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From: Loryn Jenkins <loryn@s054.aone.net.au>
Subject: Re: Software landmines (loops)
Date: 1998/09/03
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Date: 1998-09-03T10:19:14+00:00
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> The termination condition is always the disjunction of the normal
> termination condition and the flags.  A disjunction is a very
> simple, straightforward logical operation, and I believe that
> the effort in comprehending a disjunction is O(n), not O(2^n), in
> the number of terms.
> 
> Look at this:
> 
> from
>         x := 1
> until
>         x > maximum
>         or error_detected
>         or user_interruption
>         or list_is_sorted
> loop
>         ...
> end
> 
> This has four conditions.  Do you really think it's 16 times harder
> to understand than just "until x > maximum"?  I'd believe it's 4
> times harder.

Mathematically, maybe. I don't think it's even four times harder,
sociologically speaking.

Obviously, this is just my personal experience reading the code the
first time: I took longer to understand the first and second portions of
the statement, because of the change in operator. However, once I had
read and comprehended the second line, the next two were real easy, real
fast.

I'm human, not machine.

And no, I *do not* figure out a truth table for every loop I write.
Instead, I use the abstractional capabilities of the tools at hand.
Bertrand Meyer described these abstractions quite nicely in the paper
located at http://www.elj.com/elj/v1/n3/bm/loop/. Just scan down until
you get to the section beginning:

	[This for me is the key reason.] 


It is interesting to note that I *like* abstracting things. Whereas many
of my colleagues (and particularly my brother, I notice), likes
approaching things procedurally. I don't know why.

Loryn Jenkins