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Solving the zebra puzzle with loco
(ns loco-playground.core
(:require [loco.core :refer :all]
[clojure.pprint :refer :all]
[loco.constraints :refer :all]))
;; http://bypacoman.blogspot.com.es/2013/08/desestructurando-el-puzzle-de-einstein.html
;; ---- Datos de referencia
(def domain
{:color [:red :blue :green :yellow :white ]
:country [:england :spain :france :norway :japan ]
:beverage [:tea :milk :tomato :coffee :beer ]
:animal [:dog :horse :fox :cat :zebra ]
:job [:detective :doctor :architect :lawyer :engineer]})
(defn ->val [prop name]
(.indexOf (domain prop) name))
(defn ->name [[prop value]]
(get-in domain [prop value]))
;; --- Funciones de ayuda para construir las restricciones
(defn all-distinct [prop]
($distinct (map (partial vector prop) (range 5))))
(defn fact
"Fija una propiedad [:color 4 :red] o enlaza dos [:color :red] <=> [:country :england]"
([[prop idx name]]
($= [prop idx] (->val prop name)))
([[prop1 name1] [prop2 name2]]
(apply $or (map #($and ($= [prop1 %] (->val prop1 name1)) ($= [prop2 %] (->val prop2 name2)))
(range 5)))))
(defn right-fact
"Enlaza una propiedad con el vecino de la derecha "
[[prop1 name1] [prop2 name2]]
(apply $or (map #($and (fact [prop1 % name1]) (fact [prop2 (inc %) name2])) (range 4))))
(defn side-fact
"Enlaza una propiedad con algún vecino (derecha o izquierda)"
[[prop1 name1] [prop2 name2]]
(apply $or
(concat
(map #($and (fact [prop1 % name1]) (fact [prop2 (inc %) name2])) (range 4))
(map #($and (fact [prop1 % name1]) (fact [prop2 (dec %) name2])) (range 1 5)))))
;; ---- Creación del modelo a resolver
(def model
(conj
;; Variables [:country i] [:animal i] [:color i] [:beverage i] [:job i] con i <- [0,5)
(for [prop (keys domain)
idx (range 5)]
($in [prop idx] (range 5)))
;; Todas las variables de cada propiedad deben ser diferentes
(all-distinct :color)
(all-distinct :animal)
(all-distinct :beverage)
(all-distinct :country)
(all-distinct :job)
;; La casa del inglés es roja
(fact [:country :england] [:color :red])
;; El español tiene un perro
(fact [:country :spain] [:animal :dog])
;; El japonés es detective
(fact [:job :detective] [:country :japan])
;; El francés bebe té
(fact [:country :france] [:beverage :tea])
;; La casa blanca está inmediatamente a la derecha de la casa verde
(right-fact [:color :green] [:color :white])
;; En la casa del medio se bebe leche
(fact [:beverage 2 :milk])
;; La casa del noruego es la primera a la izquierda
(fact [:country 0 :norway])
;; La casa vecina al noruego es azul
(side-fact [:country :norway] [:color :blue])
;; La casa amarilla es del médico
(fact [:color :yellow] [:job :doctor])
;; El vecino del médico tiene un caballo
(side-fact [:job :doctor] [:animal :horse])
;; El vecino del inglés es arquitecto
(side-fact [:country :england] [:job :architect])
;; El vecino del arquitecto tiene un zorro
(side-fact [:job :architect] [:animal :fox])
;; El abogado bebe zumo de tomate
(fact [:job :lawyer] [:beverage :tomato])
;; El ingeniero tiene un gato
(fact [:job :engineer] [:animal :cat])
;; En la casa verde se bebe café
(fact [:color :green] [:beverage :coffee])))
(defn solve []
(letfn [(format-prop [[[name idx] val]]
[name (->name [name val])])]
(->> (solution model)
(group-by (fn [[[name idx] _]] idx))
(map (fn [[idx props]] [idx (sort-by first (map format-prop props))]))
(sort-by first))))
(print "\n\n------ SOLUTION -------\n\n")
(pprint (solve))
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