fact: CoInductive cER (p q : X -> Prop) (w : X) : Prop := | ER0 : p w -> q w -> cER p q w | ERs v : q w -> e w v -> cER p q v -> cER p q w.
imports: mathcomp.ssreflect.ssreflect mathcomp(all_ssreflect) CompDecModal.libs(edone bcase fset base modular_hilbert sltype)