1 files changed, 57 insertions, 12 deletions
diff --git a/gee/iterator.vala b/gee/iterator.vala
index 8b243e6..b22fa10 100644
--- a/gee/iterator.vala
+++ b/gee/iterator.vala
@@ -2,6 +2,7 @@
  *
  * Copyright (C) 2007-2008  Jürg Billeter
  * Copyright (C) 2009  Didier Villevalois, Maciej Piechotka
+ * Copyright (C) 2010-2011  Maciej Piechotka
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -27,14 +28,14 @@
  * An iterator over a collection.
  *
  * Gee's iterators are "on-track" iterators. They always point to an item
- * except before the first call to {@link next} or {@link first}, or, when an
- * item has been removed, until the next call to {@link next} or {@link first}.
+ * except before the first call to {@link next}, or, when an
+ * item has been removed, until the next call to {@link next}.
  *
  * Please note that when the iterator is out of track, neither {@link get} nor
  * {@link remove} are defined and both will fail. After the next call to
- * {@link next} or {@link first}, they will be defined again.
+ * {@link next}, they will be defined again.
  */
-public interface Gee.Iterator<G> : Object {
+public interface Gee.Iterator<G> : Object, Traversable<G> {
 	/**
 	 * Advances to the next element in the iteration.
 	 *
@@ -50,13 +51,6 @@ public interface Gee.Iterator<G> : Object {
 	public abstract bool has_next ();
 
 	/**
-	 * Rewinds to the first element in the iteration.
-	 *
-	 * @return ``true`` if the iterator has a first element
-	 */
-	public abstract bool first ();
-
-	/**
 	 * Returns the current element in the iteration.
 	 *
 	 * @return the current element in the iteration
@@ -66,8 +60,59 @@ public interface Gee.Iterator<G> : Object {
 	/**
 	 * Removes the current element in the iteration. The cursor is set in an
 	 * in-between state. Both {@link get} and {@link remove} will fail until
-	 * the next move of the cursor (calling {@link next} or {@link first}).
+	 * the next move of the cursor (calling {@link next}).
 	 */
 	public abstract void remove ();
+	
+	/**
+	 * Determines wheather the call to {@link get} is legal. It is false at the
+	 * beginning and after {@link remove} call and true otherwise.
+	 */
+	public abstract bool valid { get; }
+	
+	/**
+	 * Determines wheather the call to {@link remove} is legal assuming the
+	 * iterator is valid. The value must not change in runtime hence the user
+	 * of iterator may cache it.
+	 */
+	public abstract bool read_only { get; }
+
+	/**
+	 * Create iterator from unfolding function. The lazy value is
+	 * force-evaluated before progressing to next element.
+	 *
+	 * @param f Unfolding function
+	 * @param current If iterator is to be valid it contains the current value of it
+	 */
+	public static Iterator<A> unfold<A> (owned UnfoldFunc<A> f, owned Lazy<G>? current = null) {
+		return new UnfoldIterator<A> ((owned) f, (owned) current);
+	}
+
+	/**
+	 * Concatinate iterators.
+	 *
+	 * @param iters Iterators of iterators
+	 * @return Iterator containg values of each iterator
+	 */
+	public static Iterator<G> concat<G> (Iterator<Iterator<G>> iters) {
+		Iterator<G>? current = null;
+		if (iters.valid)
+			current = iters.get ();
+		return unfold<G> (() => {
+			while (true) {
+				if (current == null) {
+					if (iters.next ()) {
+						current = iters.get ();
+					} else {
+						return null;
+					}
+				} else if (current.next ()) {
+					return new Lazy<G>.from_value (current.get ());
+				} else {
+					current = null;
+				}
+			}
+		});
+	}
 }