conwaytang/CS381 — pull request #1 by ChaoPen (2013-05-03 00:36:35+00:00)
Title: Update HW3.hs

I think you should pop _ should be changed to pop k
because you want to pop out k > 1 element from the top of the stack so if the rank is (1,0), the stack can have only one element and cause no error. But it is impossible