//  (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



#include <boost/math/special_functions/log1p.hpp>

#include <boost/math/special_functions/expm1.hpp>

#include <boost/math/special_functions/math_fwd.hpp>

#include <boost/assert.hpp>



namespace boost{ namespace math{ namespace detail{



template <class T, class Policy>

inline T powm1_imp(const T a, const T z, const Policy& pol)

{

   BOOST_MATH_STD_USING



   if((fabs(a) < 1) || (fabs(z) < 1))

   {

      T p = log(a) * z;

      if(fabs(p) < 2)

         return boost::math::expm1(p, pol);

      // otherwise fall though:

   }

   return pow(a, z) - 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



#endif // BOOST_MATH_POWM1









