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/* boost random/triangle_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: triangle_distribution.hpp,v 1.11 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_TRIANGLE_DISTRIBUTION_HPP
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#define BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP
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#include <cmath>
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#include <cassert>
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#include <boost/random/uniform_01.hpp>
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namespace boost {
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// triangle distribution, with a smallest, b most probable, and c largest
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// value.
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template<class RealType = double>
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class triangle_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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explicit triangle_distribution(result_type a = result_type(0),
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result_type b = result_type(0.5),
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result_type c = result_type(1))
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: _a(a), _b(b), _c(c)
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{
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assert(_a <= _b && _b <= _c);
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init();
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}
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// compiler-generated copy ctor and assignment operator are fine
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result_type a() const { return _a; }
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result_type b() const { return _b; }
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result_type c() const { return _c; }
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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::sqrt;
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#endif
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result_type u = eng();
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if( u <= q1 )
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return _a + p1*sqrt(u);
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else
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return _c - d3*sqrt(d2*u-d1);
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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 triangle_distribution& td)
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{
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os << td._a << " " << td._b << " " << td._c;
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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, triangle_distribution& td)
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{
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is >> std::ws >> td._a >> std::ws >> td._b >> std::ws >> td._c;
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td.init();
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return is;
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}
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#endif
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private:
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void init()
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{
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#ifndef BOOST_NO_STDC_NAMESPACE
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using std::sqrt;
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#endif
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d1 = _b - _a;
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d2 = _c - _a;
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d3 = sqrt(_c - _b);
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q1 = d1 / d2;
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p1 = sqrt(d1 * d2);
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}
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result_type _a, _b, _c;
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result_type d1, d2, d3, q1, p1;
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};
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} // namespace boost
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#endif // BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP
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