Re: grammar switch statement

[Franz Beil <franz.beil@temis-group.com>]

With an optional default_clause, you'll get a shift-reduce error 
because, if the default_clause is empty, a case_clause is ambiguous 
between a pre_case_clause and a post_case_clause.
Franz

russel.lindsay@centrelink.gov.au wrote:

> Hi,
>
> I have defined a switch statement in my grammar as follows (and it 
> works):
>
> switch =
>    T.switch left_parenthese expression right_parenthese case_block;
>
> case_block =
>    left_brace case_clause* right_brace
>    |{default} left_brace [pre]:case_clause* default_clause 
> [post]:case_clause* right_brace;
>
> case_clause =
>    case expression colon statement*;
>
> default_clause =
>    default colon statement*;
>
>
> however, if i change the case_block to following it does not work:
>
> case_block =
>    left_brace [pre]:case_clause* default_clause? [post]:case_clause* 
> right_brace;
>
>
> Can anybody see what is wrong with the definition, or have i not 
> provided enough information?
>
> thankyou all,
>
>
> russel
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