arithmetic constraints puzzle with Clojure / Loco

loco_example.clj

;; cf https://github.com/aengelberg/loco/blob/master/test/loco/integer/sendmoremoney1.clj
(ns constrained-grouping.core
  (:use loco.constraints
        loco.core))
      
(defn initialize-digits [vars]
  (for [v vars]
    ($in v 0 9)))

(def letters
  [:o :n :e :t :h :r :l :v :w :y])

(def puzzle-model
  (concat (initialize-digits letters)
          [($distinct letters)
           ($> :o 0)
           ($> :t 0)
           ($> :e 0)
           ($= ($+ ($* 3 ($scalar [:o :n :e] [100 10 1]))
                   ($* 2 ($scalar [:t :h :r :e :e] [10000 1000 100 10 1]))
                   ($scalar [:e :l :e :v :e :n] [100000 10000 1000 100 10 1]))
               ($scalar [:t :w :e :n :t :y] [100000 10000 1000 100 10 1]))]))
(time (solutions puzzle-model))
;; "Elapsed time: 61.496745 msecs"
;; ({:y 8, :r 7, :v 1, :o 2, :n 3, :w 4, :e 5, :l 0, :h 9, :t 6})