proposition: Lemma memNfinsupp f k : (k \notin finsupp f) = (f k == default k).
proof: Proof. by rewrite mem_finsupp negbK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)