;;;; cl-scopes/util/iter

;;;; iterators, queues, and other sequentially accessible stuff
;;;; producing items (objects) like: numbers, strings, symbols, lists, ...

(defpackage :scopes/util/iter
  (:use :common-lisp)
  (:export #:next #:value
           #:list-iterator))

(in-package :scopes/util/iter)

;;;; iterators

(defgeneric next (it))
(defgeneric value (it))

(defclass list-iterator ()
  ((data :reader data :initarg :data :initform nil)
   (cur :accessor cur)))

(defmethod initialize-instance :after ((it list-iterator) &key &allow-other-keys)
  (setf (cur it) (cons nil (data it))))

(defmethod next ((it list-iterator))
  (pop (cur it))
  (null (cur it)))

(defmethod value ((it list-iterator))
  (car (cur it)))