import { IIterable, IIterator, IterableOrArrayLike } from '../algorithm/iteration';
/**
 * A generic FIFO queue data structure.
 */
export declare class Queue<T> implements IIterable<T> {
    /**
     * Construct a new queue.
     *
     * @param values - The initial values for the queue.
     */
    constructor(values?: IterableOrArrayLike<T>);
    /**
     * Test whether the queue is empty.
     *
     * @returns `true` if the queue is empty, `false` otherwise.
     *
     * #### Notes
     * This is a read-only property.
     *
     * #### Complexity
     * Constant.
     *
     * #### Iterator Validity
     * No changes.
     */
    readonly isEmpty: boolean;
    /**
     * Get the length of the queue.
     *
     * @return The number of values in the queue.
     *
     * #### Notes
     * This is a read-only property.
     *
     * #### Complexity
     * Constant.
     *
     * #### Iterator Validity
     * No changes.
     */
    readonly length: number;
    /**
     * Get the value at the front of the queue.
     *
     * @returns The value at the front of the queue, or `undefined` if
     *   the queue is empty.
     *
     * #### Notes
     * This is a read-only property.
     *
     * #### Complexity
     * Constant.
     *
     * #### Iterator Validity
     * No changes.
     */
    readonly front: T;
    /**
     * Get the value at the back of the queue.
     *
     * @returns The value at the back of the queue, or `undefined` if
     *   the queue is empty.
     *
     * #### Notes
     * This is a read-only property.
     *
     * #### Complexity
     * Constant.
     *
     * #### Iterator Validity
     * No changes.
     */
    readonly back: T;
    /**
     * Create an iterator over the values in the queue.
     *
     * @returns A new iterator starting at the front of the queue.
     *
     * #### Complexity
     * Constant.
     *
     * #### Iterator Validity
     * No changes.
     */
    iter(): IIterator<T>;
    /**
     * Add a value to the back of the queue.
     *
     * @param value - The value to add to the back of the queue.
     *
     * @returns The new length of the queue.
     *
     * #### Complexity
     * Constant.
     *
     * #### Iterator Validity
     * No changes.
     */
    pushBack(value: T): number;
    /**
     * Remove and return the value at the front of the queue.
     *
     * @returns The value at the front of the queue, or `undefined` if
     *   the queue is empty.
     *
     * #### Complexity
     * Constant.
     *
     * #### Iterator Validity
     * Iterators pointing at the removed value are invalidated.
     */
    popFront(): T;
    /**
     * Remove all values from the queue.
     *
     * #### Complexity
     * Linear.
     *
     * #### Iterator Validity
     * All current iterators are invalidated.
     */
    clear(): void;
    /**
     * Swap the contents of the queue with the contents of another.
     *
     * @param other - The other queue holding the contents to swap.
     *
     * #### Complexity
     * Constant.
     *
     * #### Iterator Validity
     * All current iterators remain valid, but will now point to the
     * contents of the other queue involved in the swap.
     */
    swap(other: Queue<T>): void;
    private _length;
    private _front;
    private _back;
}