For docs - are we performing in place updates to collections.rst ?
On Thursday, September 3, 2015 at 10:04:22 AM UTC-4, Michael Francis wrote:
>
> I will likely do so, it's quite a common action to take.
>
> Fortunately with typeof( ( 1,2 ) ) == Tuple{Int64,Int64} there is a
> significantly greater consistency in 0.4 vs 0.3
>
> Though how would one correctly access the 'nth' elements type ?
>
> It brings up a question regarding parameterized types, how should (or
> should) one access/refer to the parameters of the type rather than an
> instance. It seems like a bad (queezy) practice to dig into the parameters
> of a type?
>
> On Thursday, September 3, 2015 at 9:41:18 AM UTC-4, Tim Holy wrote:
>>
>> base/dict.jl defines keytype and valtype, but they are not exported. You
>> could
>> file a pull request that exports them (it would be a 2-line patch, though
>> you
>> might want to add a test to make sure they stay exported).
>>
>> --Tim
>>
>> On Thursday, September 03, 2015 06:37:02 AM Michael Francis wrote:
>> > In the short term I have defined the following in the offending package
>> for
>> > v0.4 only
>> >
>> > function keytype( dict )
>> > return eltype( dict ).parameters[1]
>> > end
>> >
>> > I agree that a standard protocol of accessing the key and value types
>> of a
>> > pair / associative is the way to go.
>> >
>> > On Thursday, September 3, 2015 at 9:31:39 AM UTC-4, Matt Bauman wrote:
>> > > Oh man that's tricky. The trouble is that you're effectively saying
>> > > `Pair{Symbol,Int}[1]`, which is the syntax for a typed array:
>> > > Pair{Symbol,Int}[:x=>1, :y=>2]. One way around this is to define:
>> > >
>> > > keytype{A,B}(::Type{Pair{A,B}}) = A
>> > > valuetype{A,B}(::Type{Pair{A,B}}) = B
>> > > pairtypes{A,B}(::Type{Pair{A,B}}) = (A,B)
>> > >
>> > > If you need this to work on 0.3, too, you can easily make these
>> functions
>> > > work for the old-style Tuples, too.
>> > >
>> > > On Thursday, September 3, 2015 at 9:06:30 AM UTC-4, Michael Francis
>> wrote:
>> > >> Incidentally
>> > >>
>> > >> eltype( Pair{String,Float64} )
>> > >>
>> > >> gives Any, that seems slightly strange as well .
>> > >>
>> > >> On Thursday, September 3, 2015 at 9:02:33 AM UTC-4, Michael Francis
>> wrote:
>> > >>> julia> eltype( Dict( :x => 1, :y => 2 ) )[1]
>> > >>> ERROR: MethodError: `convert` has no method matching
>> convert(::Type{Pair
>> > >>> {Symbol,Int64}}, ::Int64)
>> > >>> This may have arisen from a call to the constructor
>> Pair{Symbol,Int64
>> > >>> }(...),
>> > >>> since type constructors fall back to convert methods.
>> > >>>
>> > >>> Closest candidates are:
>> > >>> Pair{A,B}(::Any, ::Any)
>> > >>> call{T}(::Type{T}, ::Any)
>> > >>> convert{T}(::Type{T}, ::T)
>> > >>>
>> > >>> in getindex at array.jl:167
>> > >>>
>> > >>> Is this intentional ? This breaks a package I am dependent on - I
>> > >>> believe the assumption was that Pair would respect the tuple API,
>> this
>> > >>> appears to not be the case ?
>> > >>>
>> > >>> collect( eltype( Dict( :x => 1, :y => 2 ) ) )
>> > >>> ERROR: MethodError: `start` has no method matching
>> start(::Type{Pair{
>> > >>> Symbol,Int64}})
>> > >>>
>> > >>> in collect at array.jl:255
>> > >>> in collect at array.jl:262
>>
>>
