Re: How to write SableCC Productions

[Roger Keays <s354157@student.uq.edu.au>]

On Tue, 5 Jun 2001, Dan Sandberg wrote:

> Hi.
>
> You can't put alternatives in parenthesis.  So:
> il_instruction = ( label colon ) ? ( il_simple_operation | il_expression
> ) ? eol ;
>
> should be
>
> il_instruction = ( label colon )? il_instruction_rest? eol;
> il_instruction_rest = {simple_operator} il_simple_operator |
>                       {expression} il_expression;
>

Is this right? I though parantheses indicated ignored alternatives. I
think what Bittkau is looking for is:

il_instruction =  labelcolon? il_instruction_rest? eol;
labelcolol = label colon
il_instruction_rest = {simple_operator} il_simple_operator |
                       {expression} il_expression;


Regards,

Roger

> [Alternatives need to be named, using the {name} notation]
>
> Also, I don't see where the label token was defined in the example you
> gave.
>
> I don't know of any tools that convert from BNF automatically.
>
> -Dan
>
> Bittkau Rainer wrote:
> >
> > I'm at the very first steps to write a compiler for the IEC 61131-3 PLC
> > language.
> > The following BNF fragment
> >
> > il_instruction ::= [label':'][il_simple_operation | il_expression] EOL {EOL}
> >
> > transformed to SableCC
> >
> > Tokens
> >   colon = ':' ;
> >   endofline = cr | lf | cr lf;
> >   eol = endofline+;
> > Productions
> >   il_instruction = ( label colon ) ? ( il_simple_operation | il_expression )
> > ? eol ;
> >
> > Error message:
> > org.sablecc.sablecc.parser.ParserException: [6,36] TSemicolon TBar excepted.
> >
> > [6,36] is the position of the first '?'
> > What is wrong with it?
> >
> > Are there any tools to do the transformation? (there are about 250 other
> > productions to do)
> >
> > TIA
> >
> > Mit freundlichen Grüssen
> > Rainer Bittkau
> >
> > Baumer Electric AG, Abt. Betriebsmittel
> > Hummelstrasse 17
> > Postfach
> > CH-8501 Frauenfeld
> > Tel. ++41 52 728 14 55; Fax. ++41 52 728 17 27
> > mailto:rbittkau@baumerelectric.com
> > http://www.baumerelectric.com
>