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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: and then... (a curiosity)
Date: Tue, 2 Sep 2008 19:11:29 -0500
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Date: 2008-09-02T19:11:29-05:00
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"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message 
news:wccprnm708a.fsf@shell01.TheWorld.com...
...
> At AdaCore, we always say "and then", never "and".  I don't like that
> style (but of course I obey it, because obeying coding conventions is a
> good thing in itself).

I can't speak for AdaCore, but we (and me personally) have a similar 
convention. It originated in code quality concerns: on the original 8086, 
"and then" could be optimized far better than "and" (because the former is 
branching, and all conditionals on the 8086 required branching; the latter 
requires Boolean values, which had to be created out of branching). These 
days, it's mostly premature optimization.

Note that I avoid the convention in two cases: where a bunch of Boolean 
values are involved (no excess branching is needed), and in rare cases when 
I need both operands evaluated. And I always comment expressions where the 
order is significant or evaluation is significant.

                              Randy.