Double-dash problem

Authoring Inform 7
1

I’ve read in several sources, that double-dash specifies an optional word in a pattern match. Perhaps it is deprecated, or only works in certain forms, because it isn’t working for me.

[code]Understand “tune radio/tv/channel/dial”, “adjust radio/tv/channel/dial”, “change --/tv/radio station/channel/dial” as tuning;
Tuning is an action applying to nothing.

Carry out tuning:
say “The radio is tuned.”;[/code]

Here’s the results:

[code]>tune radio
The radio is tuned.

adjust tv
The radio is tuned.

change tv station
The radio is tuned.

change station
I didn’t understand that sentence.

change – station
The radio is tuned.[/code]

Am I misunderstanding something?

Wes

2

The – notation doesn’t apply to verb grammar in that way. Which is pretty much what you’ve already observed.

3

Though this works:

Understand "tune --/the dial" as tuning;

Does it just no work with more than one optional word?

4

It doesn’t work for me. TUNE DIAL gives “I didn’t understand that sentence.” (You already have another grammar rule that matches TUNE DIAL.)

Anyway it would be much better to have the tuning action apply to one thing, have just one “tune [something]” grammar rule and give all those synonyms to the radio object.

5

No doubt, but this was just an example. I’d like to understand the functionality of double-dash.