Skip to content

Preserve types in reduce(vcat) and reduce(hcat) #347

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
aplavin wants to merge 4 commits into
base: master
Choose a base branch
from
Open

Preserve types in reduce(vcat) and reduce(hcat) #347

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
33e985c
make reduce(vcat) as type-preserving as vcat()
aplavin Mar 12, 2026
9400c98
tighten eltype on vcat+
aplavin Mar 12, 2026
20f255c
minor cleanup
aplavin Mar 12, 2026
a9bd097
cleaner error & error tests
aplavin Mar 12, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
22 changes: 20 additions & 2 deletions src/structarray.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -452,18 +452,36 @@ function Base.sizehint!(s::StructArray, i::Integer)
return s
end

_cateltype(::Type{T}, newcols::Tup) where {T<:Tup} = eltypes(newcols)
_cateltype(::Type{T}, newcols::Tup) where {T} = T

function _reducecat_structarray(op, A::AbstractVector{<:StructArray})
isempty(A) && return Base.mapreduce_empty(eltype, promote_type, eltype(A))
cols = map(components, A)
firstcols = first(cols)
all(col -> keys(col) == keys(firstcols), cols) || throw(ArgumentError("StructArray columns must have matching keys."))
newcols = map(key -> reduce(op, map(Base.Fix2(getindex, key), cols)), keys(firstcols))
typedcols = strip_params(typeof(firstcols))(newcols)
T = _cateltype(mapreduce(eltype, promote_type, A), typedcols)
return StructArray{T}(typedcols)
end

for op in [:cat, :hcat, :vcat]
curried_op = Symbol(:curried, op)
@eval begin
function Base.$op(arg::StructArray, others::StructArray...; kwargs...)
$curried_op(A...) = $op(A...; kwargs...)
args = (arg, others...)
T = mapreduce(eltype, promote_type, args)
StructArray{T}(map($curried_op, map(components, args)...))
newcols = map($curried_op, map(components, args)...)
T = _cateltype(mapreduce(eltype, promote_type, args), newcols)
StructArray{T}(newcols)
end
end
end

Base.reduce(::typeof(vcat), A::AbstractVector{<:StructArray}) = _reducecat_structarray(vcat, A)
Base.reduce(::typeof(hcat), A::AbstractVector{<:StructArray}) = _reducecat_structarray(hcat, A)

Base.copy(s::StructArray{T}) where {T} = StructArray{T}(map(copy, components(s)))

for type in (
Expand Down
48 changes: 48 additions & 0 deletions test/runtests.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -693,6 +693,54 @@ end
@test @inferred(vcat(t3)) == t3
@inferred vcat(t3, t3)
@inferred vcat(t3, collect(t3))
a = StructArray(y = Union{Missing, Int}[missing])
b = StructArray(y = [3])
c = StructArray(y = Union{Missing, Int}[4])
vcatted = vcat(a, b, c)
@test eltype(vcatted) === NamedTuple{(:y,), Tuple{Union{Missing, Int}}}
reduced_vcat = reduce(vcat, [a, b, c])
@test eltype(reduced_vcat) === eltype(vcatted)
@test isequal(reduced_vcat, vcatted)
@test reduced_vcat.y isa Vector{Union{Missing, Int}}
hcatted = hcat(reshape(a, 1, 1), reshape(b, 1, 1), reshape(c, 1, 1))
@test eltype(hcatted) === NamedTuple{(:y,), Tuple{Union{Missing, Int}}}
reduced_hcat = reduce(hcat, [reshape(a, 1, 1), reshape(b, 1, 1), reshape(c, 1, 1)])
@test eltype(reduced_hcat) === eltype(hcatted)
@test isequal(reduced_hcat, hcatted)
@test reduced_hcat.y isa Matrix{Union{Missing, Int}}

struct CatTestType{A, B}
a::A
b::B
end
custom_a = StructArray{CatTestType{Int, Missing}}((a = [1], b = Missing[missing]))
custom_b = StructArray{CatTestType{Int, Int}}((a = [2], b = [3]))
custom_vcat = vcat(custom_a, custom_b, custom_a)
@test custom_vcat == CatTestType{Int}[CatTestType(1, missing), CatTestType(2, 3), CatTestType(1, missing)]
@test custom_vcat.b isa Vector{Union{Missing, Int}}
reduced_custom_vcat = reduce(vcat, [custom_a, custom_b, custom_a])
@test isequal(reduced_custom_vcat, custom_vcat)
@test eltype(reduced_custom_vcat) === eltype(custom_vcat) === CatTestType{Int}
@test reduced_custom_vcat.b isa Vector{Union{Missing, Int}}

# error behavior is consistent between reduce(vcat) and vcat(), and is generally reasonable
mismatched_names_a = StructArray(a = [1], b = [2])
mismatched_names_b = StructArray(x = [3], y = [4])
@test_throws ArgumentError vcat(mismatched_names_a, mismatched_names_b)
@test_throws ArgumentError reduce(vcat, [mismatched_names_a, mismatched_names_b])
mixed_rowtype_a = StructArray(re = [1.0], im = [2.0])
mixed_rowtype_b = StructArray(ComplexF64[3 + 4im])
@test_throws ArgumentError vcat(mixed_rowtype_a, mixed_rowtype_b)
@test_throws ArgumentError reduce(vcat, [mixed_rowtype_a, mixed_rowtype_b])
different_names_a = StructArray(a = [1])
different_names_b = StructArray(x = [2], y = [3], z = [4])
@test_throws ArgumentError vcat(different_names_a, different_names_b)
@test_throws ArgumentError reduce(vcat, [different_names_a, different_names_b])
different_lengths_a = StructArray(([1], [2], [3]))
different_lengths_b = StructArray(([4], [5]))
@test_throws ArgumentError reduce(vcat, [different_lengths_a, different_lengths_b])
@test_throws ArgumentError reduce(hcat, [reshape(different_lengths_a, 1, 1), reshape(different_lengths_b, 1, 1)])

# Check that `cat(dims=1)` doesn't commit type piracy (#254)
# We only test that this works, the return value is immaterial
@test cat(dims=1) == vcat()
Expand Down
Loading