Re: Parser LL(*)

George Neuner <gneuner2@comcast.net>
Sat, 19 Mar 2022 21:14:59 -0400

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Related articles
Parser LL(*) borucki.andrzej@gmail.com (Andy) (2022-03-18)
Re: Parser LL(*) gneuner2@comcast.net (George Neuner) (2022-03-19)
LL(*) christopher.f.clark@compiler-resources.com (Christopher F Clark) (2022-03-20)
Re: LL(*) gneuner2@comcast.net (George Neuner) (2022-03-21)
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From: George Neuner <gneuner2@comcast.net>
Newsgroups: comp.compilers
Date: Sat, 19 Mar 2022 21:14:59 -0400
Organization: A noiseless patient Spider
References: 22-03-039
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Keywords: parse, LL(1)
Posted-Date: 19 Mar 2022 22:30:19 EDT

On Fri, 18 Mar 2022 11:38:48 -0700 (PDT), Andy
<borucki.andrzej@gmail.com> wrote:


>Many language construction needs lookahead depth known in runtime, for
>example difference between function declarations and definitions.
>LL(*) is described in
> https://www.antlr.org/papers/allstar-techreport.pdf.
>This is only one place about LL(*) info?


Terence Parr both invented LL(*) and is the author of the ANTLR tool.
AFAIK, Parr's own papers and books are the only sources of information
about the method.




>If is the simplest idea make LL(1) with several conflicts and first
>speculative trying all paths, and backtrack?


No, the simplest idea was LL(k) with a fixed value of 'k'. I don't
believe Parr developed the method, but he was one of the pioneers of
using it. Parr authored PCCTS which used LL(k), and early versions of
ANTLR [prior to LL(*)] also used it.


LL(*) eliminates the need for the developer to figure out what 'k' is
optimal for the grammar: too low results in conflicts, too high may
waste processing effort.




>How do speedup it with cache?


??? Lookahead tokens already are cached.




>How make speculative trying in function calls?


Sorry, I'm not sure what you are asking.




George

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