; using [matchure "0.10.1"]

(use '[matchure])

(defn-match rpn'
    ([ [?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 ")

; works like a charm ;-)