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48 lines
912 B
48 lines
912 B
function Queue () {
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this.head = new Item('head', null)
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}
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module.exports = Queue
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Queue.prototype.append = function append (kind, value) {
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var item = new Item(kind, value)
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this.head.prepend(item)
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return item
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}
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Queue.prototype.isEmpty = function isEmpty () {
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return this.head.prev === this.head
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}
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Queue.prototype.first = function first () {
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return this.head.next
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}
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function Item (kind, value) {
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this.prev = this
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this.next = this
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this.kind = kind
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this.value = value
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}
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Item.prototype.prepend = function prepend (other) {
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other.prev = this.prev
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other.next = this
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other.prev.next = other
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other.next.prev = other
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}
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Item.prototype.dequeue = function dequeue () {
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var prev = this.prev
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var next = this.next
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prev.next = next
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next.prev = prev
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this.prev = this
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this.next = this
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return this.value
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}
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Item.prototype.isEmpty = function isEmpty () {
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return this.prev === this
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}
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