(in-package :araneida) ;; (foldr (lambda (x y) (string-append x "; " y)) '(" 3" "2" "1")) ;; => 3; 2; 1 ;; (foldr (lambda (x y) (string-append "(" x "; " y ")")) '(" 3" "2" "1")) ;; => ( 3; (2; 1)) (defun foldr (func list)   "Fold FUNC over LIST, starting at the right-hand end"   (cond ((null (cdr list))          (car list))         (t          (funcall func (car list) (foldr func (cdr list) ))))) ;; (foldl (lambda (x y) (string-append x "; " y)) '(" 3" "2" "1")) ;; => 3; 2; 1 ;; (foldl (lambda (x y) (string-append "(" x "; " y ")")) '(" 3" "2" "1")) ;; => (( 3; 2); 1) (defun foldl (f lst) (foldr (lambda (y x) (funcall f x y)) (reverse lst))) (defun join (delimiter elements)   "Returns a new string consisting of ELEMENTS with DELIMITERs between them.  Elements are converted to strings as if by PRINC-TO-STRING"   (with-output-to-string (o)     (loop for front on elements           if (> (length front) 1)           do (progn (princ (car front) o) (princ delimiter o))           else           do (princ (car front) o)))) (defun choose-best (list test &key (key 'identity))   "Effectively equivalent to (elt (sort list test :key key) 0) but potentially faster"     (loop for el in list         for so-far = el then (if (funcall test (funcall key el)                                           (funcall key so-far))                                  el                                so-far)         finally (return so-far))) #| (choose-best '(#\1 #\2 #\1 #\8 #\3 #\0) #'> :key #'char-code) => 8 |#