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From: Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: GNAT 4.4.5 order of conditional processing?
Date: Tue, 15 Nov 2011 16:08:37 -0700
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Date: 2011-11-15T16:08:37-07:00
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On 11/15/2011 01:30 PM, awdorrin wrote:
> Given an IF statement such as the following:
>
> if X = Y and not A and B
>
> How does GNAT handle the processing of the conditional statements?
> Will "X = Y" be processed first, and if false, will the rest be
> skipped?

The language specifies that all the conditions must be evaluated. A compiler 
that does differently isn't Ada.

To skip later conditions, use the "short-circuit" forms "and then" and "or else":

if P /= null and then P.all = Sentinel then

if P = null or else P.all = Sentinel then

Note that the short circuit forms should not be considered optimizations. With 
modern processors, unnecessary short-circuit forms may sometimes be slower than 
the regular equivalents.

-- 
Jeff Carter
"I feel as though somebody stepped on my tongue
with muddy feet."
Never Give a Sucker an Even Break
112