;;;; cl-scopes/forge - may the forge be with you!

;;;; A Forth-like interpreter implemented in Common Lisp.

(defpackage :scopes/forge/sf
  (:use :common-lisp)
  (:local-nicknames (:iter :scopes/util/iter))
  (:export #:*input* #:*stack*
           #:proc-list #:proc-input
           #:add
           #:pushd #:popd))

(defpackage :sf-builtin)
(defpackage :sf-user)

(in-package :scopes/forge/sf)

(defvar *stack* nil)
(defvar *input* nil)

;;;; core definitions

(defun proc-list (lst)
  (setf *input* (make-instance 'iter:list-iterator :data lst))
  (proc-input))

(defun proc-input ()
  (let ((inp *input*))
    (do ((item (iter:next inp) (iter:next inp)))
        ((null item))
      (proc-item item))))

(defun proc-item (item)
  (typecase item
    (symbol (funcall item))
    (t (pushd item))))

(defun reg2 (sym fn)
  (setf (fdefinition sym) #'(lambda ()
    (pushd (funcall fn (popd) (popd))))))

(defun pushd (v)
  (push v *stack*))

(defun popd ()
  (pop *stack*))

;;;; builtins

(reg2 'add #'+)