CellIterator not broadcast safe

[sebastianpech]

I haven't looked into the details of that issue (Opened it as a reminder) and tbh I don't know much about the inner workings of broadcast and materialize. As the current id is mutated in the CellIterator the first example only picks up the last id. Any ideas if there's a possible fix for that?

Wrong

julia> cellid.(CellIterator(dh))
22754-element Array{Int64,1}:
 22754
 22754
 22754
 22754
 22754
 22754
     ⋮
 22754
 22754
 22754
 22754
 22754

Correct

julia> map(CellIterator(dh)) do cell
           cellid(cell)
       end
22754-element Array{Int64,1}:
     1
     2
     3
     4
     5
     6
     ⋮
 22750
 22751
 22752
 22753
 22754

[fredrikekre]

julia> struct Iter
           max::Int
           x::Base.RefValue{Int}
           Iter(x) = new(x, Ref(1))
       end
       Base.length(iter::Iter) = iter.max
       function Base.iterate(iter::Iter, state=1)
           iter.x[] = state
           if state > iter.max
               return nothing
           else
               return iter, state+1
           end
       end
       get_x(iter::Iter) = iter.x[];

julia> iter = Iter(5);

julia> get_x.(iter)
5-element Array{Int64,1}:
 6
 6
 6
 6
 6

so looks like broadcasting is not iterating somehow?

[KristofferC]

Isn't the problem that there is ever only one Iter object in the array (they all refer to the same object) so iter.x will always be the same thing.

[fredrikekre]

But we extract the immutable Int at each iteration?

[fredrikekre]

E.g. this works:

julia> collect(get_x(y) for y in iter)
5-element Array{Int64,1}:
 1
 2
 3
 4
 5

[fredrikekre]

I guess this happens because broadcasting is lazy and iterates through once before actually calling get_x.

[KristofferC]

Oh, I misread the example completely.