Queue/Definition

editable example

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ghul

use IO.Std.write_line

use Collections.LIST

use System.InvalidOperationException

class QUEUE[T] is

_items: LIST[T]

init() is

_items = LIST[T]()

si

is_empty: bool => _items.count == 0

push(value: T) is

_items.add(value)

si

pop() -> T is

assert !is_empty else

InvalidOperationException("the queue is empty")

let value = _items[0]

_items.remove_at(0)

return value

si

si

let queue = QUEUE[string]()

write_line("empty: {queue.is_empty}")

queue.push("first")

queue.push("second")

queue.push("third")

write_line("empty: {queue.is_empty}")

while !queue.is_empty do

write_line("pop: {queue.pop()}")

od

write_line("empty: {queue.is_empty}")

try

queue.pop()

catch e: InvalidOperationException

write_line("pop: {e.message}")

yrt

empty: True
empty: False
pop:   first
pop:   second
pop:   third
empty: True
pop:   the queue is empty