In reply to csivas@gmail.com:
Normally the keyword unsupported is due to the tool limitation for that you need to contact your tool’s vendor, as I tried your code and it compiled, and ran without errors, or do as the log file is telling you “Rewrite the method to avoid unsupported constructs.”
Also you can check the LRM section 18.5.12 Functions in constraints to see what are the restrictions about calling functions in constraints, as they can change the order on how constraints are solved
HTH,
-R