[il-antlr-interest: 27979] Re: [antlr-interest] Request for Change regarding Lexer (?)

2010-02-18 Thread Gavin Lambert 
At 09:27 17/02/2010, I wrote:
 It'd be nice if there was some way to express a negative match
 via a syntactic predicate, eg:
FOOLIST: 'foo[' (('foo') = ~ | ID)+ ']';
 (where '~' in an alt basically means break, ie. match nothing
 and terminate the innermost loop.)
 Or, perhaps better:
FOOLIST: 'foo[' (('foo') ~= ID)+ ']';
 (where '~=' means only take this path if the predicate 
*fails*)

Another possible syntax might be to allow ~ to act on sequences as 
well as sets.  Then you could use either of these:
   FOOLIST: 'foo[' ((~'foo') = ID)+ ']';
   FOOLIST: 'foo[' ((~('f' 'o' 'o')) = ID)+ ']';

This approach might be even more useful than the first, although 
it's harder to define what the result should be if you try to make 
a sequence out of both negative and positive sequences (ie. what 
should ~'foo' 'bar' mean?  Is it any three characters except 
'foo', followed by 'bar', or any number of characters except 
'foo', followed by 'bar'?  Or just meaningless?  What if it were 
~('foo'|'quux') 'bar'?  [Assuming this is all at lexer context, 
so these are sequences of characters rather than individual 
tokens.]).


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[il-antlr-interest: 27980] [antlr-interest] C# example of lexical filter mode ??

2010-02-18 Thread John Pool 
In The Definitive ANTLR Reference, at page 113 there is an example of a
lexer grammar, with at the end of the section the remark 'Lexical filter
mode is generally not used with a parser because the lexer yields an
incomplete stream of tokens.' 

 

I declared the fuzzy parser as follows: 

FuzzyParser lexer = new FuzzyParser (new ANTLRFileStream (sourceFileName));
// derives from Lexer class

Question: how do I 'execute' such a grammar lexer in C# without feeding it
into a parser? 

 

I tried downloading http://www.antlr.org/download/examples-v3.tar.gz, as
suggested in the book, but that URL won't open. 

Regards, John Pool 

 


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[il-antlr-interest: 27981] Re: [antlr-interest] C# example of lexical filter mode ??

2010-02-18 Thread Bart Kiers 
Hi John,


On Thu, Feb 18, 2010 at 7:52 PM, John Pool j.p...@ision.nl wrote:

 ...

 Question: how do I 'execute' such a grammar lexer in C# without feeding it
 into a parser?


You probably meant to instantiate a FuzzyLexer instead of a FuzzyParser
(unless your lexer grammar is called FuzzyParser, of course...).
Try this:

ANTLRStringStream in = new ANTLRStringStream(...some source
as a String...);
FuzzyLexer lexer = new FuzzyLexer(in);
CommonTokenStream tokens = new CommonTokenStream(lexer);
for(Object obj : tokens.getTokens()) {
Token token = (Token)obj;
System.out.println(token);
}

Although the code above is Java, the C# variant can't be that much
different.

For a complete example how to use such a lexer, see the first answer from
this post on Stackoverflow:
http://stackoverflow.com/questions/2284571/how-to-match-a-comment-unless-its-in-a-quoted-string





 I tried downloading http://www.antlr.org/download/examples-v3.tar.gz, as
 suggested in the book, but that URL won't open.


No problem here: I can download that file just fine.

Regards,

Bart.

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[il-antlr-interest: 27982] [antlr-interest] Java Grammar that outputs AST

2010-02-18 Thread venkat medhaj 
Hi,
 Is there any Java grammar file available that outputs the AST. Say for
example, I have a Java file and I want to output the AST for that file on
the eclipse console like the one thats done in the video tutorials. I am
trying to see how an AST looks like for a test Java file. All I could find
on the website was a java 1.6  .g file but it doesnt output the AST as
such.
That would be great if I could the required grammar file.

Thanks,
-V

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[il-antlr-interest: 27983] Re: [antlr-interest] Request for Change regarding Lexer (?)

2010-02-18 Thread kferrio 
Gavin,

Of your three ideas ...two equivalents in one post and a third more powerful 
one in this post ... I currently like the second equivalent from the first 
post...viz ~= for two reasons.  First I think your third form is so powerful 
as to encourage abuse and expose a lot of strange edge-cases for Terence to 
anticipate and guard against.  Not sure, but seems possible.  Second I just 
like having one token (second equivalent) instead of two tokens (first 
equivalent) to express the idea cleanly.  Admittedly this is a style preference 
and I have been accused of questionable  taste more than once.  :)  Your idea 
is helpful I would use it regardless of how it is expressed in antlr.

Cheers,
Kyle 

Sent from my Verizon Wireless BlackBerry

-Original Message-
From: Gavin Lambert an...@mirality.co.nz
Date: Fri, 19 Feb 2010 07:38:11 
To: Terence Parrpa...@cs.usfca.edu
Cc: antlr-interest@antlr.org
Subject: Re: [antlr-interest] Request for Change regarding Lexer (?)

At 09:27 17/02/2010, I wrote:
 It'd be nice if there was some way to express a negative match
 via a syntactic predicate, eg:
FOOLIST: 'foo[' (('foo') = ~ | ID)+ ']';
 (where '~' in an alt basically means break, ie. match nothing
 and terminate the innermost loop.)
 Or, perhaps better:
FOOLIST: 'foo[' (('foo') ~= ID)+ ']';
 (where '~=' means only take this path if the predicate 
*fails*)

Another possible syntax might be to allow ~ to act on sequences as 
well as sets.  Then you could use either of these:
   FOOLIST: 'foo[' ((~'foo') = ID)+ ']';
   FOOLIST: 'foo[' ((~('f' 'o' 'o')) = ID)+ ']';

This approach might be even more useful than the first, although 
it's harder to define what the result should be if you try to make 
a sequence out of both negative and positive sequences (ie. what 
should ~'foo' 'bar' mean?  Is it any three characters except 
'foo', followed by 'bar', or any number of characters except 
'foo', followed by 'bar'?  Or just meaningless?  What if it were 
~('foo'|'quux') 'bar'?  [Assuming this is all at lexer context, 
so these are sequences of characters rather than individual 
tokens.]).


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