| | | Immutable stacks | Contents |
If you need a last-in-first-out sequence, you can use a Stack. You push an element onto a stack with push, pop an element with pop, and peek at the top of the stack without removing it with top. All of these operations are constant time.
Here are some simple operations performed on a stack:
scala> val stack = scala.collection.immutable.Stack.empty
stack: scala.collection.immutable.Stack[Nothing] = Stack()
scala> val hasOne = stack.push(1)
hasOne: scala.collection.immutable.Stack[Int] = Stack(1)
scala> stack
stack: scala.collection.immutable.Stack[Nothing] = Stack()
scala> hasOne.top
res20: Int = 1
scala> hasOne.pop
res19: scala.collection.immutable.Stack[Int] = Stack()
Immutable stacks are used rarely in Scala programs because their functionality is subsumed by lists: A push on an immutable stack is the same as a :: on a list and a pop on a stack is the same a tail on a list.
Next: Immutable Queues
| | | Immutable stacks | Contents |