233 lines
7.1 KiB
C++
233 lines
7.1 KiB
C++
/* boost random/triangle_distribution.hpp header file
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*
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* Copyright Jens Maurer 2000-2001
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* Copyright Steven Watanabe 2011
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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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* $Id$
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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 <boost/config/no_tr1/cmath.hpp>
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#include <iosfwd>
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#include <ios>
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#include <istream>
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#include <boost/assert.hpp>
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#include <boost/random/detail/config.hpp>
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#include <boost/random/detail/operators.hpp>
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#include <boost/random/uniform_01.hpp>
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namespace boost {
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namespace random {
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/**
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* Instantiations of @c triangle_distribution model a \random_distribution.
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* A @c triangle_distribution has three parameters, @c a, @c b, and @c c,
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* which are the smallest, the most probable and the largest values of
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* the distribution respectively.
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*/
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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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class param_type
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{
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public:
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typedef triangle_distribution distribution_type;
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/** Constructs the parameters of a @c triangle_distribution. */
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explicit param_type(RealType a_arg = RealType(0.0),
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RealType b_arg = RealType(0.5),
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RealType c_arg = RealType(1.0))
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: _a(a_arg), _b(b_arg), _c(c_arg)
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{
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BOOST_ASSERT(_a <= _b && _b <= _c);
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}
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/** Returns the minimum value of the distribution. */
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RealType a() const { return _a; }
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/** Returns the mode of the distribution. */
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RealType b() const { return _b; }
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/** Returns the maximum value of the distribution. */
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RealType c() const { return _c; }
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/** Writes the parameters to a @c std::ostream. */
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BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, param_type, parm)
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{
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os << parm._a << " " << parm._b << " " << parm._c;
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return os;
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}
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/** Reads the parameters from a @c std::istream. */
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BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, param_type, parm)
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{
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double a_in, b_in, c_in;
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if(is >> a_in >> std::ws >> b_in >> std::ws >> c_in) {
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if(a_in <= b_in && b_in <= c_in) {
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parm._a = a_in;
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parm._b = b_in;
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parm._c = c_in;
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} else {
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is.setstate(std::ios_base::failbit);
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}
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}
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return is;
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}
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/** Returns true if the two sets of parameters are equal. */
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BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(param_type, lhs, rhs)
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{ return lhs._a == rhs._a && lhs._b == rhs._b && lhs._c == rhs._c; }
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/** Returns true if the two sets of parameters are different. */
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BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(param_type)
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private:
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RealType _a;
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RealType _b;
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RealType _c;
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};
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/**
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* Constructs a @c triangle_distribution with the parameters
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* @c a, @c b, and @c c.
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*
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* Preconditions: a <= b <= c.
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*/
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explicit triangle_distribution(RealType a_arg = RealType(0.0),
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RealType b_arg = RealType(0.5),
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RealType c_arg = RealType(1.0))
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: _a(a_arg), _b(b_arg), _c(c_arg)
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{
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BOOST_ASSERT(_a <= _b && _b <= _c);
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init();
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}
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/** Constructs a @c triangle_distribution from its parameters. */
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explicit triangle_distribution(const param_type& parm)
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: _a(parm.a()), _b(parm.b()), _c(parm.c())
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{
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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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/** Returns the @c a parameter of the distribution */
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result_type a() const { return _a; }
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/** Returns the @c b parameter of the distribution */
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result_type b() const { return _b; }
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/** Returns the @c c parameter of the distribution */
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result_type c() const { return _c; }
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/** Returns the smallest value that the distribution can produce. */
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RealType min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _a; }
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/** Returns the largest value that the distribution can produce. */
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RealType max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return _c; }
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/** Returns the parameters of the distribution. */
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param_type param() const { return param_type(_a, _b, _c); }
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/** Sets the parameters of the distribution. */
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void param(const param_type& parm)
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{
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_a = parm.a();
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_b = parm.b();
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_c = parm.c();
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init();
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}
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/**
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* Effects: Subsequent uses of the distribution do not depend
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* on values produced by any engine prior to invoking reset.
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*/
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void reset() { }
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/**
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* Returns a random variate distributed according to the
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* triangle distribution.
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*/
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template<class Engine>
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result_type operator()(Engine& eng)
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{
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using std::sqrt;
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result_type u = uniform_01<result_type>()(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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/**
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* Returns a random variate distributed according to the
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* triangle distribution with parameters specified by param.
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*/
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template<class Engine>
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result_type operator()(Engine& eng, const param_type& parm)
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{ return triangle_distribution(parm)(eng); }
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/** Writes the distribution to a @c std::ostream. */
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BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, triangle_distribution, td)
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{
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os << td.param();
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return os;
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}
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/** Reads the distribution from a @c std::istream. */
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BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, triangle_distribution, td)
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{
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param_type parm;
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if(is >> parm) {
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td.param(parm);
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}
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return is;
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}
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/**
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* Returns true if the two distributions will produce identical
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* sequences of values given equal generators.
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*/
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BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(triangle_distribution, lhs, rhs)
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{ return lhs._a == rhs._a && lhs._b == rhs._b && lhs._c == rhs._c; }
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/**
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* Returns true if the two distributions may produce different
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* sequences of values given equal generators.
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*/
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BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(triangle_distribution)
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private:
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/// \cond show_private
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void init()
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{
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using std::sqrt;
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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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/// \endcond
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RealType _a, _b, _c;
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RealType d1, d2, d3, q1, p1;
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};
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} // namespace random
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using random::triangle_distribution;
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} // namespace boost
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#endif // BOOST_RANDOM_TRIANGLE_DISTRIBUTION_HPP
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