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Diffstat (limited to 'gcc-4.4.3/libstdc++-v3/include/tr1/beta_function.tcc')
| -rw-r--r-- | gcc-4.4.3/libstdc++-v3/include/tr1/beta_function.tcc | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/gcc-4.4.3/libstdc++-v3/include/tr1/beta_function.tcc b/gcc-4.4.3/libstdc++-v3/include/tr1/beta_function.tcc new file mode 100644 index 000000000..f9d18604d --- /dev/null +++ b/gcc-4.4.3/libstdc++-v3/include/tr1/beta_function.tcc @@ -0,0 +1,197 @@ +// Special functions -*- C++ -*- + +// Copyright (C) 2006, 2007, 2008, 2009 +// Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. +// +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. +// +// Under Section 7 of GPL version 3, you are granted additional +// permissions described in the GCC Runtime Library Exception, version +// 3.1, as published by the Free Software Foundation. + +// You should have received a copy of the GNU General Public License and +// a copy of the GCC Runtime Library Exception along with this program; +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see +// <http://www.gnu.org/licenses/>. + +/** @file tr1/beta_function.tcc + * This is an internal header file, included by other library headers. + * You should not attempt to use it directly. + */ + +// +// ISO C++ 14882 TR1: 5.2 Special functions +// + +// Written by Edward Smith-Rowland based on: +// (1) Handbook of Mathematical Functions, +// ed. Milton Abramowitz and Irene A. Stegun, +// Dover Publications, +// Section 6, pp. 253-266 +// (2) The Gnu Scientific Library, http://www.gnu.org/software/gsl +// (3) Numerical Recipes in C, by W. H. Press, S. A. Teukolsky, +// W. T. Vetterling, B. P. Flannery, Cambridge University Press (1992), +// 2nd ed, pp. 213-216 +// (4) Gamma, Exploring Euler's Constant, Julian Havil, +// Princeton, 2003. + +#ifndef _GLIBCXX_TR1_BETA_FUNCTION_TCC +#define _GLIBCXX_TR1_BETA_FUNCTION_TCC 1 + +namespace std +{ +namespace tr1 +{ + + // [5.2] Special functions + + // Implementation-space details. + namespace __detail + { + + /** + * @brief Return the beta function: \f$B(x,y)\f$. + * + * The beta function is defined by + * @f[ + * B(x,y) = \frac{\Gamma(x)\Gamma(y)}{\Gamma(x+y)} + * @f] + * + * @param __x The first argument of the beta function. + * @param __y The second argument of the beta function. + * @return The beta function. + */ + template<typename _Tp> + _Tp + __beta_gamma(_Tp __x, _Tp __y) + { + + _Tp __bet; +#if _GLIBCXX_USE_C99_MATH_TR1 + if (__x > __y) + { + __bet = std::tr1::tgamma(__x) + / std::tr1::tgamma(__x + __y); + __bet *= std::tr1::tgamma(__y); + } + else + { + __bet = std::tr1::tgamma(__y) + / std::tr1::tgamma(__x + __y); + __bet *= std::tr1::tgamma(__x); + } +#else + if (__x > __y) + { + __bet = __gamma(__x) / __gamma(__x + __y); + __bet *= __gamma(__y); + } + else + { + __bet = __gamma(__y) / __gamma(__x + __y); + __bet *= __gamma(__x); + } +#endif + + return __bet; + } + + /** + * @brief Return the beta function \f$B(x,y)\f$ using + * the log gamma functions. + * + * The beta function is defined by + * @f[ + * B(x,y) = \frac{\Gamma(x)\Gamma(y)}{\Gamma(x+y)} + * @f] + * + * @param __x The first argument of the beta function. + * @param __y The second argument of the beta function. + * @return The beta function. + */ + template<typename _Tp> + _Tp + __beta_lgamma(_Tp __x, _Tp __y) + { +#if _GLIBCXX_USE_C99_MATH_TR1 + _Tp __bet = std::tr1::lgamma(__x) + + std::tr1::lgamma(__y) + - std::tr1::lgamma(__x + __y); +#else + _Tp __bet = __log_gamma(__x) + + __log_gamma(__y) + - __log_gamma(__x + __y); +#endif + __bet = std::exp(__bet); + return __bet; + } + + + /** + * @brief Return the beta function \f$B(x,y)\f$ using + * the product form. + * + * The beta function is defined by + * @f[ + * B(x,y) = \frac{\Gamma(x)\Gamma(y)}{\Gamma(x+y)} + * @f] + * + * @param __x The first argument of the beta function. + * @param __y The second argument of the beta function. + * @return The beta function. + */ + template<typename _Tp> + _Tp + __beta_product(_Tp __x, _Tp __y) + { + + _Tp __bet = (__x + __y) / (__x * __y); + + unsigned int __max_iter = 1000000; + for (unsigned int __k = 1; __k < __max_iter; ++__k) + { + _Tp __term = (_Tp(1) + (__x + __y) / __k) + / ((_Tp(1) + __x / __k) * (_Tp(1) + __y / __k)); + __bet *= __term; + } + + return __bet; + } + + + /** + * @brief Return the beta function \f$ B(x,y) \f$. + * + * The beta function is defined by + * @f[ + * B(x,y) = \frac{\Gamma(x)\Gamma(y)}{\Gamma(x+y)} + * @f] + * + * @param __x The first argument of the beta function. + * @param __y The second argument of the beta function. + * @return The beta function. + */ + template<typename _Tp> + inline _Tp + __beta(_Tp __x, _Tp __y) + { + if (__isnan(__x) || __isnan(__y)) + return std::numeric_limits<_Tp>::quiet_NaN(); + else + return __beta_lgamma(__x, __y); + } + + } // namespace std::tr1::__detail +} +} + +#endif // __GLIBCXX_TR1_BETA_FUNCTION_TCC |