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

Lemma evalDet_equiv_symm : forall (A : Set)(c1 c2 : Comp A), evalDet_equiv c1 c2 -> evalDet_equiv c2 c1.