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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
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 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: LALR parser question
Date: Tue, 30 Apr 2013 03:19:26 +0200
Organization: Ada @ Home
Message-ID: <op.wwbxyoz9ule2fv@cardamome>
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Date: 2013-04-30T03:19:26+02:00
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Le Sun, 28 Apr 2013 16:43:06 +0200, Dmitry A. Kazakov  =

<mailbox@dmitry-kazakov.de> a =C3=A9crit:

> On Sun, 28 Apr 2013 08:37:33 -0500, Stephen Leake wrote:
>
>> Any other ways to handle this problem?
>
> Recursive decent parser.

Or return to the original ascent parser:

http://en.wikipedia.org/wiki/LALR_parser
> In 1965, Donald Knuth invented the LR parser (Left to Right,
> Rightmost derivation). The LR parser can recognize any
> deterministic context-free language in linear-bounded time.
> However, rightmost derivation has very large memory requirements
> and implementing an LR parser was impractical due to the limited
> memory of computers at that time. To address this shortcoming, in
> 1969, Frank DeRemer proposed two simplified versions of the LR
> parser, namely the Look-Ahead LR (LALR)

And above in the introduction, commenting about LALR:
> The simplification that takes place results in a parser with
> significantly reduced memory requirements but decreased language
> recognition power.

This suggest LALR is limited by design and the original LR was less  =

limited.

I did a top=E2=80=91down (decent) parser some many years ago, and was no=
t that  =

much happy with neither. Either ascent, decent, left=E2=80=91right or ri=
ght=E2=80=91left,  =

they all requires to torture the grammar to make the parser generator  =

happy.

Note: GNAT uses a hand=E2=80=91written parser (I'm pretty sure to rememb=
er I've  =

seen it somewhere).


-- =

=E2=80=9CSyntactic sugar causes cancer of the semi-colons.=E2=80=9D [1]
=E2=80=9CStructured Programming supports the law of the excluded muddle.=
=E2=80=9D [1]
[1]: Epigrams on Programming =E2=80=94 Alan J. =E2=80=94 P. Yale Univers=
ity