __d2._M_param; }
+
+      /**
+       * @brief Inserts a %discrete_distribution random number distribution
+       * @p __x into the output stream @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %discrete_distribution random number distribution.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _IntType1, typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::discrete_distribution<_IntType1>& __x);
+
+      /**
+       * @brief Extracts a %discrete_distribution random number distribution
+       * @p __x from the input stream @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x A %discrete_distribution random number
+       *            generator engine.
+       *
+       * @returns The input stream with @p __x extracted or in an error
+       *          state.
+       */
+      template<typename _IntType1, typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::discrete_distribution<_IntType1>& __x);
+
+    private:
+      param_type _M_param;
+    };
+
+  /**
+    * @brief Return true if two discrete distributions have different
+    *        parameters.
+    */
+  template<typename _IntType>
+    inline bool
+    operator!=(const std::discrete_distribution<_IntType>& __d1,
+              const std::discrete_distribution<_IntType>& __d2)
+    { return !(__d1 == __d2); }
+
+
+  /**
+   * @brief A piecewise_constant_distribution random number distribution.
+   *
+   * The formula for the piecewise constant probability mass function is
+   *
+   */
+  template<typename _RealType = double>
+    class piecewise_constant_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef piecewise_constant_distribution<_RealType> distribution_type;
+       friend class piecewise_constant_distribution<_RealType>;
+
+       param_type()
+       : _M_int(), _M_den(), _M_cp()
+       { }
+
+       template<typename _InputIteratorB, typename _InputIteratorW>
+         param_type(_InputIteratorB __bfirst,
+                    _InputIteratorB __bend,
+                    _InputIteratorW __wbegin);
+
+       template<typename _Func>
+         param_type(initializer_list<_RealType> __bi, _Func __fw);
+
+       template<typename _Func>
+         param_type(size_t __nw, _RealType __xmin, _RealType __xmax,
+                    _Func __fw);
+
+       // See: http://cpp-next.com/archive/2010/10/implicit-move-must-go/
+       param_type(const param_type&) = default;
+       param_type& operator=(const param_type&) = default;
+
+       std::vector<_RealType>
+       intervals() const
+       {
+         if (_M_int.empty())
+           {
+             std::vector<_RealType> __tmp(2);
+             __tmp[1] = _RealType(1);
+             return __tmp;
+           }
+         else
+           return _M_int;
+       }
+
+       std::vector<double>
+       densities() const
+       { return _M_den.empty() ? std::vector<double>(1, 1.0) : _M_den; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return __p1._M_int == __p2._M_int && __p1._M_den == __p2._M_den; }
+
+      private:
+       void
+       _M_initialize();
+
+       std::vector<_RealType> _M_int;
+       std::vector<double> _M_den;
+       std::vector<double> _M_cp;
+      };
+
+      explicit
+      piecewise_constant_distribution()
+      : _M_param()
+      { }
+
+      template<typename _InputIteratorB, typename _InputIteratorW>
+       piecewise_constant_distribution(_InputIteratorB __bfirst,
+                                       _InputIteratorB __bend,
+                                       _InputIteratorW __wbegin)
+       : _M_param(__bfirst, __bend, __wbegin)
+       { }
+
+      template<typename _Func>
+       piecewise_constant_distribution(initializer_list<_RealType> __bl,
+                                       _Func __fw)
+       : _M_param(__bl, __fw)
+       { }
+
+      template<typename _Func>
+       piecewise_constant_distribution(size_t __nw,
+                                       _RealType __xmin, _RealType __xmax,
+                                       _Func __fw)
+       : _M_param(__nw, __xmin, __xmax, __fw)
+       { }
+
+      explicit
+      piecewise_constant_distribution(const param_type& __p)
+      : _M_param(__p)
+      { }
+
+      /**
+       * @brief Resets the distribution state.
+       */
+      void
+      reset()
+      { }
+
+      /**
+       * @brief Returns a vector of the intervals.
+       */
+      std::vector<_RealType>
+      intervals() const
+      {
+       if (_M_param._M_int.empty())
+         {
+           std::vector<_RealType> __tmp(2);
+           __tmp[1] = _RealType(1);
+           return __tmp;
+         }
+       else
+         return _M_param._M_int;
+      }
+
+      /**
+       * @brief Returns a vector of the probability densities.
+       */
+      std::vector<double>
+      densities() const
+      {
+       return _M_param._M_den.empty()
+         ? std::vector<double>(1, 1.0) : _M_param._M_den;
+      }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      {
+       return _M_param._M_int.empty()
+         ? result_type(0) : _M_param._M_int.front();
+      }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      {
+       return _M_param._M_int.empty()
+         ? result_type(1) : _M_param._M_int.back();
+      }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+      /**
+       * @brief Return true if two piecewise constant distributions have the
+       *        same parameters.
+       */
+      friend bool
+      operator==(const piecewise_constant_distribution& __d1,
+                const piecewise_constant_distribution& __d2)
+      { return __d1._M_param == __d2._M_param; }
+
+      /**
+       * @brief Inserts a %piecewise_constan_distribution random
+       *        number distribution @p __x into the output stream @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %piecewise_constan_distribution random number
+       *             distribution.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       * an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::piecewise_constant_distribution<_RealType1>& __x);
+
+      /**
+       * @brief Extracts a %piecewise_constan_distribution random
+       *        number distribution @p __x from the input stream @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x A %piecewise_constan_distribution random number
+       *            generator engine.
+       *
+       * @returns The input stream with @p __x extracted or in an error
+       *          state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::piecewise_constant_distribution<_RealType1>& __x);
+
+    private:
+      param_type _M_param;
+    };
+
+  /**
+    * @brief Return true if two piecewise constant distributions have 
+    *        different parameters.
+   */
+  template<typename _RealType>
+    inline bool
+    operator!=(const std::piecewise_constant_distribution<_RealType>& __d1,
+              const std::piecewise_constant_distribution<_RealType>& __d2)
+    { return !(__d1 == __d2); }
+
+
+  /**
+   * @brief A piecewise_linear_distribution random number distribution.
+   *
+   * The formula for the piecewise linear probability mass function is
+   *
+   */
+  template<typename _RealType = double>
+    class piecewise_linear_distribution
+    {
+      static_assert(std::is_floating_point<_RealType>::value,
+                   "template argument not a floating point type");
+
+    public:
+      /** The type of the range of the distribution. */
+      typedef _RealType result_type;
+      /** Parameter type. */
+      struct param_type
+      {
+       typedef piecewise_linear_distribution<_RealType> distribution_type;
+       friend class piecewise_linear_distribution<_RealType>;
+
+       param_type()
+       : _M_int(), _M_den(), _M_cp(), _M_m()
+       { }
+
+       template<typename _InputIteratorB, typename _InputIteratorW>
+         param_type(_InputIteratorB __bfirst,
+                    _InputIteratorB __bend,
+                    _InputIteratorW __wbegin);
+
+       template<typename _Func>
+         param_type(initializer_list<_RealType> __bl, _Func __fw);
+
+       template<typename _Func>
+         param_type(size_t __nw, _RealType __xmin, _RealType __xmax,
+                    _Func __fw);
+
+       // See: http://cpp-next.com/archive/2010/10/implicit-move-must-go/
+       param_type(const param_type&) = default;
+       param_type& operator=(const param_type&) = default;
+
+       std::vector<_RealType>
+       intervals() const
+       {
+         if (_M_int.empty())
+           {
+             std::vector<_RealType> __tmp(2);
+             __tmp[1] = _RealType(1);
+             return __tmp;
+           }
+         else
+           return _M_int;
+       }
+
+       std::vector<double>
+       densities() const
+       { return _M_den.empty() ? std::vector<double>(2, 1.0) : _M_den; }
+
+       friend bool
+       operator==(const param_type& __p1, const param_type& __p2)
+       { return (__p1._M_int == __p2._M_int
+                 && __p1._M_den == __p2._M_den); }
+
+      private:
+       void
+       _M_initialize();
+
+       std::vector<_RealType> _M_int;
+       std::vector<double> _M_den;
+       std::vector<double> _M_cp;
+       std::vector<double> _M_m;
+      };
+
+      explicit
+      piecewise_linear_distribution()
+      : _M_param()
+      { }
+
+      template<typename _InputIteratorB, typename _InputIteratorW>
+       piecewise_linear_distribution(_InputIteratorB __bfirst,
+                                     _InputIteratorB __bend,
+                                     _InputIteratorW __wbegin)
+       : _M_param(__bfirst, __bend, __wbegin)
+       { }
+
+      template<typename _Func>
+       piecewise_linear_distribution(initializer_list<_RealType> __bl,
+                                     _Func __fw)
+       : _M_param(__bl, __fw)
+       { }
+
+      template<typename _Func>
+       piecewise_linear_distribution(size_t __nw,
+                                     _RealType __xmin, _RealType __xmax,
+                                     _Func __fw)
+       : _M_param(__nw, __xmin, __xmax, __fw)
+       { }
+
+      explicit
+      piecewise_linear_distribution(const param_type& __p)
+      : _M_param(__p)
+      { }
+
+      /**
+       * Resets the distribution state.
+       */
+      void
+      reset()
+      { }
+
+      /**
+       * @brief Return the intervals of the distribution.
+       */
+      std::vector<_RealType>
+      intervals() const
+      {
+       if (_M_param._M_int.empty())
+         {
+           std::vector<_RealType> __tmp(2);
+           __tmp[1] = _RealType(1);
+           return __tmp;
+         }
+       else
+         return _M_param._M_int;
+      }
+
+      /**
+       * @brief Return a vector of the probability densities of the
+       *        distribution.
+       */
+      std::vector<double>
+      densities() const
+      {
+       return _M_param._M_den.empty()
+         ? std::vector<double>(2, 1.0) : _M_param._M_den;
+      }
+
+      /**
+       * @brief Returns the parameter set of the distribution.
+       */
+      param_type
+      param() const
+      { return _M_param; }
+
+      /**
+       * @brief Sets the parameter set of the distribution.
+       * @param __param The new parameter set of the distribution.
+       */
+      void
+      param(const param_type& __param)
+      { _M_param = __param; }
+
+      /**
+       * @brief Returns the greatest lower bound value of the distribution.
+       */
+      result_type
+      min() const
+      {
+       return _M_param._M_int.empty()
+         ? result_type(0) : _M_param._M_int.front();
+      }
+
+      /**
+       * @brief Returns the least upper bound value of the distribution.
+       */
+      result_type
+      max() const
+      {
+       return _M_param._M_int.empty()
+         ? result_type(1) : _M_param._M_int.back();
+      }
+
+      /**
+       * @brief Generating functions.
+       */
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng)
+       { return this->operator()(__urng, _M_param); }
+
+      template<typename _UniformRandomNumberGenerator>
+       result_type
+       operator()(_UniformRandomNumberGenerator& __urng,
+                  const param_type& __p);
+
+      /**
+       * @brief Return true if two piecewise linear distributions have the
+       *        same parameters.
+       */
+      friend bool
+      operator==(const piecewise_linear_distribution& __d1,
+                const piecewise_linear_distribution& __d2)
+      { return __d1._M_param == __d2._M_param; }
+
+      /**
+       * @brief Inserts a %piecewise_linear_distribution random number
+       *        distribution @p __x into the output stream @p __os.
+       *
+       * @param __os An output stream.
+       * @param __x  A %piecewise_linear_distribution random number
+       *             distribution.
+       *
+       * @returns The output stream with the state of @p __x inserted or in
+       *          an error state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_ostream<_CharT, _Traits>&
+       operator<<(std::basic_ostream<_CharT, _Traits>& __os,
+                  const std::piecewise_linear_distribution<_RealType1>& __x);
+
+      /**
+       * @brief Extracts a %piecewise_linear_distribution random number
+       *        distribution @p __x from the input stream @p __is.
+       *
+       * @param __is An input stream.
+       * @param __x  A %piecewise_linear_distribution random number
+       *             generator engine.
+       *
+       * @returns The input stream with @p __x extracted or in an error
+       *          state.
+       */
+      template<typename _RealType1, typename _CharT, typename _Traits>
+       friend std::basic_istream<_CharT, _Traits>&
+       operator>>(std::basic_istream<_CharT, _Traits>& __is,
+                  std::piecewise_linear_distribution<_RealType1>& __x);
+
+    private:
+      param_type _M_param;
+    };
+
+  /**
+    * @brief Return true if two piecewise linear distributions have
+    *        different parameters.
+   */
+  template<typename _RealType>
+    inline bool
+    operator!=(const std::piecewise_linear_distribution<_RealType>& __d1,
+              const std::piecewise_linear_distribution<_RealType>& __d2)
+    { return !(__d1 == __d2); }
+
+
+  /* @} */ // group random_distributions_poisson
+
+  /* @} */ // group random_distributions
+
+  /**
+   * @addtogroup random_utilities Random Number Utilities
+   * @ingroup random
+   * @{
+   */
+
+  /**
+   * @brief The seed_seq class generates sequences of seeds for random
+   *        number generators.
+   */
+  class seed_seq
+  {
+
+  public:
+    /** The type of the seed vales. */
+    typedef uint_least32_t result_type;
+
+    /** Default constructor. */
+    seed_seq()
+    : _M_v()
+    { }
+
+    template<typename _IntType>
+      seed_seq(std::initializer_list<_IntType> il);
+
+    template<typename _InputIterator>
+      seed_seq(_InputIterator __begin, _InputIterator __end);
+
+    // generating functions
+    template<typename _RandomAccessIterator>
+      void
+      generate(_RandomAccessIterator __begin, _RandomAccessIterator __end);
+
+    // property functions
+    size_t size() const
+    { return _M_v.size(); }
+
+    template<typename OutputIterator>
+      void
+      param(OutputIterator __dest) const
+      { std::copy(_M_v.begin(), _M_v.end(), __dest); }
+
+  private:
+    ///
+    std::vector<result_type> _M_v;
+  };
+
+  /* @} */ // group random_utilities
+
+  /* @} */ // group random
+
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+
+#endif