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Make zero on array of arrays etc apply recursively #51458

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Merged
merged 6 commits into from
Feb 12, 2024
Merged

Make zero on array of arrays etc apply recursively #51458

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8384dab
Make zero on array of arrays apply recursively
oxinabox Sep 26, 2023
fb235de
add trailing newline
oxinabox Sep 27, 2023
49981d4
Fix whitespace
oxinabox Sep 27, 2023
67e2fb5
Merge branch 'master' into ox/zero
vtjnash Feb 10, 2024
958bfbe
Update test/abstractarray.jl
inkydragon Feb 11, 2024
773fad3
Merge branch 'master' into ox/zero
DilumAluthge Feb 11, 2024
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1 change: 1 addition & 0 deletions NEWS.md
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Expand Up @@ -109,6 +109,7 @@ New library features
automatically.
* `@timed` now additionally returns the elapsed compilation and recompilation time ([#52889])
* `filter` can now act on a `NamedTuple` ([#50795]).
* `zero(::AbstractArray)` now applies recursively, so `zero([[1,2],[3,4,5]])` now produces the additive identity `[[0,0],[0,0,0]]` rather than erroring ([#38064]).

Standard library changes
------------------------
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3 changes: 2 additions & 1 deletion base/abstractarray.jl
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Expand Up @@ -1217,7 +1217,8 @@ function copymutable(a::AbstractArray)
end
copymutable(itr) = collect(itr)

zero(x::AbstractArray{T}) where {T} = fill!(similar(x, typeof(zero(T))), zero(T))
zero(x::AbstractArray{T}) where {T<:Number} = fill!(similar(x, typeof(zero(T))), zero(T))
zero(x::AbstractArray) = map(zero, x)
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Should this use broadcasting instead, as custom sparse arrays might define their own broadcast styles and don't need to iterate over the entire array?

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maybe? idk

Custom sparse arrays should probably be implementing their own zero function outright.
Since they likely have their own opinions about whether or not to store structural zeros etc (the SparseArrays stdlib does this).

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It's also a whole lot easier to define a single-argument map(f, ::CustomArray) than it is to define your own broadcast style. I think the map is fine; it's straightforward and obvious and even enables the laser-focused map(::typeof(zero), ::CustomArray).


## iteration support for arrays by iterating over `eachindex` in the array ##
# Allows fast iteration by default for both IndexLinear and IndexCartesian arrays
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11 changes: 11 additions & 0 deletions test/abstractarray.jl
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Expand Up @@ -1950,3 +1950,14 @@ end
@test repeat(f, 2, 3, 4) === FillArrays.Fill(3, (8, 6, 4))
@test repeat(f, inner=(1,2), outer=(3,1)) === FillArrays.Fill(3, (12, 4))
end

@testset "zero" begin
@test zero([1 2; 3 4]) isa Matrix{Int}
@test zero([1 2; 3 4]) == [0 0; 0 0]

@test zero([1.0]) isa Vector{Float64}
@test zero([1.0]) == [0.0]

@test zero([[2,2], [3,3,3]]) isa Vector{Vector{Int}}
@test zero([[2,2], [3,3,3]]) == [[0,0], [0, 0, 0]]
end