ClojureでSEND+MORE=MONEYを解いた

smm/core.clj

(ns smm.core
  (:refer-clojure :exclude [==])
  (:use [clojure.core.logic])
  (:require [clojure.core.logic.fd :as fd]))

;;;   S E N D
;;; + M O R E
;;; ---------
;;; M O N E Y

(defn digitso [nums n]
  (fresh [h t]
    (conso h t nums)
    (conde
      [(emptyo t) (== h n)]
      [(fresh [n0 nn]
         (fd/* nn 10 n0)
         (fd/+ n0 h n)
         (digitso t nn))])))

(defn solve []
  (run 2 [q]
    (fresh [s e n d m o r y send more money]
      (fd/in s e n d m o r y (fd/domain 0 1 2 3 4 5 6 7 8 9))
      (fd/!= s 0) (fd/!= m 0)
      (fd/distinct [s e n d m o r y])
      (digitso [d n e s] send)
      (digitso [e r o m] more)
      (digitso [y e n o m] money)
      (fd/+ send more money)
      (== q [s e n d '+ m o r e '=  m o n e y]))))

user=> (use 'smm.core)
user=> (solve)
([9 5 6 7 + 1 0 8 5 = 1 0 6 5 2])