| /* 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 60755 2010-03-22 00:45:06Z steven_watanabe $ |
| * |
| * Revision history |
| * 2001-02-18 moved to individual header files |
| */ |
| |
| #ifndef BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP |
| #define BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP |
| |
| #include <boost/config/no_tr1/cmath.hpp> |
| #include <cassert> |
| #include <boost/random/detail/config.hpp> |
| #include <boost/random/uniform_01.hpp> |
| |
| namespace boost { |
| |
| /** |
| * Instantiations of @c triangle_distribution model a \random_distribution. |
| * A @c triangle_distribution has three parameters, @c a, @c b, and @c c, |
| * which are the smallest, the most probable and the largest values of |
| * the distribution respectively. |
| */ |
| template<class RealType = double> |
| class triangle_distribution |
| { |
| public: |
| typedef RealType input_type; |
| typedef RealType result_type; |
| |
| /** |
| * Constructs a @c triangle_distribution with the parameters |
| * @c a, @c b, and @c c. |
| * |
| * Preconditions: a <= b <= c. |
| */ |
| explicit triangle_distribution(result_type a_arg = result_type(0), |
| result_type b_arg = result_type(0.5), |
| result_type c_arg = result_type(1)) |
| : _a(a_arg), _b(b_arg), _c(c_arg) |
| { |
| assert(_a <= _b && _b <= _c); |
| init(); |
| } |
| |
| // compiler-generated copy ctor and assignment operator are fine |
| |
| /** Returns the @c a parameter of the distribution */ |
| result_type a() const { return _a; } |
| /** Returns the @c b parameter of the distribution */ |
| result_type b() const { return _b; } |
| /** Returns the @c c parameter of the distribution */ |
| 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); |
| } |
| |
| #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 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: |
| /// \cond hide_private_members |
| 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); |
| } |
| /// \endcond |
| |
| result_type _a, _b, _c; |
| result_type d1, d2, d3, q1, p1; |
| }; |
| |
| } // namespace boost |
| |
| #endif // BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP |