Propagate `Double64` through `sign` function

[DanielDoehring]

julia> typeof(sign(Double64(42)))
Float64

In my opinion, the sign function should return an integer, but as the standard/Base Julia version seems to return a Float, I would like to see this propagating through.

[JeffreySarnoff]

you want sign(Double64(_)) to return a Double64?

[DanielDoehring]

Yes, to match the expected behaviour as documented for floating point datatypes 👍