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

diff --git a/lib/pipeline.nit b/lib/pipeline.nit
index 055823f..54be22b 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]
@@ -35,7 +34,9 @@ redef interface Iterator[E]
 
 	# Filter: sort with a given `comparator`.
 	# Important: require O(n) memory.
-	fun sort_with(comparator: Comparator[E]): Iterator[E]
+	#
+	#     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
 		comparator.sort(a)
@@ -72,6 +73,8 @@ redef interface Iterator[E]
 	# When the first iterator is terminated, the second is started.
 	#
 	#     assert ([1..20[.iterator + [20..40[.iterator).to_a	     ==  ([1..40[).to_a
+	#
+	# SEE: `Iterator2`
 	fun +(other: Iterator[E]): Iterator[E]
 	do
 		return new PipeJoin[E](self, other)
@@ -79,7 +82,7 @@ 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 +90,7 @@ 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)
@@ -99,7 +102,7 @@ redef interface Iterator[E]
 	#
 	#     var i = [1,2,3,4,5].iterator
 	#     assert i.head(2).to_a   == [1,2]
-	#     i.to_a		      == [3,4,5]
+	#     assert i.to_a           == [3,4,5]
 	fun head(length: Int): Iterator[E]
 	do
 		return new PipeHead[E](self, length)
@@ -158,6 +161,134 @@ redef interface Iterator[E]
 	end
 end
 
+# Concatenates a sequence of iterators.
+#
+# Wraps an iterator of sub-iterators and iterates over the elements of the
+# sub-iterators.
+#
+# ~~~nit
+# var i: Iterator[Int]
+# var empty = new Array[Int]
+#
+# i = new Iterator2[Int]([
+# 	[1, 2, 3].iterator,
+# 	empty.iterator,
+# 	[4, 5].iterator
+# ].iterator)
+# assert i.to_a == [1, 2, 3, 4, 5]
+#
+# i = new Iterator2[Int]([
+# 	empty.iterator,
+# 	[42].iterator,
+# 	empty.iterator
+# ].iterator)
+# assert i.to_a == [42]
+# ~~~
+#
+# SEE: `Iterator::+`
+class Iterator2[E]
+	super Iterator[E]
+
+	# The inner iterator over sub-iterators.
+	var inner: Iterator[Iterator[E]]
+
+	redef fun finish
+	do
+		var i = current_iterator
+		if i != null then i.finish
+	end
+
+	redef fun is_ok
+	do
+		var i = current_iterator
+		if i == null then return false
+		return i.is_ok
+	end
+
+	redef fun item
+	do
+		var i = current_iterator
+		assert i != null
+		return i.item
+	end
+
+	redef fun next
+	do
+		var i = current_iterator
+		assert i != null
+		i.next
+	end
+
+	redef fun start
+	do
+		var i = current_iterator
+		if i != null then i.start
+	end
+
+	private var previous_iterator: nullable Iterator[E] = null
+
+	private fun current_iterator: nullable Iterator[E]
+	do
+		if previous_iterator == null then
+			# Get the first sub-iterator.
+			if inner.is_ok then
+				previous_iterator = inner.item
+				previous_iterator.start
+				inner.next
+			else
+				return null
+			end
+		end
+		# Get the first sub-iterator that has a current item.
+		while inner.is_ok and not previous_iterator.is_ok do
+			previous_iterator.finish
+			previous_iterator = inner.item
+			previous_iterator.start
+			inner.next
+		end
+		return previous_iterator
+	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.
 #
@@ -294,13 +425,7 @@ private class PipeSkip[E]
 	var source: Iterator[E]
 	var skip_item: E
 
-	init(source: Iterator[E], skip_item: E)
-	do
-		self.source = source
-		self.skip_item = skip_item
-
-		do_skip
-	end
+	init do do_skip
 
 	fun do_skip
 	do
@@ -345,10 +470,8 @@ private class PipeSkipTail[E]
 
 	var lasts = new List[E]
 
-	init(source: Iterator[E], length: Int)
+	init
 	do
-		self.source = source
-		self.length = length
 		var lasts = self.lasts
 		while source.is_ok and lasts.length < length do
 			lasts.push(source.item)
@@ -375,13 +498,7 @@ private class PipeSelect[E]
 
 	var predicate: Function[E, Bool]
 
-	init(source: Iterator[E], predicate: Function[E, Bool])
-	do
-		self.source = source
-		self.predicate = predicate
-
-		do_skip
-	end
+	init do do_skip
 
 	fun do_skip
 	do