;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; This program is free software; you can redistribute it and/or
;; modify it under the terms of the GNU General Public License as
;; published by the Free Software Foundation; either version 2 of
;; the License, or (at your option) any later version.
;;
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with this program; if not, contact:
;;
;; Free Software Foundation           Voice:  +1-617-542-5942
;; 51 Franklin Street, Fifth Floor    Fax:    +1-617-542-2652
;; Boston, MA  02110-1301,  USA       gnu@gnu.org
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(define (make-table-collector)
  (let          ;;; variable slots
      ((total 0)  ;;; Numeric total
       (rows '()) ;;; Collection of items into total
       (count 0)) ;;; Number of elements
    (let 
	((adder (lambda (amount pos)
		  (set! total (+ total amount))
		  (set! rows (cons pos rows))
		  (set! count (+ count 1))))
	 (gettotal (lambda () total))
	 (getcount (lambda () count))
	 (getrows (lambda () rows))
	 (resetall (lambda ()
		     (set! total 0)
		     (set! rows '())
		     (set! count 0))))
      (lambda (action value . rowdata)
	(case action
	  ((add) (adder value rowdata))
	  ((total) (gettotal))
	  ((getcount) (getcount))
	  ((getrows) (getrows))
	  ((reset) (resetall)))))))

;;; Here's how it looks:
; > (define a (make-table-collector))
; > (a 'add 2)
; > (a 'add 4 5 6)
; > (a 'add 6 7 8)
; > (a 'add 9 10)
; > (a 'getcount #f)
; 4
; > (a 'total #f)
; 21
; > (a 'getrows #f)
; ((10) (7 8) (5 6) ())
; > (a 'reset #f)
; > (list (a 'getcount #f) (a 'total #f) (a 'getrows #f))
; (0 0 ())
; >