proposition: Lemma cond_dom k f : ~~ C k -> k \in dom f = false.
proof: Proof. by apply: contraTF=>/dom_cond ->. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)