Re: Algol 68

Wed, 19 Aug 87 17:02:27 EDT

          From comp.compilers

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From: harvard!rutgers!petsd!cjh
Date: Wed, 19 Aug 87 17:02:27 EDT
Newsgroups: comp.compilers
In-Reply-To: <652@ima.ISC.COM>
References: <646@ima.ISC.COM> <648@ima.ISC.COM>
Organization: Perkin-Elmer DSG, Tinton Falls, N.J.

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.

Full-Name: Christopher J. Henrich
UUCP: ...!hjuxa!petsd!cjh
US Mail: MS 313; Concurrent Computer Corporation;
                        106 Apple St; Tinton Falls, NJ 07724
Phone: (201) 758-7288
Concurrent Computer Corporation is a Perkin-Elmer company.

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