13.13. Relations involving values

Although most of the examples in this chapter have involved objects, relations can connect almost any values together. We can create relations in groups, one to various relations, various to one relations, one to one relations, and various to various relations for any combination of kinds. For example:

to find out what "caviar" belongs with. It's still harder to find out if it belongs with anything at all -- in theory we would have to try every possibility, which of course is impossible. Instead we have these phrases:

Of course, there might be many answers to this question, so perhaps these are neater:

Finally, it's sometimes useful to get at the list of all values which can appear on the left or right hand side of a relation. We need tongue-twister like wording to do it, but:

For efficiency reasons, there are no guarantees about what order these lists have - but they can of course always be sorted when found.

238

ExampleMeet Market
A case in which relations give characters multiple values of the same kind.

We have already seen that we can give things value properties -- a lamp has a brightness, for instance. Relations give us additional flexibility: since we may relate various things to various values, it is possible to describe a thing as having more than one value at the same time.

To demonstrate:

"Meet Market" by "K M and Eric Rossing"

Feature is a kind of value. The features are snub-nosed, gangly, comely, bright-eyed, and sulky.

Appearance relates various persons to various features. The verb to appear means the appearance relation.

Meet Market is a room.

Bob, Carol, Ted, and Alice are people in the Meet Market.

Bob appears snub-nosed and gangly.

Ted appears sulky and snub-nosed.

Carol appears comely and bright-eyed.

Alice appears bright-eyed and comely.

Yourself appears sulky and gangly.

Instead of looking:
    say "The snub-nosed ones: [list of people who appear snub-nosed][line break]";
    say "The gangly ones: [list of people who appear gangly][line break]";
    say "The comely ones: [list of people who appear comely][line break]";
    say "The bright-eyed ones: [list of people who appear bright-eyed][line break]";
    say "The sulky ones: [list of people who appear sulky][paragraph break]".

Test me with "look".

The same logic might be used to provide characters who have complex mood states: a person might be angry and sad, not merely one or the other -- feelings being what they are.

239

ExampleFor Demonstration Purposes
A character who learns new actions by watching the player performing them.

Suppose we want to have a character who can dynamically learn new actions by observing the player performing them. We could do this by adding the actions to a list of things the character can do, but using a relation to express the same idea allows for tidier, easier-to-read code.

Thanks to Jesse McGrew for the initial design of this example.

"For Demonstration Purposes"

Section 1 - Procedure

Capability relates various people to various stored actions. The verb to be capable of means the capability relation.

Persuasion rule:
    let CA be the current action with no specific actor;
    if the person asked is capable of CA:
        persuasion succeeds;
    otherwise:
        say "[The person asked] look[s] confused. Maybe a demonstration would help.";
        persuasion fails.

The action requester is an object that varies. The action requester variable translates into I6 as "act_requester".

To decide which action is the current action with no specific actor:
    let old actor be the person asked;
    let old requester be the action requester;
    now the person asked is the player;
    now the action requester is nothing;
    let CA be the current action;
    now the person asked is the old actor;
    now the action requester is the old requester;
    decide on CA.

The learning by observation rule is listed after the report stage rule in the specific action-processing rules.

Definition: a person is other if he is not the player.

This is the learning by observation rule:
    repeat with the viewer running through other people who can see the player:
        if the player is the actor and viewer is not capable of the current action:
            say "[The viewer] watches your behavior with interest. Seems like [they] [are] learning.";
            now the viewer is capable of the current action.

Section 2 - Scenario

The Daily Planet is a room. Clark is here. He is a man.

When play begins:
now Clark is capable of taking inventory.

Test me with "Clark, inventory / Clark, x me / x me / Clark, x me".

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