fact: Definition upd k v h := if h is Def hs ns then if decP (@idP (k != null)) is left pf then Def (@upd_nullP _ _ v pf ns) else Undef else Undef.
imports: Coq(ssreflect ssrbool ssrfun Eqdep) mathcomp(ssrnat eqtype seq path) pcm(options axioms finmap) pcm(pcm unionmap)