fact: Definition zip f1 f2 : option (finMap K V) := match f1, f2 with FinMap s1 pf1, FinMap s2 pf2 => match zip' s1 s2 as z return zip' s1 s2 = z -> _ with Some s => fun pf => Some (FinMap (zip_sorted' pf1 pf)) | None => fun pf => None end (erefl _) end.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path) pcm(options)