[antlr-interest] Someting about range (to change)

Fabien Hermenier hermenierfabien at gmail.com
Tue Jun 28 20:57:51 PDT 2011


Hi

I am sorry, but this is another problem related to sequence of integer. 
I don't understand my error(s), despite severals
pass on the wiki page related to this use case.

I want to parse a string with a "sequence" parameter into it, such as 
"toto-[2 ..3]-toto".
Here is a short version of the grammar that works perfectly:
---
grammar tryout;

options {
     k=3;
}
fragment Digit :'0'..'9';
DEC_NUMBER: '1'..'9' Digit*;

fragment Letter    :'a'..'z'|'A'..'Z';

WS    :    ('\n'|'\r'|'\t'|' ') {$channel=HIDDEN;};
LEFTY: (Letter|Digit) (Letter|Digit|'-')* '[';
RIGHTY: ']' (('-' (Letter|Digit))|Letter|Digit)* ;


number :DEC_NUMBER; //HEX_NUMBER, OCT_NUMBER, ... are following but 
removed for this example.

range: LEFTY number '..' number RIGHTY;
---

This grammar accepts "toto-[1..3]-toto" or "toto-[1 .. 3]-toto".
Now, I want to be able to accept the LEFTY token or the RIGHTY token 
even if they contains a '.' inside (not at the beginning). So I've 
modified LEFTY as following:
LEFTY: (Letter|Digit) ('.'|Letter|Digit|'-')* '[';

Now, ANTLR does no longer accept "toto-[1..3]-toto". It requires at 
least one space between the first number and the range.
I have read the wiki page related to range, integer, and so one. But in 
my case, I don't see where my grammar is ambiguous as no token
can start with a '.' . So it seems there is a concept I don't get. Can 
anyone try to help me ?

Thanks in advance,
Fabien.


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