if a = Union(T,U) where T is a Datatype, you can get it from a.types.
在 2015年6月12日星期五 UTC+8上午3:53:43，David Gold写道：
>
> Just the opposite =p I don't know what T is, but I'd like to be able work
> with it. For instance, if somebody gives me an Array{Union(T, U)}, where I
> know U but not T, I'd like to be able to return an Array{T}.
>
> On Thursday, June 11, 2015 at 3:29:02 PM UTC-4, Jameson wrote:
>>
>> Are you looking for the type-intersection perhaps?
>>
>> julia> typeintersect(Union(Int,Float64), Float64)
>> Float64
>>
>>
>> On Thu, Jun 11, 2015 at 3:15 PM David Gold <[email protected]> wrote:
>>
>>> I want the following function
>>>
>>> function t_or_void{T}(::Type{Union(T, Void)})
>>> return T
>>> end
>>>
>>> to work like this:
>>>
>>> julia> t_or_void(Union(Int, Void))
>>> Int64
>>>
>>> But in reality, it does this:
>>>
>>> julia> t_or_void(Union(Int, Void))
>>> UnionType
>>>
>>> Is there a way to make this work, or a way to extract T from Union(T,
>>> Void)? The 'Void' isn't special -- it could be any determinate type.
>>>
>>> Thanks,
>>> D
>>>
>>
