Negating an unsigned effectively causes it to overflow.. it flips all bits
(rather than the sign bit... which doesnt exist)
*julia> **bits(x)*
*"0000000000000000000000000000000000000000000000000000000000000100"*
*julia> **bits(-x)*
*"1111111111111111111111111111111111111111111111111111111111111100"*
So the start of the range you create is greater than typemax(Int64).
*julia> **-x:x*
*0xfffffffffffffffc:0xfffffffffffffffb*
If you need negation, you need a signed integer, I think.
Regards
-
Avik
On Wednesday, 3 June 2015 06:12:19 UTC+1, Pete Williams wrote:
> Hi, I'm not sure what the right way to form the range -X:X is when X is
> Uint64. It works as expected for smaller Uints
>
> *julia> **Q = uint(4)*
>
> *0x0000000000000004*
>
>
> *julia> **M = 0x4*
>
> *0x04*
>
>
> *julia> **typeof(Q)*
>
> *Uint64*
>
>
> *julia> **typeof(M)*
>
> *Uint8*
>
>
> *julia> **[-1*M:M]*
>
> *9-element Array{Int64,1}:*
>
> * -4*
>
> * -3*
>
> * -2*
>
> * -1*
>
> * 0*
>
> * 1*
>
> * 2*
>
> * 3*
>
> * 4*
>
>
> *julia> **[-1*Q:Q]*
>
> *ERROR: OverflowError()*
>
> * in vcat at range.jl:500*
>
> obviously I can make an Int64 copy of the Uint64 to fix this, but I'd like
> to know if there is a more graceful way to do this. Thanks.
>
