Re: multi-language parsing by using yacc

bobduff@world.std.com (Robert A Duff)
Mon, 21 Aug 1995 16:33:51 GMT

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Newsgroups: comp.compilers
From: bobduff@world.std.com (Robert A Duff)
Keywords: yacc
Organization: The World Public Access UNIX, Brookline, MA
References: 95-08-097 95-08-136
Date: Mon, 21 Aug 1995 16:33:51 GMT

Erik Corry <ehcorry@inet.uni-c.dk> wrote:
>My experience is that it is difficult to report good error messages from
>a Yacc parser, though admittedly gcc does very well.


GNAT (the GNU Ada compiler) uses a hand-written recursive-descent
parser. It generates *excellent* syntactic error messages, IMHO.
The syntax of Ada is far from trivial, and is full of ambiguities.


>[It's true, parsing C++ with yacc is quite hard because the syntax is quite
>context dependent and in a few cases ambiguous. Some people think this says
>at least as much about the design of C++ as about yacc. -John]


"Some people" would say that all this fancy parser-generating technology
is a waste of time, since if you design the language to have a simple
syntax, a hand-written parser is trivial. Plain old Lisp, for example
-- it would be silly to use yacc for that.


- Bob
--


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