add more utility functions (JuliaArrays#26)

* add pair constructor

* add StructVector

* added empty and indexstyle

* export StructVector

* add columns colnames and ncols

* test columns

* test empty

Author: Pietro Vertechi

src/StructArrays.jl

@@ -1,7 +1,7 @@
 module StructArrays
 
 import Requires
-export StructArray
+export StructArray, StructVector
 
 include("interface.jl")
 include("structarray.jl")

src/structarray.jl

@@ -19,14 +19,22 @@ end
 
 StructArray{T}(c::C) where {T, C<:Tuple} = StructArray{T}(NamedTuple{fields(T)}(c))
 StructArray{T}(c::C) where {T, C<:NamedTuple} = StructArray{T, length(size(c[1])), C}(c)
+StructArray{T}(c::C) where {T, C<:Pair} = StructArray{T}(Tuple(c))
 StructArray(c::C) where {C<:NamedTuple} = StructArray{eltypes(C)}(c)
 StructArray(c::C) where {C<:Tuple} = StructArray{eltypes(C)}(c)
+StructArray(c::Pair{P, Q}) where {P, Q} = StructArray{Pair{eltype(P), eltype(Q)}}(c)
 
 StructArray{T}(; kwargs...) where {T} = StructArray{T}(values(kwargs))
 StructArray(; kwargs...) = StructArray(values(kwargs))
 
 StructArray{T}(args...) where {T} = StructArray{T}(NamedTuple{fields(T)}(args))
 
+const StructVector{T, C<:NamedTuple} = StructArray{T, 1, C}
+StructVector{T}(args...; kwargs...) where {T} = StructArray{T}(args...; kwargs...)
+StructVector(args...; kwargs...) = StructArray(args...; kwargs...)
+
+Base.IndexStyle(::Type{StructArray{T, N, C}}) where {T, N, C} = Base.IndexStyle(gettypes(C).parameters[1])
+
 _undef_array(::Type{T}, sz; unwrap = t -> false) where {T} = unwrap(T) ? StructArray{T}(undef, sz; unwrap = unwrap) : Array{T}(undef, sz)
 
 _similar(v::AbstractArray, ::Type{Z}; unwrap = t -> false) where {Z} =
@@ -53,6 +61,12 @@ StructArray(s::StructArray) = copy(s)
 Base.convert(::Type{StructArray}, v::AbstractArray) = StructArray(v)
 
 columns(s::StructArray) = getfield(s, :columns)
+columns(v::AbstractVector) = v
+ncols(v::AbstractVector) = 1
+ncols(v::StructArray{T, N, C}) where {T, N, C} = length(getnames(C))
+colnames(v::AbstractVector) = (1,)
+colnames(v::StructArray{T, N, C}) where {T, N, C} = getnames(C)
+
 Base.getproperty(s::StructArray, key::Symbol) = getfield(columns(s), key)
 Base.getproperty(s::StructArray, key::Int) = getfield(columns(s), key)
 Base.propertynames(s::StructArray) = fieldnames(typeof(columns(s)))
@@ -106,6 +120,10 @@ function Base.resize!(s::StructArray, i::Integer)
     return s
 end
 
+function Base.empty!(s::StructArray)
+    foreachcolumn(empty!, s)
+end
+
 for op in [:hcat, :vcat]
     @eval begin
         function Base.$op(args::StructArray...)

test/runtests.jl

@@ -12,6 +12,21 @@ using Test
     @test (@inferred view(t, 2, 1:2)) == StructArray((a = view(a, 2, 1:2), b = view(b, 2, 1:2)))
 end
 
+@testset "columns" begin
+    t = StructArray(a = 1:10, b = rand(Bool, 10))
+    @test StructArrays.ncols(t) == 2
+    @test StructArrays.colnames(t) == (:a, :b)
+    @test StructArrays.ncols(t.a) == 1
+    @test StructArrays.colnames(t.a) == (1,)
+end
+
+@testset "empty" begin
+    s = StructVector(a = [1, 2, 3], b = ["a", "b", "c"])
+    empty!(s)
+    @test isempty(s.a)
+    @test isempty(s.b)
+end
+
 @testset "constructor from existing array" begin
     v = rand(ComplexF64, 5, 3)
     t = @inferred StructArray(v)