### Author Topic: Did you know that FRED can't count to 100?  (Read 381 times)

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#### General Battuta

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##### Did you know that FRED can't count to 100?
(This only applies to certain percentage-based values)

Set a ship's weapon ETS to 0 (lock it so the AI can't put power back in weapons). Set its weapon energy to 0.

Add 1 to the ship's weapon energy percent every second.

You'll never hit 100!

#### Mobius

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##### Re: Did you know that FRED can't count to 100?
Did you know that the 100th argument in a SEXP will be marked as "0"?
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#### TopAce

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##### Re: Did you know that FRED can't count to 100?
Is this similar to the Y2K problem in its foundation?
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##### Re: Did you know that FRED can't count to 100?
Is this similar to the Y2K problem in its foundation?
Not quite. It's a floating-point rounding error; certain numbers that are nice, round numbers in decimal (like 0.52, since Battuta ran into this problem at 52%) aren't nice, round numbers in binary. Since the SEXP code turns that floating-point number into an integer through truncation, 52% winds up rounding into 51, so when 1 is added it just brings it back up to 52... where it started. Technically, we could fix this (by using a higher precision floating-point format and/or rounding instead of truncating), but it's honestly a very low-priority problem (since you can work around it by just using an increment larger than 1).
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schrĂ¶dinbug (noun) - a bug that manifests itself in running software after a programmer notices that the code should never have worked in the first place.

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"I am one of the best FREDders on Earth" -General Battuta

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<MageKing17> "There's probably a reason the code is the way it is" is a very dangerous line of thought.
<MageKing17> Because the "reason" often turns out to be "nobody noticed it was wrong".
(the very next day)
<MageKing17> this ****ing code did it to me again
<MageKing17> "That doesn't really make sense to me, but I'll assume it was being done for a reason."
<MageKing17> **** ME
<MageKing17> THE REASON IS PEOPLE ARE STUPID
<MageKing17> ESPECIALLY ME

<MageKing17> God damn, I do not understand how this is breaking.
<MageKing17> Everything points to "this should work fine", and yet it's clearly not working.
<MjnMixael> 2 hours later... "God damn, how did this ever work at all?!"
(...)
<MageKing17> so
<MageKing17> more than two hours
<MageKing17> but once again we have reached the inevitable conclusion
<MageKing17> How did this code ever work in the first place!?

<@The_E> Welcome to OpenGL, where standards compliance is optional, and error reporting inconsistent

<MageKing17> It was all working perfectly until I actually tried it on an actual mission.

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<MageKing17> TIL the entire homing code is held up by shoestrings and duct tape, basically.