testmodule.lisp

(defun golomb-forest (&rest args)
  (if (and (oddp (length args)) (null (car (last args))))
      (sentinel-change. (golomb-forest-1 0 args))
      (golomb-forest-1 0 args)))

(defun golomb-forest-1 (size lst)
  (cond ((null lst) nil)
	((= size 0) (cons (car lst) (golomb-forest-1 1 (cdr lst))))
	(t (let ((siz (expt 2 size)))
	     (if (> siz (length lst))
		 (cons (tree-1 size lst) nil)
		 (cons (tree-1 size (subseq lst 0 siz))
		       (golomb-forest-1 (1+ size) (subseq lst siz))))))))

(defun tree (&rest args)
  (tree-1 (ceiling (log (length args) 2)) args))

(defun tree-1 (size lst)
  (let ((si (expt 2 (1- size)))
	(len (length lst)))
    (if (= size 1)
	(if (= len 2)
	    (cons (car lst) (cadr lst))
	    lst)
	(if (>= si len)
	    (cons (tree-1 (1- size) lst) nil)
	    (cons (tree-1 (1- size) (subseq lst 0 si))
		  (tree-1 (1- size) (subseq lst si)))))))

(defun translate (expr)
  (if (atom expr)
      expr
      (apply 'golomb-forest (mapcar 'translate expr))))

(defun conser (x)
  (if (atom x)
      (format nil "~A" x)
      (concatenate 'string 
		   (format nil "(~A . " (conser (car x))) 
		   (format nil "~A)" (conser (cdr x))))))

(defun repl (&optional (a nil))
  (format t "~&> ")
  (loop (progn (let ((message (read)))
		 (if (keywordp message)
		     (return 'quit)
		     (format t (conser (eval. (translate message) (golomb-forest-1 0 a))))))
	       (format t "~&> "))))