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From: logant@lafcol.lafayette.edu (Logan Tracy H)
Subject: Possible project for youngster
Originator: news@lafcol
Sender: usenet@Lehigh.EDU
Message-ID: <1993Dec28.133655.17705@Lehigh.EDU>
Date: Tue, 28 Dec 1993 13:36:55 GMT
Nntp-Posting-Host: lafcol
Organization: Lafayette College, Easton PA
Keywords: backtracking memory youngster
Lines: 30


Recently a 5th-grade teacher tried a puzzle on me: five persons
live in five row-houses, of five colors....  I'd seen similar
puzzles, looked too hard to be fun (for me); I suggested it might
make a fun Logo project tho for a motivated youngster.  "Property
lists," I debonairly said.

A bit later I realized I'd better go see if indeed I could do it
via Logo!  Don't know if such puzzles are classically over- or
under-determined, or if there are clever ways of doing them; I
just tried backtracking.

My original attack was to assign everyone some permutation of all properties
and then test against the specs ("the person in the green
house has a dog"), but that method ran out of memory, so I tested
as soon as I assigned enuf relevant properties.  On a Sun, using Brian
Harvey's no-graphics version, that seemed to have worked.

Questions:  1. has anyone tried this with a youngster?  If so, was
the youngster able to evolve and test procedures that eventually
led to doing the whole problem?  Or is it not a good project,
requiring too big steps?  A version of the puzzle with only four,
or three, characters might help, seems to me.

2. What about memory in such situations?  Apart from smart code,
are there ways of keeping memory from being a problem (garbage
collection forced every so often???) so a youngster wouldn't have to
wrestle with that, at least not right off?    -tracy

logant @ lafcol.lafayette.edu