Antlr v3 & Trees (was: [antlr-interest] if-then-else - Grammar generates faulty parser code)

[Monty Zukowski]

On Apr 22, 2004, at 9:26 PM, Terence Parr wrote:

> My typical example of where you want a "placeholder" is when you have
> multiple optional things in a row.  For example, the expressions in a
> FOR statement.  Do you want
>
> forRule : #(FOR (expr)? (expr)? (expr)?) ;
>
> ??  Probably not as the grammar is inherently ambiguous.  Position has
> "meaning" in this case.
>
> Is that a good example?


Well, my select statement is multiple optional things in a row:

> selectStatement
> 	:
> 	queryExpression
> 	(computeClause)?
> 	(forClause)?
> 	(optionClause)?
> 	;

And I'm arguing that it's ok in this case because the grammar is not 
ambiguous.  So is the rule "when you have multiple optional things in a 
row and it is ambiguous?"  Or are there other considerations too?

Monty



 
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