classDocs / Queue

Queue

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Object → Queue

A queue is a first-in-first-out (FIFO) data structure object.

Values are appended at one end and removed from the other by default (push appends to the front, pop removes from the back), so the earliest-pushed value is the first one popped.

Both push and pop accept an optional flag to operate on the opposite end instead, which lets the same object also be used as a deque.

Elements are stored between the back and front indices, which are advanced/rewound as values are pushed and popped, and are reset to 0 whenever the queue becomes empty.

Constructor

Queue(): Queue

Fields

Name	Type	Description
`front`	`integer`	The front of the queue. Read-only
`back`	`integer`	The back of the queue. Read-only

Methods

`clear`	Empties the queue, removing every value and resetting front and back to 0.
`isEmpty`	Checks if the queue is empty.
`iterator`	Returns an iterator for the queue.
`peek`	Returns the value at the front of the queue or the back if from_tail is true.
`pop`	Removes and returns the value at the back of the queue or the front if from_tail is true.
`push`	Appends a value to the end of the queue or the front if to_head is true.

#Queue:clear

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function Queue:clear()

Empties the queue, removing every value and resetting front and back to 0.

#Queue:isEmpty

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function Queue:isEmpty(): boolean

Checks if the queue is empty.

Returns

Type	Name	Description
`boolean`	`is_empty`	Returns `true` if the queue has no values, otherwise `false`.

#Queue:iterator

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function Queue:iterator(from_tail?: boolean): (fun( queue: Queue<T>, from_tail: boolean ): T), Queue<T>, boolean

Returns an iterator for the queue.

Parameters

Name	Type	Description
`from_tail`optional	`boolean`	If `true`, returns an iterator for the back of the queue.

Returns

Type	Name	Description
`fun( queue: Queue<T>, from_tail: boolean ): T`	`iterator`	The iterator function.
`Queue<T>`	`queue`	The queue being iterated over.
`boolean`	`from_tail`	`true` if the iterator is for the back of the queue.

#Queue:peek

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function Queue:peek(from_tail?: boolean): T | nil

Returns the value at the front of the queue or the back if from_tail is true.

Parameters

Name	Type	Description
`from_tail`optional	`boolean`	If `true`, returns the value at the back of the queue.

Returns

Type	Name	Description
`T \| nil`	`value`	The value at the front of the queue, or `nil` if the queue is empty.

#Queue:pop

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function Queue:pop(from_tail?: boolean): T | nil

Removes and returns the value at the back of the queue or the front if from_tail is true.

Parameters

Name	Type	Description
`from_tail`optional	`boolean`	If `true`, removes and returns the value at the front of the queue.

Returns

Type	Name	Description
`T \| nil`	`value`	The value at the back of the queue or the front if `from_tail` is `true`, or `nil` if the queue is empty.

#Queue:push

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function Queue:push(value: T, to_head?: boolean)

Appends a value to the end of the queue or the front if to_head is true.

Parameters

Name	Type	Description
`value`	`T`	The value to append.
`to_head`optional	`boolean`	If `true`, appends the value to the front of the queue.