Clojure.spec Chess 960

spec960.txt

(ns sssmakespec.c960
  (:require [clojure.spec.alpha :as s]
            [clojure.spec.gen.alpha :as gen]))

(def correct-pieces? #(= {\R 2, \K 1, \B 2, \Q 1, \N 2} (frequencies %)))  ;; The right pieces and only the right peices
(def bishops-opposite? #(odd? (+ (.indexOf (vec %) \B) (.lastIndexOf (vec %) \B))))  ;; one bishop on even squares one on odd
(def K-between-R? #(< (.indexOf (vec %) \R) (.indexOf (vec %) \K) (.lastIndexOf (vec %) \R)))  ;;King between the rooks

(s/def ::validc960  (s/and string?
                           correct-pieces?
                           bishops-opposite?
                           K-between-R?))

(defn makeseq []
  (->> ["Q" "K" "R" "R" "B" "B" "N" "N"]
     (shuffle)
     (apply str)))

(def possible-gamelist
  (->> (repeatedly makeseq)
       (filter #(s/valid? ::validc960 %))
       (distinct)
       (take 960)))

(defn get-game []
  (nth possible-gamelist (rand-int 960)))