dnl Available from the GNU Autoconf Macro Archive at:
dnl http://www.gnu.org/software/ac-archive/htmldoc/ac_cxx_have_complex.html
dnl
AC_DEFUN([AC_CXX_HAVE_COMPLEX],
[AC_CACHE_CHECK(whether the compiler has complex<T>,
ac_cv_cxx_have_complex,
[AC_LANG_SAVE
 AC_LANG_CPLUSPLUS
 AC_TRY_COMPILE([#include <complex>
using namespace std;
],[complex<float> a; complex<double> b; return 0;],
 ac_cv_cxx_have_complex=yes, ac_cv_cxx_have_complex=no)
 AC_LANG_RESTORE
])
if test "$ac_cv_cxx_have_complex" = yes; then
  AC_DEFINE(HAVE_COMPLEX,,[define if the compiler has complex<T>])
fi
])
