From @life.ai.mit.edu:ziggy@hx.lcs.mit.edu Wed Nov 13 00:48:26 1991
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Date: Wed, 13 Nov 91 00:47:43 EST
From: "Michael R. Blair" <ziggy@hx.lcs.mit.edu>
Message-Id: <9111130547.AA05021@hx.LCS.MIT.EDU>
To: jcbourne@athena.mit.edu
Subject: Re:  ps8, prob 4
Cc: 6001-staff@ai.mit.edu
Status: R

Julie commented that some people are having a hard time with the last
problem on ps8. Good. It makes them think a little... and then
suddenly dawns on them.  I don't think this is too hard since it only
took me a few minutes to figure out waht is going on and I had never
seen the problem set before (nor AMBScheme)

Anyway, here is the give-away to the last problem...


(define (parse-sentence) (parse '()))


If they truly ignore the sentence in check-word then this will pass
the (NULL? ...) test for termination.

The problem is utterly trivial if you give students this hint.  I
think it would be more productive to just leave the problem alone and
let the students puzzle over it a bit. It makes them think a little
about just how this whole parsing thing works. It is probably fair to
play Socratic Method if some student gets seriously wedged, though.

It's a little subtle, but not impossible.

 ziggy

