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§6.11. A word about in
What does "in" mean? It's worth just a brief diversion to cover this, because "in" has two subtly different meanings.
Meaning 1. Usually, if X is "in" Y then this is because of containment. A croquet ball is "in" a croquet box, which is "in" the Summerhouse. This is the standard meaning, and is the one which happens if we write something like:
or if we ask a question like:
This kind of "in" talks only about direct containment. If we ask
then the answer is that it isn't - it is in the box which is itself in the Summerhouse, but that's not the same thing.
This is almost always the meaning of "in" that we intend. This is only one of a number of relationships between objects - there are also "part of", "on", "worn by" and "carried by", for example. If we have
...then "if the bird feed is in the sundial" won't be true: the relationship here is one called support (being on top of, in effect), not containment. But there's no confusion because "on" and "in" are different words, so it's no problem that they have different meanings.
Meaning 2. Much less common. If X is "in" Y and Y is a region, then the meaning is slightly different. Suppose the Garden Area is a region, and contains several rooms - the Croquet Lawn, the Terrace and so on. Then
if the croquet box is in the Garden Area, ...
if the bird feed is in the Garden Area, ...
if the Terrace is in the Garden Area, ...
are all true. This seems very natural, but in fact is quite different from the first meaning of "in". It allows rooms (and even other regions) to be "in" a region, and it allows indirect containment.
How Inform decides. So which meaning does Inform use, and when? Since these two meanings are so different, it clearly matters.
The answer is that meaning 1 is always the meaning of "X is in Y" unless Y is explicitly the name of a region. Thus:
is meaning 2, because "Garden Area" is the name of a region. That seems fair enough, but values are indeed sometimes given names (becoming "variables", or values "that vary"). Suppose "mystery value" is a name for a value which is an object, but which has different identities at different times. Then Inform reads
as meaning 1, because whatever "mystery value" is, it isn't explicitly a region name, even if from time to time it might happen to be equal to a region.
That sometimes makes meaning 2 difficult to express. If we ever need it, and this is fairly rare, we can write it like so:
because "regionally in" is always meaning 2 of "in".