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From: hbaker@netcom.com (Henry Baker)
Subject: Re: Prefix syntax
Message-ID: <hbaker-2503950823410001@192.0.2.1>
Sender: hbaker@netcom21.netcom.com
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References: <18426.9503201324@subnode.aiai.ed.ac.uk> <neves-2003951134150001@129.105.100.185> <hbaker-2103951221550001@192.0.2.1> <1995Mar22.171609.167@den.mmc.com> <1995Mar23.150306.4307@VFL.Paramax.COM>
Date: Sat, 25 Mar 1995 16:19:54 GMT
Lines: 47
Xref: glinda.oz.cs.cmu.edu comp.lang.dylan:3866 comp.lang.lisp:17180

In article <1995Mar23.150306.4307@VFL.Paramax.COM>,
dave@gvls1.vfl.paramax.com (David Lee Matuszek) wrote:

> In article <1995Mar22.171609.167@den.mmc.com>,
britt@tigercat.den.mmc.com (Dan Britt) writes:
> |> In article <hbaker-2103951221550001@192.0.2.1>, hbaker@netcom.com
(Henry Baker) writes:
> |> ...
> |> |> Re recursion:  In my experience of teaching undergraduates, recursion is
> |> |> far easier to teach and understand than iteration.  The _only_
people who
> |> |> had any problem with recursion were those who had had their brains
damaged
> |> |> (perhaps permanently) due to early exposure to Basic and/or assembly
> |> |> language.
> |> 
> |> I beg to differ.  Recursion is conceptually much more complex due to the
> |> need to imagine multiple calls to a function INSIDE that function, with
> |> different arguments.  Getting the stopping condition right can be a pain.
> |> (Though in truth I may have some lingering impairment from exposure to
> |> Forth, FORTRAN, IDL, RTPL, C, Pascal, etc. :-))
> 
> Gee, I get to disagree with both of you!  :-)
> 
> I disagree with Henry Baker in the cause of having problems with recursion.
> In my not-so-humble opinion (I've been teaching CS since 1969), the reason
> people have trouble with recursion lies in the way it is taught.  Prior
> knowledge of BASIC, much as I hate to admit it, is correlated with better
> grades in introductory Pascal classes.

I don't doubt it, since Pascal prefers iteration over recursion.  Also, the
non-interactive nature of Pascal makes the students unbelievably
conservative, because they have a finite amount of time in which to
do their homework.  With interactive Lisp and APL, on the other hand, the
students can play with a few examples, and quickly reach an understanding.

My experience stems from teaching Lisp, Pascal and APL.  Interestingly
enough, the _computer science_ undergraduates (usually the ones with
previous assembler and/or BASIC experience) were the ones having great
difficulty with recursion.  The pre-med, pre-law, physics and chemistry
students did just fine (not at all what I would have guessed in advance).

Go figure.

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