[antlr-interest] about range float and stuff
Bart Kiers
bkiers at gmail.com
Fri Nov 4 10:03:13 PDT 2011
For what it's worth, I found the Wiki entry I based my suggestion on:
http://www.antlr.org/wiki/pages/viewpage.action?pageId=3604497
Regards,
Bart.
On Fri, Nov 4, 2011 at 3:11 PM, Bart Kiers <bkiers at gmail.com> wrote:
> You're welcome Fabien, but note that it most likely looks a lot like
> something I found on the ANTLR Wiki: so I can't claim credit for it
> (perhaps a small part! :)).
> I'll have a look later on and see if I can dig up the Wiki page.
>
> Regards,
>
> Bart.
>
>
> On Fri, Nov 4, 2011 at 3:04 PM, Fabien Hermenier <
> hermenierfabien at gmail.com> wrote:
>
>> Thanks Bart, I think I have understand your approach and indeed, it
>> seems beautiful and simple.
>> I will try your solution during the week-end.
>>
>> Fabien.
>>
>> Le 04/11/11 02:48, Bart Kiers a écrit :
>>
>> 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+point,+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.
>>>
>>>
>>>
>>>
>>> List: http://www.antlr.org/mailman/listinfo/antlr-interest
>>> Unsubscribe:
>>> http://www.antlr.org/mailman/options/antlr-interest/your-email-address
>>>
>>
>>
>>
>
More information about the antlr-interest
mailing list