Add uncons to FingerTree

jbgi · jbgi · commit 3812a832501f · 2016-06-19T16:20:45.000+02:00
diff --git a/core/src/main/java/fj/data/fingertrees/FingerTree.java b/core/src/main/java/fj/data/fingertrees/FingerTree.java
@@ -167,6 +167,18 @@ public final Option<A> headOption() {
       return isEmpty() ? Option.none() : Option.some(head());
   }
 
+  /**
+   * Performs a reduction on this finger tree using the given arguments.
+   *
+   * @param nil  The value to return if this finger tree is empty.
+   * @param cons The function to apply to the head and tail of this finger tree  if it is not empty.
+   * @return A reduction on this finger tree.
+   */
+  public final <B> B uncons(B nil, F2<A, FingerTree<V, A>, B> cons) {
+    return isEmpty() ? nil : cons.f(head(), tail());
+  }
+
+
   /**
    * The last element of this tree. This is an O(1) operation.
    *
