map over PaddedAxis fails

[fonsp]

It seems like Base.map(::Function, ::PaddedAxis) is implemented, but it fails for this basic use case:

julia> using AxisIndices

julia> a = AxisArray(3:4, one_pad(sym_pad=2));

julia> i = eachindex(a)
one_pad(SimpleAxis(1:2); sym_pad=2)

julia> map(identity, i)
ERROR: ArgumentError: invalid index: AxisIndices.FillPad{typeof(oneunit)}(oneunit) of type AxisIndices.FillPad{typeof(oneunit)}
Stacktrace:
 [1] to_index(::Function) at ./indices.jl:297
 [2] to_index(::Array{Int64,1}, ::Function) at ./indices.jl:274
 [3] to_indices at ./indices.jl:325 [inlined]
 [4] to_indices at ./indices.jl:322 [inlined]
 [5] setindex! at ./abstractarray.jl:1149 [inlined]
 [6] unsafe_set_element! at /home/fons/.julia/packages/AxisIndices/eTKfQ/src/axis_array.jl:433 [inlined]
 [7] unsafe_setindex! at /home/fons/.julia/packages/ArrayInterface/rw2kK/src/indexing.jl:501 [inlined]
 [8] unsafe_setindex! at /home/fons/.julia/packages/ArrayInterface/rw2kK/src/indexing.jl:500 [inlined]
 [9] setindex! at /home/fons/.julia/packages/ArrayInterface/rw2kK/src/indexing.jl:487 [inlined]
 [10] setindex! at /home/fons/.julia/packages/AxisIndices/eTKfQ/src/arrays.jl:427 [inlined]
 [11] collect_to_with_first!(::AxisArray{Int64,1,Array{Int64,1},Tuple{AxisIndices.PaddedAxis{AxisIndices.FillPad{typeof(oneunit)},Int64,Int64,Int64,SimpleAxis{Int64,Base.OneTo{Int64}}}}}, ::Int64, ::Base.Generator{AxisIndices.PaddedAxis{AxisIndices.FillPad{typeof(oneunit)},Int64,Int64,Int64,SimpleAxis{Int64,Base.OneTo{Int64}}},typeof(identity)}, ::Int64) at ./array.jl:711
 [12] _collect at ./array.jl:706 [inlined]
 [13] collect_similar(::AxisIndices.PaddedAxis{AxisIndices.FillPad{typeof(oneunit)},Int64,Int64,Int64,SimpleAxis{Int64,Base.OneTo{Int64}}}, ::Base.Generator{AxisIndices.PaddedAxis{AxisIndices.FillPad{typeof(oneunit)},Int64,Int64,Int64,SimpleAxis{Int64,Base.OneTo{Int64}}},typeof(identity)}) at ./array.jl:630
 [14] map(::Function, ::AxisIndices.PaddedAxis{AxisIndices.FillPad{typeof(oneunit)},Int64,Int64,Int64,SimpleAxis{Int64,Base.OneTo{Int64}}}) at ./abstractarray.jl:2158
 [15] top-level scope at REPL[6]:1

[Tokazama]

Before I claim to have a fix for this, what is the return you want from map(identity, i)?

[fonsp]

I'm not familiar with AxisIndicies, just found the bug and wrote a quick issue 😊

Maybe this is useful: in OffsetArrays, the result is also an offset array:

julia> using OffsetArrays

julia> a = OffsetArray(zeros(3), 20:22)
3-element OffsetArray(::Array{Float64,1}, 20:22) with eltype Float64 with indices 20:22:
 0.0
 0.0
 0.0

julia> i = eachindex(a)
OffsetArrays.IdOffsetRange(20:22)

julia> result = map(identity, i)
3-element OffsetArray(::Array{Int64,1}, 20:22) with eltype Int64 with indices 20:22:
 20
 21
 22

julia> result[1]
ERROR: BoundsError: attempt to access 3-element OffsetArray(::Array{Int64,1}, 20:22) with eltype Int64 with indices 20:22 at index [1]
Stacktrace:
 [1] throw_boundserror(::OffsetArray{Int64,1,Array{Int64,1}}, ::Tuple{Int64}) at ./abstractarray.jl:537
 [2] checkbounds at ./abstractarray.jl:502 [inlined]
 [3] getindex(::OffsetArray{Int64,1,Array{Int64,1}}, ::Int64) at /home/fons/.julia/packages/OffsetArrays/7j7P7/src/OffsetArrays.jl:275
 [4] top-level scope at REPL[7]:1

julia> result[20]
20

[fonsp]

I think the general trend is that the result of map should have a structure similar to its input.

[Tokazama]

I'm not familiar with AxisIndicies, just found the bug and wrote a quick issue 😊

Thank you. It is greatly appreciated!

Maybe this is useful: in OffsetArrays, the result is also an offset array:

I borrowed liberally from concepts there so if you have AxisArray(3:4, offset(2)) it already does this but I missed a minor detail with padded axes.

How's this?

julia> a = AxisArray(3:4, one_pad(sym_pad=2));

julia> i = eachindex(a)
one_pad(SimpleAxis(1:2); sym_pad=2)

julia> map(identity, i)
6-element AxisArray(::Array{Int64,1}
  • axes:
     1 = -1:4
)
      1 
  -1  -1
  0    0
  1    1
  2    2
  3    3
  4    4  

[fonsp]

perfect!

[Tokazama]

Fixed in v0.7.1