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?
>>>
>>
>>
