this post was submitted on 15 Sep 2024
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Programming
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Why restrict to 54-bit signed integers? Is there some common language I'm not thinking of that has this as its limit?
Edit: Found it myself, it's the range where you can store an integer in a double precision float without error. I suppose that makes sense for maximum compatibility, but feels gross if we're already identifying value types. I don't come from a web-dev/js background, though, so maybe it makes more sense there.
Because
numberis a double, and IEEE754 specifies the mantissa of double-precision numbers as 53bits+sign.Meaning, it's the highest integer precision that a double-precision object can express.
It's not about compatibility. It's because JSON only has a
numbertype which covers both floating point and integers, andnumberis implemented as a double-precision value. If you have to express integers with a double-precision type, when you go beyond 53bits you will start to experience loss of precision, which goes completely against the notion of an integer.I didn't think you realize just how much code is written in JavaScript these days.