Hi Bill,
It works for a single argument, but not for multiple ones. I have a
self-contained example:
--8<---------------cut here---------------start------------->8---
module Foos
type Foo{T <: Tuple}
end
m1{T}(f::Foo{Tuple{T}}, index::T...) = 42 # suggested by Bill Hart
m2{T}(f::Foo{T}, index::T...) = 42 # what I thought would work
_m3{T}(f::Foo{T}, index::T) = 42 # indirect solution
m3{T}(f::Foo{T}, index...) = _m3(f, index)
end
f1 = Foos.Foo{Tuple{Int}}()
Foos.m1(f1, 9) # works
Foos.m2(f1, 9) # won't work
Foos.m3(f1, 9) # works
f2 = Foos.Foo{Tuple{Int,Symbol}}()
Foos.m1(f2, 9, :a) # won't work
Foos.m2(f2, 9, :a) # won't work
Foos.m3(f2, 9, :a) # indirect, works
--8<---------------cut here---------------end--------------->8---
For more than one argument, only the indirect solution works.
Best,
Tamas
On Wed, Mar 23 2016, via julia-users wrote:
> The following seems to work, but I'm not sure whether it was what you
> wanted:
>
> import Base.getindex
>
> type Foo{T <: Tuple}
> end
>
> getindex{T}(f::Foo{Tuple{T}}, index::T...) = 42
>
> Foo{Tuple{Int}}()[9]
>
> Bill.
>
> On Wednesday, 23 March 2016 14:38:20 UTC+1, Tamas Papp wrote:
>>
>> Hi,
>>
>> My understanding was that ... in a method argument forms a tuple, but I
>> don't know how to dispatch on that. Self-contained example:
>>
>> import Base.getindex
>>
>> type Foo{T <: Tuple}
>> end
>>
>> getindex{T}(f::Foo{T}, index::T...) = 42
>>
>> Foo{Tuple{Int}}()[9] ## won't match
>>
>> ## workaround with wrapper:
>>
>> _mygetindex{T}(f::Foo{T}, index::T) = 42
>> mygetindex{T}(f::Foo{T}, index...) = _mygetindex(f, index)
>>
>> mygetindex(Foo{Tuple{Int}}(), 9)
>>
>> Is it possible to make it work without a wrapper in current Julia?
>>
>> Best,
>>
>> Tamas
>>
