Chris@16: //  Copyright (c) 2007 John Maddock
Chris@16: //  Use, modification and distribution are subject to the
Chris@16: //  Boost Software License, Version 1.0. (See accompanying file
Chris@16: //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: #ifndef BOOST_MATH_COS_PI_HPP
Chris@16: #define BOOST_MATH_COS_PI_HPP
Chris@16: 
Chris@16: #ifdef _MSC_VER
Chris@16: #pragma once
Chris@16: #endif
Chris@16: 
Chris@16: #include <boost/config/no_tr1/cmath.hpp>
Chris@16: #include <boost/math/tools/config.hpp>
Chris@16: #include <boost/math/special_functions/trunc.hpp>
Chris@16: #include <boost/math/tools/promotion.hpp>
Chris@16: #include <boost/math/constants/constants.hpp>
Chris@16: 
Chris@16: namespace boost{ namespace math{ namespace detail{
Chris@16: 
Chris@16: template <class T, class Policy>
Chris@16: T cos_pi_imp(T x, const Policy& pol)
Chris@16: {
Chris@16:    BOOST_MATH_STD_USING // ADL of std names
Chris@16:    // cos of pi*x:
Chris@16:    bool invert = false;
Chris@16:    if(fabs(x) < 0.5)
Chris@16:       return cos(constants::pi<T>() * x);
Chris@16: 
Chris@16:    if(x < 1)
Chris@16:    {
Chris@16:       x = -x;
Chris@16:    }
Chris@16:    T rem = floor(x);
Chris@16:    if(itrunc(rem, pol) & 1)
Chris@16:       invert = !invert;
Chris@16:    rem = x - rem;
Chris@16:    if(rem > 0.5f)
Chris@16:    {
Chris@16:       rem = 1 - rem;
Chris@16:       invert = !invert;
Chris@16:    }
Chris@16:    if(rem == 0.5f)
Chris@16:       return 0;
Chris@16:    
Chris@16:    rem = cos(constants::pi<T>() * rem);
Chris@16:    return invert ? T(-rem) : rem;
Chris@16: }
Chris@16: 
Chris@16: } // namespace detail
Chris@16: 
Chris@16: template <class T, class Policy>
Chris@16: inline typename tools::promote_args<T>::type cos_pi(T x, const Policy& pol)
Chris@16: {
Chris@16:    typedef typename tools::promote_args<T>::type result_type;
Chris@16:    return boost::math::detail::cos_pi_imp<result_type>(x, pol);
Chris@16: }
Chris@16: 
Chris@16: template <class T>
Chris@16: inline typename tools::promote_args<T>::type cos_pi(T x)
Chris@16: {
Chris@16:    return boost::math::cos_pi(x, policies::policy<>());
Chris@16: }
Chris@16: 
Chris@16: } // namespace math
Chris@16: } // namespace boost
Chris@16: #endif
Chris@16: