Put corresponds on Iterator.

I guess we can look forward to more and more duplication in the
collections. I had to cut and paste the doc comment too, or at least
I have no idea how to avoid that given the file I took it from was in
parallel somewhere.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/library/scala/collection/Iterator.scala b/src/library/scala/collection/Iterator.scala
index 3b2a7c7820..e9a7906527 100644
--- a/src/library/scala/collection/Iterator.scala
+++ b/src/library/scala/collection/Iterator.scala
@@ -391,6 +391,24 @@ trait Iterator[+A] extends TraversableOnce[A] {
 
     def next() = if (hasNext) { hdDefined = false; hd } else empty.next()
   }
+  
+  /** Tests whether every element of this iterator relates to the
+   *  corresponding element of another collection by satisfying a test predicate.
+   *
+   *  @param   that    the other collection
+   *  @param   p       the test predicate, which relates elements from both collections
+   *  @tparam  B       the type of the elements of `that`
+   *  @return          `true` if both collections have the same length and
+   *                   `p(x, y)` is `true` for all corresponding elements `x` of this iterator
+   *                   and `y` of `that`, otherwise `false`
+   */
+  def corresponds[B](that: GenTraversableOnce[B])(p: (A, B) => Boolean): Boolean = {
+    val that0 = that.toIterator
+    while (hasNext && that0.hasNext)
+      if (!p(next, that0.next)) return false
+
+    hasNext == that0.hasNext
+  }
 
   /** Creates an iterator over all the elements of this iterator that
    *  satisfy the predicate `p`. The order of the elements