Answer to Exercise 42

| ANSWER TO EXERCISE 42
| Two reasons. Firstly, there are times when we want to be able to trap orders to other people, which `react_before` does not. Secondly, the player's `react_before` rule is not necessarily the first to react. In the case of the player's deafness, a cuckoo may have already used `react_before` to sing. But it would have been safe to use `GamePreRoutine`, if a little untidy (because a rule about the player would not be part of the player's definition, which makes for confusing source code). See Section 9 for the exact sequence of events when actions are processed.

Back to the exercise in section 19

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