fact: Definition bind_pre : pre := fun i => exists (Vi : valid i) (Pi : i \In pre_of e1), forall x m, prog_of e1 _ Vi Pi (Val x) m -> pre_of (e2 x) m.
imports: mathcomp(ssreflect ssrbool ssrfun ssrnat eqtype seq) pcm(options axioms pred prelude) pcm(pcm unionmap heap) htt(domain)