cKanren Racket
https://github.com/niitsuma/cKanren
fork from http://rkrishnan.org/blog/2012/01/09/ckanren/
and little bug fixed
Usage:same
also can use (require cKanren)
#lang racket (require cKanren) (run* (q) (== q 3))
more extension (but still buggy)
https://github.com/niitsuma/Racket-miniKanren/tree/recursive