(defn constant[value]
  (fn [v] value))

(defn variable[value]
  (fn [arguments] (arguments value)))

(defn binary [action]
  (fn [left right]
    (fn [variable]
      (action (left variable) (right variable)))))

(defn unary [action]
  (fn [left]
    (fn [variable]
      (action (left variable)))))

(def add (binary +))

(def subtract (binary -))

(def multiply (binary *))

(def divide (binary (fn[^double a ^double b] (/ a b))))

(def negate (unary -))

(def sin(unary (fn[^double a] (Math/sin a))))

(def cos (unary (fn[^double a] (Math/cos a))))

(def BinaryActions {'+ add '- subtract '* multiply '/ divide})

(def UnaryAction {'negate negate 'sin sin 'cos cos})

(defn parser[string]
  (cond (number? string) (constant string)
        (symbol? string) (variable (str string))
        (seq? string)
                         (if (UnaryAction (first string))
                             ((UnaryAction (first string)) (parser (second string)))

                             ((BinaryActions (first string)) (parser (second string)) (parser (nth string 2))))))

(defn parseFunction[string]
  (parser (read-string string)))