[antlr-interest] Token Stream Rewriting

[Bart Kiers]

Is your `merge(String, List, String)` method returning a java.util.ArrayList
instead of a Tree?

Regards,

Bart.


On Wed, Jun 22, 2011 at 8:04 AM, Fabien Hermenier <hermenierfabien at gmail.com
> wrote:

> Hi
>
> I have some troubles with token stream rewriting. Below is the piece of
> ANTLR code. I have a grammar, with an AST as output and Java
> as the target. I want to insert a sequence of token into the stream.
>
> I have followed the page
>
> http://www.antlr.org/wiki/display/~admin/2007/06/28/Token+stream+rewriting+with+rewrite+rules
> and adapted the example that interest me. A piece of the code is
> following. Basically, in the alternative of 'explodedSet', I get the
> return values of other rules and do some stuff in the merge method. This
> one returns a list of String as explained in the online example.
>
>
> explodedSet: '{' (setContent (',' setContent)*)? '}' -> ^(EXPLODED_SET
> setContent+)
>     | {List l = new LinkedList();}LEFTY
> r1=brace_content{l.add($r1.ret);} (','
> r2=brace_content{l.add($r2.ret);})* RIGHTY
>     -> {
>     merge($LEFTY.text,l,$RIGHTY.text)
>     };
>
> brace_content returns [List ret]:
>          st=number ('..' ed=number)? {$ret = new LinkedList(); for (int
> i = $st.val; i <= $ed.val; i++) {$ret.add(i);}}
>            | NAME {$ret = new LinkedList(); $ret.add($NAME.text);};
>
> The code compiles well but at runtime, I've got this exception:
>
> Caused by: java.lang.ClassCastException: java.util.ArrayList cannot be
> cast to org.antlr.runtime.tree.Tree
>     at
> org.antlr.runtime.tree.BaseTreeAdaptor.addChild(BaseTreeAdaptor.java:107)
>     at Parser.explodedSet(Parser.java:560)
>
> So, the return value of merge does not seems to be converted into tokens
> nor Tree. Does someone has an idea ?
>
>
> Fabien.
>
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