squarespec.clj

(ns squarespec
  (:require [clojure.spec :as s]
            [clojure.spec.gen :as sgen]
            [clojure.spec.test :as stest]))

;; Implementation
(defn square
  "Define a square path given an origin and length."
  [[x1 y1 :as origin] length]
  (let [x2 (+ x1 length)
        y2 (+ y1 length)]
    [origin [x2 y1] [x2 y2] [x1 y2]]))

;; Specification
(s/def ::scalar
  (s/or :int int?
        :double (s/double-in :NaN? false :infinite? false)))

(s/def ::point
  (s/coll-of ::scalar :kind sequential? :count 2))

(s/def ::points
  (s/coll-of ::point :kind sequential?))

(s/fdef square
        :args (s/cat :origin ::point :length ::scalar)
        :ret ::points
        :fn (fn [{[x1 y1 :as origin] :args
                    ret :ret}]
                (and (= origin (second ret))
                     (= 4 (count ret)))))