diff -r 000000000000 -r e25dbfce40e9 samples/effectivelist/src/org/apidesign/effectivelist/List.scala
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/samples/effectivelist/src/org/apidesign/effectivelist/List.scala	Fri Aug 31 20:16:57 2012 +0200
@@ -0,0 +1,74 @@
+package org.apidesign.effectivelist
+
+/** 
+ * Implementation of add and remove efficient list. It has just one
+ * restriction - its items need to carry additional information to help
+ * the list to be effective. All items must extend trait {@link Listable}:
+ * <pre>
+ * <b>case class</b> Person(name : String) <b>extends</b> Listable[Person]
+ * </pre>
+ */
+final class List[T <: Listable[T]] {
+  private var item : T = _
+  private final var EMPTY : T = _
+  
+  final def get(index : Int) : T = {
+    var pos : T = item;
+    for (i <- 1 to index) {
+      pos = pos.next;
+      if (pos == item) {
+        throw new IndexOutOfBoundsException()
+      }
+    }
+    return pos
+  }
+  
+  final def size() : Int = {
+    if (item == EMPTY) {
+      return 0
+    }
+    var size = 0
+    var pos : T = item
+    do {
+      size = size + 1
+      pos = pos.next
+    } while (pos != item)
+    return size
+  }
+  
+  final def add(toAdd : T) : Boolean = {
+    if (toAdd.prev != EMPTY) {
+      return false
+    }
+    
+    if (item == null) {
+      item = toAdd
+      toAdd.next = toAdd
+      toAdd.prev = toAdd
+      return true
+    } else {
+      toAdd.prev = item.prev
+      item.prev.next = toAdd
+      item.prev = toAdd
+      toAdd.next = item
+      return true
+    }
+  }
+  final def remove(toRemove : T) : Boolean = {
+    if (toRemove.prev == EMPTY) {
+      return false
+    } else {
+      toRemove.prev.next = toRemove.next
+      toRemove.next.prev = toRemove.prev;
+      if (item.next == item) {
+        item = EMPTY
+      }
+      if (item == toRemove) {
+        item = toRemove.next
+      }
+      toRemove.next = EMPTY
+      toRemove.prev = EMPTY
+      return true
+    }
+  }
+}