Immutable data structures

How do you implement a POP operation on a STACK without returning multiple values?

not sure why you wouldn't want to modify the original one, but I guess an immutable stack would just create a new stack object and populate it with the same shit in the original one, sans the top thing to be popped

I guess you could use a generic class array, like Object[], and the popped value would be index 0, and the new stack would be index 1