[antlr-interest] "back to the future" (merged lexer / parser spec)

[Anthony Youngman]

Ask Monty ... "List<List<int>>" is only too legal in AREV (and similar) BASICs.

I don't know how good a filter would be at parsing that, but it might well help - especially as the original language was *defined* using a state transition table ...

Oh - Jens also missed the possibility that either or both the "<"s could be the "less than" operator :-) that's the trap AREV has to watch out for :-)

Cheers,
Wol

-----Original Message-----
From: Terence Parr [mailto:parrt at cs.usfca.edu] 
Sent: 23 November 2004 17:30
To: antlr-interest at yahoogroups.com
Subject: Re: [antlr-interest] "back to the future" (merged lexer / parser spec)



On Nov 23, 2004, at 4:21 AM, Jens Theeß wrote:

>
>
> Terence Parr wrote:
>
>> With this merged spec, ultimately I would like to do context-sensitive
>> (goal-oriented) lexing so we could handle things like the C++ nested
>> template lexing issue.  With input "List<List<int>>" you don't know in
>> the lexer w/o context if the final ">>" is two '>' or one '>>' 
>> (shift).
>>
> I don't know if it's come up before, but "list<list<int>>" actually
> isn't legal in c++. Haven't got the ANSI spec here but at least g++
> 3.3.3 complains with an "error: `>>' should be `> >' in template class
> name". You have to write "list<list<int> >" instead, which should be
> lexable without context. Don't know how it's with the java generics 
> though.

I'm pretty sure java allows >> and makes the lexer track context to get 
the correct answer.

> Anyway, context-sensitive lexing is a feature I'd like to see. When I

Me too!

> find the time (next year or decade), I intend to write a parser for
> Wiki-text using antlr, and I think that this new lexing could come in
> handy there.

Have you seen my TML?  It's wiki-inspired (though I like it better 
<wink>).

http://www.antlr.org/TML/index.tml

Ter
--
CS Professor & Grad Director, University of San Francisco
Creator, ANTLR Parser Generator, http://www.antlr.org
Cofounder, http://www.jguru.com
Cofounder, http://www.knowspam.net enjoy email again!





 
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