(use '[clojure.core.match.core :only [match] ])


; this is expected to work


(defn rpn'[ stack symb ]
    (match [stack symb]
        [ [x y & z ] "*" ] (cons (* x y ) z)
        [ [x y & z ] "+" ] (cons (+ x y ) z)
        [ x "sum" ] [ (reduce + x) ]
        [ x y ] (cons (read-string y) x)
            ))

(defn calculator'[ input ]
    (first (reduce rpn' [] (re-seq #"\S+" input))))

(calculator' " 1 2 10 2 3 + * sum ")




; like this below, but it doesn't, why?



(defn rpn[ stack symb ]
    (match [stack symb]
        [ x "*" ] (cons (* (first x) (second x) ) (drop 2 x))
        [ x "+" ] (cons (+ (first x) (second x) ) (drop 2 x))
        [ x "sum" ] [ (reduce + x) ]
        [ x y ] (cons (read-string y) x)
            ))

(defn calculator[ input ]
    (first (reduce rpn [] (re-seq #"\S+" input))))

(calculator " 1 2 10 2 3 + * sum ")


; and standard clojure destruction

(let [ [ x y & z ] '( 2 3 4 5) ]
    (println x)
    (println y)
    (println z))