unparsing in clojure

unparse.clj

(declare unparse)

(defn unparse-args [lang args]
  (cond
    (map? (first args))
    (update-vals (first args) (partial unparse lang))
    :else
    (mapv (partial unparse lang) args)))

(defn unparse [lang data]
  (if-not (coll? data)
    data
    (let [[prim & args ] data
          unparse-fn (get lang prim)]
      (assert unparse-fn (pr-str [prim args]))
      (unparse-fn (unparse-args lang args)))))

(defn binary-operation [op]
  (fn [[a b]]
    (str a " " op " " b)))

(def lang
  {:select #(str "SELECT * FROM "
                 (:table %)
                 " WHERE "
                 (:where %))
   :and (binary-operation "AND")
   := (binary-operation "=")})

#_
(unparse lang
         [:select {:table "moi"
                   :where [:and [:= "a" 1] [:= "b" 2]]}])
;; => "SELECT * FROM moi WHERE a = 1 AND b = 2"