sl@0: /* boost random/triangle_distribution.hpp header file
sl@0:  *
sl@0:  * Copyright Jens Maurer 2000-2001
sl@0:  * Distributed under the Boost Software License, Version 1.0. (See
sl@0:  * accompanying file LICENSE_1_0.txt or copy at
sl@0:  * http://www.boost.org/LICENSE_1_0.txt)
sl@0:  *
sl@0:  * See http://www.boost.org for most recent version including documentation.
sl@0:  *
sl@0:  * $Id: triangle_distribution.hpp,v 1.11 2004/07/27 03:43:32 dgregor Exp $
sl@0:  *
sl@0:  * Revision history
sl@0:  *  2001-02-18  moved to individual header files
sl@0:  */
sl@0: 
sl@0: #ifndef BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP
sl@0: #define BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP
sl@0: 
sl@0: #include <cmath>
sl@0: #include <cassert>
sl@0: #include <boost/random/uniform_01.hpp>
sl@0: 
sl@0: namespace boost {
sl@0: 
sl@0: // triangle distribution, with a smallest, b most probable, and c largest
sl@0: // value.
sl@0: template<class RealType = double>
sl@0: class triangle_distribution
sl@0: {
sl@0: public:
sl@0:   typedef RealType input_type;
sl@0:   typedef RealType result_type;
sl@0: 
sl@0:   explicit triangle_distribution(result_type a = result_type(0),
sl@0:                                  result_type b = result_type(0.5),
sl@0:                                  result_type c = result_type(1))
sl@0:     : _a(a), _b(b), _c(c)
sl@0:   {
sl@0:     assert(_a <= _b && _b <= _c);
sl@0:     init();
sl@0:   }
sl@0: 
sl@0:   // compiler-generated copy ctor and assignment operator are fine
sl@0:   result_type a() const { return _a; }
sl@0:   result_type b() const { return _b; }
sl@0:   result_type c() const { return _c; }
sl@0: 
sl@0:   void reset() { }
sl@0: 
sl@0:   template<class Engine>
sl@0:   result_type operator()(Engine& eng)
sl@0:   {
sl@0: #ifndef BOOST_NO_STDC_NAMESPACE
sl@0:     using std::sqrt;
sl@0: #endif
sl@0:     result_type u = eng();
sl@0:     if( u <= q1 )
sl@0:       return _a + p1*sqrt(u);
sl@0:     else
sl@0:       return _c - d3*sqrt(d2*u-d1);
sl@0:   }
sl@0: 
sl@0: #if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)
sl@0:   template<class CharT, class Traits>
sl@0:   friend std::basic_ostream<CharT,Traits>&
sl@0:   operator<<(std::basic_ostream<CharT,Traits>& os, const triangle_distribution& td)
sl@0:   {
sl@0:     os << td._a << " " << td._b << " " << td._c;
sl@0:     return os;
sl@0:   }
sl@0: 
sl@0:   template<class CharT, class Traits>
sl@0:   friend std::basic_istream<CharT,Traits>&
sl@0:   operator>>(std::basic_istream<CharT,Traits>& is, triangle_distribution& td)
sl@0:   {
sl@0:     is >> std::ws >> td._a >> std::ws >> td._b >> std::ws >> td._c;
sl@0:     td.init();
sl@0:     return is;
sl@0:   }
sl@0: #endif
sl@0: 
sl@0: private:
sl@0:   void init()
sl@0:   {
sl@0: #ifndef BOOST_NO_STDC_NAMESPACE
sl@0:     using std::sqrt;
sl@0: #endif
sl@0:     d1 = _b - _a;
sl@0:     d2 = _c - _a;
sl@0:     d3 = sqrt(_c - _b);
sl@0:     q1 = d1 / d2;
sl@0:     p1 = sqrt(d1 * d2);
sl@0:   }
sl@0: 
sl@0:   result_type _a, _b, _c;
sl@0:   result_type d1, d2, d3, q1, p1;
sl@0: };
sl@0: 
sl@0: } // namespace boost
sl@0: 
sl@0: #endif // BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP