diff --git a/code/uniform_int_dist.h b/code/uniform_int_dist.h
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+// Class template uniform_int_distribution -*- C++ -*-
+
+// Copyright (C) 2009-2017 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/uniform_int_dist.h
+ *  This is an internal header file, included by other library headers.
+ *  Do not attempt to use it directly. @headername{random}
+ */
+
+#ifndef _GLIBCXX_BITS_UNIFORM_INT_DIST_H
+#define _GLIBCXX_BITS_UNIFORM_INT_DIST_H
+
+#include <type_traits>
+#include <limits>
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+
+  namespace __detail
+  {
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+    /* Determine whether number is a power of 2.  */
+    template<typename _Tp>
+      inline bool
+      _Power_of_2(_Tp __x)
+      {
+	return ((__x - 1) & __x) == 0;
+      };
+_GLIBCXX_END_NAMESPACE_VERSION
+  }
+
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+  /**
+   * @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 must be 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_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; }
+
+	friend bool
+	operator!=(const param_type& __p1, const param_type& __p2)
+	{ return !(__p1 == __p2); }
+
+      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);
+
+      template<typename _ForwardIterator,
+	       typename _UniformRandomNumberGenerator>
+	void
+	__generate(_ForwardIterator __f, _ForwardIterator __t,
+		   _UniformRandomNumberGenerator& __urng)
+	{ this->__generate(__f, __t, __urng, _M_param); }
+
+      template<typename _ForwardIterator,
+	       typename _UniformRandomNumberGenerator>
+	void
+	__generate(_ForwardIterator __f, _ForwardIterator __t,
+		   _UniformRandomNumberGenerator& __urng,
+		   const param_type& __p)
+	{ this->__generate_impl(__f, __t, __urng, __p); }
+
+      template<typename _UniformRandomNumberGenerator>
+	void
+	__generate(result_type* __f, result_type* __t,
+		   _UniformRandomNumberGenerator& __urng,
+		   const param_type& __p)
+	{ this->__generate_impl(__f, __t, __urng, __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:
+      template<typename _ForwardIterator,
+	       typename _UniformRandomNumberGenerator>
+	void
+	__generate_impl(_ForwardIterator __f, _ForwardIterator __t,
+			_UniformRandomNumberGenerator& __urng,
+			const param_type& __p);
+
+      param_type _M_param;
+    };
+
+  template<typename _IntType>
+    template<typename _UniformRandomNumberGenerator>
+      typename uniform_int_distribution<_IntType>::result_type
+      uniform_int_distribution<_IntType>::
+      operator()(_UniformRandomNumberGenerator& __urng,
+		 const param_type& __param)
+      {
+	typedef typename _UniformRandomNumberGenerator::result_type
+	  _Gresult_type;
+	typedef typename std::make_unsigned<result_type>::type __utype;
+	typedef typename std::common_type<_Gresult_type, __utype>::type
+	  __uctype;
+
+	const __uctype __urngmin = __urng.min();
+	const __uctype __urngmax = __urng.max();
+	const __uctype __urngrange = __urngmax - __urngmin;
+	const __uctype __urange
+	  = __uctype(__param.b()) - __uctype(__param.a());
+
+	__uctype __ret;
+
+	if (__urngrange > __urange)
+	  {
+	    // downscaling
+	    const __uctype __uerange = __urange + 1; // __urange can be zero
+	    const __uctype __scaling = __urngrange / __uerange;
+	    const __uctype __past = __uerange * __scaling;
+	    do
+	      __ret = __uctype(__urng()) - __urngmin;
+	    while (__ret >= __past);
+	    __ret /= __scaling;
+	  }
+	else if (__urngrange < __urange)
+	  {
+	    // upscaling
+	    /*
+	      Note that every value in [0, urange]
+	      can be written uniquely as
+
+	      (urngrange + 1) * high + low
+
+	      where
+
+	      high in [0, urange / (urngrange + 1)]
+
+	      and
+
+	      low in [0, urngrange].
+	    */
+	    __uctype __tmp; // wraparound control
+	    do
+	      {
+		const __uctype __uerngrange = __urngrange + 1;
+		__tmp = (__uerngrange * operator()
+			 (__urng, param_type(0, __urange / __uerngrange)));
+		__ret = __tmp + (__uctype(__urng()) - __urngmin);
+	      }
+	    while (__ret > __urange || __ret < __tmp);
+	  }
+	else
+	  __ret = __uctype(__urng()) - __urngmin;
+
+	return __ret + __param.a();
+      }
+
+
+  template<typename _IntType>
+    template<typename _ForwardIterator,
+	     typename _UniformRandomNumberGenerator>
+      void
+      uniform_int_distribution<_IntType>::
+      __generate_impl(_ForwardIterator __f, _ForwardIterator __t,
+		      _UniformRandomNumberGenerator& __urng,
+		      const param_type& __param)
+      {
+	__glibcxx_function_requires(_ForwardIteratorConcept<_ForwardIterator>)
+	typedef typename _UniformRandomNumberGenerator::result_type
+	  _Gresult_type;
+	typedef typename std::make_unsigned<result_type>::type __utype;
+	typedef typename std::common_type<_Gresult_type, __utype>::type
+	  __uctype;
+
+	const __uctype __urngmin = __urng.min();
+	const __uctype __urngmax = __urng.max();
+	const __uctype __urngrange = __urngmax - __urngmin;
+	const __uctype __urange
+	  = __uctype(__param.b()) - __uctype(__param.a());
+
+	__uctype __ret;
+
+	if (__urngrange > __urange)
+	  {
+	    if (__detail::_Power_of_2(__urngrange + 1)
+		&& __detail::_Power_of_2(__urange + 1))
+	      {
+		while (__f != __t)
+		  {
+		    __ret = __uctype(__urng()) - __urngmin;
+		    *__f++ = (__ret & __urange) + __param.a();
+		  }
+	      }
+	    else
+	      {
+		// downscaling
+		const __uctype __uerange = __urange + 1; // __urange can be zero
+		const __uctype __scaling = __urngrange / __uerange;
+		const __uctype __past = __uerange * __scaling;
+		while (__f != __t)
+		  {
+		    do
+		      __ret = __uctype(__urng()) - __urngmin;
+		    while (__ret >= __past);
+		    *__f++ = __ret / __scaling + __param.a();
+		  }
+	      }
+	  }
+	else if (__urngrange < __urange)
+	  {
+	    // upscaling
+	    /*
+	      Note that every value in [0, urange]
+	      can be written uniquely as
+
+	      (urngrange + 1) * high + low
+
+	      where
+
+	      high in [0, urange / (urngrange + 1)]
+
+	      and
+
+	      low in [0, urngrange].
+	    */
+	    __uctype __tmp; // wraparound control
+	    while (__f != __t)
+	      {
+		do
+		  {
+		    const __uctype __uerngrange = __urngrange + 1;
+		    __tmp = (__uerngrange * operator()
+			     (__urng, param_type(0, __urange / __uerngrange)));
+		    __ret = __tmp + (__uctype(__urng()) - __urngmin);
+		  }
+		while (__ret > __urange || __ret < __tmp);
+		*__f++ = __ret;
+	      }
+	  }
+	else
+	  while (__f != __t)
+	    *__f++ = __uctype(__urng()) - __urngmin + __param.a();
+      }
+
+  // operator!= and operator<< and operator>> are defined in <bits/random.h>
+
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+
+#endif