/* boost random/triangle_distribution.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: triangle_distribution.hpp,v 1.11 2004/07/27 03:43:32 dgregor Exp $

  *

  * Revision history

  *  2001-02-18  moved to individual header files

  */

 #ifndef BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP

 #define BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP

 #include <cmath>

 #include <cassert>

 #include <boost/random/uniform_01.hpp>

 namespace boost {

 // triangle distribution, with a smallest, b most probable, and c largest

 // value.

 template<class RealType = double>

 class triangle_distribution

 {

 public:

   typedef RealType input_type;

   typedef RealType result_type;

   explicit triangle_distribution(result_type a = result_type(0),

                                  result_type b = result_type(0.5),

                                  result_type c = result_type(1))

     : _a(a), _b(b), _c(c)

   {

     assert(_a <= _b && _b <= _c);

     init();

   }

   // compiler-generated copy ctor and assignment operator are fine

   result_type a() const { return _a; }

   result_type b() const { return _b; }

   result_type c() const { return _c; }

   void reset() { }

   template<class Engine>

   result_type operator()(Engine& eng)

   {

 #ifndef BOOST_NO_STDC_NAMESPACE

     using std::sqrt;

 #endif

     result_type u = eng();

     if( u <= q1 )

       return _a + p1*sqrt(u);

     else

       return _c - d3*sqrt(d2*u-d1);

   }

 #if !defined(BOOST_NO_OPERATORS_IN_NAMESPACE) && !defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)

   template<class CharT, class Traits>

   friend std::basic_ostream<CharT,Traits>&

   operator<<(std::basic_ostream<CharT,Traits>& os, const triangle_distribution& td)

   {

     os << td._a << " " << td._b << " " << td._c;

     return os;

   }

   template<class CharT, class Traits>

   friend std::basic_istream<CharT,Traits>&

   operator>>(std::basic_istream<CharT,Traits>& is, triangle_distribution& td)

   {

     is >> std::ws >> td._a >> std::ws >> td._b >> std::ws >> td._c;

     td.init();

     return is;

   }

 #endif

 private:

   void init()

   {

 #ifndef BOOST_NO_STDC_NAMESPACE

     using std::sqrt;

 #endif

     d1 = _b - _a;

     d2 = _c - _a;

     d3 = sqrt(_c - _b);

     q1 = d1 / d2;

     p1 = sqrt(d1 * d2);

   }

   result_type _a, _b, _c;

   result_type d1, d2, d3, q1, p1;

 };

 } // namespace boost

 #endif // BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP