infix math dsl macro to clojure

infix_math_dsl.clj

(defmacro infix-math-dsl [form]
  (letfn [(parse [x]
            (cond
              (number? x)
              {:node :number :value x}

              (symbol? x)
              (let [s (str x)]
                (if (contains? #{"+" "-" "*" "/"} s)
                  {:node :op :value x}
                  {:node :ident :value s}))

              (list? x)
              {:node :list :value (mapv parse x)}

              :else
              {:node :error :value (pr-str x)}))

          (evaluate [node]
            (case (:node node)
              :number (:value node)
              :string (:value node)
              :ident  (symbol (:value node))

              :list
              (if (-> node :value count (not= 3))
                (throw (ex-info (str "Parse error: " (-> node :value count)) {:node node}))
                (let [value (:value node)
                      left  (evaluate (nth value 0))
                      op    (:value (nth value 1))
                      right (evaluate (nth value 2))]
                  `(~op ~left ~right)))

              :op (throw (ex-info "Unexpected operator node" {:node node}))

              :error (throw (ex-info (:value node)))))]
    (-> form parse evaluate)))

(infix-math-dsl (1 + (2 - 3))) ;; => 0
(macroexpand '(infix-math-dsl (1 + (2 - 3)))) ;; => (+ 1 (- 2 3))