On Wednesday, August 12, 2015 at 12:15:19 AM UTC-4, Stefan Karpinski wrote:
>
> You can't create a value whose concrete type is Tuple{AbstractString,
> AbstractString} but you can create values that are of that type and you can
> create an instance of Vector{Tuple{AbstractString, AbstractString}}:
>
> julia> baz(a::Vector{Tuple{AbstractString, AbstractString}}) = 3
> baz (generic function with 1 method)
>
> julia> baz(Vector{Tuple{AbstractString,AbstractString}}())
> 3
>
>
>
Interesting. Does that really work in 0.4? I tried to replicate in 0.3 with
Vector{(AbstractMatrix,AbstractMatrix)}()
> type cannot be constructed
What kind of object is a Vector{Tuple{AbstractString,AbstractString}}()?
Does it have memory allocated to it? What is that construction good for?
Cédric
>
>
> On Wed, Aug 12, 2015 at 12:09 AM, Cedric St-Jean <[email protected]
> <javascript:>> wrote:
>
>> Is it correct to say that:
>>
>> baz(a::Vector{Tuple{AbstractString, AbstractString}}) = 3
>>
>> is uncallable, since we can't instantiate an AbstractString? Maybe it
>> should trigger an error/warning on definition.
>>
>> Cédric
>>
>> On Tuesday, August 11, 2015 at 4:18:38 PM UTC-4, Stefan Karpinski wrote:
>>>
>>> Same thing – even though
>>>
>>> Tuple{ASCIIString,ASCIIString} <: Tuple{String,String} <: Tuple
>>>
>>>
>>> due to invariance, we still have these:
>>>
>>> !(Vector{Tuple{String,String}} <: Vector{Tuple})
>>>
>>> !(Vector{Tuple{ASCIIString,ASCIIString}} <: Vector{Tuple})
>>> !(Vector{Tuple{ASCIIString,ASCIIString}} <: Vector{Tuple{String,String}
>>> })
>>>
>>>
>>> On Tue, Aug 11, 2015 at 4:13 PM, Seth <[email protected]> wrote:
>>>
>>>> Thanks, Stefan. I understand that causing the problem for baz(), but
>>>> why does this explain bar()'s failure?
>>>>
>>>> On Tuesday, August 11, 2015 at 1:10:27 PM UTC-7, Stefan Karpinski wrote:
>>>>>
>>>>> Parametric typing in Julia is invariant, so
>>>>>
>>>>> !(Vector{Tuple{ASCIIString,ASCIIString}} <:
>>>>> Vector{Tuple{String,String}})
>>>>>
>>>>>
>>>>> even though
>>>>>
>>>>> Tuple{ASCIIString,ASCIIString} <: Tuple{String,String}.
>>>>>
>>>>>
>>>>> See:
>>>>> http://docs.julialang.org/en/release-0.3/manual/types/#parametric-composite-types
>>>>>
>>>>> On Tue, Aug 11, 2015 at 1:26 PM, Seth <[email protected]> wrote:
>>>>>
>>>>>> Consider
>>>>>>
>>>>>> foo(a::Vector) = 1
>>>>>> bar(a::Vector{Tuple}) = 2
>>>>>> baz(a::Vector{Tuple{AbstractString, AbstractString}}) = 3
>>>>>>
>>>>>>
>>>>>> foo(a::AbstractString) = foo([(a,a)])
>>>>>> bar(a::AbstractString) = bar([(a,a)])
>>>>>> baz(a::AbstractString) = baz([(a,a)])
>>>>>>
>>>>>> Results:
>>>>>>
>>>>>> julia> foo("a")
>>>>>> 1
>>>>>>
>>>>>> julia> bar("a")
>>>>>> ERROR: MethodError: `bar` has no method matching
>>>>>> bar(::Array{Tuple{ASCIIString,ASCIIString},1})
>>>>>> in bar at none:1
>>>>>>
>>>>>> julia> baz("a")
>>>>>> ERROR: MethodError: `bar` has no method matching
>>>>>> bar(::Array{Tuple{ASCIIString,ASCIIString},1})
>>>>>> in baz at none:1
>>>>>>
>>>>>> I understand why foo() works, but why do bar() or baz() both fail?
>>>>>>
>>>>>
>>>>>
>>>
>
