nat).((drop h d c1 c2) \to (\forall (c3: C).(\forall (hds: PList).((drop1 hds
c2 c3) \to (drop1 (PCons h d hds) c1 c3)))))))).
-let rec ptrans (hds: PList) on hds: nat \to PList \def \lambda (i:
+rec definition ptrans (hds: PList) on hds: nat \to PList \def \lambda (i:
nat).(match hds with [PNil \Rightarrow PNil | (PCons h d hds0) \Rightarrow
(let j \def (trans hds0 i) in (let q \def (ptrans hds0 i) in (match (blt j d)
with [true \Rightarrow (PCons h (minus d (S j)) q) | false \Rightarrow