check that F in needs_bracketing/2 is an atom

diff --git a/src/toplevel.pl b/src/toplevel.pl
index 2cfe04f5acd16857879b7669e6349803f651777f..d9c1f5c4436fd18844bca606ab398830aea7b369 100644 (file)
--- a/src/toplevel.pl
+++ b/src/toplevel.pl
@@ -208,6 +208,7 @@ needs_bracketing(Value, Op) :-
     nonvar(Value),
     \+ integer(Value),
     functor(Value, F, Arity),
+    atom(F),
     current_op(FPrec, FSpec, F),
     current_op(EqPrec, EqSpec, Op),
     arity_specifier(Arity, FSpec),