[antlr-interest] about range float and stuff

[Bart Kiers]

I don't understand what you mean.

Bart.


On Fri, Nov 4, 2011 at 5:33 PM, Jim Idle <jimi at temporal-wave.com> wrote:

> It won't make it more difficult, and the lexer already does what Fabien
> asks.
>
> Jim
>
> > -----Original Message-----
> > From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> > bounces at antlr.org] On Behalf Of Bart Kiers
> > Sent: Friday, November 04, 2011 1:48 AM
> > To: Fabien Hermenier
> > Cc: antlr-interest at antlr.org
> > Subject: Re: [antlr-interest] about range float and stuff
> >
> > Hi Fabien,
> >
> > Handling this in the parser will make your life much harder than it has
> > to.
> > Doing it in the lexer, you will need a bit of custom code, but I'd go
> > for something similar to this (something like it is on the WIki
> > somewhere, but can't find it...):
> >
> > grammar RangeDemo;
> >
> > @lexer::members {
> >
> >   java.util.Queue<Token> tokens = new java.util.LinkedList<Token>();
> >
> >   public void offer(int ttype, String ttext) {
> >     emit(new CommonToken(ttype, ttext));
> >   }
> >
> >   @Override
> >   public void emit(Token t) {
> >     state.token = t;
> >     tokens.offer(t);
> >   }
> >
> >   @Override
> >   public Token nextToken() {
> >     super.nextToken();
> >     return tokens.isEmpty() ? Token.EOF_TOKEN : tokens.poll();
> >   }
> > }
> >
> > parse
> >   :  (t=. {System.out.printf("\%-10s \%s\n", tokenNames[$t.type],
> > $t.text);})* EOF
> >   ;
> >
> > FLOAT
> >   :  INT '..'   {offer(INT, $INT.text); offer(RANGE, "..");}
> >   |  OCTAL '..' {offer(OCTAL, $OCTAL.text); offer(RANGE, "..");}
> >   |  '.' DIGITS
> >   |  DIGITS '.' DIGITS?
> >   ;
> >
> > RANGE
> >   :  '..'
> >   ;
> >
> > INT
> >   :  '1'..'9' DIGIT*
> >   |  '0'
> >   ;
> >
> > OCTAL
> >   :  '0' ('0'..'7')+
> >   ;
> >
> > fragment DIGITS : DIGIT+;
> > fragment DIGIT  : '0'..'9';
> >
> > SPACE
> >   :  (' ' | '\t' | '\r' | '\n') {skip();}
> >   ;
> >
> > And if you run the class:
> >
> > import org.antlr.runtime.*;
> >
> > public class Main {
> >   public static void main(String[] args) throws Exception {
> >     String src = "..07..8.5 1.9..02 1..3.4";
> >     RangeDemoLexer lexer = new RangeDemoLexer(new
> > ANTLRStringStream(src));
> >     RangeDemoParser parser = new RangeDemoParser(new
> > CommonTokenStream(lexer));
> >     System.out.println("Parsing: '" + src + "'");
> >     parser.parse();
> >   }
> > }
> >
> > You'll see the following being printed to the console:
> >
> > Parsing: '..07..8.5 1.9..02 1..3.4'
> > RANGE      ..
> > OCTAL      07
> > RANGE      ..
> > FLOAT      8.5
> > FLOAT      1.9
> > RANGE      ..
> > OCTAL      02
> > INT        1
> > RANGE      ..
> > FLOAT      3.4
> >
> >
> > Regards,
> >
> > Bart.
> >
> >
> >
> > On Fri, Nov 4, 2011 at 7:28 AM, Fabien Hermenier
> > <hermenierfabien at gmail.com>wrote:
> >
> > > Hi
> > >
> > > In an earlier version of my language, I had to parse range of
> > integers
> > > in various base. Now I want to include float. I have read
> > >
> > >
> > http://www.antlr.org/wiki/display/ANTLR3/Lexer+grammar+for+floating+po
> > > int,+dot,+range,+time+specs
> > > but I've still got some questions.
> > >
> > > All the work seems to be done at the lexer level so the type of the
> > > following tokens will be as example:
> > > 5 : DECIMAL_LITTERAL
> > > 07 : OCTAL_LITTERAL
> > > 7.5: FLOATING_POINT_LITTERAL
> > > 5..7 : DOTDOT
> > >
> > > In the last example, the result is not very convenient because I will
> > > still have to extract the bounds and compute their type by myself
> > > which seems quite redundant with the job performed by the lexer.
> > > May be I am missing something ?
> > >
> > > I would rather be able to express the range at the parser level which
> > > seems much more convenient to me:
> > > range: FLOATING_POINT_LITTERAL DOTDOT FLOATING_POINT_LITTERAL.
> > > In this way, I will also be able to manage the possible spaces
> > between
> > > the bounds and the DOTDOT.
> > >
> > > So, am I right to try to parse range at the parser level ? Or is
> > there
> > > a solution to extract easily the bounds with their type if I am doing
> > > the job at the lexer level ?
> > >
> > > Thanks in advance,
> > > Fabien.
> > >
> > >
> > >
> > >
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