28 lines
517 B
Text
28 lines
517 B
Text
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def makeQueue() {
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def [var head, var tail] := Ref.promise()
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def writer {
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to enqueue(value) {
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def [nh, nt] := Ref.promise()
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tail.resolve([value, nh])
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tail := nt
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}
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}
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def reader {
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to empty() { return !Ref.isResolved(head) }
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to dequeue(whenEmpty) {
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if (Ref.isResolved(head)) {
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def [value, next] := head
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head := next
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return value
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} else {
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throw.eject(whenEmpty, "pop() of empty queue")
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}
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}
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}
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return [reader, writer]
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}
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