Re: Query re optimising hcrs

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Article #5665

#5665

From: Steven Ryan
Date: Sat, 30 Jul 1988 21:13

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>                     Only if the order that logical expressions is calculated
>is undefined is this optimization reasonable.

That is why it is better to leave the order of evaluation undefined.
 
>	if( (p != NULL) && (*p == VALUE) )
>
>where I check that the pointer is good and then check the value.  Reorganize
>this and all hell will break loose.

C, Algol60, and Algol68 provide an alternate construct which safe, explicit,
and lets the operators be just operators:

         if ( p==nil ? false : *p==value )

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!attcan!uunet!lll-winken!lll-lcc!mordor!joyce!sri-unix!garth!smryan

References: <561@etive.ed.ac.uk> <24414@think.UUCP> <3678@hcr.UUCP>

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Path: arc1-ca.pugleaf.net!utzoo!utgpu!attcan!uunet!lll-winken!lll-lcc!mordor!joyce!sri-unix!garth!smryan
From: smryan@garth.UUCP (Steven Ryan)
Newsgroups: comp.lang.misc
Subject: Re: Query re optimising hcrs
Message-ID: <1113@garth.UUCP>
Date: 30 Jul 88 21:13:37 GMT
References: <561@etive.ed.ac.uk> <24414@think.UUCP> <3678@hcr.UUCP>
Reply-To: smryan@garth.UUCP (Steven Ryan)
Organization: INTERGRAPH (APD) -- Palo Alto, CA
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