ceph/src/boost/libs/math/include/boost/math/special_functions/powm1.hpp

   1 //  (C) Copyright John Maddock 2006.
   2 //  Use, modification and distribution are subject to the
   3 //  Boost Software License, Version 1.0. (See accompanying file
   4 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   5
   6 #ifndef BOOST_MATH_POWM1
   7 #define BOOST_MATH_POWM1
   8
   9 #ifdef _MSC_VER
  10 #pragma once
  11 #pragma warning(push)
  12 #pragma warning(disable:4702) // Unreachable code (release mode only warning)
  13 #endif
  14
  15 #include <boost/math/special_functions/math_fwd.hpp>
  16 #include <boost/math/special_functions/log1p.hpp>
  17 #include <boost/math/special_functions/expm1.hpp>
  18 #include <boost/math/special_functions/trunc.hpp>
  19 #include <boost/assert.hpp>
  20
  21 namespace boost{ namespace math{ namespace detail{
  22
  23 template <class T, class Policy>
  24 inline T powm1_imp(const T x, const T y, const Policy& pol)
  25 {
  26    BOOST_MATH_STD_USING
  27    static const char* function = "boost::math::powm1<%1%>(%1%, %1%)";
  28
  29    if (x > 0)
  30    {
  31       if ((fabs(y * (x - 1)) < 0.5) || (fabs(y) < 0.2))
  32       {
  33          // We don't have any good/quick approximation for log(x) * y
  34          // so just try it and see:
  35          T l = y * log(x);
  36          if (l < 0.5)
  37             return boost::math::expm1(l);
  38          if (l > boost::math::tools::log_max_value<T>())
  39             return boost::math::policies::raise_overflow_error<T>(function, 0, pol);
  40          // fall through....
  41       }
  42    }
  43    else
  44    {
  45       // y had better be an integer:
  46       if (boost::math::trunc(y) != y)
  47          return boost::math::policies::raise_domain_error<T>(function, "For non-integral exponent, expected base > 0 but got %1%", x, pol);
  48       if (boost::math::trunc(y / 2) == y / 2)
  49          return powm1_imp(T(-x), y, pol);
  50    }
  51    return pow(x, y) - 1;
  52 }
  53
  54 } // detail
  55
  56 template <class T1, class T2>
  57 inline typename tools::promote_args<T1, T2>::type
  58    powm1(const T1 a, const T2 z)
  59 {
  60    typedef typename tools::promote_args<T1, T2>::type result_type;
  61    return detail::powm1_imp(static_cast<result_type>(a), static_cast<result_type>(z), policies::policy<>());
  62 }
  63
  64 template <class T1, class T2, class Policy>
  65 inline typename tools::promote_args<T1, T2>::type
  66    powm1(const T1 a, const T2 z, const Policy& pol)
  67 {
  68    typedef typename tools::promote_args<T1, T2>::type result_type;
  69    return detail::powm1_imp(static_cast<result_type>(a), static_cast<result_type>(z), pol);
  70 }
  71
  72 } // namespace math
  73 } // namespace boost
  74
  75 #ifdef _MSC_VER
  76 #pragma warning(pop)
  77 #endif
  78
  79 #endif // BOOST_MATH_POWM1
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