[antlr-interest] Who can tell me what's the mean of # in the .g file of parser?

[Bryan Ewbank]

Blasted mailer defaults :-( ... ... ...


On 10/24/06, Yu Tao <yutao at td-tech.com> wrote:
> I can not find these grammer meaning in the manual doc, who can tell me which
> this means?

--- --- ---
Definition of The # Forms
--- --- ---

It means, "a tree node with....".  The forms seen are:

   #[ ... ]    -- create a single node with the given type and text
   #( ... )    -- create a tree with the first argument as root and all
                  following arguments as children
                  >>> NOTE THAT THE ARGUMENTS CAN BE LISTS <<<
   #foo        -- reference the (possibly created) tree associated with the
                  (sub)production named "foo"
   ##          -- an alias for the (possibly created) tree associated with the
                  current production

--- --- ---
Some Examples
--- --- ---

> expressionList
>     : expression (COMMA! expression)*
>        { #expressionList = #(#[ELIST,"ELIST"], #expressionList); }
>     ;

The last line means "create a tree with root ELIST/"ELIST", and use whatever
has been generated for #expressionList as the children.

--- --- ---

> expressionList
>     : expression (COMMA! expression)*
>        { ## = #(#[ELIST,"ELIST"], ##); }
>     ;

This means exactly the same thing, but is more easily understood and less error
prone if you change the name of the production.

--- --- ---

> superClassClause!
>     : ( "extends" id:identifier )?
>        { ## = #(#[EXTENDS_CLAUSE,"EXTENDS_CLAUSE"],id); }
>     ;

Here, ## (the tree for superClassClaus) is defined to be a simple AST with
EXTEND_CLAUSE as the root and the tree (list) returned by the production named
"id" as it's child or children.

--- --- ---

Hope this helps,
- Bryan Ewbank