Definition evalDet_equiv(A : Set)(c1 c2 : Comp A) :=
  (forall s y, evalDet c1 s y <-> evalDet c2 s y).

Theorem evalDet_bind_assoc : forall (A : Set)(c1 : Comp A)(B C : Set)(c2 : A -> Comp B)(c3 : B -> Comp C), evalDet_equiv (Bind (Bind c1 c2) c3) (Bind c1 (fun a => (Bind (c2 a) c3))).