Re: Beginner help with LALR(1) closure

Kent Rollins (kentr@rollinssoft.com) wrote:
: 1. I've downloaded a few YACC-able grammars and I've noticed that
: they all have left-recusive grammars...


: In order to get around the
: problem, I used a technique from a previous chapter which
: eliminates left-recursion (B) from LL grammars. I would like to
: know how the LALR(1) closure process avoids left recursion.


Watch out! I don't believe it is a well known fact, but in general an
LALR grammar that is transformed using the standard left recursion
removal algorithm will not be LALR afterwards. So apart from the fact
that your solution is over engineered (see other posts), it is also
incorrect.


                                                                  Adrian


--
    Dr Adrian Johnstone, Dean of the Science Faculty, Dept of Computer Science,
        Royal Holloway, University of London, Egham, Surrey, TW20 0EX, England.
Email: adrian@dcs.rhbnc.ac.uk Tel: +44 (0)1784 443425 Fax: +44 (0)1784 443420
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