Oyster Wide Shut

As we've seen in earlier examples such as "Equipment List", it is possible to vary the way Inform creates inventory listings in general (to create lists that look more like paragraphs of prose, lists divided between what the player is wearing and what he isn't, and so on). We can also use activities to alter the printing of specific objects' names and contents, as with the "omit contents in listing" feature after printing the name of something.

We may find, however, that we would like a great deal more control over Inform's printing of inventory details, not just as a special effect for a few items, but throughout the game.

We start by turning off Inform's native property writer:

This is very much like the library's standard behavior, but with the exception that "giving inventory information" or even "giving brief inventory information" are omitted. Here's how we supplant it:

Now, our property-aggregation rulebook is going to look at a given object and decide on a list of features that should be mentioned in inventory. We'll start by producing something quite similar to Inform's default behavior:

Notice that we don't need to write any rules about how to print that list of text: because Inform is printing out a list, it will automatically insert commas, spaces, and the word "and" where appropriate; and it will automatically follow the "use serial comma" option, if we have it set.

Now we're free to meddle. Let's give the player a bunch of possessions that will be listed in interesting ways in inventory:

Now suppose that we don't want the oyster to say "closed" when it's closed. Instead, we'd like it to say "clamped shut". As this is the only property the oyster will ever have, we can simply override his whole property-aggregation rulebook:

That's fine for the oyster because "clamped shut" is the only property he'll ever have. What if we'd like instead just to revise the way the sack (and only the sack) gets described as providing light?

Now the flashlight (and any other regular light sources we might add to the game) will be described as "providing light", but the sack will only be said to be gently glowing -- a bit more appropriate for its rather fainter gleam.

We might also wish to add a systematic feature across the board to include a new property in the inventory list? Let's say the player can enchant his possessions, and enchanted possessions should thereafter be listed accordingly:

Further variations are possible as well: if we used a "before printing the name…" rather than an "after printing the name…" rule, we could automatically generate lines like "an open and empty phosphorescent plastic sack", removing some of the artificiality of the parentheses.

Or we could add more logic to the rules about which properties are mentioned, so that some features of objects were mentioned in inventory only if the player was wearing the correct detection device, like so: