math/special_functions/hypergeometric_1F0.hpp

0001
0002 ///////////////////////////////////////////////////////////////////////////////
0003 //  Copyright 2014 Anton Bikineev
0004 //  Copyright 2014 Christopher Kormanyos
0005 //  Copyright 2014 John Maddock
0006 //  Copyright 2014 Paul Bristow
0007 //  Distributed under the Boost
0008 //  Software License, Version 1.0. (See accompanying file
0009 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0010
0011 #ifndef BOOST_MATH_HYPERGEOMETRIC_1F0_HPP
0012 #define BOOST_MATH_HYPERGEOMETRIC_1F0_HPP
0013
0014 #include <boost/math/policies/policy.hpp>
0015 #include <boost/math/policies/error_handling.hpp>
0016 #include <boost/math/tools/promotion.hpp>
0017
0018
0019 namespace boost { namespace math { namespace detail {
0020
0021 template <class T, class Policy>
0022 inline T hypergeometric_1F0_imp(const T& a, const T& z, const Policy& pol)
0023 {
0024    static const char* function = "boost::math::hypergeometric_1F0<%1%,%1%>(%1%, %1%)";
0025    BOOST_MATH_STD_USING // pow
0026
0027    if (z == 1)
0028       return policies::raise_pole_error<T>(
0029          function,
0030          "Evaluation of 1F0 with z = %1%.",
0031          z,
0032          pol);
0033    if (1 - z < 0)
0034    {
0035       if (floor(a) != a)
0036          return policies::raise_domain_error<T>(function,
0037             "Result is complex when a is non-integral and z > 1, but got z = %1%", z, pol);
0038    }
0039    // more naive and convergent method than series
0040    return pow(T(1 - z), T(-a));
0041 }
0042
0043 } // namespace detail
0044
0045 template <class T1, class T2, class Policy>
0046 inline typename tools::promote_args<T1, T2>::type hypergeometric_1F0(T1 a, T2 z, const Policy&)
0047 {
0048    BOOST_FPU_EXCEPTION_GUARD
0049    typedef typename tools::promote_args<T1, T2>::type result_type;
0050    typedef typename policies::evaluation<result_type, Policy>::type value_type;
0051    typedef typename policies::normalise<
0052       Policy,
0053       policies::promote_float<false>,
0054       policies::promote_double<false>,
0055       policies::discrete_quantile<>,
0056       policies::assert_undefined<> >::type forwarding_policy;
0057    return policies::checked_narrowing_cast<result_type, Policy>(
0058       detail::hypergeometric_1F0_imp<value_type>(
0059          static_cast<value_type>(a),
0060          static_cast<value_type>(z),
0061          forwarding_policy()),
0062       "boost::math::hypergeometric_1F0<%1%>(%1%,%1%)");
0063 }
0064
0065 template <class T1, class T2>
0066 inline typename tools::promote_args<T1, T2>::type hypergeometric_1F0(T1 a, T2 z)
0067 {
0068    return hypergeometric_1F0(a, z, policies::policy<>());
0069 }
0070
0071
0072   } } // namespace boost::math
0073
0074 #endif // BOOST_MATH_HYPERGEOMETRIC_1F0_HPP