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erdos/rpn.clj

Created June 7, 2017 08:35
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Simple Reverse Polish Notation Calculator in Clojure
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rpn.clj
(defn rpn [s]
(first (reduce (fn [[s1 s2 & ss :as stack] op]
(case op
+ (cons (+ s1 s2) ss)
- (cons (- s1 s2) ss)
* (cons (* s1 s2) ss)
/ (cons (/ s1 s2) ss)
, (cons op stack)))
() (read-string (str \( s \))))))
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erdos commented Jun 7, 2017

this should also do it.

(defn rpn [s]
    (first (reduce (fn [[s1 s2 & ss :as stack] op]
                     (try (cons ((eval op) s1 s2) ss)
                          (catch Exception _ (cons op stack))))
                   () (read-string (str \( s \))))))

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