;;;;;;;;;;;;;;;;;;;; Callback Sequence ;;;;;;;;;;;;;;;;;;;;;

 (export sequence (macro (name args init ...rest)
  (var ~name
    (function ~args
      ((function ()
        (#args-erase-head init)
        ~@init
        (var next null)
        (var ___curr -1)
        (var ___actions [ ~@rest ])
        (set next
          (function ()
            (var ne (get ++___curr ___actions))
            (if? ne
              ne
              (throw "Call to (next) beyond sequence."))))
        (((next)))))))))