+dnl ** check for math library
+dnl Keep that check as early as possible.
+dnl as we need to know whether we need libm
+dnl for math functions or not
+dnl (see http://hackage.haskell.org/trac/ghc/ticket/3730)
+AC_SEARCH_LIBS(atan, m,
+ [AC_DEFINE([HAVE_LIBM], [1], [Define to 1 if you need to link with libm])])
+