fact: Structure try_form A B i (e1 : A -> ST B) (e2 : exn -> ST B) r (p : Prop) := TryForm {try_pivot :> ST A; _ : p -> vrf i (try try_pivot e1 e2) r}.
imports: mathcomp(ssreflect ssrbool ssrnat eqtype seq ssrfun) pcm(options axioms pred prelude) pcm(pcm autopcm unionmap heap) htt(model)