Added filter and uncurried foldLeft and foldRight to FingerTree

mperry · mperry · commit e60244511f4b · 2014-08-14T06:25:55.000+10:00
diff --git a/core/src/main/java/fj/data/fingertrees/FingerTree.java b/core/src/main/java/fj/data/fingertrees/FingerTree.java
@@ -1,9 +1,7 @@
 package fj.data.fingertrees;
 
-import fj.F;
-import fj.P2;
+import fj.*;
 import fj.data.Seq;
-import fj.Monoid;
 
 /**
  * Provides 2-3 finger trees, a functional representation of persistent sequences supporting access to the ends in
@@ -32,6 +30,10 @@ public abstract class FingerTree<V, A> {
    */
   public abstract <B> B foldRight(final F<A, F<B, B>> f, final B z);
 
+    public <B> B foldRight(final F2<A, B, B> f, final B z) {
+        return foldRight(F2Functions.curry(f), z);
+    }
+
   /**
    * Folds the tree to the right with the given function.
    *
@@ -49,6 +51,10 @@ public abstract class FingerTree<V, A> {
    */
   public abstract <B> B foldLeft(final F<B, F<A, B>> f, final B z);
 
+    public <B> B foldLeft(final F2<B, A, B> f, final B z) {
+        return foldLeft(F2Functions.curry(f), z);
+    }
+
   /**
    * Folds the tree to the left with the given function.
    *
@@ -67,6 +73,11 @@ public abstract class FingerTree<V, A> {
    */
   public abstract <B> FingerTree<V, B> map(final F<A, B> f, final Measured<V, B> m);
 
+    public <B> FingerTree<V, A> filter(final F<A, Boolean> f) {
+        FingerTree<V, A> tree = new Empty<V, A>(m);
+        return foldLeft((acc, a) -> f.f(a) ? acc.snoc(a) : acc, tree);
+    }
+
   /**
    * Returns the sum of this tree's annotations.
    *
