Imported gcc-4.4.3

[msp430-gcc.git] / libstdc++-v3 / include / tr1 / beta_function.tcc

diff --git a/libstdc++-v3/include/tr1/beta_function.tcc b/libstdc++-v3/include/tr1/beta_function.tcc
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+// 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