string-calculator.clj

(ns string-calculator
  "My implementation of http://osherove.com/tdd-kata-1/"
  (:use [clojure.test :only (is)])
  (:require [clojure.tools.reader.edn :as edn]
            [clojure.string :as string :refer [join split]]))

; CODE

(defn parse-numbers [x]
  (map edn/read-string
       (if-let [[_ delimiter numbers] (first (re-seq #"//(.)\n(.+)" x))]
         (split numbers (re-pattern (if (or (= "." delimiter) (= "|" delimiter))
                                      (str "\\" delimiter)
                                      delimiter)))
         (split x #",|\n"))))

(defn add [x]
  (if (empty? x)
    0
    (let [numbers (parse-numbers x)]
      (when-let [negatives (not-empty (filter neg? numbers))]
        (throw (Exception. (str "negatives not allowed: " (join "," negatives)))))
      (reduce + numbers))))

; TEST

(is (= 0 (add ""))
    "Add \"\" should be 0")
(is (= 1 (add "1"))
    "Add \"1\" should be 1")
(is (= 3 (add "1,2"))
    "Add \"1,2\" should be 3")
(is (= (+ 1 2 3 4 5 6 7) (add "1,2,3,4,5,6,7"))
    "Add \"1,2,3,4,5,6,7\" should be its sum")
(is (= 6 (add "1\n2,3"))
    "Add \"1\n2,3\" should be 6")
(is (= 3 (add "//;\n1;2"))
    "Add \"//;\n1;2\" should be 3")
(is (= 3( add "//.\n1.2"))
    "Add \"//.\n1.2\" should be 3")
(is (= 3( add "//|\n1|2"))
    "Add \"//|\n1|2\" should be 3")
(is (thrown? Exception (add "-1"))
    "Add \"-1\" should be \"negatives not allowed: -1")
(is (thrown? Exception (add "-1,-2,3,-4"))
    "Add \"-1,-2,3,-4\" should be \"negatives not allowed: -1,-2,-4")