jank-arithmetic.clj

(ns arithmetic.core
  (:require [clojure.string :as string]))

(defn tokenize [expr]
  (string/split expr #"\s+"))

(defn -main [& [expr]]
  (let [tokens (tokenize expr)
        reduction (reduce (fn [acc token]
                            (case token
                              "+" (assoc acc :op +)
                              "-" (assoc acc :op -)
                              (if-some [op (:op acc)]
                                (-> (update acc :result op (read-string token))
                                    (assoc :op nil))
                                (assoc acc :result (read-string token)))))
                          {:result 0
                           :op nil}
                          tokens)]
    (println (:result reduction))))