Answer to Exercise 4

| ANSWER TO EXERCISE 4
| Put any validation rules desired into the `GamePreRoutine`. For example, the following will filter out any stray `Drop` actions for unheld objects:
    [ GamePreRoutine;
      if (action==Drop && noun notin player)
          "You aren't holding ", (the) noun, ".";
      rfalse;
    ];

Back to the exercise in section 9

Mechanically translated to HTML from third edition as revised 16 May 1997. Copyright © Graham Nelson 1993, 1994, 1995, 1996, 1997: all rights reserved.