;; Figure 6.1: Utility functions
(defun single? (lst)
	(and (consp lst) (null (cdr lst))))
	
(defun append1 (lst obj)
	(append lst (list obj)))
	
(defun map-int (fn n)
	(let ((acc nil))
		(dotimes (i n)
			(push (funcall fn i) acc))
		(nreverse acc)))

(defun filter (fn lst)
	(let ((acc nil))
		(dolist (x lst)
			(let ((val (funcall fn x)))
				(if val (push val acc))))
		(nreverse acc)))
		
(defun most (fn lst)
	(if (null lst)
		(values nil)
		(let* ((wins (car lst))
			(max (funcall fn wins)))
		(dolist (obj (cdr lst))
			(let ((score (funcall fn obj)))
				(when (> score max)
					(setf wins obj
						max score))))
		(values wins))))