| Chapter 16: Understanding |

| 16.7. Understanding any, understanding rooms

Ordinarily, if we write

> Understand "manipulate [something]".

then the "[something]" will only match what is within reach or sight: this is the concept of "scope", which is what prevents a player from spookily acting on objects from a distance. The parser itself prevents the manipulation rules from ever being invoked on such distant items, which is as it should be.

Sometimes, though, we positively want to allow this possibility. If we use the special word "any", as in

> Understand "manipulate [any door]".

then any door, anywhere in the model world, can be allowed in the player's command. (Of course, the manipulation rules may not do what the player hopes: all that has happened is that the command is now possible to type.) The "any" can be followed by any description of items or rooms, and the latter opens up new possibilities, since rooms are ordinarily never allowed to be named in the player's commands.

For example, the following gives the player the ability to walk between rooms without giving explicit directions of movement.

> Going by name is an action applying to one thing.

> Carry out going by name: say "You walk to [the noun]."; move the player to the noun.

> Understand "go to [any adjacent visited room]" as going by name.

(This is really only a sketch: in a finished work, "go to" would produce helpful errors if non-adjacent but visited rooms were named, and we might also worry about rules applying to movement, because the method above will circumvent them.)

233
| Example One of Those Mornings A FIND command that allows the player to find a lost object anywhere

234
| Example Actaeon A FOLLOW command allowing the player to pursue a person who has just left the room.

Suppose we want the player to be able to go after characters who are moving around the map. The trick, of course, is that once characters are gone they are no longer visible to "follow [person]", so we need "follow [any person]" to find them. "Actaeon" A person has a room called last location. Understand "follow [any person]" as following. Understand the commands "chase" and "pursue" as "follow". Following is an action applying to one visible thing. Check following: if the noun is the player, say "Wherever you go, there you are." instead; if the noun is visible, say "[The noun] is right here." instead; if the last location of the noun is not the location, say "It's not clear where [the noun] has gone." instead. Here again the best route comes in handy: Carry out following: let the destination be the location of the noun; if the destination is not a room, say "[The noun] isn't anywhere you can follow." instead; let aim be the best route from the location to the destination; say "(heading [aim])[line break]"; try going aim. Corinth is a room. Athens is east of Corinth. Epidaurus is southeast of Corinth and east of Mycenae. Mycenae is south of Corinth. Olympia is west of Mycenae. Argos is south of Mycenae. Thebes is northwest of Athens. Pylos is south of Olympia. Sparta is east of Pylos and south of Argos. Delphi is northwest of Thebes. Artemis is a woman in Corinth. We do also have to make sure that whenever we move a person from room to room, we record where they were moved from; otherwise, our clever restrictions about whom the player can pursue will not work properly. To move (pawn - a person) tidily to (target - a room): change the last location of the pawn to the holder of the pawn; move the pawn to the target. Every turn: let current location be the location of Artemis; let next location be a random room which is adjacent to the current location; if Artemis is visible, say "Artemis heads to [the next location]."; move Artemis tidily to next location; if Artemis is visible, say "Artemis arrives from [the current location]." Test me with "wait / follow artemis / follow artemis / follow artemis".

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