Attempt at the string calculator kata in Clojure http://nimblepros.com/media/36628/string%20calculator%20kata.pdf

core.clj

(ns kata-1.core)

(defn- str->nums [s]
  (map read-string (re-seq #"[\d]+|[-\d]+" s)))

(defn add [s]
  (let [nums (str->nums s)]
    (when-let [neg-nums (not-empty (filter neg? nums))]
      (throw (Exception. (str "Negatives not allowed:" neg-nums))))
    (reduce + (filter #(<= % 1000) nums))))

core_test.clj

(ns kata-1.core-test
  (:require [kata-1.core :refer :all])
  (:use expectations))

;; step 1
(expect 0 (add ""))
(expect 1 (add "1"))
(expect 3 (add "1,2"))

;; step 2
(expect 6 (add "1,1,1,2,1"))

;; step 3
(expect 6 (add "1\n2,3"))

;; step 4
(expect 3 (add "//;\n1;2"))

;; step 5
(expect Exception (add "-1,2"))
(expect Exception (add "2,-4,3,-5"))

;; step 6
(expect 2 (add "1001,2"))

;; step 7
(expect 6 (add "//[****]\n1***2***3"))

;; step 8
(expect 6 (add "//[*][%]\n1*2%3"))

;; step 9
(expect 6 (add "//[*][%]\n1**2%%%3"))

project.clj

(defproject kata-1 "0.1.0-SNAPSHOT"
  :description "FIXME: write description"
  :url "http://example.com/FIXME"
  :license {:name "Eclipse Public License"
            :url "http://www.eclipse.org/legal/epl-v10.html"}
  :dependencies [[org.clojure/clojure "1.5.1"]
                 [expectations "1.4.52"]]
  :plugins [[lein-autoexpect "1.0"]])