.. efun:: int referencep(mixed arg)

  returns true if arg was passed by reference to the current function, instead of the usual call-by-value.

  Note that arg has to be passed by reference to the efun, a.g. ``referencep(&x)``.

  .. seealso:: :syntax:`reference` :efun:`clonep`, :efun:`closurep`, :efun:`floatp`, :efun:`mappingp`, :efun:`objectp`, :efun:`intp`, :efun:`pointerp`, :efun:`stringp`, :efun:`symbolp`, :efun:`structp`