;  Purpose: To demonstrate incrementing a counter.
;  Copyright © 2004 by Rupert Russell
;  e-mail: r.russell@ballarat.edu.au
;  URL: http://velorum.ballarat.edu.au/~rrussell/microworlds/
;  Created: October 29, 2004
;
;  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, write to the Free Software
;  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
; ---------------------------------------------------------------------



to setup
  make "counter 0				; create the counter and set its initial value to 0
  show_value_of_counter
  cg
end

to increment
   carefully [show_value_of_counter] [setup] 	; check that the counter has been created
						; if the counter has not been created then the 
						; command carefully will not cause an 
						; error but will run the procedure setup
   cg 
   if :counter < 10 [				; if the current value of :counter 
						; is less than 10 then
      make "counter :counter + 1		; increment the :counter by 1
      show_value_of_counter			; show the vale of the :counter
   ]
   stamp_turtles
end

to decrement
   carefully [show_value_of_counter] [setup]	; check that the counter has been created
						; if the counter has not been created then the 
						; command carefully will not cause an error 
						; but will run the procedure setup

   if :counter > -10 [
      make "counter :counter - 1 		; decrement the counter by 1
   ]

   cg
   show_value_of_counter
   stamp_turtles

end

to show_value_of_counter
   ct
   if :counter = -10 [
        insert ( sentence   "Minimum "value "reached )	;  Minimum value reached      
   ]

   if :counter = 10 [
        insert ( sentence "Maximum "value "reached  )	; Maximum value reached
      ]

  ; insert the value of the counter in the current text box
   if (and :counter > -10 :counter < 10) [
         insert ( sentence "The "counters "value "is "  )	
         insert :counter
      ]
end

to stamp_turtles

   if :counter = 0 [
      setshape "clear_sq
      stamp
   ]

   if :counter > 0 [
      setshape "clear_sq
      stamp

      repeat :counter  [
      setshape "green_sq
      fd 18
      stamp
      ]
   ]

   if :counter < 0 [
      setshape "clear_sq
      stamp

      setshape "red_sq
      repeat abs :counter [
      bk 18
      stamp
         ]
   ]

   if :counter = 0 [
      setshape "clear_sq
      stamp
   ]
end

to reset
   ct
   cg
   make "counter 0
   show_value_of_counter
   stamp_turtles
end