proposition: Lemma ifR_cases : ifR_spec ifR.
proof: Proof. have [haveP | notP] := classical P; [left | right] => //. by apply: def_sup => [|y []-[_ []] //]; left. by apply: def_sup => [|y []-[_ [] //]]; right. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq order) mathcomp(ssralg ssrnum ssrint rat) fourcolor(real) Coq(Setoid Morphisms)