Re: How to write SableCC Productions

[Dan Sandberg <dan@siliconpoetry.com>]

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;

[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