macro.clj

(defmacro phase-fn
  ([argvec] identity)
  ([argvec & forms]
     `(fn [session# ~@argvec]
        (--> session#
             ~(first forms)
             ~(fn [x#] (do (println x#) x#))
             ~(if (seq (rest forms))
                `((phase-fn ~argvec ~@(rest forms)))
                `((phase-fn ~argvec)))))))


(defmacro phase-fn
  ([argvec] identity)
  ([argvec & forms]
     (let [subphase# (first forms)
           left# (rest forms)]
       `(fn [session# ~@argvec]
          (--> session#
               ~subphase#
               ~@(when (seq left#)
                   [`((phase-fn ~argvec ~@left#))])))))