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From: johnl@ima.UUCP
Newsgroups: mod.compilers
Subject: Re: advice needed re: parsing C decl syntax
Message-ID: <287@ima.UUCP>
Date: Tue, 9-Dec-86 12:12:14 EST
Article-I.D.: ima.287
Posted: Tue Dec  9 12:12:14 1986
Date-Received: Sun, 14-Dec-86 01:00:48 EST
Reply-To: Steve Vegdahl 
Lines: 31
Approved: 
Cc: (Paul Tarvydas) csri!toronto.edu!tarvydas

Paul Tarvydas writes:
>I'm still reluctant to use a straight LALR table parser for reasons of
>(ahem) efficiency.  Things like expressions & statements are wonderful
>candidates for recursive-descent.
> ...
>Has anybody successfully married LR parsing with recursive-descent
>techniques?  Are there any other clean tricks/techniques I could use?

At the most recent Compiler Construction Conference (SigPlan notices,
July 1986), Thomas Pennello presented a technique for "compiling" the
parse-tables directly into (assembly) code, which apparently speeds up
the parsing process by a factor of 6-10.

>[But I really don't see the point.  Yacc certainly has its problems, but
>excessively slow parsing has never seemed to be one of them.  -John]

In his conclusions, Pennello also echoes this opinion:
    "Trying to speed up an LR parser may seem like beating as dead
    horse, since LR parsers are already reasonably fast."

Still, I think the paper is worth reading.

		Steve Vegdahl
		Computer Research Lab
		Tektronix Labs
		Beaverton, Oregon
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