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+/* boost random/uniform_int.hpp header file
+ *
+ * Copyright Jens Maurer 2000-2001
+ * 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.hpp 60755 2010-03-22 00:45:06Z 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_HPP
+#define BOOST_RANDOM_UNIFORM_INT_HPP
+
+#include <cassert>
+#include <iostream>
+#include <boost/config.hpp>
+#include <boost/limits.hpp>
+#include <boost/static_assert.hpp>
+#include <boost/detail/workaround.hpp>
+#include <boost/random/detail/config.hpp>
+#include <boost/random/detail/signed_unsigned_tools.hpp>
+#include <boost/type_traits/make_unsigned.hpp>
+
+namespace boost {
+
+/**
+ * The distribution function uniform_int models a \random_distribution.
+ * On each invocation, it returns a random integer value uniformly
+ * distributed in the set of integer numbers {min, min+1, min+2, ..., max}.
+ *
+ * The template parameter IntType shall denote an integer-like value type.
+ */
+template<class IntType = int>
+class uniform_int
+{
+public:
+ typedef IntType input_type;
+ typedef IntType result_type;
+
+ /// \cond hide_private_members
+ typedef typename make_unsigned<result_type>::type range_type;
+ /// \endcond
+
+ /**
+ * Constructs a uniform_int object. @c min and @c max are
+ * the parameters of the distribution.
+ *
+ * Requires: min <= max
+ */
+ explicit uniform_int(IntType min_arg = 0, IntType max_arg = 9)
+ : _min(min_arg), _max(max_arg)
+ {
+#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
+ // MSVC fails BOOST_STATIC_ASSERT with std::numeric_limits at class scope
+ BOOST_STATIC_ASSERT(std::numeric_limits<IntType>::is_integer);
+#endif
+ assert(min_arg <= max_arg);
+ init();
+ }
+
+ /**
+ * Returns: The "min" parameter of the distribution
+ */
+ result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _min; }
+ /**
+ * Returns: The "max" parameter of the distribution
+ */
+ result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _max; }
+ void reset() { }
+
+ // can't have member function templates out-of-line due to MSVC bugs
+ template<class Engine>
+ result_type operator()(Engine& eng)
+ {
+ return generate(eng, _min, _max, _range);
+ }
+
+ template<class Engine>
+ result_type operator()(Engine& eng, result_type n)
+ {
+ assert(n > 0);
+
+ if (n == 1)
+ {
+ return 0;
+ }
+
+ return generate(eng, 0, n - 1, n - 1);
+ }
+
+#ifndef BOOST_RANDOM_NO_STREAM_OPERATORS
+ template<class CharT, class Traits>
+ friend std::basic_ostream<CharT,Traits>&
+ operator<<(std::basic_ostream<CharT,Traits>& os, const uniform_int& ud)
+ {
+ os << ud._min << " " << ud._max;
+ return os;
+ }
+
+ template<class CharT, class Traits>
+ friend std::basic_istream<CharT,Traits>&
+ operator>>(std::basic_istream<CharT,Traits>& is, uniform_int& ud)
+ {
+ is >> std::ws >> ud._min >> std::ws >> ud._max;
+ ud.init();
+ return is;
+ }
+#endif
+
+private:
+
+#ifdef BOOST_MSVC
+#pragma warning(push)
+// disable division by zero warning, since we can't
+// actually divide by zero.
+#pragma warning(disable:4723)
+#endif
+
+ /// \cond hide_private_members
+ template<class Engine>
+ static result_type generate(Engine& eng, result_type min_value, result_type /*max_value*/, range_type range)
+ {
+ typedef typename Engine::result_type base_result;
+ // ranges are always unsigned
+ typedef typename make_unsigned<base_result>::type base_unsigned;
+ 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 = uniform_int<range_type>(0, range/mult)(eng);
+ 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
+
+ void init()
+ {
+ _range = random::detail::subtract<result_type>()(_max, _min);
+ }
+
+ /// \endcond
+
+ // The result_type may be signed or unsigned, but the _range is always
+ // unsigned.
+ result_type _min, _max;
+ range_type _range;
+};
+
+} // namespace boost
+
+#endif // BOOST_RANDOM_UNIFORM_INT_HPP