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From: johnl@ima.UUCP
Newsgroups: comp.compilers
Subject: Re: Algol 68
Message-ID: <675@ima.ISC.COM>
Date: Wed, 19-Aug-87 17:02:27 EDT
Article-I.D.: ima.675
Posted: Wed Aug 19 17:02:27 1987
Date-Received: Sat, 22-Aug-87 06:17:13 EDT
References: <646@ima.ISC.COM> <648@ima.ISC.COM>
Sender: johnl@ima.ISC.COM
Reply-To: harvard!rutgers!petsd!cjh
Organization: Perkin-Elmer DSG, Tinton Falls, N.J.
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Approved: compilers@ima.UUCP
In-Reply-To: <652@ima.ISC.COM>


In article <652@ima.ISC.COM> Stanley Shebs writes:
>Two-level grammars have the same problem that attribute grammars do -
>they are based on the belief that the world is linear strings of tokens.
>Sooner or later, simple grammars don't work, so people have introduced
>some pretty bizarre schemes to patch things up.  (My first response to
>attribute grammars was the word "kludge".)  

It has always seemed to me that attribute grammars, based as they are on
the parse tree, are a step up from linear strings of tokens.

My two complaints about AG are:
1) Because they generate long-distance dependencies (e.g. the type of
   an identifier depends on a declaration, *somewhere*) the
   evaluation is expensive (without optimizing tricks).
2) Attribute evaluator generators that I have seen have been too closely
   tied to particular languages.  For instance, one that I know
   of generates a monolithic Pascal program.  Suppose you would
   prefer Modula 2, in several compilation units, or Ada, or C...?
   Too bad.

Can someone propose an alternative to attribute grammars, as a
way to specify context-sensitive syntax in a form suitable
for machine processing?  I would be interested to know.  The
answer doesn't have to solve the *whole* problem of compilation;
if you can bite off a substantial chunk, that's worth while.


Regards,
Chris
--
Full-Name:  Christopher J. Henrich
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