fact: Definition contravariant_d {B A : Type} (F: (B -> pred A) -> (B -> pred A)) : Prop := forall (P Q: B -> pred A), (forall x, P x |-- Q x) -> (forall x, F Q x |-- F P x).
imports: CertiGraph.msl_ext.ramify_tactics CertiGraph.msl_ext.msl_ext VST.msl.msl_direct CertiGraph.msl_ext.sepalg