proposition: Lemma sup_default E : ~ has_sup E -> sup E == 0.
proof: Proof. by split=> [|a [] [] //]; right. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq order) mathcomp(ssralg ssrnum ssrint rat) fourcolor(real) Coq(Setoid Morphisms)