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Start of Chapter 18: Activities |
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Back to §18.2. How activities work |
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Onward to §18.4. While clauses |
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§18.3. Rules applied to activities
The activity "printing the name of something" is the process of printing up the name of something on screen: ordinarily, this means saying the text in its "printed name" property.
As with actions, rules can be attached to activities which change or augment what would normally happen. In fact the situation is simpler, because (unlike an action) an activity almost always finishes, so we almost always do reach its "after" stage. There are also only three rulebooks attached to an activity, as compared with the six affecting an action.
The three rulebooks for printing the name are called "before printing the name", "for printing the name" and "after printing the name", and this is the general pattern. What happens is:
1. All "before printing the name of" rules are considered;
2. The most specific, applicable "rule for printing the name of" is considered;
3. All "after printing the name of" rules are considered.
Whereas an action's later stages never take place if an early stage ends unexpectedly, an activity always goes through all three of its stages. Invoking the word "instead" in a before rule for an action will terminate not only the before rules but the whole action: the same thing for an activity will only terminate the before rules, and the for and after rules will take place as usual.
The actual task is usually carried out by one single rule tucked into the back of the "for..." rulebook: it is the rule for printing the name of whatever is concerned, hence the name. Inform's standard activities are all of this pattern: they start out with no "before" or "after" rules, and just one "for" rule.
Why the part about an activity only "almost always" finishing? One reason is that the story might end during it; but another is that it's possible, though uncommon, to abandon an activity partway. Very few of the activities supplied with Inform ever do this, and those that do are noted in the sections which follow.