def cmset_not(x,y):
	"""
Usage:

>>> cmset_not(x,y)

returning the index of the elements of array x which are not present in the
array y. 

This is equivalent to using the IDL command
SET = CMSET_OP(A, 'AND', /NOT2, B, /INDEX)   ; A but not B
i.e. performs the same thing as the IDL routine cmset_op from
http://cow.physics.wisc.edu/~craigm/idl/idl.html.
	"""
	
	idel=[]	# list of indexes of x elements which NOT in y
	i=0
	for xx in x:
		if xx not in y: idel.append(i)
		i=i+1
		
	return idel