Signed bitwise shift

[esen]

Signed bitwise shift doesn't work.

Example:

Int(65764) >> 16   // gives 1
Int(-65764) >> 16   // gives -2

BigInt(65764) >> 16   // gives -1
BigInt(-65764) >> 16   // gives -1, must be -2

[tgymnich]

Thanks for brining this up. Our Signed Big Integer implementation uses a sign bit and an unsigned magnitude. When we perform a right shift on a BigInt we basically just shift the magnitude right.

In contrast, right shifting Int is a right shift on the Two's complement representation of that integer, where the top most bits are filled with ones.

The behavior of a right shift of negative integers is in theory implementation dependent. Though I think it could be beneficial for the BigInt implementation to behave like the Swift Int implementation (and the majority of other implementations e.g. python, ...).