that makes sense. many thanks!
在 2015年10月28日星期三 UTC+8下午3:14:26，Tomas Lycken写道：
>
> With a type declared like that, any access of the field x will be type
> unstable, which means that Julia’s JIT compiler will emit much more
> defensive, and thus slower, code.
>
> The solution is to declare a *parametric* type:
>
> type MyType{T<:Union{Int64, Float64}}
> x::T
> end
>
> That way, MyType(3) and MyType(3.0) will now be instances of different
> types, and the compiler can generate fast code. (You can still write
> functions that dispatch on just MyType, so you don’t loose any expressive
> power…)
>
> // T
>
> On Wednesday, October 28, 2015 at 5:10:09 AM UTC+1, Gnimuc Key wrote:
>
> Avoid type Unions in fields ¶
>>>
>>> <http://docs.julialang.org/en/latest/manual/style-guide/#avoid-strange-type-unions>
>>> type MyType
>>> ...
>>> x::Union{Void,T}
>>> end
>>
>>
>> I'm wondering whether it's a good style or not to write something like
>> this:
>>
>> type MyType
>> ...
>> x::Union{Int64,Float64}end
>>
>> what's the side effects of using Union like this?
>>
>
>
