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Groups > comp.compilers > #2420
| From | anton@mips.complang.tuwien.ac.at (Anton Ertl) |
|---|---|
| Newsgroups | comp.compilers |
| Subject | Re: A minimal LL(1) parser generator ? |
| Date | 2019-12-31 16:30 +0000 |
| Organization | Institut fuer Computersprachen, Technische Universitaet Wien |
| Message-ID | <19-12-040@comp.compilers> (permalink) |
| References | <19-12-016@comp.compilers> <19-12-030@comp.compilers> <19-12-032@comp.compilers> |
carlglassberg@gmail.com writes:
>Gray's meta notation uses a postix operator "&&" for "separator list".
>
>"&&" seems particularly elegant and interesting:
>
>If Gray: "a b &&" ---> EBNF: "a { b a }"
>
>then I assume:
>
>"a b && c &&" ---> "a { b a } { c a }"
The left operand of the second && would be "a b &&", so the whole
thing would be equivalent to
a {b a} {c {a {b a}}}
a (( b || c )) &&
would parse the same strings, but with different parse trees; so if
you add actions, the results would probably be different.
>and so on ...
>
>Further "a b && b && ..." ===> "a b &&"
They describe the same strings, yes. However, the former has an
ambiguous grammar that allows to parse "aba" in two ways: either the b
is the first b or the second one. In Gray, this leads to a conflict
(it just can deal with LL(1) grammars), and I guess one of these
parsing options never be exercised, which means that it works as if
you had written "a b &&" in the first place.
- anton
--
M. Anton Ertl
anton@mips.complang.tuwien.ac.at
http://www.complang.tuwien.ac.at/anton/
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A minimal LL(1) parser generator ? Andy <borucki.andrzej@gmail.com> - 2019-12-21 19:07 -0800
Re: A minimal LL(1) parser generator ? arnold@skeeve.com (Aharon Robbins) - 2019-12-22 19:29 +0000
Re: A minimal LL(1) parser generator ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2019-12-26 16:21 +0000
Re: A minimal LL(1) parser generator ? carlglassberg@gmail.com - 2019-12-29 14:47 -0800
Re: A minimal LL(1) parser generator ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2019-12-31 16:30 +0000
Re: A minimal LL(1) parser generator ? carlglassberg@gmail.com - 2020-01-01 01:02 -0800
Re: A minimal LL(1) parser generator ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2020-01-02 17:25 +0000
Re: A minimal LL(1) parser generator ? carlglassberg@gmail.com - 2020-01-05 11:59 -0800
Re: A minimal LL(1) parser generator ? carlglassberg@gmail.com - 2020-01-05 13:59 -0800
Re: A minimal LL(1) parser generator ? carlglassberg@gmail.com - 2020-01-05 14:44 -0800
Re: A minimal LL(1) parser generator ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2020-01-22 17:12 +0000
Re: A minimal LL(1) parser generator ? carlglassberg@gmail.com - 2020-01-23 02:41 -0800
Re: A minimal LL(1) parser generator ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2020-01-25 18:25 +0000
Re: A minimal LL(1) parser generator ? gaztoast@gmail.com - 2019-12-31 07:10 -0800
Re: A minimal LL(1) parser generator ? honey crisis <gaztoast@gmail.com> - 2020-01-02 08:50 -0800
Re: A minimal LL(1) parser generator ? George Neuner <gneuner2@comcast.net> - 2020-01-02 13:16 -0500
Re: A minimal LL(1) parser generator ? rockbrentwood@gmail.com - 2020-01-04 10:37 -0800
Re: A minimal LL(1) parser generator ? honey crisis <gaztoast@gmail.com> - 2020-01-05 05:05 -0800
Branched gotos was: Re: A minimal LL(1) parser generator ? Christopher F Clark <christopher.f.clark@compiler-resources.com> - 2020-01-06 08:47 +0200
Re: Branched gotos was: Re: A minimal LL(1) parser generator ? Ben Hanson <jamin.hanson@googlemail.com> - 2020-01-07 11:32 -0800
Re: A minimal LL(1) parser generator ? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2020-01-22 17:08 +0000
Re: A minimal LL(1) parser generator ? "Fred J. Scipione" <FredJScipione@alum.RPI.edu> - 2020-01-25 15:27 -0500
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