0x00:0xff is empty

[johnmyleswhite]

[convert(Uint8, 0):convert(Uint8, 255)]

On my system, this produces seemingly random output.

[jiahao]

Possibly related:

julia> for i in 0x00:0xff #no output
        println(i)
       end

julia> length(0x00:0xff)
256

[johnmyleswhite]

I think I raised an issue about that exact behavior at one point in the past, but thought it had been fixed once before.

[StefanKarpinski]

I noticed this yesterday for Uint16.

[ivarne]

Isn't this a dup of #5550?

# base/ranges.jl
done{T<:Integer}(r::Range1{T}, i) = i==oftype(T, r.start+r.len)

julia> dump(convert(Uint8, 0):convert(Uint8, 255))
Range1{Uint8} 
  start: Uint8 0
  len: Int64 256

julia> oftype(Uint8, 0+256)
0x00

The iteration seems to be done before it has started because of overflow. The allocated array will not be written to and thus appear random.

[ivarne]

julia> done(a,start(convert(Uint8, 0):convert(Uint8, 255)))
true

[simonster]

#5550 looks related but not quite the same. I believe #6266 fixes this without breaking anything.

[mschauer]

Yes, #5550 not quite, because in random.jl a range is first transformed to an alternative representation where the length is saved as small unsigned integer and not as Int64 like here (this representation is a part of the type RandIntGen, see there).

[JeffBezanson]

This is also part of #5585, and is fixed on my branch jb/newrange1.