(defun single? (lst)
(and (consp lst)
(null (cdr lst))))CL-USER> (single? nil)
NIL
CL-USER> (single? '(a))
T(defun append1 (lst obj)
(append lst (list obj)))CL-USER> (append1 '(a b c d) 'e)
(A B C D E)(defun map-int (fn n)
(let ((acc nil))
(dotimes (i n)
(push (funcall fn i) acc))
(nreverse acc)))
CL-USER> (map-int #'(lambda (x) (+ x 1)) 5)(1 2 3 4 5)
(defun filter (fn lst)
(let ((acc nil))
(dolist (x lst)
(let ((val (funcall fn x)))
(if val (push val acc))))
(nreverse acc)))
CL-USER> (filter #'(lambda (x) (+ x 1)) '(1 2 3 4 5))
(2 3 4 5 6)
CL-USER> (filter #'(lambda (x)
(and (evenp x) (+ x 10)))
'(1 2 3 4 5))
(12 14)
CL-USER> (defun most (fn lst)
(if (null lst)
(values nil 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 max))))
MOST
CL-USER> (most #'length '((a b) (a b c) (a)))
(A B C)
3