OBStack is a very simple implementation of a stack data structure (last in, first out) in Cocoa.
It supports the following operations:
- push: push a new object onto the stack.
- pop: retrieve the topmost object and remove it from the stack.
- top: retrieve the topmost object without removing it from the stack.
- length/height/count: the number of items on the stack.
- isEmpty: a boolean value if the stack is currently empty.
Internally, OBStack encapsulates a NSMutableArray to hold the stack objects.