Definition unary_op_beq a b :=
match a, b with
  | Onotbool, Onotbool
  | Onotint, Onotint
  | Oneg, Oneg
  | Oabsfloat, Oabsfloat => true
  | _, _ => false
end.

Lemma unary_op_beq_sound : forall a b, unary_op_beq a b = true -> a = b .