proposition: Lemma absN x : `|- x| == `|x|.
proof: Proof. by split=> a; rewrite !ltcE /abs_cut oppK => -[]. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq order) mathcomp(ssralg ssrnum ssrint rat) fourcolor(real) Coq(Setoid Morphisms)