fact: Definition abst_iff (pol : bool) (k: kind) (f1 f2: TFormula TX AF k) : TFormula TX AF k := abs_iff (REC (negb pol) f1) (REC false f2) (REC pol f1) (REC true f2) (IFF (abst_simpl f1) (abst_simpl f2)).
imports: List Refl Bool Relation_Definitions Setoid