DF-21 Forums

[sheepandshepherd]

I remember reading somewhere that the INF function Message: prev_stop does not send an elevator to the previous stop number, but to the last stop it was at. Usually, this wouldn't matter, because an elevator normally goes only in one direction . . . even when using the Goto_stop message, the elevator will still pass over the stops in between the starting point and destination stop. Does anyone know how exactly this works?

I'm assuming that the Prev_stop message will have the same function in DarkXL as in DF. The difference may be small, but in rare cases it could affect how an elevator functions correctly.

[lucius]

None of the current levels use "prev_stop" yet, so I haven't tested it yet. I think, right now, its treated as the reverse to "next_stop" - meaning it would just go to the previous stop in the list.

The "Dark Forces SPECS" says the following: "Sends an elevator to its previous stop." which may be ambiguous. Where did you read that it goes to the last stop it was at instead of the previous stop in the list?

If I test it and you're correct then I'll gladly change it - I want it to be correct after all. I am curious where it was documented more clearly - if you are correct - it might help.

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[sheepandshepherd]

Mmmmm, I'm really not sure . . . at first I thought it was in the INF tutorial by Jereth Kok, but I just went over that one while working on some INF in my level, and that's not it . . . it could have possibly been one of the INF tricks showcase levels.
Just to clarify . . . whoever wrote that was also confused about the exact purpose. I think the best way to figure it out is to create a small test level and run it in original DF to see what happens.

[The MAZZTer]

I think the issue was that prev_stop does not work as expected; while you would rightly expect it to do the opposite of next_stop, it only moves the elevator to the last stop it was at. Let me illustrate the difference in an example.

Our example elevator has stops we'll call 1 2 and 3. It starts at 1.

We send two next_stops followed by two prev_stops.

We expect the elevator to travel to 2, and then 3, and then 2, and then 1.

However, instead it travels to 2, and 3, and then 2, and then 3 again!

Let's analyze the logic starting at stop 3 with the first prev_stop. prev_stop has us move to the last stop the elevator was at.... before moving to 3 we were at 2. So we go back to 2. The next prev_stop has us move to the last stop... we were last at 3! So we move back to 3.

At least, I THINK that was the problem. I haven't actually tried it lately (I probably have avoided using the message altogether for just that reason).

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[lucius]

Well, fortunately, that is really easy to code so if that's the way its supposed to work then so be it... Again I'll test it at some point to be sure. Thanks for all the input.

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[Fenwar]

I think I ran into some ambiguity with it appearing to have had both effects, depending on the circumstances, and removed it from my INF altogether for the same reason as Mega. Mind you the INF execution can get a bit buggy when a large number of messages are flying about (as in Operation Zero X) and I did encounter the phenomenon of "dropped" messages (presumably there's a message stack somewhere which has a fixed size, or something) so it might not be ambiguous, just counter-intuitive.

[sheepandshepherd]

Ugh, great . . . you know, this particular message would be a lot more useful if it always moved the elevator to the previous stop number (as in, from 3 to 2, etc) . . . but it could mess up existing levels if the author did count on it working the way Mega explained it. What do you think, lucius? Maybe, leave PREV_STOP the way it was in DF, but add a new extended mode message that works the more useful way. Just a suggestion, in case anyone else thinks it would be useful.

[The MAZZTer]

REAL_PREV_STOP

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[klasodeth]

Or maybe just DEC_STOP (decrement stop).

[lucius]