Re: Why separate Lexical & Parser Generators

Anders Andersson <andand@csd.uu.se>
Thu, 6 Oct 1994 13:11:02 GMT

          From comp.compilers

Related articles
Why separate Lexical & Parser Generators heronj@smtplink.NGC.COM (John Heron) (1994-10-05)
Re: Why separate Lexical & Parser Generators andand@csd.uu.se (Anders Andersson) (1994-10-06)
Re: Why separate Lexical & Parser Generators leichter@zodiac.rutgers.edu (1994-10-06)
Re: Why separate Lexical & Parser Generators morrison@hal.cs.uiuc.edu (1994-10-07)
Re: Why separate Lexical & Parser Generators johnl@cs.indiana.edu (John Lacey) (1994-10-10)
Re: Why separate Lexical & Parser Generators hagerman@ece.cmu.edu (1994-10-10)
Re: Why separate Lexical & Parser Generators wrs@apple.com (Walter Smith) (1994-10-10)
Re: Why separate Lexical & Parser Generators cef@geodesic.com (Charles Fiterman) (1994-10-11)
[5 later articles]
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Newsgroups: comp.compilers
From: Anders Andersson <andand@csd.uu.se>
Keywords: lex, yacc, design
Organization: Compilers Central
References: 94-10-028
Date: Thu, 6 Oct 1994 13:11:02 GMT

John Heron <heronj@smtplink.NGC.COM> writes:
  > Pardon me if this question is naive. Why have a separate parser generator
  > and lexical analyzer generator?
[...]


In addition to our moderator's comments one might add:


We have lots of implicit shift/reduced and sometimes reduce/reduce
conflicts in the regular portion of the grammar that corresponds to the
longest match and first match rules in Lex. Also, many languages, like C,
have difficult constructions (typedef:ed names in C) that require the
lexical analyzer to do smart things. In a common grammar this corresponds
to some form of conditional parsing rules, so we must add stuff like that.


There have been some research into lexical analyzer free parsing. For
example:
Salomon, D.J. and Cormack, G.V. Scannerless NSLR(1) Parsing of Programming
Languages, ACM SIGPLAN Conference on Programming Language Design and
Implementation, June 21-23, 1989.


Anders Andersson
andand@csd.uu.se
--


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