Splits string by delimiter; default delimiter is \#space. (split-string "1 2 3 4") evaluates to ("1" "2" "3" "4").

split-string.lisp

(defun split-string (str &key (delimiter #\space))
  (defun split-string-rec (str str-list delimiter-pos)
    (if delimiter-pos
	    (let ((current (subseq str 0 delimiter-pos))
	          (remaining (subseq str (+ delimiter-pos 1) (length str))))
	        (split-string-rec remaining
			                  (push current str-list)
			                  (position delimiter remaining)))
	    (reverse (push str str-list))))
  (split-string-rec str nil (position delimiter str)))