rebcabin/LeibsTown — pull request #4 by rebcabin (2012-12-11 02:33:46+00:00)
Title: Add exceptions to top and next

Bit of a judgment call -- when the stack is empty or deficient in
height, return what??? I could return 0, but that's the additive
identity .. I could return 1, but that's the multiplicative identity.
When in doubt, throw.