def intersection (a, b):
ta = avl.newavl(a)
result = avl.newavl()
for x in b:
if ta.has_key (x):
result.insert (x)
ta.remove (x)
return result
def __init__ (self, set=None):
if set == None:
self.items = avl.newavl()
elif type(set) == type([]):
self.items = avl.newavl(set[:])
elif type(set) == type(self):
self.items = avl.newavl(set.items)
else:
self.items = avl.newavl(set)
def difference (a, b):
result = avl.newavl(a)
for key in b:
if a.has_key (key):
result.remove (key)
return result
def union (a, b):
result = avl.newavl(a)
for key in b:
if not a.has_key(key):
result.insert(key)
return result
