X-Git-Url: http://nitlanguage.org

diff --git a/lib/pipeline.nit b/lib/pipeline.nit
index 31d007b..d3428f0 100644
--- a/lib/pipeline.nit
+++ b/lib/pipeline.nit
@@ -14,9 +14,8 @@
 
 # Pipelined filters and operations on iterators.
 #
-# This module enhance `Iterator`s with some methods that enable a
-# pipeline-like programing that offers the manupulation of
-# collections trough connected filters with reasonable memory constraints.
+# This module enhances `Iterator` with some methods that enable a pipeline-like programing.
+# The processing of elements in a pipeline is done trough connected filters that are implemented with reasonable memory constraints.
 module pipeline
 
 redef interface Iterator[E]
@@ -35,6 +34,8 @@ redef interface Iterator[E]
 
 	# Filter: sort with a given `comparator`.
 	# Important: require O(n) memory.
+	#
+	#     assert ["a", "c", "b"].iterator.sort_with(alpha_comparator).to_a  == ["a", "b", "c"]
 	fun sort_with(comparator: Comparator): Iterator[E]
 	do
 		var a = self.to_a
@@ -79,7 +80,7 @@ redef interface Iterator[E]
 
 	# Alternate each item with `e`.
 	#
-	#    assert [1,2,3].iterator.alternate(0).to_a		     ==  [1,0,2,0,3]
+	#     assert [1,2,3].iterator.alternate(0).to_a		     ==  [1,0,2,0,3]
 	fun alternate(e: E): Iterator[E]
 	do
 		return new PipeAlternate[E](self, e)
@@ -87,7 +88,7 @@ redef interface Iterator[E]
 
 	# Filter: reject a given `item`.
 	#
-	#    assert [1,1,2,1,3].iterator.skip(1).to_a		     ==  [2,3]
+	#     assert [1,1,2,1,3].iterator.skip(1).to_a		     ==  [2,3]
 	fun skip(item: E): Iterator[E]
 	do
 		return new PipeSkip[E](self, item)
@@ -158,6 +159,45 @@ redef interface Iterator[E]
 	end
 end
 
+# Wraps an iterator to skip nulls.
+#
+# ~~~nit
+# var i: Iterator[Int]
+#
+# i = new NullSkipper[Int]([null, 1, null, 2, null: nullable Int].iterator)
+# assert i.to_a == [1, 2]
+#
+# i = new NullSkipper[Int]([1, null, 2, 3: nullable Int].iterator)
+# assert i.to_a == [1, 2, 3]
+# ~~~
+class NullSkipper[E: Object]
+	super Iterator[E]
+
+	# The inner iterator.
+	var inner: Iterator[nullable E]
+
+	redef fun finish do inner.finish
+
+	redef fun is_ok do
+		skip_nulls
+		return inner.is_ok
+	end
+
+	redef fun item do
+		skip_nulls
+		return inner.item.as(E)
+	end
+
+	redef fun next do
+		inner.next
+		skip_nulls
+	end
+
+	private fun skip_nulls do
+		while inner.is_ok and inner.item == null do inner.next
+	end
+end
+
 # Interface that reify a function.
 # Concrete subclasses must implements the `apply` method.
 #