| Chapter 17: Activities |

| 17.27. Printing a parser error

1. When it happens. The parser is the part of the run-time software, included in all works produced by Inform, which tries to match the player's command against the grammar provided by the work. When it is unable to make a valid match, the parser prints an error to the player: for instance,

> > BIFURCATE TREE
> That's not a verb I recognise.

There are some 18 possible messages, and we can distinguish them using the following conditions:

> if the parser error is didn't understand...
> if the parser error is only understood as far as...
> if the parser error is didn't understand that number...
> if the parser error is can't see any such thing...
> if the parser error is said too little...
> if the parser error is aren't holding that...
> if the parser error is can't use multiple objects...
> if the parser error is can only use multiple objects...
> if the parser error is not sure what it refers to...
> if the parser error is excepted something not included...
> if the parser error is can only do that to something animate...
> if the parser error is not a verb I recognise...
> if the parser error is not something you need to refer to...
> if the parser error is can't see it at the moment...
> if the parser error is didn't understand the way that finished...
> if the parser error is not enough of those available...
> if the parser error is nothing to do...
> if the parser error is I beg your pardon...

2. The default behaviour. Prints the message in question.

3. Examples. (a) Perhaps for newcomers:

> After printing a parser error:
> say "If you are new to interactive fiction, you may like to try typing HELP."

(b) Or to give the parser a certain amount of character:

> Rule for printing a parser error when parser error is I beg your pardon:
> say "What's that? Speak up, speak up." instead.

> Rule for printing a parser error:
> say "That's a rum thing to say, and no mistake." instead.

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