proposition: Lemma eq_creal_sym x y : x == y -> y == x.
proof: Proof. by move=> eq_xy /neq_creal_sym. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(ssrfun ssrbool eqtype ssrnat seq choice fintype) mathcomp(bigop order ssralg ssrnum ssrint rat poly polydiv polyorder) mathcomp(perm matrix mxpoly polyXY binomial bigenough)