--- /dev/null
+/* boost random/uniform_int_distribution.hpp header file
+ *
+ * Copyright Jens Maurer 2000-2001
+ * Copyright Steven Watanabe 2011
+ * Distributed under the Boost Software License, Version 1.0. (See
+ * accompanying file LICENSE_1_0.txt or copy at
+ * http://www.boost.org/LICENSE_1_0.txt)
+ *
+ * See http://www.boost.org for most recent version including documentation.
+ *
+ * $Id: uniform_int_distribution.hpp 71018 2011-04-05 21:27:52Z steven_watanabe $
+ *
+ * Revision history
+ * 2001-04-08 added min<max assertion (N. Becker)
+ * 2001-02-18 moved to individual header files
+ */
+
+#ifndef BOOST_RANDOM_UNIFORM_INT_DISTRIBUTION_HPP
+#define BOOST_RANDOM_UNIFORM_INT_DISTRIBUTION_HPP
+
+#include <iosfwd>
+#include <ios>
+#include <istream>
+#include <boost/config.hpp>
+#include <boost/limits.hpp>
+#include <boost/assert.hpp>
+#include <boost/random/detail/config.hpp>
+#include <boost/random/detail/operators.hpp>
+#include <boost/random/detail/uniform_int_float.hpp>
+#include <boost/random/detail/signed_unsigned_tools.hpp>
+#include <boost/type_traits/make_unsigned.hpp>
+#include <boost/type_traits/is_integral.hpp>
+
+namespace boost {
+namespace random {
+namespace detail {
+
+
+#ifdef BOOST_MSVC
+#pragma warning(push)
+// disable division by zero warning, since we can't
+// actually divide by zero.
+#pragma warning(disable:4723)
+#endif
+
+template<class Engine, class T>
+T generate_uniform_int(
+ Engine& eng, T min_value, T max_value,
+ boost::mpl::true_ /** is_integral<Engine::result_type> */)
+{
+ typedef T result_type;
+ typedef typename make_unsigned<T>::type range_type;
+ typedef typename Engine::result_type base_result;
+ // ranges are always unsigned
+ typedef typename make_unsigned<base_result>::type base_unsigned;
+ const range_type range = random::detail::subtract<result_type>()(max_value, min_value);
+ const base_result bmin = (eng.min)();
+ const base_unsigned brange =
+ random::detail::subtract<base_result>()((eng.max)(), (eng.min)());
+
+ if(range == 0) {
+ return min_value;
+ } else if(brange == range) {
+ // this will probably never happen in real life
+ // basically nothing to do; just take care we don't overflow / underflow
+ base_unsigned v = random::detail::subtract<base_result>()(eng(), bmin);
+ return random::detail::add<base_unsigned, result_type>()(v, min_value);
+ } else if(brange < range) {
+ // use rejection method to handle things like 0..3 --> 0..4
+ for(;;) {
+ // concatenate several invocations of the base RNG
+ // take extra care to avoid overflows
+
+ // limit == floor((range+1)/(brange+1))
+ // Therefore limit*(brange+1) <= range+1
+ range_type limit;
+ if(range == (std::numeric_limits<range_type>::max)()) {
+ limit = range/(range_type(brange)+1);
+ if(range % (range_type(brange)+1) == range_type(brange))
+ ++limit;
+ } else {
+ limit = (range+1)/(range_type(brange)+1);
+ }
+
+ // We consider "result" as expressed to base (brange+1):
+ // For every power of (brange+1), we determine a random factor
+ range_type result = range_type(0);
+ range_type mult = range_type(1);
+
+ // loop invariants:
+ // result < mult
+ // mult <= range
+ while(mult <= limit) {
+ // Postcondition: result <= range, thus no overflow
+ //
+ // limit*(brange+1)<=range+1 def. of limit (1)
+ // eng()-bmin<=brange eng() post. (2)
+ // and mult<=limit. loop condition (3)
+ // Therefore mult*(eng()-bmin+1)<=range+1 by (1),(2),(3) (4)
+ // Therefore mult*(eng()-bmin)+mult<=range+1 rearranging (4) (5)
+ // result<mult loop invariant (6)
+ // Therefore result+mult*(eng()-bmin)<range+1 by (5), (6) (7)
+ //
+ // Postcondition: result < mult*(brange+1)
+ //
+ // result<mult loop invariant (1)
+ // eng()-bmin<=brange eng() post. (2)
+ // Therefore result+mult*(eng()-bmin) <
+ // mult+mult*(eng()-bmin) by (1) (3)
+ // Therefore result+(eng()-bmin)*mult <
+ // mult+mult*brange by (2), (3) (4)
+ // Therefore result+(eng()-bmin)*mult <
+ // mult*(brange+1) by (4)
+ result += static_cast<range_type>(random::detail::subtract<base_result>()(eng(), bmin) * mult);
+
+ // equivalent to (mult * (brange+1)) == range+1, but avoids overflow.
+ if(mult * range_type(brange) == range - mult + 1) {
+ // The destination range is an integer power of
+ // the generator's range.
+ return(result);
+ }
+
+ // Postcondition: mult <= range
+ //
+ // limit*(brange+1)<=range+1 def. of limit (1)
+ // mult<=limit loop condition (2)
+ // Therefore mult*(brange+1)<=range+1 by (1), (2) (3)
+ // mult*(brange+1)!=range+1 preceding if (4)
+ // Therefore mult*(brange+1)<range+1 by (3), (4) (5)
+ //
+ // Postcondition: result < mult
+ //
+ // See the second postcondition on the change to result.
+ mult *= range_type(brange)+range_type(1);
+ }
+ // loop postcondition: range/mult < brange+1
+ //
+ // mult > limit loop condition (1)
+ // Suppose range/mult >= brange+1 Assumption (2)
+ // range >= mult*(brange+1) by (2) (3)
+ // range+1 > mult*(brange+1) by (3) (4)
+ // range+1 > (limit+1)*(brange+1) by (1), (4) (5)
+ // (range+1)/(brange+1) > limit+1 by (5) (6)
+ // limit < floor((range+1)/(brange+1)) by (6) (7)
+ // limit==floor((range+1)/(brange+1)) def. of limit (8)
+ // not (2) reductio (9)
+ //
+ // loop postcondition: (range/mult)*mult+(mult-1) >= range
+ //
+ // (range/mult)*mult + range%mult == range identity (1)
+ // range%mult < mult def. of % (2)
+ // (range/mult)*mult+mult > range by (1), (2) (3)
+ // (range/mult)*mult+(mult-1) >= range by (3) (4)
+ //
+ // Note that the maximum value of result at this point is (mult-1),
+ // so after this final step, we generate numbers that can be
+ // at least as large as range. We have to really careful to avoid
+ // overflow in this final addition and in the rejection. Anything
+ // that overflows is larger than range and can thus be rejected.
+
+ // range/mult < brange+1 -> no endless loop
+ range_type result_increment =
+ generate_uniform_int(
+ eng,
+ static_cast<range_type>(0),
+ static_cast<range_type>(range/mult),
+ boost::mpl::true_());
+ if((std::numeric_limits<range_type>::max)() / mult < result_increment) {
+ // The multiplcation would overflow. Reject immediately.
+ continue;
+ }
+ result_increment *= mult;
+ // unsigned integers are guaranteed to wrap on overflow.
+ result += result_increment;
+ if(result < result_increment) {
+ // The addition overflowed. Reject.
+ continue;
+ }
+ if(result > range) {
+ // Too big. Reject.
+ continue;
+ }
+ return random::detail::add<range_type, result_type>()(result, min_value);
+ }
+ } else { // brange > range
+ base_unsigned bucket_size;
+ // it's safe to add 1 to range, as long as we cast it first,
+ // because we know that it is less than brange. However,
+ // we do need to be careful not to cause overflow by adding 1
+ // to brange.
+ if(brange == (std::numeric_limits<base_unsigned>::max)()) {
+ bucket_size = brange / (static_cast<base_unsigned>(range)+1);
+ if(brange % (static_cast<base_unsigned>(range)+1) == static_cast<base_unsigned>(range)) {
+ ++bucket_size;
+ }
+ } else {
+ bucket_size = (brange+1) / (static_cast<base_unsigned>(range)+1);
+ }
+ for(;;) {
+ base_unsigned result =
+ random::detail::subtract<base_result>()(eng(), bmin);
+ result /= bucket_size;
+ // result and range are non-negative, and result is possibly larger
+ // than range, so the cast is safe
+ if(result <= static_cast<base_unsigned>(range))
+ return random::detail::add<base_unsigned, result_type>()(result, min_value);
+ }
+ }
+}
+
+#ifdef BOOST_MSVC
+#pragma warning(pop)
+#endif
+
+template<class Engine, class T>
+inline T generate_uniform_int(
+ Engine& eng, T min_value, T max_value,
+ boost::mpl::false_ /** is_integral<Engine::result_type> */)
+{
+ uniform_int_float<Engine> wrapper(eng);
+ return generate_uniform_int(wrapper, min_value, max_value, boost::mpl::true_());
+}
+
+template<class Engine, class T>
+inline T generate_uniform_int(Engine& eng, T min_value, T max_value)
+{
+ typedef typename Engine::result_type base_result;
+ return generate_uniform_int(eng, min_value, max_value,
+ boost::is_integral<base_result>());
+}
+
+}
+
+/**
+ * The class template uniform_int_distribution models a \random_distribution.
+ * On each invocation, it returns a random integer value uniformly
+ * distributed in the set of integers {min, min+1, min+2, ..., max}.
+ *
+ * The template parameter IntType shall denote an integer-like value type.
+ */
+template<class IntType = int>
+class uniform_int_distribution
+{
+public:
+ typedef IntType input_type;
+ typedef IntType result_type;
+
+ class param_type
+ {
+ public:
+
+ typedef uniform_int_distribution distribution_type;
+
+ /**
+ * Constructs the parameters of a uniform_int_distribution.
+ *
+ * Requires min <= max
+ */
+ explicit param_type(
+ IntType min_arg = 0,
+ IntType max_arg = (std::numeric_limits<IntType>::max)())
+ : _min(min_arg), _max(max_arg)
+ {
+ BOOST_ASSERT(_min <= _max);
+ }
+
+ /** Returns the minimum value of the distribution. */
+ IntType a() const { return _min; }
+ /** Returns the maximum value of the distribution. */
+ IntType b() const { return _max; }
+
+ /** Writes the parameters to a @c std::ostream. */
+ BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm)
+ {
+ os << parm._min << " " << parm._max;
+ return os;
+ }
+
+ /** Reads the parameters from a @c std::istream. */
+ BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm)
+ {
+ IntType min_in, max_in;
+ if(is >> min_in >> std::ws >> max_in) {
+ if(min_in <= max_in) {
+ parm._min = min_in;
+ parm._max = max_in;
+ } else {
+ is.setstate(std::ios_base::failbit);
+ }
+ }
+ return is;
+ }
+
+ /** Returns true if the two sets of parameters are equal. */
+ BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs)
+ { return lhs._min == rhs._min && lhs._max == rhs._max; }
+
+ /** Returns true if the two sets of parameters are different. */
+ BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type)
+
+ private:
+
+ IntType _min;
+ IntType _max;
+ };
+
+ /**
+ * Constructs a uniform_int_distribution. @c min and @c max are
+ * the parameters of the distribution.
+ *
+ * Requires: min <= max
+ */
+ explicit uniform_int_distribution(
+ IntType min_arg = 0,
+ IntType max_arg = (std::numeric_limits<IntType>::max)())
+ : _min(min_arg), _max(max_arg)
+ {
+ BOOST_ASSERT(min_arg <= max_arg);
+ }
+ /** Constructs a uniform_int_distribution from its parameters. */
+ explicit uniform_int_distribution(const param_type& parm)
+ : _min(parm.a()), _max(parm.b()) {}
+
+ /** Returns the minimum value of the distribution */
+ IntType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _min; }
+ /** Returns the maximum value of the distribution */
+ IntType max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _max; }
+
+ /** Returns the minimum value of the distribution */
+ IntType a() const { return _min; }
+ /** Returns the maximum value of the distribution */
+ IntType b() const { return _max; }
+
+ /** Returns the parameters of the distribution. */
+ param_type param() const { return param_type(_min, _max); }
+ /** Sets the parameters of the distribution. */
+ void param(const param_type& parm)
+ {
+ _min = parm.a();
+ _max = parm.b();
+ }
+
+ /**
+ * Effects: Subsequent uses of the distribution do not depend
+ * on values produced by any engine prior to invoking reset.
+ */
+ void reset() { }
+
+ /** Returns an integer uniformly distributed in the range [min, max]. */
+ template<class Engine>
+ result_type operator()(Engine& eng) const
+ { return detail::generate_uniform_int(eng, _min, _max); }
+
+ /**
+ * Returns an integer uniformly distributed in the range
+ * [param.a(), param.b()].
+ */
+ template<class Engine>
+ result_type operator()(Engine& eng, const param_type& parm) const
+ { return detail::generate_uniform_int(eng, parm.a(), parm.b()); }
+
+ /** Writes the distribution to a @c std::ostream. */
+ BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, uniform_int_distribution, ud)
+ {
+ os << ud.param();
+ return os;
+ }
+
+ /** Reads the distribution from a @c std::istream. */
+ BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, uniform_int_distribution, ud)
+ {
+ param_type parm;
+ if(is >> parm) {
+ ud.param(parm);
+ }
+ return is;
+ }
+
+ /**
+ * Returns true if the two distributions will produce identical sequences
+ * of values given equal generators.
+ */
+ BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(uniform_int_distribution, lhs, rhs)
+ { return lhs._min == rhs._min && lhs._max == rhs._max; }
+
+ /**
+ * Returns true if the two distributions may produce different sequences
+ * of values given equal generators.
+ */
+ BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(uniform_int_distribution)
+
+private:
+ IntType _min;
+ IntType _max;
+};
+
+} // namespace random
+} // namespace boost
+
+#endif // BOOST_RANDOM_UNIFORM_INT_HPP
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