[antlr-interest] Lexer grammar for filtering

[Bart Kiers]

Hi Balazs,

Since PC is not a parser rule, you need to account for the space(s) between
'PC_HASH_VALUE' and DIGIT.
And since you've set `filter=true`, you don't need a fall-through rule ELSE,
AFAIK.

Regards,

Bart.


On Mon, Oct 17, 2011 at 11:15 AM, Balazs Varnai <bvarnai at gmail.com> wrote:

> Hi All,
>
> I have a simple grammar to collapse white-spaces and comment from a c
> source
> code input. Also I would like to filter out some variables with a specific
> name. These have a strict format, so no "real" C parsing needed.
> Works fine but for example a line "#define PC_HASH_VALUE 1" is not
> recognized. As far I remember from previous ANTLR usage, this was working
> straight away. Any suggestions? Thanks!
>
> /* **** [ CODE ] **** */
> lexer grammar Collapse;
>
> options {
>  language = Java;
>  filter = true;
> }
> @header {
> package rewriter;
> import java.util.*;
> import java.io.*;
>
> }
>
> @members {
> PrintStream out;
>
> public Collapse(CharStream input, PrintStream out) {
>    this(input);
>    this.out = out;
> }
> }
>
> PC: 'PC_HASH_VALUE' text=DIGIT {$channel=HIDDEN;};
>
> fragment
> DIGIT: '0'..'9';
>
> COMMENT
>    :   '//' ~('\n'|'\r')* '\r'? '\n' {$channel=HIDDEN;}
>    |   '/*' ( options {greedy=false;} : . )* '*/' {$channel=HIDDEN;}
>    ;
>
> WS  :   ( ' '
>        | '\t'
>        | '\r'
>        | '\n'
>        ) {$channel=HIDDEN;}
>    ;
>
> ELSE : c=. {out.print((char)$c);} ; // match any char and emit
> /* **** [ END ] **** */
>
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