[antlr-interest] How to remove mutual left recursion from this grammar?

[Jim Idle]

rul    :  contains_expr    ;

contains_expr: 'CONTAINS' contains_expression
                  //'CONTAINS' contains_or
        ;

contains_expression : primary (('OR'|'AND'|'XOR') primary)*
        ;

primary
  : '(' contains_expression ')'
  | class_expression
  ;


Jim

> -----Original Message-----
> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> bounces at antlr.org] On Behalf Of Seref Arikan
> Sent: Wednesday, January 04, 2012 9:35 AM
> To: antlr-interest at antlr.org
> Subject: [antlr-interest] How to remove mutual left recursion from this
> grammar?
>
> Greetings,
> This simple grammar represents a setup  I could not fix. Obviously the
> target is to create nested boolean statements, but I could not fix the
> recursion. This pattern repeats in a larger grammar, so solving this
> will help me fix more problems. Any clues that you can think of?
>
> //---------------------------------------------------------------------
> -----------
> grammar testg;
>
> rul    :  contains_expr    ;
>
> contains_expr: 'CONTAINS' contains_expression
>                   //'CONTAINS' contains_or
>         ;
>
> contains_expression : class_expression
>                         | contains_expression_boolean
>                         |'(' contains_expression_boolean ')'
>         ;
>
> contains_expression_boolean : contains_expression 'OR'
> contains_expression
>                               | contains_expression 'AND'
> contains_expression
>                               | contains_expression 'XOR'
> contains_expression
>         ;
>
>
>
>
> class_expression
>     : ID
>     ;
>
>
>
> ID  :    ('a'..'z'|'A'..'Z'|'_') ('a'..'z'|'A'..'Z'|'0'..'9'|'_')*
>     ;
>
>
>
> Best regards
> Seref
>
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