evaluation-of-segment-reader.lisp

CL-USER> (segment-reader t #\/ 3)
あいう/えおか/きくけ/
("あいう" "えおか" "きくけ")
CL-USER> 

segment-reader-with-do.lisp

;;; SEGMENT-READER with DO

(defun segment-reader (stream ch n)
  (do ((n n (1- n))
       (acc nil
	    (push
	     (do ((curr (read-char stream)
			(read-char stream))
		  (chars nil (push curr chars)))
		 ((char= ch curr) (coerce (nreverse chars) 'string)))
	     acc)))
      ((< n 1) (nreverse acc))))

segment-reader.lisp

;;; SEGMENT-READER

;; Scheme-style
(defun segment-reader (stream ch n &optional (acc nil))
  (labels ((iter (chars curr)
	     (if (char= ch curr)
		 (coerce (reverse chars) 'string)
		 (iter (cons curr chars) (read-char stream)))))
    (if (< n 1)
	(reverse acc)
	(segment-reader stream ch (1- n)
			(cons (iter nil (read-char stream)) acc)))))