Chapter 9: Time
9.11. Future events

We often want to arrange for something to happen at some point in the future. Here is yet another timepiece:

An egg-timer is in the Chamber. "A plastic egg timer in the shape of a chicken can be pressed to set it going." Instead of pushing the egg-timer: say "It begins to mark time."; the egg-timer clucks in four turns from now.

At the time when the egg-timer clucks: say "Cluck! Cluck! Cluck! says the egg-timer."

The event here is called "the egg-timer clucks". It only happens if we instruct so, which we do by writing

the egg-timer clucks in four turns from now

meaning four turns after the turn in which the egg-timer is pushed. We could alternatively describe this future moment as something like "in 18 minutes from now", or "at 4:15 PM".

If we know in advance what time we want something to happen, we can more simply write:

At 4 PM: say "The great bells of the clock tower chime four."

(Note that in either case such rules begin with the word "at": they are the only rules allowed to begin with the word "at".)


111
 Example  MRE
Hunger that eventually kills the player, and foodstuffs that can delay the inevitable by different amounts of time.

112
 Example  Empire
A train which follows a schedule, stopping at a number of different locations.

113
 Example  Scheduling an eclipse
To schedule an eclipse of the sun, which involves a number of related events.

First we define the events, and then we create a phrase to schedule them:

When the penumbra appears:
    say "The sunlight dies away to an eerie, brownish penumbra."
When the eclipse begins:
    say "The moon passes across the disc of the sun, plunging the world into darkness.";
    now the Chamber is dark.
When the eclipse ends:
    say "The moon passes away from the sun, and a gloomy penumbral light returns.";
    now the Chamber is lighted.
When normal sunlight returns:
    say "The sun shines once more bright in the sky, not to be eclipsed again on this spot for another thirty-seven years."

To schedule an eclipse for (totality - a time):
    the penumbra appears at two minutes before totality;
    the eclipse begins at totality;
    the eclipse ends at three minutes after totality;
    normal sunlight returns at five minutes after totality.

Now we make use of the new phrase:

When play begins, schedule an eclipse for 3:27 PM.

We shall see much more about creating phrases later. Their advantage is that they enable a complicated sequence of operations to be given a meaningful name, and that they can be re-used many times as needed.


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