For example, given the arrays [1,2] and [1,2,3,4], produce this array: [2,3,4,5,3,4,5,6].

In Python, this would look like this:

a = [1,2]
b = [1,2,3,4]
c = []
for x in a:
	for y in b:
		c.append( x + y )
		
print c
#  [2, 3, 4, 5, 3, 4, 5, 6]

In ICE, one way to do this would be to add
[1,1,1,1,2,2,2,2]
to
[1,2,3,4,1,2,3,4]

Here’s an ICE tree that does just that:

This ICE tree uses the modulo trick, and the scalar-to-integer truncation trick.

You can see a variation of this in this Softimage mailing list post..