The Facts Were These

Occasionally it happens that we want to process an action on multiple items differently than we would if the player had just typed each of the individual actions separately. In this example, the reason is that we can only successfully GIVE items when their combined value passes a certain threshold amount; otherwise the recipient will reject them.

This works as an implementation of money, if we give value only to cash objects (though several other implementations of cash are available, most of which are simpler and more efficient). We could also imagine a mechanic like this being used for a bargaining or auction game as well, given a society that deals in objects rather than credits.

In order to consider all the items in the gift at once, we create an action that applies to multiple objects, but will in fact test the whole object collection during the first pass and print a definitive answer to whether the action succeeded. All subsequent times the game consults the rulebook will be stopped at the very beginning. No further processing will occur or output be printed.

We start by creating the idea that everything in the game has a monetary value:

A subtlety here: we say "things preferably held" to prefer items that the player is holding (so if the player has two dollars in hand and a third lies on the ground, he will use just the two he has).

The second grammar line allows Inform to match things that aren't held if it can't make up the list from things that are. If all three dollars are on the ground, the player can pick them up before spending them.

We do not, however, make multiply-giving apply to a "carried" item, because that will generate implicit takes of those items in a way that will mess up our action reporting. Instead, we're going to build the implicit takes into the system in a different way, one that permits us to collate the reports more attractively and print a short, one-sentence list of anything that the player had to pick up.

This is for record-keeping purposes so that we can print an attractive list of what was given at the end of the turn.

"Already gave at the office" is the perhaps-excessively-named flag that keeps track of whether we've already done this action once.

The following rule is longish because it processes the entire list at once, generating implicit takes if necessary (but processing those implicit takes silently according to its own special rule, so that the output can be managed attractively). We are also, at the same time, calculating the total value of the player's offer.

The bit about making some items "marked for listing", above, rather than printing the list directly, is that using the "[the list of….]" syntax guarantees that Inform will respect grouping rules in writing its description. For instance, if the player has automatically taken all three dollars, the output will say "the three dollars" instead of "the dollar, the dollar, and the dollar."

Now we create our own variation of implicitly taking in order to customize the output for the multiply-giving action. The "ungivability rules" should disallow any object that the player absolutely cannot take, because we want "carry out the implicitly taking activity" to succeed every time -- and therefore not print out any less-attractive results from implicit takes that don't succeed. Otherwise, the player's GIVE TREE AND DOG TO ATTENDANT might produce the reply "That's fixed in place" -- without specifying which object is fixed in place.

Because of the way this works, we will want to be careful: if we have any "instead of taking…" rules for special objects in the game, we should be sure to mirror those with an ungivability rule to print something more suitable in the case that the player tries taking that object as part of the multiple giving action.

And since we don't want to list the individual objects separately:

And now, since this ought to work symmetrically if the player provides just one high-value item:

As we've seen elsewhere, the giving action by default returns a refusal, but is also written to start working if we remove the blockage. So we do that here, and revise the report rule to match the report rule we have for multiple giving.

After each instance of the multiply-giving action, we need to clear the variables we used to track its state. We could do this in "Before reading a command", but that's unsafe because the player might type GIVE PIE AND CAP TO ATTENDANT. GIVE DOLLARS TO ATTENDANT. all on a single line, and we would like to be able to clear the variables between one action and the next. The correct place to attach this behavior is immediately before the generate action rule, thus:

PURLOIN, used in the tests here, is a special debugging command that allows the player to acquire objects that wouldn't otherwise be possible to take. It is only active in non-release versions of the story. For more about debugging commands, see the chapter on Testing and Debugging.