fact: Definition wider_real xr yr := match xr, yr with | AnySign, _ => true | Sign sx, Sign sy => wider_sign sx sy | Sign _, AnySign => false end.
imports: HB(structures) Coq(ssreflect ssrfun ssrbool) mathcomp(ssrnat eqtype choice order ssralg ssrnum ssrint) mathcomp(mathcomp_extra)