Section feq.
Variables A B:Type.
Definition feq (f g: A -> B):=forall a, (f a)=(g a).
Infix "=f":= feq  (at level 80, right associativity).
Hint Unfold feq.
intuition.
Qed.

Lemma feq_sym: forall f g, f =f g-> g =f f.