[hchen19@beeblebrox parser]$ python
Python 1.5.2 (#1, Jul  5 2001, 03:02:19)  [GCC 2.96 20000731 (Red Hat Linux 7.1 2 on linux-i386
Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
>>> from data import *
>>> from parser import *
>>> from tree import *
>>> p=Parser()
>>> t=p.parse('2+3')
>>> t.root.interpret({})
5.0
>>> t=p.parse('2+3*$1$1')
>>> t.root.interpret({(1,1):Data(1,1,5)})
17.0
>>>