feat: add lazy skip and take methods to Sequence with SkipSequence and TakeSequence classes

Implement `skip(count)` and `take(count)` on the Sequence class, backed by new SkipSequence and TakeSequence wrapper classes that lazily skip or limit iteration. Includes documentation in the sequence module markdown, core source definitions, and unit tests for edge cases (zero, negative, and overflow counts).
2017-03-15 14:15:00 +00:00
parent 10928fb5de 4555a47465
commit 38b92435bf
5 changed files with 155 additions and 0 deletions
@@ -125,6 +125,23 @@ It is a runtime error to call this on an empty sequence.
 Similar to above, but uses `seed` for the initial value of the accumulator. If
 the sequence is empty, returns `seed`.

+### **skip**(count)
+
+Creates a new sequence that skips the first `count` elements of the original
+sequence.
+
+The returned sequence is *lazy*. The first `count` elements are only skipped
+once you start to iterate the returned sequence. Changes to the original
+sequence will be reflected in the filtered sequence.
+
+### **take**(count)
+
+Creates a new sequence that iterates only the first `count` elements of the
+original sequence.
+
+The returned sequence is *lazy*. Changes to the original sequence will be
+reflected in the filtered sequence.
+
 ### **toList**

 Creates a [list][] containing all the elements in the sequence.