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0 pointsdeadowl10y ago0 comments

x >>> 0 changes a negative integer to an unsigned (positive) 32-bit integer. You can have integers greater than 32 bits. They're represented internally as floats. Bitwise operators make 32-bit assumptions, with the top bit as a sign bit, unless you do x >>> 0, in which case you can revert a sign bit overflow back to a positive integer. If you have a positive integer that's greater than 32 bits, x >>> 0 === x fails. The expression (84294967295 >>> 0 === 84294967295) is false.

Don't even get me started on negative zero.

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tripzilch10y ago

I thought all numbers in Javascript were represented as 64-bit floats. Therefore you can do correct integer math up to 53 bits without getting into too much weirdness (bigger than that and the weirdness is guaranteed).

I didn't know the >>> operator converts to 32-bit. How does it do that? Mask off the top bits? Or give you a NaN if it's bigger?

But (and someone please correct me if I'm wrong), at the end of the line it's still represented as a 64-bit float internally and accurately.

j / k navigate · click thread line to collapse

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tripzilch10y ago

I didn't know the >>> operator converts to 32-bit. How does it do that? Mask off the top bits? Or give you a NaN if it's bigger?

But (and someone please correct me if I'm wrong), at the end of the line it's still represented as a 64-bit float internally and accurately.

j / k navigate · click thread line to collapse