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code_ordonnee/boost/math/special_functions/powm1.hpp

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+//  (C) Copyright John Maddock 2006.
+//  Use, modification and distribution are subject to 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)
+
+#ifndef BOOST_MATH_POWM1
+#define BOOST_MATH_POWM1
+
+#ifdef _MSC_VER
+#pragma once
+#pragma warning(push)
+#pragma warning(disable:4702) // Unreachable code (release mode only warning)
+#endif
+
+#include <boost/math/special_functions/math_fwd.hpp>
+#include <boost/math/special_functions/log1p.hpp>
+#include <boost/math/special_functions/expm1.hpp>
+#include <boost/math/special_functions/trunc.hpp>
+#include <boost/assert.hpp>
+
+namespace boost{ namespace math{ namespace detail{
+
+template <class T, class Policy>
+inline T powm1_imp(const T x, const T y, const Policy& pol)
+{
+   BOOST_MATH_STD_USING
+   static const char* function = "boost::math::powm1<%1%>(%1%, %1%)";
+
+   if (x > 0)
+   {
+      if ((fabs(y * (x - 1)) < 0.5) || (fabs(y) < 0.2))
+      {
+         // We don't have any good/quick approximation for log(x) * y
+         // so just try it and see:
+         T l = y * log(x);
+         if (l < 0.5)
+            return boost::math::expm1(l);
+         if (l > boost::math::tools::log_max_value<T>())
+            return boost::math::policies::raise_overflow_error<T>(function, 0, pol);
+         // fall through....
+      }
+   }
+   else
+   {
+      // y had better be an integer:
+      if (boost::math::trunc(y) != y)
+         return boost::math::policies::raise_domain_error<T>(function, "For non-integral exponent, expected base > 0 but got %1%", x, pol);
+      if (boost::math::trunc(y / 2) == y / 2)
+         return powm1_imp(T(-x), y, pol);
+   }
+   return pow(x, y) - 1;
+}
+
+} // detail
+
+template <class T1, class T2>
+inline typename tools::promote_args<T1, T2>::type 
+   powm1(const T1 a, const T2 z)
+{
+   typedef typename tools::promote_args<T1, T2>::type result_type;
+   return detail::powm1_imp(static_cast<result_type>(a), static_cast<result_type>(z), policies::policy<>());
+}
+
+template <class T1, class T2, class Policy>
+inline typename tools::promote_args<T1, T2>::type 
+   powm1(const T1 a, const T2 z, const Policy& pol)
+{
+   typedef typename tools::promote_args<T1, T2>::type result_type;
+   return detail::powm1_imp(static_cast<result_type>(a), static_cast<result_type>(z), pol);
+}
+
+} // namespace math
+} // namespace boost
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+#endif // BOOST_MATH_POWM1
+
+
+
+
+