On Sat, Sep 12, 2015 at 6:48 AM, Tim Holy <[email protected]> wrote:
> The problem with this approach:
>
> julia> function foo(mt::MyType)
> T = mt.parameters[1]
should be `typeof(mt)` or sth like that.
> a = Array(T, 5)
> a[3] = 7
> a
> end
> foo (generic function with 1 method)
>
> julia> @code_warntype foo(MyType{Int,Float64}())
> Variables:
> mt::MyType{Int64,Float64}
> T::Union{}
> a::Union{}
>
> Body:
> begin # none, line 2:
> T = (Main.getindex)((top(getfield))
> (mt::MyType{Int64,Float64},:parameters)::Union{},1)::Union{} # none, line 3:
> a = call(Main.Array,T::Union{},5)::Union{} # none, line 4:
> (Main.setindex!)(a::Union{},7,3)::Union{} # none, line 5:
> return a::Union{}
> end::Union{}
>
>
> Those Union{}s will kill performance.
And these should be `Any`.
>
> --Tim
>
> On Friday, September 11, 2015 12:54:12 PM David Gold wrote:
>> I'm not convinced it's more Julian to use such a helper function, since it
>> will needlessly compile a different method for each distinct set of
>> parameters. Directly accessing the `parameter` field of the type in
>> question avoids this.
>>
>> On Friday, September 11, 2015 at 12:30:16 PM UTC-7, Josh Langsfeld wrote:
>> > You can access the 'parameters' field of a type instance object. But the
>> > standard Julian way to get type parameters is to just define a helper
>> > function:
>> >
>> > typeparams{A,B}(::Type{T{A,B}}) = A,B
>> >
>> > On Friday, September 11, 2015 at 3:20:17 PM UTC-4, Erik Schnetter wrote:
>> >> Is there a function in Julia that allows accessing the parameters of a
>> >> type?
>> >>
>> >> For example, if I have
>> >>
>> >> type T{A,B} end
>> >>
>> >> then I'd like a way to convert `T{Int, Char}` to `(Int, Char)`.
>> >>
>> >> In other words, is there a way to get at the contents of `DataType`
>> >> objects?
>> >>
>> >> Thanks,
>> >> -erik
>
