"PicoLisp "For backtracking, Pilog (PicoLisp Prolog) is the natural choice."
http://rosettacode.org/wiki/Amb#PicoLisp (I didn't see any other example that was obviously smaller than picolisp.) -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
