[antlr-interest] Question about recursion

[micheal_jor <open.zone at virgin.net>]

> I just noticed recursion was rejected when the rule was the first 
rule
> of the right part.
>  
> expr
>             :           MINUS expr
> ;
>  
> ..is ok
>  
> expr
>             :           expr MINUS 
> ;
>  
> ..is not okay

ANTLR is an LL(k) parser. Please the docs on the site for what that 
means and why left-recursive grammars generate errors with ANTLR. 

This might also help:
http://www.csee.umbc.edu/331/fall02/0101/notes/pdf/4parsing.pdf

> If there a way to allow the second example in an ANTLR grammar ?
> therorically that ahould be accepted, it's a correct rule of the 
BNF.

It isn't about BNF/EBNF. It's about leftmost derivation in LL(k) 
parsers.

Cheers,

Micheal



 

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