Common Lisp the Language, 2nd Edition
PREFACE: Generators and gatherers are yet another approach, closely related to series, to providing iteration in a functional style.
The remainder of this chapter consists of a description by Crispin Perdue and Richard C. Waters of their work on an existing implementation of generators and gatherers. I have edited the chapter only very lightly to conform to the overall style of this book. Please see the Preface to this book for more information about the genesis of the generators/gatherers approach and its relationship to the work of X3J13.
-Guy L. Steele Jr.