why i missing declaration but still able to complie?

[Peter Cheung]

Hi

    why i missing declare PETER but still able to complie?

grammar Assembler;

NL : '\r'? '\n';

ID : [a-zA-Z] [a-zA-Z0-9]+;

LINE_COMMENT : ';' ~[\r\n]*;

assemble : lines

| EOF

;

lines : (PETER line NL+)*

;

line : statement

| statement comment

| comment

;

statement : ID+;

comment : LINE_COMMENT

;

Thanks

[Kevin Cummings]

On 08/23/17 14:05, Peter Cheung wrote:
> Hi
>
> why i missing declare PETER but still able to complie?
>
> grammar Assembler;
>
> NL:'\r'? '\n';
> ID:[a-zA-Z] [a-zA-Z0-9]+;
> LINE_COMMENT:';' ~[\r\n]*;
>
> assemble:lines
> |EOF
> ;
>
> lines:(PETER line NL+)*

At this point, ANTLR sees a new token (PETER) and creates a token id for
it (look at your token types file). You won't see the error until
runtime when your parser can't find a token with that ID because your
lexer does not does not create one. Always declare all of your named
tokens in lexer rules, lest ANTLR create one for you that you can't
match. I believe this is an artifact of how ANTLR handles unnamed
literal tokens.

> ;

>
> line:statement
> |statement comment
> |comment
> ;
>
> statement:ID+;
>
> comment:LINE_COMMENT
> ;
>
> Thanks
>

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--
Kevin J. Cummings
cumm...@kjchome.homeip.net
cumm...@kjc386.framingham.ma.us
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