diff -r 000000000000 -r e25dbfce40e9 samples/effectivelist/src/org/apidesign/effectivelist/Listable.scala
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/samples/effectivelist/src/org/apidesign/effectivelist/Listable.scala	Fri Aug 31 20:16:57 2012 +0200
@@ -0,0 +1,9 @@
+package org.apidesign.effectivelist
+
+/** A member of a {@link List} that makes keeping references
+ * to previous and next items in the list effective.
+ */
+trait Listable[T <: Listable[T]] {
+  private[effectivelist] var prev : T = _
+  private[effectivelist] var next : T = _
+}