Definition Fixm (x: A) : B := Wf.Fix (well_founded_ltof A measure) (fun (x: A) => B) F x.

(* Specifications: *)
Theorem unroll_Fixm: forall x, Fixm x = F (fun (y: A) (P: measure y < measure x) => Fixm y).
Theorem unroll_Fixm: forall x, Fixm x = F (fun (y: A) (P: measure y < measure x) => Fixm y).