I-JSON (short for "Internet JSON") is a restricted profile of JSON designed to maximize interoperability and increase confidence that software can process it successfully with predictable results.
Because number is 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.
I suppose that makes sense for maximum compatibility, but feels gross if we’re already identifying value types.
It’s not about compatibility. It’s because JSON only has a number type which covers both floating point and integers, and number is 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.
Why restrict to 54-bit signed integers? Is there some common language I’m not thinking of that has this as its limit?
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.