R help - Mar 2007 - Problem with user defined split function in Rpart

Dear all,
I'm trying to manage with user defined split function in rpart. I (hope) 
correctly defined three functions (eval, split, init) I need.
I tested these function by executing them step by step and they work 
correctly.
When I try to build the tree by the rpart command (by specifying method= the 
list of the my three functions) I get no errors but the tree I obtain 
contains only the root !
I tried in different ways to understand the reason why the tree does not 
grow up but I had not success ...
The only strange thing I observed is that the CP parameter in summary.rpart 
is negative

         CP nsplit rel error
1 -1.011038      0         1

Where does the problem lie ?
Thank you for any helpful suggestion.

Paolo Radaelli

Paolo Radaelli
Dipartimento di Metodi Quantitativi per le Scienze Economiche ed Aziendali
Facolt? di Economia
Universit? degli Studi di Milano-Bicocca
P.zza dell'Ateneo Nuovo, 1
20126 Milano
Italy
e-mail paolo.radaelli a unimib.it