proposition: Lemma lastkeyUnPtE u2 u1 h t : last_key (h \+ t \-> u1) = last_key (h \+ t \-> u2).
proof: Proof. by rewrite !(joinC h); apply: lastkeyPtUnE. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval) pcm(options prelude pred finmap rtc seqext useqord uslice uconsec)