fact: Definition contravariant {B A : Type} {AG: ageable A} (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: VST.msl.msl_standard VST.msl.corable CertiGraph.msl_ext.ramify_tactics CertiGraph.msl_ext.msl_ext CertiGraph.msl_ext.sepalg