parse-number-range parses LOOP's convenient "for-as-arithmetic" syntax into 5 simple values. The values are from, to, limit-kind (:inclusive, :exclusive or nil if unbounded), by (step) and direction (+ or -)). Further related utilities are provided. Intended for easy implementation of analogous functionality in other constructs.

parse-number-range is in Quicklisp:

(ql:quickload "parse-number-range")

See the project's home for further information. Actual documentation is in the README.
This library is in the Public Domain. See the UNLICENSE file for details.