Windows and Tic-Tac-Toe!

By Andy Cohen, Human Factors Engineer, MacTutor Contributing Editor

This month the Lisp Listener will feature a program written by Dean Ritz of ExperTelligence. The program is a Tic-Tac-Toe game which uses all of the functions described in previous issues. However, before discussing the game I'd like to present a subject long overdue.

Menus In ExperLisp

Creating a menu on the menu bar is actually a pretty straight forward, though nonintuitve, operation. In creating a menu one must use one of the special "hooks" in ExperLisp. There are also hooks for printing. Those will eventually be covered in future installments. The first step in creating a menu must be the identification of what the menu items will do. Menu items can call functions or perform assignment. If the items call defined functions, these functions should already be defined and the function names known. One then defines a function which returns a menu and a menu item on the condition that a certain menu and item position is selected. One easy way to do this uses a conditional which has not yet been discussed.

SELECTQ acts like COND since it has a clause and returns something based on the value of the clause. The first item following the term SELECTQ is the key-form . Each of the test items which follow are evaluated and the one which is the equivalent of the key-form causes the return of it's corresponding value or list. For example;

(defun what (x)
  (selectq x
           (1 'one)
           (2 'two)
           (t 'all)))

(what 1)
one
(what 3)
all

In the above, the selectq evaluates the passed value (x) for equality with the first atoms of each of the three following lists. If the atom is equal to the passed value, the atom following the first is returned. As in COND the "t" forces the return of the atom "all". In assigning menu item positions one may have a SELECTQ within a SELECTQ. The first level SELECTQ finds the menu, the second finds the menu item. For example:

(defun menuselect (themenu theitem)
  (selectq themenu
     (10 (selectq theitem
           (1 (function1B))
           (2 (function2B))
           (3 (function3B))))
     (11 (selectq theitem 
           (1 (function1A))
           (2 (function2A))
           (3 (function3A))))))

The first SELECTQ locates which group of items belong to the menu number assigned to "themenu". The second SELECTQ locates the item belonging to the item number assigned to "theitem". After one generates the above defined function one must assign the values returned by the function to the special menu-hook;

(setq ªmenuhook menusel)

One then assigns a label to the "NEWMENU" function (It is a built in function) and it's elements. This must be done with the ID number that one wants to assign to the menu as well as the menu title. For example:

(setq mymenu (newmenu 10 "menu B"))

Using this label one then assigns the item labels to the menu as follows:

(appendmenu mymenu "function1B")
(appendmenu mymenu "function2B")
(appendmenu mymenu "function3B")

or one may do it all in one list as follows:

(appendmenu mymenu " function1B; function2B;
function3B")

One then inserts the menu with:

(insertmenu mymenu 0)

Then draws it with:

(drawmenubar)

The entire sample with dummy functions follows:

(defun function1A ()
  (print "function 1A"))

(defun function2A ()
  (print "function 2A"))

(defun function3A ()
  (print "function 3A"))

(defun function1B ()
  (print "function 1B"))

(defun function2B ()
  (print "function 2B"))

(defun function3B ()
  (print "function 3B"))




(defun menuselect (themenu theitem)
  (selectq themenu
     (10 (selectq theitem
           (1 (function1B))
           (2 (function2B))
           (3 (function3B))))
     (11 (selectq theitem 
           (1 (function1A))
           (2 (function2A))
           (3 (function3A))))))

(setq ªmenuhook menuselect)

(setq mymenu (newmenu 10 "menu B")
      grmenu (newmenu 11 "menu A"))

(appendmenu grmenu 
«function1A;function2A;function3A»)
(appendmenu mymenu
 "function1B;function2B;function3B")


(insertmenu grmenu 0)       ;0=the beforeID #
(insertmenu mymenu 0)

(drawmenubar)

Note that in the INSERTMENU lists I used "0" as the before ID number. The number zero indicates that I want to place the menu to the right of any already existing menus.

One may call any of the six defined functions by selecting a menu item rather then by typing the function name into the Listener Window. We can see now that an application in ExperLisp can consist of a large number of functions which do not necessarily call each other. A function, when called, can provide some service on data or graphics as a stand alone utility. The operator can then change the data or graphics by calling up another function from the menu.

Another menu example follows:

(Defun number (x)
   (cond ((= 1 x) '(the number is one))
          ((= 2 x) '(the number is two))
          ((= 3 x) '(the number is three))
          ((= 4 x) '(the number is four))
          ((= 5 x) '(the number is five))
          ((= 6 x) '(the number is six))
          ((= 7 x) '(the number is seven))
          ((= 8 x) '(the number is eight))
          ((= 9 x) '(the number is nine))
          ((= 10 x) '(the number is ten))))
          
(defun order (themenu theitem)
  (if (not (eq nil std_graf)) (std_graf 'selectwindow))
  (selectq themenu
     (10 (selectq theitem 
           (1 (number 1))
           (2 (number 2))
           (3 (number 3))
           (4 (number 4))
           (5 (number 5))
           (6 (number 6))
           (7 (number 7))
           (8 (number 8))
           (9 (number 9))
           (10 (number 10))))))
     
(setq ªmenuhook order)

(setq mymenu (newmenu 10 "numbers"))

(appendmenu mymenu «one; two; three; four;
              four; five; six; seven; eight; nine; ten»)

(insertmenu mymenu 0)

(drawmenubar)

Deleting A Menu

Deleting a menu is easily accomplished by using the built in DELETEMENU and DISPOSEMENU functions. DELETEMENU actually deletes the menu from the menu bar. DISPOSEMENU releases the memory used by the just deleted menu. One should then redraw the menu bar with DRAWMENUBAR.

(deletemenu 10)
(disposemenu mymenu)
(drawmenubar)

Tic-Tac-Toe

While the following has very little that has not been discussed in previous Lisp Listener installments, there is a lot which is in different form. For example the use of SETQ for multiple assignment. ExperLisp accepts the spaces between the symbols and the stuff assigned to them as dividers. However, these spaces are ignored by ExperLisp whether they consist of one space, mutiple spaces or one line. Therefore, one may make multiple assignment in a formatted manner for easier reading. See PLACES below.

In the function named "random.choice" MEMQ is used. MEMQ is similar to MEMBER. Where member tests to see if the given atom is a member of a list using EQUAL, MEMQ uses EQ. EQUAL test equality of characters regardless of whether they are upper case or lower case. EQ returns "t" only if the two items are virtually identical. MEMQ returns the same as MEMBER (that is, when the tested atom is contained in the tested list it is returned along with all the atoms which followed it in the list tested for the membership).

PUSH (used in defined function "Player2") is similar to APPEND. It does a CONS of the item following into a list.

Figure 1 is the functional breakdown of the Tic-Tac-Toe game. TOE calls WINNER? and PLAYERS which return values. TOE also calls DRAWBOARD which does what it's title suggests. Both WINNER? and PLAYERS refer to subfunctions which use subsubfunctions. WINNER? calculates whether or not the game was either won or was a draw by looking at the number of moves made. If WINNER? returns nil then there is no winner yet and PLAYERS is called. PLAYERS checks to the current player's turn and calls either PLAYER1 or PLAYER2 based on which turn it is. PLAYER1 is the computer's moves. It uses NEXT.MOVE, WINNIN.MOVE and RANDOM.CHOICE to generate the move. Player2 uses POSITION and PT.IN.RECT to allow the human player to enter a move using the mouse. To start the game enter "(TOE)" into the Listener Window.

;**************************
;Tic-Tac-Toe wrtten by Dean Ritz
;PLACES is a list of pairs.  The first element of each  
;list of pairs represents the position (1-9).  The last 
;second element in each list of pairs is a boundary
;list for the piece which fits into that position.
;TURN remembers whose turn it is (player 1 or 2).
;WINS is a list of the 8 possible winning sets.  The
;program checks possible moves against this list.
;*********************************
(defun toe ()
  (setq 
    p1 nil 
    p2 nil ;Set the chosen positions to empty lists.
    places '((1 (-85 -85 -35 -35)) (2 (-85 -25 -35 25)) 
             (3 (-85 35 -35 85)) (4 (-25 -85 25 -35 )) 
             (5 (-25 -25 25 25)) (6 (-25 35 25 85)) 
             (7 (35 -85 85 -35)) (8 (35 -25 85 25)) 
             (9 (35 35 85 85)))
    wins '((1 2 3) (4 5 6) (7 8 9) (1 4 7) (2 5 8) 
           (3 6 9) (1 5 9) (3 5 7))
    turn 1
    std_graf (newgrafwindow '(45 5 320 500)))
  (send std_graf 'setwtitle "Tic Tac Toe")
  (send std_graf 'showwindow)
  (send std_graf 'selectwindow)
  (textface 0)
  (drawboard)
  (while (not (winner?)) (players))
  (cond ((check wins p2)
         (fillrect '(-110 -201 10 -100) white)
         (moveto -200 0)
         (drawstring "You win!!"))
        ((check wins p1)
         (fillrect '(-110 -201 10 -100) white)
         (moveto -200 0) 
         (drawstring "The Macintosh wins!!"))
        (t
          (fillrect '(-110 -201 10 -100) white)
          (moveto -200 0) 
          (drawstring "Cat's game.")))
  (dotimes (i 1800) (add1 3))
  (std_graf 'closewindow)
  (setq std_graf nil))

;**************************************
(defun drawboard ()
 (pendown)
 (penpat gray)
 (framerect '(-90 -90 90 90))
 (framerect '(-90 -32 90 32))
 (framerect '(-32 -90 32 90))
 (penpat black))

;**************************************
;WINNER? uses brute force to see if their is a
; winner.  If turn is 1, then it checks
; to see if player 2 won the game
; with the last move.



(defun winner? ()
  (cond ((< 8 (+ (length p1) (length p2))) t)
        ((and (= turn 1)
              (check wins p2)) 2)
        (t 
          (and (check wins p1) 1))))

;**************************************
(defun check (for against)
  (cond ((null for) nil)
        ((members (car for) against) t)
        (t (check (cdr for) against))))

;**************************************
;MEMBERS works recursively to see if all of the
;elements of the list :L1
;are members of the list :L2.

(defun members (l1 l2)
  (cond ((null l1) t)
        ((memq (car l1) l2)
         (members (cdr l1) l2))))

;**************************************
;This toggles the variables which determines whose
; turn it is.

(defun players ()
  (cond ((= turn 1)
         (player1) 
         (setq turn 2))
        (t 
          (player2) 
          (setq turn 1))))

;**************************************
;This runs the computer player's move.

(defun player1 (&aux choice)
  (fillrect '(-110 -201 10 -100) white)
  (moveto -200 0) (drawstring "Macintosh")
  (setq choice (next.move)
        p1 (cons choice p1))
  (filloval (car (last (assq choice places))) ltgray))

;**************************************
;this is the psuedo brains of the whole thing.  The
; goal is first to select a move that wins, then
; select a move that blocks,
;otherwise just select any untaken shot.

(defun next.move ()
  (prog (tempo)
        (setq tempo (winning.move 1 p1))
        (if tempo (return tempo))
        (setq tempo (winning.move 1 p2))
        (if tempo (return tempo))
        (random.choice)))

;**************************************
(defun winning.move (count p)
  (prog ()
        begin
        (cond ((or (memq count p1) (memq count p2))
               (setq count (iadd count 1)) 
               (go begin))
              ((> count 9) (return nil))
              ((check wins (cons count p)) (return count))
              (t (winning.move (iadd 1 count) p)))))

;**************************************
;This returns a randomly chosen position that has not
;already been chosen.

(defun random.choice ()
  (prog (temp)
        loop
        (setq temp (iadd 1 (random 9)))
        (if (or (memq temp p1) (memq temp p2))
            (go loop)  ;If that position is chosen, get another.
            temp)))  ;Otherwise output the position.

;**************************************
;This manages the human player's move.

(defun player2 ()
  (prog (choice)
        (fillrect '(-110 -201 10 -100) white)
        (moveto -200 0) 
        (drawstring "You")
        loop
        (setq choice (position))
        (if (or (memq choice p1) (memq choice p2))
            (go loop))
        (push choice p2)
        (filloval (car (last (assq choice places))) gray)))

;**************************************
;This gets a position from the mouse.

(defun position ()
  (prog (pt count)
        begin
        (if (not (button)) (go begin))
        (setq pt (getmouse))
        (if (not (pt.in.rect 
                   (car pt) (car (last pt)) 
                   '(-85 -85 85 85)))
            (go begin))
        
        (setq count 1)  ;incremented for a position number
        pointer
        (if (pt.in.rect (car pt) 
                        (car (last pt))
                        (car (last (nth (isub count 1) places))))
            (return count)
            (progn 
              (setq count (iadd count 1))
              (go pointer)))))

;**************************************
;PT.IN.RECT tests to see whether a
;specific X and Y coordiate lies within 
;a given boundary rectangle :RECT.
;RECT should be a list of [TOP LEFT BOTTOM
; RIGHT] coordinates.

(defun pt.in.rect (x y rect)
  (and (< x (nth 3 rect))
       (  x (nth 1 rect))
       (¾ y (nth 2 rect))
       (  y (nth 0 rect))
       t))  ;returns T if true, NIL otherwise

Next month will include an indepth description of MacScheme, the first installment of an ExperOps5 tutorial and a couple more Lisp functions.