模拟 haskell do 环境的 clojure 宏

sample.clj

;; parsec.clj
(defmacro =>>
    "Threads the state through the parsers. Inserts state as the
  parameter in the first parser. If there are more parsers,
  inserts the first residue as the second state in second parser, etc.
  If a parser throw exception, throw it and exit, else return all bind result
  as a dictionay and residue data.
    "
    [data & forms]
    (loop [data (list (list return {}) data), forms forms]
        (if forms
            (let [form (first forms)
                    need-bind (and (seq? form) (symbol? (first form)) (keyword? (second form)) (= (name (first form)) "<-"))
                    func (if need-bind (nth form 2) form)
                    tail (if need-bind
                            (let [key (second form)]
                                `(let [[results# data#] ~data, [result# residue#] (~func data#)]
                                (list (assoc results# ~key result#) residue#)))
                            `(let [[results# data#] ~data, [result# residue#] (~func data#)]
                                (list results# residue#)))]
                    (recur tail (next forms)))
            data)))
            
  ;; retrun in atom.clj
  (defn return [value]
    (fn [data] (list value data)))