Updated collections documentation.

README.md

@@ -38,6 +38,10 @@ This library provides basic arithmetic abstractions like Percentages. See the [r
 
 This library provides support to express optional values and required values, that can be unknown at the beginning of an execution. See the [related documentation.](docs/BindingsAndOptionals.md)
 
+## Collections
+
+This library provides additional abstractions for Collections. See the [related documentation.](docs/Collections.md)
+
 ## Contributing
 
 If you want to help check the [contribution guidelines.](CONTRIBUTING.md)

docs/Collections.md

@@ -0,0 +1,15 @@
+# Collections
+
+## Circular Iterator
+
+A `CircularIterator` provides an abstraction to iterate over a collection rolling over when the end is reached:
+
+```smalltalk
+| iterator |
+iterator := CircularIterator cyclingOver: 'abc'.
+iterator next "$a".
+iterator next "$b".
+iterator next "$c".
+iterator next "$a".
+iterator next "$b".
+```