proposition: Lemma addRAC x y z : x + y + z == x + z + y.
proof: Proof. by rewrite -!addRA (addRC y). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div order) mathcomp(ssralg ssrnum ssrint rat intdiv) Coq(Morphisms Setoid) fourcolor(real realsyntax)