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From: sb463ba@l1-hrz.uni-duisburg.de (Georg Bauhaus)
Subject: Re: if statements
Date: 2000/11/08
Message-ID: <8ucae4$l95$1@news-hrz.uni-duisburg.de>#1/1
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References: <8tvbcq$8201@news.cis.okstate.edu>
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Organization: Gerhard-Mercator-Universitaet - Gesamthochschule Duisburg
Newsgroups: comp.lang.ada
Date: 2000-11-08T00:00:00+00:00
List-Id: <comp.lang.ada>

Alejandro Villanueva (190921@cepsz.unizar.es) wrote:

: please, we are here to help other people... isn't it????

But how?

I remember seeing a = a + 1 in a desk calculator's
BASIC and I was desperate, because I could not see
that this was not a declaration of equality, until
I found out that "=" was actually ":=". Now if
the problem had been "Swap"ping (like in this thread,
partly), and I had not yet
heard that you can't just exchange the values of
two variables in some programming language, ie without
a helper variable or one of the other ingenuities
presented earlier in this thread, I think I would have
found a reformulation of the problem that used more
familiar 'objects' quite useful to gain an understanding.
Something along:

"If, late at night at some party, you mistakenly put the rest
 of the beer into a glass suitable for wine, and the rest of
 the wine into a glass suitable for beer, what can you do
 to exchange the fluids?"

I can't say if this will actually help someone, but
it might, i think, help their imagination;
most people have two hands and can take up A and B in
either and are quite ready to say, 

A :=: B;

as is at least the x86. Isn't having to introduce additional
memory or calculation part of the new unfamiliar way of thinking
when programming, and isn't this much better explained 
with words (before formal training) than with
T: = A; A:= B; B:= T; alone?

I'm still thankful for exactly this happening on c.l.a with
"more advanced" data structures and tricks. (And should I
add that I do not think that John English doesn't
explain?)