;; histogram.el -- simple histogram builder

;; Usage:  1. (histo-print NUMBER-LIST) makes a histogram for NUMBER-LIST, and
;;            prints it out in the buffer `*histogram*'.
;;         2. (histo-buffer BUFFERNAME) creates a histogram from a BUFFER that has one number 
;;            on each line.

(defun plusses (n)
  (cond ((= n 0) "")
	(t (concat "+" (plusses (- n 1))))))

(defun histo-print (number-list)
  (pop-to-buffer (generate-new-buffer "*histogram*"))
  (let ((x 100) (out "")) 
    (while (>= x 0)
      (setq out (concat out (format "%3s | " x) (plusses (count x number-list)) "\n"))
		   (decf x))
    (insert out))
  (goto-char (point-min)))

(defun histo-buffer-to-list (buffer)
  "Transform a buffer of integers into a list of integers."
  (pop-to-buffer buffer)
  (goto-char (point-min))
  (let ((liste '()))
    (while (search-forward-regexp "[0-9]+" nil t)
      (setq liste (cons (string-to-number (match-string-no-properties 0)) liste)))))

(defun histo-buffer (buffer)
  (interactive "bMake histogram from buffer: ")
  (histo-print (histo-buffer-to-list buffer)))

;; end of file histogram.el