Re: parsing theory dubts

haberg@math.su.se (Hans Aberg)
30 Mar 2003 21:19:22 -0500

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parsing theory dubts davide.rizzo78@tin.it (Davide Rizzo) (2003-03-30)
Re: parsing theory dubts haberg@math.su.se (2003-03-30)
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From: haberg@math.su.se (Hans Aberg)
Newsgroups: comp.compilers
Date: 30 Mar 2003 21:19:22 -0500
Organization: Mathematics
References: 03-03-177
Keywords: parse, comment
Posted-Date: 30 Mar 2003 21:19:22 EST

"Davide Rizzo" <davide.rizzo78@tin.it> wrote:


>[... LALR is a superset of LL. ... -John]


Thise is not entirely true. Here is a quote from Akim Demaille in the Help
Bison list 2002/01/17:


>>>>
This is not absolutely true, although it is in practice. IIRC the
result holds when there are no empty rules. See for instance


                http://compilers.iecc.com/comparch/article/93-09-025


or the errata of Andrew Appel about this book on compiler
implementation:


                http://www.cs.princeton.edu/~appel/modern/basic/ml/errata.html


                Page 64. Figure 3.26 incorrectly shows LL(1) as a subset of
                SLR. In fact, LL(1) is not even a subset of LALR(1): there is
                an LL(1) grammar that is not LALR(1).
<<<<


    Hans Aberg * Anti-spam: remove "remove." from email address.
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[Oh, right. Oops. -John]

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