1 // Copyright (c) 2007 John Maddock
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_COS_PI_HPP
7 #define BOOST_MATH_COS_PI_HPP
8
9 #ifdef _MSC_VER
10 #pragma once
11 #endif
12
13 #include <cmath>
14 #include <boost/math/special_functions/math_fwd.hpp>
15 #include <boost/math/tools/config.hpp>
16 #include <boost/math/special_functions/trunc.hpp>
17 #include <boost/math/tools/promotion.hpp>
18 #include <boost/math/constants/constants.hpp>
19
20 namespace boost{ namespace math{ namespace detail{
21
22 template <class T, class Policy>
23 T cos_pi_imp(T x, const Policy& pol)
24 {
25 BOOST_MATH_STD_USING // ADL of std names
26 // cos of pi*x:
27 bool invert = false;
28 if(fabs(x) < 0.25)
29 return cos(constants::pi<T>() * x);
30
31 if(x < 0)
32 {
33 x = -x;
34 }
35 T rem = floor(x);
36 if(iconvert(rem, pol) & 1)
37 invert = !invert;
38 rem = x - rem;
39 if(rem > 0.5f)
40 {
41 rem = 1 - rem;
42 invert = !invert;
43 }
44 if(rem == 0.5f)
45 return 0;
46
47 if(rem > 0.25f)
48 {
49 rem = 0.5f - rem;
50 rem = sin(constants::pi<T>() * rem);
51 }
52 else
53 rem = cos(constants::pi<T>() * rem);
54 return invert ? T(-rem) : rem;
55 }
56
57 } // namespace detail
58
59 template <class T, class Policy>
cos_pi(T x,const Policy &)60 inline typename tools::promote_args<T>::type cos_pi(T x, const Policy&)
61 {
62 typedef typename tools::promote_args<T>::type result_type;
63 typedef typename policies::evaluation<result_type, Policy>::type value_type;
64 typedef typename policies::normalise<
65 Policy,
66 policies::promote_float<false>,
67 policies::promote_double<false>,
68 policies::discrete_quantile<>,
69 policies::assert_undefined<>,
70 // We want to ignore overflows since the result is in [-1,1] and the
71 // check slows the code down considerably.
72 policies::overflow_error<policies::ignore_error> >::type forwarding_policy;
73 return policies::checked_narrowing_cast<result_type, forwarding_policy>(boost::math::detail::cos_pi_imp<value_type>(x, forwarding_policy()), "cos_pi");
74 }
75
76 template <class T>
cos_pi(T x)77 inline typename tools::promote_args<T>::type cos_pi(T x)
78 {
79 return boost::math::cos_pi(x, policies::policy<>());
80 }
81
82 } // namespace math
83 } // namespace boost
84 #endif
85
86