proposition: Fact nneg_addr_closed : addr_closed (@nneg R).
proof: Proof. by split; [apply: lexx | apply: addr_ge0]. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(ssrAC div fintype path bigop order finset fingroup) mathcomp(ssralg poly)