ListSeq - laforge49/Asynchronous-Functional-Programming GitHub Wiki

The implementation of a sequence actor over a list is pretty straight forward.

class ListSeq[V](list: java.util.List[V])
  extends Sequence(mailbox, factory) {
  var outdated = false

  override def first(msg: AnyRef, rf: Any => Unit) {
    if (list.isEmpty) rf(null)
    else rf(KVPair(0, list.get(0)))
  }

  override def current(msg: AnyRef, rf: Any => Unit) {
    if (outdated) throw new IllegalStateException("underlying list has been updated")
    var key = msg.asInstanceOf[Current[Int]].key
    if (key < 0) key = 0
    if (key >= list.size) rf(null)
    else rf(KVPair(key, list.get(key)))
  }

  override def next(msg: AnyRef, rf: Any => Unit) {
    if (outdated) throw new IllegalStateException("underlying list has been updated")
    var key = msg.asInstanceOf[Next[Int]].key
    if (key < 0) key = 0
    else key = key + 1
    if (key >= list.size) rf(null)
    else rf(KVPair(key, list.get(key)))
  }
}

The keys of the sequence range from 0 through list.size - 1.

Here's the test code for synchronous operation.

val fact = new java.util.ArrayList[Int]
fact.add(0)
fact.add(1)
fact.add(2)
fact.add(6)
fact.add(24)
val factSeq = new ListSeq(fact)
println(Future(factSeq, First()))
println(Future(factSeq, Current(3)))
println(Future(factSeq, Next(3)))
println(Future(factSeq, Next(4)))

And the output.

KVPair(0,0)
KVPair(3,6)
KVPair(4,24)
null

Here's the test code for asynchronous operation.

val fact = new java.util.ArrayList[Int]
fact.add(0)
fact.add(1)
fact.add(2)
fact.add(6)
fact.add(24)
val factSeq = new ListSeq(fact)
factSeq.setMailbox(new ReactorMailbox)
println(Future(factSeq, Next(4)))
fact.add(120)
println(Future(factSeq, Next(4)))

And here's the output for the second test.

null
KVPair(5,120)

ListTest

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