[antlr-interest] Re: HELP NEWBIE: How can I simplify Tree Parser grammar.

lgcraymer lgc at mail1.jpl.nasa.gov
Sun May 11 20:48:10 PDT 2003


Unfortunately, the only way to do this with the current 
implementation is to change the type on the root nodes (previous 
tree walking or parsing phase).  Not recommended--I'd suggest living 
with what you have.

--Loring


--- In antlr-interest at yahoogroups.com, "ghassempoory" 
<ghassempoory at n...> wrote:
> I have a simple expression parser that generates an expression
> tree. I have written a tree parser to walk this tree for further
> processing. The tree parser looks a bit like :
> 
> expression:
>        #(MUL expression expression)
>     |  #(DIV expression expression)
>     |  #(ADD expression expression)
>     |  #(SUB expression expression)
>     |  IDENTIFIER
>     |  NUMBER
>     ;
> 
> Well, this works fine.However I would like to simplify this by
> doing soemthing like:
> 
> expression:
>        #(opnode expression expression)
>     |  IDENTIFIER
>     |  NUMBER
>     ;
> 
> opnode:
>         MUL | DIV | ADD | SUB
>     ;
> 
> ANTLR does not like this, it insists that the tree roots
> should be specified directly.
> 
> Is there anyway that I could factor out the root nodes?


 

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