On 12/06/2010 12:20 PM, Markus Lottmann wrote:
> Hi,
>
> i am quite new to antlr and dont understand whats wrong with the
> following grammar:
>
> grammar test2;
> options{
> backtrack=false;
> }
> octal_literal
> : '0' octal_digit*;
>
> octal_digit
> : '0'..'7';
>
> The error is:
>
> [18:17:06] warning(200): test2.g:6:8: Decision can match input such as
> "EOF" using multiple alternatives: 1, 2
> As a result, alternative(s) 2 were disabled for that input
> [18:17:06] error(201): test2.g:6:8: The following alternatives can never
> be matched: 2
To begin with, octal_literal and octal_digit are parser rules and not
token rules? This means that (assuming you discard whitespace) that the
strings "0 1 2 3" and "0123" are both valid octal_literals.
Did you mean to write:
octal_literal : '0' octal_digit+ ;
Is the character '0' an octal_digit or the beginning of an
octal_literal? To me, this is ambiguous as to which you want.
OCTAL_LITERAL : '0' OCTAL_DIGIT+
;
fragment
OCTAL_DIGIT : '0' .. '7'
;
Might be closer to what you intend here.
> Thanks so far.
> Greetings,
> ML
--
Kevin J. Cummings
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