13.8. The built-in verbs and their meanings

| Chapter 13: Relations |

| 13.8. The built-in verbs and their meanings

It is all very well to define new relations, but this does nothing if there is no way to assert that they are true, or to ask whether they are true or false. That requires a verb: in fact, a relation is nothing more than what Inform uses as the "meaning" of a verb. The assertion verbs built in to Inform have the following built-in relations as their meanings:

> Verb - Relation
> to be - equality relation
> to have - possession relation
> to contain - containment relation
> to support - support relation
> to carry - carrying relation
> to wear - wearing relation
> to incorporate - incorporation relation

Two of Inform's built-in relations are expressed using prepositions instead:

> Preposition - Relation
> to be part of - (reversed) incorporation relation
> to be adjacent to - adjacency relation

It would be easy to make verbs for these if we wanted ("to adjoin", say) using the techniques of the next section.

The verb to be is grammatically different from any other, and its meaning is too complicated to be fully expressed by any one relation. A great deal of the Inform program is given over to its "meaning", which we are not allowed to change or imitate. The "equality relation" is simple enough, and is the one implied by conditions like

> if the score is 20, ...

but to be can have more complicated implications - "if Mr Wickham is hungry" clearly doesn't test whether two quantities are equal. Fortunately the other verbs are much simpler.

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