[antlr-interest] Token Stream Rewriting

Fabien Hermenier hermenierfabien at gmail.com
Tue Jun 21 23:30:31 PDT 2011


In fact, I've badly readed the help. So yet, it is running a String that 
should be tokenized (then translated into tree I suppose) at run time.

Le 22/06/11 00:28, Bart Kiers a écrit :
> 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 <mailto: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
>     <http://www.antlr.org/wiki/display/%7Eadmin/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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>


-- 
Fabien Hermenier
Postdoctoral researcher at Flux
http://sites.google.com/site/hermenierfabien/home



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