This is an implementation of the series package as described in the Appendix of Common Lisp The Language (the book is available in the form of the cltl package). . It was proposed as a more functional replacement for the build-in LOOP macro, but never gained the status of official standard. . In general this package can do almost all iteration constructs in an extensible way and produces quite fast optimised code. . This is an old package without upstream but stable and quite bugfree.