Implement Base.empty

Author: oschulz

src/array_of_similar_arrays.jl

@@ -161,6 +161,7 @@ end
 function Base.similar(A::ArrayOfSimilarArrays{T,M,N}, ::Type{<:AbstractArray{U}}, dims::Dims) where {T,M,N,U}
     data = A.data
     size_inner, size_outer = split_tuple(size(data), Val{M}())
+    # ToDo: Don't use similar if data is an ElasticArray?
     ArrayOfSimilarArrays{T,M,N}(similar(data, U, size_inner..., dims...))
 end
 
@@ -313,6 +314,17 @@ end
 # Will need equivalent of resize! that resizes in front of data instead of in back:
 # popfirst!(V::ArrayOfSimilarArrays) = ...
 
+function Base.empty(A::VectorOfSimilarArrays{T,M}, ::Type{<:AbstractArray{U}}) where {T,M,U}
+    data = A.data
+    size_inner, size_outer = split_tuple(size(data), Val{1}())
+    empty_size_outer = map(x -> zero(x), size_outer)
+
+    # ToDo: Don't use similar if data is an ElasticArray?
+    VectorOfSimilarArrays{T,M}(similar(data, U, size_inner..., empty_size_outer...))
+end
+
+Base.empty(A::VectorOfSimilarArrays{T,M}) where {T,M} = empty(A, Array{T})
+
 
 
 const ArrayOfSimilarVectors{

src/vector_of_arrays.jl

@@ -379,6 +379,14 @@ function Base.push!(A::VectorOfArrays{T,N}, x::AbstractArray{U,N}) where {T,N,U}
 end
 
 
+function Base.empty(A::VectorOfArrays{T,N}) where {T,N}
+    empty_data = empty(A.data)
+    empty_elem_ptr = push!(empty(A.elem_ptr), firstindex(empty_data))
+    empty_kernel_size = empty(A.kernel_size)
+    VectorOfArrays(empty_data, empty_elem_ptr, empty_kernel_size, no_consistency_checks)
+end
+
+
 function UnsafeArrays.uview(A::VectorOfArrays)
     VectorOfArrays(
         uview(A.data),

test/array_of_similar_arrays.jl

@@ -184,6 +184,14 @@ using UnsafeArrays
     end
 
 
+    @testset "empty" begin
+        A = [rand(2,3), rand(2,3), rand(2,3)]
+        B = ArrayOfSimilarArrays(A)
+        @test typeof(@inferred empty(B)) == typeof(B)
+        @test empty(A) == empty(B)
+    end
+
+
     @testset "examples" begin
         A_flat = rand(2,3,4,5,6)
         A_nested = nestedview(A_flat, 2)

test/vector_of_arrays.jl

@@ -104,12 +104,21 @@ using ArraysOfArrays: full_consistency_checks, append_elemptr!
         A = ref_AoA3(Float32, 3);
         B = VectorOfArrays(A);
 
-        @test typeof(@inferred copy(A)) == typeof(A)
+        @test typeof(@inferred copy(B)) == typeof(B)
         @test copy(A) == A
         @test copy(A) == B
     end
 
 
+    @testset "empty" begin
+        A = ref_AoA3(Float32, 3);
+        B = VectorOfArrays(A);
+
+        @test typeof(@inferred empty(B)) == typeof(B)
+        @test empty(A) == empty(B)
+    end
+
+
     @testset "examples" begin
         VA = VectorOfArrays{Float64, 2}()