| Chapter 13: Relations |

| 13.4. To carry, to wear, to have

Inform has altogether five mutually exclusive ways in which one thing can be physically joined to another one:

> containment relation - The coin is in the purse.
> support relation - The coin is on the table.
> incorporation relation - The coin is part of the sculpture.
> carrying relation - The coin is carried by Peter.
> wearing relation - The jacket is worn by Peter.

This is why we cannot have

> The coin is on the table.
> The coin is part of the table.

simultaneously, and it is a rare exception to the general rule that having one relation does not affect having another.

But there is also a sixth relation used in Inform for these meanings: the possession relation, which is the meaning of the verb "to have". At first sight this looks the same as the carrying relation, but in fact it is a convenient shorthand for "carrying or wearing", provided for conditions rather than assertions:

> if Mr Darcy has a wet shirt ...

will be true during play if he is either carrying or wearing the shirt.

Still another relation exists which can be tested, but not declared to be true or false: the concealment relation, which is the meaning of the verb "to conceal". So we can ask:

> if Mr Darcy conceals a fob watch ...

180
| Example Interrogation A wand which, when waved, reveals the concealed items carried by people the player can see.

Previous | Contents | Next