/usr/include/boost/math/special_functions
Edit: /usr/include/boost/math/special_functions/sinc.hpp (3409B)
// boost sinc.hpp header file
// (C) Copyright Hubert Holin 2001.
// Distributed under 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)
// See http://www.boost.org for updates, documentation, and revision history.
#ifndef BOOST_SINC_HPP
#define BOOST_SINC_HPP
#ifdef _MSC_VER
#pragma once
#endif
#include
#include
#include
#include
#include
#include
#include
#include
#include
// These are the the "Sinus Cardinal" functions.
namespace boost
{
namespace math
{
namespace detail
{
// This is the "Sinus Cardinal" of index Pi.
template
inline T sinc_pi_imp(const T x)
{
BOOST_MATH_STD_USING
if (abs(x) >= 3.3 * tools::forth_root_epsilon())
{
return(sin(x)/x);
}
else
{
// |x| < (eps*120)^(1/4)
return 1 - x * x / 6;
}
}
} // namespace detail
template
inline typename tools::promote_args::type sinc_pi(T x)
{
typedef typename tools::promote_args::type result_type;
return detail::sinc_pi_imp(static_cast(x));
}
template
inline typename tools::promote_args::type sinc_pi(T x, const Policy&)
{
typedef typename tools::promote_args::type result_type;
return detail::sinc_pi_imp(static_cast(x));
}
#ifndef BOOST_NO_TEMPLATE_TEMPLATES
template class U>
inline U sinc_pi(const U x)
{
BOOST_MATH_STD_USING
using ::std::numeric_limits;
T const taylor_0_bound = tools::epsilon();
T const taylor_2_bound = tools::root_epsilon();
T const taylor_n_bound = tools::forth_root_epsilon();
if (abs(x) >= taylor_n_bound)
{
return(sin(x)/x);
}
else
{
// approximation by taylor series in x at 0 up to order 0
#ifdef __MWERKS__
U result = static_cast >(1);
#else
U result = U(1);
#endif
if (abs(x) >= taylor_0_bound)
{
U x2 = x*x;
// approximation by taylor series in x at 0 up to order 2
result -= x2/static_cast(6);
if (abs(x) >= taylor_2_bound)
{
// approximation by taylor series in x at 0 up to order 4
result += (x2*x2)/static_cast(120);
}
}
return(result);
}
}
template class U, class Policy>
inline U sinc_pi(const U x, const Policy&)
{
return sinc_pi(x);
}
#endif /* BOOST_NO_TEMPLATE_TEMPLATES */
}
}
#endif /* BOOST_SINC_HPP */