# 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]
# 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)
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.
#