proposition: Lemma mem0_itvcc_xNx x : (0 \in `[- x, x]) = (0 <= x).
proof: Proof. by rewrite itv_boundlr [in LHS]/<=%O /= oppr_le0 andbb. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(div fintype bigop order ssralg finset fingroup) mathcomp(ssrnum)