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the-infocom-files / zork-substrate

Substrate for the Zork Trilogy Original Editions
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Suggestion: Add PRE-THROW and similar #8

Open eriktorbjorn opened 5 years ago

eriktorbjorn commented 5 years ago

While testing Zork I, I've found a depressing number of cases where you can throw away objects that you shouldn't be able to, e.g. your hands.

The V-THROW routine handles this by calling IDROP to see if the object can be let go of, but that's only the default behavior. Any object that handles the "THROW" verb doesn't automatically get that protection.

Adding a PRE-THROW action might do the trick. It wouldn't have to be very complicated:

<ROUTINE PRE-THROW ()
     <RETURN <NOT <IDROP>>>>

I think we can assume that IDROP prints its own error message when it fails.

Of course, the same thing would probably have to be done for V-THROW-OFF and V-OVERBOARD as well. Plus any other that I may have missed.

eriktorbjorn commented 5 years ago

This type of bug can be seen in at least the following bug reports:

eriktorbjorn commented 5 years ago

On second thought, calling IDROP in PRE-THROW is probably not such a good idea after all. What if a later action routine decides that you don't want to throw the object after all? Then you'll have dropped it.

So if we want to fix this in PRE-THROW it would have to be by calling a routine that goes through the motions of dropping the object, without actually dropping it. That should be easy enough.

eriktorbjorn commented 5 years ago

Another example of a throwing bug: https://github.com/the-infocom-files/zork2/issues/18

Though in this one, the hands remain where they are.

eriktorbjorn commented 5 years ago

On the other hand, the usual fix (e.g. in CLIFF-OBJECT-F) seems to simply be to check <IN? ,PRSO, WINNER> so maybe that's what we should do as well?