Tic-Tac-Toe

Tic-Tac-Toe

A behavioral program for the game of Tic-Tac-Toe

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Game Description

Two players, X and O, alternately mark squares on a 3X3 grid whose squares are identified by <row,column> pairs: <0,0>, <0,1>, ...,<2,2>. The winner is the player who manages to form a full horizontal, vertical or diagonal line with three of his/her marks. If the entire grid becomes marked but no player has formed a line, the result is a draw.

In our example, player X should be played by a human user, and player O is played by the application. Each move (marking of a square by a player) is represented by an event, X_<row,col> or O_<row,col>. Three additional events, XWin, OWin, and draw$, represent the respective victories and a draw.

A play of the game may be described as a sequence of events. E.g., the sequence

X_<0,0>, O_<1,1>, X_<2,1>, O_<0,2>, X_<2,0>, O_<1,0>, X_<2,2>, XWin describes a play in which X wins, and whose final configuration is:28.

Figure 1: An LSC describing the basic move of a memory game. Note the red and blue elements in the diagram, indicating hot and cold LSC messages and conditions.

b-Threads

Rules of the game

• SquareTaken: block further marking of a square already marked by X or O.
• EnforceTurns: alternately block O moves while waiting for X moves, and vice versa (we assume that X always plays first).
• DetectXWin: wait for placement of three X marks in a line and request XWin.
• DetectOWin: wait for placement of three O marks in a line and request OWin.
• DetectDraw: wait for nine moves and request draw event.