Stack: remove the newest item first

1 min read

A stack removes the most recently added item first. Use it for undo steps or work that should be handled in reverse order.

Import: import system.collections; · Availability: desktop, browser, and Node.

import system;
import system.collections;

fun main() {
    let steps = Stack<string>();
    steps.push("first");
    steps.push("second");
    System.println(steps.pop().unwrap_or("empty"));
}

This prints second. push adds an item. pop removes the newest item and returns Option<T>. peek reads it without removing it. An empty stack returns None.

Member	Returns	Effect
Stack<T>()	Stack<T>	Empty stack.
push(value)	void	Adds an item on top.
pop()	Option<T>	Removes and returns the top item.
peek()	Option<T>	Top item, left on the stack.
clear()	void	Removes every item.
.length	int	Number of items.
is_empty()	bool	true when the stack has no items.

A for loop visits items from the bottom (oldest) to the top (newest) without removing them. Stacks also have the query helpers such as filter and any.

See all Stack signatures and Queue for arrival-order processing.