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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) | |
20effc67 | 37 | return boost::math::expm1(l, pol); |
7c673cae FG |
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 | |
80 | ||
81 | ||
82 | ||
83 | ||
84 |