At 06:18 9/08/2009, Tomasz Jastrzebski wrote:
>Now I understand that the only reasonable such declaration must
>look like:
>
>multExpr
> : primaryExpr (('*' | '/') primaryExpr)*
> ;
Actually, you *could* use this:
multExpr
: primaryExpr (('*' | '/') multExpr)?
;
The recursion would even make it easier to apply the rewrites as
you want. The downside of this is that it will only work properly
for left-associative operators (unlike the original, which can be
done either way). Using the * is generally preferred practice
though; avoids using up stack space :)
>After adding rewrite rules this may look like that:
>addExpr
> : (multExpr -> multExpr) ( (o='+' | o='-') e=multExpr -> ^($o
> $addExpr $e) )*
> ;
>multExpr
> : (primaryExpr -> primaryExpr) ( (o='*' | o='/') e=primaryExpr
> -> ^($o $multExpr $e) )*
> ;
Yes, this is a good way to do it.
>I would think that now I can simply replace:
>-> ^($o $addExpr $e)
>with
>-> ^(BIN_EXPR<BinaryExpression>[o.text, $addExpr.tree, $e.tree]>)
>
>- but not. $addExpr.tree in the second version is always NIL.
Have you tried just using $addExpr instead of $addExpr.tree? (Not
sure if that's valid, but it's worth trying.) Also, your o.text
should be $o.text; although you're going to lose some context in
your tree by not keeping the full token objects.
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