;;; cl-scopes/forge/seq-functioinal.list
;;; a functional closure-based implementation of 
;;; sequence with three pointers

;;; not used, stored here for later reference

(defun make-seq ()
  (let* ((start (list nil))
         (cur start)
         (end start)
         (args (list start cur end)))
    #'(lambda (fn) 
        (setf args (apply fn args)))))

(defun seq-all (seq)
  (let (rv)
    (funcall seq #'(lambda (start cur end) 
                     (setf rv (cdr start))
                     (list start cur end)))
    rv))

(defun seq-cur (seq)
  (let (rv)
    (funcall seq #'(lambda (start cur end) 
                     (setf rv (car cur))
                     (list start cur end)))
    rv))

(defun seq-end (seq)
  (let (rv)
    (funcall seq #'(lambda (start cur end) 
                     (setf rv (car end))
                     (list start cur end)))
    rv))

(defun seq-next (seq)
  (let (rv)
    (funcall seq #'(lambda (start cur end) 
                     (pop cur)
                     (setf rv (car cur))
                     (list start cur end)))
    rv))

(defun seq-add (seq v)
    (funcall seq #'(lambda (start cur end)
                     (setf (cdr end) (list v))
                     (pop end)
                     (list start cur end)))
    nil)