Incorrect argument checks in FastDct.ts about nayuki-web-published-code HOT 5 CLOSED

Wow, what was I thinking?! Thanks for pointing this out. Now I realize that I wrote && instead of ||.

I still need to exclude length 0 because it's not a power of 2 and the Lee Fast DCT doesn't handle that case. As for checking n <= 0 instead of n == 0, it's to be extra defensive in languages like C# that have signed integer types.

I made the fixes now, to all affected languages: 3bf2d8f

from nayuki-web-published-code.

I just want to double-check, does the new logic look correct to you now?

from nayuki-web-published-code.

Yes, I think the new logic looks correct. On another note, what mandates the power of 2 length? There doesn't seem to be anything in the math that needs a power of 2 length. I'm guessing it has something to do with particular cases which can be precomputed/shortcuts can be made if the length is a power of 2?

from nayuki-web-published-code.

The Lee fast DCT does some work on the input array, then divides it in half, recurses on each half, and recombines them. If the original length is a power of 2, then we can recurse all the way down to a base case of length 1, instead of some other odd length.

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Right, interesting. Anyway, I believe this issue is fixed now. Thanks :)

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