proposition: Lemma dom_inN k1 k2 f1 f2 : valid (f1 \+ f2) -> k1 \in dom f1 -> k2 \in dom f2 -> k1 != k2.
proof: Proof. by case: (k1 =P k2) =>// <- W H /(dom_inNLX W H). Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)