[antlr-interest] Smalltalk-like grammar? Easy! Decimal number? Help!

[Oti]

Hi Kevin and Jim,

the following NUMBER lexer rule works pretty well for me:

NUMBER
	:	( '+' | '-' ) ?
		( ( ( '1' .. '9' ) ( '0' .. '9' )* ) | '0' )
		( '.' ( '0' | ( '0' .. '9' )* ( '1' .. '9' ) ) ) ?
		;

Just as an example how to prevent leading and trailing zeroes.
It reflects my recognition of how a simple "number" should look like, so YMMV.

Best wishes,
Oti.

On 11/1/07, Jim Idle <jimi at temporal-wave.com> wrote:
> See much discussion of this issue over the last 2 or 3 weeks, but you need a
> predicate on your number rule, and your DECIMAL and DIGIT and LETTER rules
> should be fragments (though you probably don't need them as separate rules
> at all really):
>
> NUMBER: ('0'..'9')+ (   ('.' '0'..'9')=> ('.' ('0'..'9')+)
>                       |
>                     )
>       ;
> fragment
> LETTER
>
>  Etc...
>
> Hope that helps :-)
>
> Jim
>
> > -----Original Message-----
> > From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> > bounces at antlr.org] On Behalf Of Kevin Twidle
> > Sent: Thursday, November 01, 2007 8:59 AM
> > To: antlr-interest at antlr.org
> > Subject: [antlr-interest] Smalltalk-like grammar? Easy! Decimal number?
> > Help!
> >
> > Hi,
> >
> > I love ANTLR! I have a quite sophisticated Smalltalk-like grammar in
> > ANTLR using an AST which works beautifully.  I have decided to allow
> > floating point numbers and have tried adding them to the grammar.
> > Now, Smalltalk uses '.' as a statement separator, numbers have a '.'
> > in them - uh-oh.
> >
> > A number should have the form:
> >
> > 12 or 12.34 but not 12.
> >
> > I want to be able to parse
> >
> > 13.
> > 13.word.
> > 14.0.13.
> >
> > to get  13,13,word,14.0,13
> >
> > all I get is
> >
> > line 1:3 required (...)+ loop did not match anything at character '\n'
> > line 2:3 required (...)+ loop did not match anything at character 'w'
> > recoverFromMismatchedToken
> > BR.recoverFromMismatchedToken
> > line 3:4 mismatched input '.13' expecting EOF
> >
> > with tokens       ord     14.0
> >
> > I have simplified my problem to the following grammar.  The problem
> > is that DECIMAL always matches the first '.' and then fails (I ran
> > through the code) it never says DECIMAL is not there, it must be a
> > statement separator!  I have tried the greedy option but then it
> > never matches the DECIMAL.  I have tried reordering, fragments,
> > greedy and now this mailing list!
> >
> > DECIMAL is optional, why does it fail?
> >
> > Any help really appreciated!
> >
> > Kevin
> >
> > grammar Number;
> > options {output = AST;}
> >
> > start :       statement ( DOT statement? )+ EOF;
> >
> > statement :   WORD | NUMBER;
> >
> > WORD  :       LETTER (LETTER | DIGIT)+;
> >
> > NUMBER        :       DIGIT+ DECIMAL?;
> >
> > DECIMAL       :       DOT DIGIT+;
> > DOT   :       '.';
> > DIGIT :       '0'..'9';
> > LETTER        :       'a'..'z' | 'A'..'Z';
> > WS      :
> >           (' '
> >           | '\t'
> >           | '\r' '\n'
> >           | '\n'
> >           ) +
> >           { $channel=HIDDEN; }
> >       ;
>
>
>