williamr@2: //  (C) Copyright John Maddock 2005.
williamr@2: //  Use, modification and distribution are subject to the
williamr@2: //  Boost Software License, Version 1.0. (See accompanying file
williamr@2: //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
williamr@2: 
williamr@2: #ifndef BOOST_MATH_COMPLEX_ATAN_INCLUDED
williamr@2: #define BOOST_MATH_COMPLEX_ATAN_INCLUDED
williamr@2: 
williamr@2: #ifndef BOOST_MATH_COMPLEX_DETAILS_INCLUDED
williamr@2: #  include <boost/math/complex/details.hpp>
williamr@2: #endif
williamr@2: #ifndef BOOST_MATH_COMPLEX_ATANH_INCLUDED
williamr@2: #  include <boost/math/complex/atanh.hpp>
williamr@2: #endif
williamr@2: 
williamr@2: namespace boost{ namespace math{
williamr@2: 
williamr@2: template<class T> 
williamr@2: std::complex<T> atan(const std::complex<T>& x)
williamr@2: {
williamr@2:    //
williamr@2:    // We're using the C99 definition here; atan(z) = -i atanh(iz):
williamr@2:    //
williamr@2:    if(x.real() == 0)
williamr@2:    {
williamr@2:       if(x.imag() == 1)
williamr@2:          return std::complex<T>(0, std::numeric_limits<T>::has_infinity ? std::numeric_limits<T>::infinity() : static_cast<T>(HUGE_VAL));
williamr@2:       if(x.imag() == -1)
williamr@2:          return std::complex<T>(0, std::numeric_limits<T>::has_infinity ? -std::numeric_limits<T>::infinity() : -static_cast<T>(HUGE_VAL));
williamr@2:    }
williamr@2:    return ::boost::math::detail::mult_minus_i(::boost::math::atanh(::boost::math::detail::mult_i(x)));
williamr@2: }
williamr@2: 
williamr@2: } } // namespaces
williamr@2: 
williamr@2: #endif // BOOST_MATH_COMPLEX_ATAN_INCLUDED