Date: Thu, 14 Nov 91 20:09:29 -0800 To: Frank_Pfenning@ALONZO.TIP.CS.CMU.EDU, types@theory.lcs.mit.edu One footnote: Actual Prolog is not only incomplete but unsound, due to the omission of the occurs check. SCHEMdoes not make a similar compromise. How come it is necessary (for speed) in the one case and not in the other?