Clamps Dictionary

(ct->fr 12) ;; => 2

(ct->fr 1) ;; => 1.0594631

(ct->fr 7) ;; => 1.4983071

(ct->fr -12) ;; => 1/2

(mapcar #'ct->fr (range 13))
;;  => (1 1.0594631 1.122462 1.1892071 1.2599211 1.3348398 1.4142135 1.4983071
;;      1.587401 1.6817929 1.7817974 1.8877486 2)