See also https://github.com/JuliaLang/julia/issues/6561
On Monday, July 14, 2014 10:48:42 AM UTC-4, Mauro wrote:
>
> Using type parameters works for me:
>
> julia> f{T<:Float64}(a::Array{(T,T)}) = eltype(a)
> f (generic function with 1 method)
>
> julia> f([(3.,4.), (4.,5.)])
> (Float64,Float64)
>
> julia> f{T<:Tuple}(a::Array{T}) = eltype(a)
> f (generic function with 2 methods)
>
> julia> f([(3,4), (4,5)])
> (Int64,Int64)
>
> The reason is invariance of parametric types. Tuple is an abstact type,
> this means that for parametric types (which arrays also belong to):
> "Even though (Float64,Float64) <: Tuple we DO NOT have
> Array{(Float64,Float64)} <: Array{Tuple}"
>
> (citing the manual:
>
> http://docs.julialang.org/en/latest/manual/types/#parametric-composite-types)
>
>
> (A side note: tuples themselves are covariant. E.g. (Int,) <: (Real,) )
>
> Last, why this worked for tuples before, I don't know. Presumably it
> was a bug and now got fixed.
>
> On Mon, 2014-07-14 at 12:01, David van Leeuwen <[email protected]
> <javascript:>> wrote:
> > Hello,
> >
> > Somewhere in the last 150 days the value of
> >
> > Array{(Float64,Float64)} <: Array{Tuple}
> >
> > changed from "true" to "false". There may be good reasons for that, I
> > can't tell.
> >
> > I would like to specify as a function argument something of the type
> > Array{Tuple}, but I can't get that matched any more. I don't know how
> to
> > make the function type more specific so that it will match again, i.e.,
> I
> > don't know how to specify the types withing the tuple. A naive
> > Array{Tuple{Float64,Float64}} does not work.
> >
> > Any ideas?
> >
> > Thanks
> >
> > ---david
>
