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From: "Warren W. Gay VE3WWG" <ve3wwg@home.com>
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Subject: Re: short-circuit control forms (& 'long names are doom')
References: <3B30F836.D700DAA3@raytheon.com> <3B32038D.F1296C79@cadence.com>
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Date: Thu, 21 Jun 2001 17:20:13 GMT
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Date: 2001-06-21T17:20:13+00:00
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Paul Graham wrote:
> "James A. Krzyzanowski" wrote:
> >
> > Looking for expert opinions...
> >
> > We have a company standard which states:
> > "standard => Use short-circuit control forms to specify the order of
> >              conditions when the failure of one condition means that
> >              the other condition will raise an exception.
> >  guideline => Avoid short-circuit control forms otherwise."
> >
> 
> Looking at the GNAT 3.13p source code, I count about 5000 occurrences of
> 'and then' and only about 400 occurrences of 'and' not followed by
> 'then'.  (This count is very approximate.)  It seems that the GNAT
> policy is to use 'and then' by default.

Before arriving at that assumption, did you examine how many of those
cases NEEDED to be that way? Since you didn't report a count of those,
then I think we can safely assume that you didn't check that.

It has been pointed out by many, that the spirit of the short-circuit
forms is to avoid exceptions in evaluating the rest of the expression.
If this is the case, then these are perfectly valid uses of the
short-circuit forms.

-- 
Warren W. Gay VE3WWG
http://members.home.net/ve3wwg