Parametrizing would also work.
function lambert_W{T<:Union(Real,Dual)(x::T)
...
end
Kevin
On Wed, Jan 22, 2014 at 11:07 AM, John Myles White <[email protected]
> wrote:
> I think many people in the Julia community would use lambert_W(x::Number)
> and then warn people not to use anything but Real or Complex.
>
> If you want full type safety, I think a Union(Real, Dual) is the way to go
> here.
>
> -- John
>
>
> On Jan 22, 2014, at 10:26 AM, Hans W Borchers <[email protected]>
> wrote:
>
> Sorry, Jason, I didn't get it. What would you propose to use in
>
> function lambert_W(x::Number)
> ...
> end
>
> to allow dual and to forbid complex numbers? Or is it some additional test
> in the body of the function.
>
> Thanks, Hans Werner
>
>
> On Wednesday, January 22, 2014 6:31:51 PM UTC+1, Jason Merrill wrote:
>>
>> On Wednesday, January 22, 2014 4:25:38 AM UTC-8, Stefan Karpinski wrote:
>>>
>>> I wonder if Dual shouldn't be a subtype of Real. Of course, you can
>>> probably have Dual complex numbers as well, but maybe those can be
>>> Complex{Dual} in that case.
>>>
>>
>> Complex{Dual} and Dual{Complex} are equally sensible notions. As long as
>> du and im commute, they're the same thing. Neither of them are "real"
>> numbers in the mathematical sense.
>>
>> I wanted to make PowerSeries work over complex numbers, but ended up
>> restricting them to a Real field for now because the type issues got
>> confusing. It would be nice if we had a more precise way to talk about the
>> relationship between algebraic number types like this.
>>
>> Sage is written by number theorists and has an interesting approach to
>> defining mathematical objects over various fields. I haven't taken the time
>> to understand exactly how their system works, though.
>>
>
>
