Definition oracle (ent: entailment) : bool :=
match VeriStar.check_entailment ent with
| VeriStar.Valid => true
| VeriStar.C_example _ => false
| VeriStar.Aborted _ _ => false
end.
Bind Scope entail_scope with entailment.
Local Open Scope entail_scope.
Definition incon (a: assertion) : bool :=
oracle (Entailment a
(Assertion (Nequ Nil Nil :: nil)
match a with (Assertion _ sigma) => sigma end)).

Lemma eq_expr (e1 e2: expr) : {e1=e2}+{e1<>e2}.