Suppose we want to add rules so that any time we examine a charred object (and most of our objects can be charred), a line about the charring is appended to the end of the object description. We could use "after examining…", but perhaps we would prefer for the sentence about the charring not to appear in its own paragraph.
This is an ideal occasion for a new activity. We look at the action index for "examining" to identify the rule that causes the old behavior (in this case, the "standard examining rule"); replace this with a new rule that calls our activity; and write our "printing the description" activity in such a way that it uses an object's description without forcing a paragraph return afterward.
Then we will use "after printing the description" to add our line about charring, and make sure that the paragraph return does occur before the prompt.
This instruction replaces a normal piece of the examine action, the standard examining rule, with another one of our own devising. (The replacement of the standard examining rule will be explained in more detail in the chapter on rulebooks.)
All we have done here is enclose what is usually just a rule inside an activity. This means that we can now write before and after rules for the activity, and also add special instructions like "Rule for printing the name of something while printing the description of something" -- this may not be likely to arise often, but Inform now has the concept of "printing the description of something" as a separate context of action. Next we add the modification that lets us append to the description without a new line:
"run paragraph on" here will mean that we do not get a paragraph break following the description, even if it ends with a period. We also insert a space, so that our follow-on comments will be properly punctuated.
The instead at the end of this line stops Inform for going on with any other "after printing the description of…" rules.
The standard library also has rules for printing additional text about containers and supporters with visible contents, and devices that are switched on; with this current system, we could add those as "after printing the description" rules as well, building up a complete paragraph if we wanted. But for simplicity we won't exemplify all of that here. The effects would be much the same as with the "charred" line.
Now, because we want to make sure that we always do get a paragraph break after our description, we add this rule last after all the other rules. "Last" and "first" rules are covered in more detail in the chapter on rulebooks.
The player's description is handled in an unusual way, and this will produce a space paragraph break there where it should not. Instead, therefore, we will add an instead for examining the player (probably a good idea anyway):
Test me with "i / x stick / x bottle / x sand / x paper / x me / burn stick / x stick / burn paper / x paper".
A pale expanse of sand, here and there developing into hillocks of grass, and a small clump of palms. The water is shallow here, and there are other islands within swimming distance -- or even wading distance, perhaps -- but none of them is any larger than your island, so it doesn't seem worth the trouble of visiting.
A few hundred feet out, the water turns darker blue, the sea floor drops away, and there is nothing to be seen all the way down to the horizon, except a couple of fluffy clouds, and an occasional bird.
The remains of your fire smolder in the stone-lined pit.
You are carrying:
a glass bottle (open)
a grain of sand
a piece of paper
> x stick
A strip of palm from the woodiest part of the leaf, about a foot and a half long.
> x bottle
You see nothing special about the glass bottle.
> x sand
You see nothing special about the grain of sand.
> x paper
A single blank sheet.
> x me
You are sunburned and there is sand in cracks you didn't know existed.
> burn stick
You hold the stick to the fire until it flares and chars.
> x stick
A strip of palm from the woodiest part of the leaf, about a foot and a half long. It is charred.
> burn paper
You hold the piece of paper to the fire until it flares and chars.
> x paper
A single blank sheet. It is charred.
The "printing a description" activity may be useful for other games, and can be imported just by lifting section 1.