[antlr-interest] Help with simple grammer.

[Matthew Douglass]

David,

I'm pretty new to all of this and I'm half replying so I can have others
check out my work, but I think you can change the definition of sequence to
element ('|' element)* and then remove pipeexpr to accomplish what you want

That should effectively define a sequence as an element followed by any
number (including 0) of pipe symbols and another element, giving you the
infinitely long sequences you want.

But like I said, I could be way off base here :)

Hope that helps,
Matthew

----- Original Message -----
From: "ooobles" <oobles at hotmail.com>
To: <antlr-interest at yahoogroups.com>
Sent: Thursday, June 12, 2003 6:56 PM
Subject: [antlr-interest] Help with simple grammer.


>
> I've been working on a grammer for a simple list based language.  I
> have a problem with getting operator precedance right.  Hopefully
> someone might spare a minute to help me out?  I'm sure it can be
> solved simply.  I'd like to create a grammer that can parse something
> like:
>
> definition: identA functionX(  identB  functionY( identC | identD |
> identE )  identF )
>
> there is only three real elements to the grammer.
>    1. a sequence..    A B C
>    2. a function..    F(  )
>    3. an optional sequence..  A | B | C
>
> so far I've go a grammer like:
>
>
> definition: IDENTIFIER COLON sequence
>     ;
>
> sequence: pipexpr ( sequence )?
>     ;
>
> pipeexpr: element ( '|' pipeexpr )?
>
> element: IDENTIFIER
>        |  identifier '(' sequence ')'
>        ;
>
>
> This will compile in Antlr without warnings.  But it seems that the
> following would be parsed as valid
>
> def: identA | identB identC
>
> Is this case something that should be checked in code, or is there a
> better way to express the grammer?
>
> Thanks,
> David.
>
>
>
>
>
>
>
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>
>



 

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