epoc32/include/stdapis/boost/random/exponential_distribution.hpp
author William Roberts <williamr@symbian.org>
Wed, 31 Mar 2010 12:33:34 +0100
branchSymbian3
changeset 4 837f303aceeb
permissions -rw-r--r--
Current Symbian^3 public API header files (from PDK 3.0.h)
This is the epoc32/include tree with the "platform" subtrees removed, and
all but a selected few mbg and rsg files removed.
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/* boost random/exponential_distribution.hpp header file
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 *
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 * Copyright Jens Maurer 2000-2001
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 * Distributed under the Boost Software License, Version 1.0. (See
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 * accompanying file LICENSE_1_0.txt or copy at
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 * http://www.boost.org/LICENSE_1_0.txt)
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 *
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 * See http://www.boost.org for most recent version including documentation.
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 *
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 * $Id: exponential_distribution.hpp,v 1.16 2004/07/27 03:43:32 dgregor Exp $
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 *
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 * Revision history
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 *  2001-02-18  moved to individual header files
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 */
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#ifndef BOOST_RANDOM_EXPONENTIAL_DISTRIBUTION_HPP
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#define BOOST_RANDOM_EXPONENTIAL_DISTRIBUTION_HPP
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#include <cmath>
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#include <cassert>
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#include <iostream>
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#include <boost/limits.hpp>
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#include <boost/static_assert.hpp>
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namespace boost {
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// exponential distribution: p(x) = lambda * exp(-lambda * x)
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template<class RealType = double>
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class exponential_distribution
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{
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public:
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  typedef RealType input_type;
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  typedef RealType result_type;
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#if !defined(BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS) && !(defined(BOOST_MSVC) && BOOST_MSVC <= 1300)
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  BOOST_STATIC_ASSERT(!std::numeric_limits<RealType>::is_integer);
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#endif
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  explicit exponential_distribution(result_type lambda = result_type(1))
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    : _lambda(lambda) { assert(lambda > result_type(0)); }
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  // compiler-generated copy ctor and assignment operator are fine
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  result_type lambda() const { return _lambda; }
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  void reset() { }
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  template<class Engine>
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  result_type operator()(Engine& eng)
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  { 
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#ifndef BOOST_NO_STDC_NAMESPACE
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    using std::log;
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#endif
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    return -result_type(1) / _lambda * log(result_type(1)-eng());
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  }
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#if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
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  template<class CharT, class Traits>
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  friend std::basic_ostream<CharT,Traits>&
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  operator<<(std::basic_ostream<CharT,Traits>& os, const exponential_distribution& ed)
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  {
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    os << ed._lambda;
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    return os;
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  }
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  template<class CharT, class Traits>
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  friend std::basic_istream<CharT,Traits>&
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  operator>>(std::basic_istream<CharT,Traits>& is, exponential_distribution& ed)
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  {
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    is >> std::ws >> ed._lambda;
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    return is;
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  }
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#endif
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private:
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  result_type _lambda;
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};
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} // namespace boost
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#endif // BOOST_RANDOM_EXPONENTIAL_DISTRIBUTION_HPP