polish calulator

polish.clj

(ns clojure.reverse-notation
    (:require [clojure.edn :as edn]))

(def operators {'+ + '- - '/ / '* *})

(defn calc
    [expr]
      (loop [[e & es] (->> expr (re-seq #"\S+") (map edn/read-string) (replace operators))
                       stack '()]
            (cond
                 (number? e) (recur es (conj stack e))
                 (fn? e) (recur es (->> stack (take 2) reverse (apply e) (conj (drop 2 stack))))
                 :default (or (peek stack) 0))))