functional list, queues and package for concurrent

stdlib/ktSrc/concurrent/FunctionalList.kt

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+package std.concurrent
+
+abstract class FunctionalList<T>(val size: Int) {
+    abstract val head: T
+    abstract val tail: FunctionalList<T>
+
+    val empty : Boolean
+    get() = size == 0
+
+    fun add(element: T) : FunctionalList<T> = FunctionalList.Standard(element, this)
+
+    fun reversed() : FunctionalList<T> {
+        if(empty)
+            return this
+
+        var cur = tail
+        var new = of(head)
+
+        while(!cur.empty) {
+            new = new.add(cur.head)
+            cur = cur.tail
+        }
+        return new
+    }
+
+    fun iterator() = object: Iterator<T> {
+        var cur = this@FunctionalList
+
+        override fun next(): T {
+            if(cur.empty)
+                throw java.util.NoSuchElementException()
+
+            val head = cur.head
+            cur = cur.tail
+            return head
+        }
+
+        override val hasNext: Boolean
+        get() = !cur.empty
+    }
+
+    class object {
+        class Empty<T>() : FunctionalList<T>(0) {
+            override val head: T
+            get() = throw java.util.NoSuchElementException()
+            override val tail: FunctionalList<T>
+            get() = throw java.util.NoSuchElementException()
+        }
+
+        class Standard<T>(override val head: T, override val tail: FunctionalList<T>) : FunctionalList<T>(tail.size+1)
+
+        fun <T> emptyList() = Empty<T>()
+
+        fun <T> of(element: T) : FunctionalList<T> = FunctionalList.Standard<T>(element,emptyList())
+    }
+}
+

stdlib/ktSrc/concurrent/FunctionalQueue.kt

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+package std.concurrent
+
+import java.util.concurrent.Executor
+import jet.Iterator
+
+class FunctionalQueue<T>(
+    val input: FunctionalList<T> = FunctionalList.emptyList<T>(),
+    val output: FunctionalList<T> = FunctionalList.emptyList<T>()) {
+
+    val size : Int
+        get() = input.size + output.size
+
+    val empty : Boolean
+        get() = size == 0
+
+    fun add(element: T) = FunctionalQueue<T>(input add element, output)
+
+    fun addFirst(element: T) = FunctionalQueue<T>(input, output add element)
+
+    fun removeFirst() : #(T,FunctionalQueue<T>) =
+        if(output.empty) {
+            if(input.empty)
+                throw java.util.NoSuchElementException()
+            else
+                FunctionalQueue<T>(FunctionalList.emptyList<T>(), input.reversed()).removeFirst()
+        }
+        else {
+            #(output.head, FunctionalQueue<T>(input, output.tail))
+        }
+}