Improve specializations of empty

Add support for empty!

Author: oschulz

src/array_of_similar_arrays.jl

@@ -344,16 +344,23 @@ 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}())
+
+function _empty_data_size(A::VectorOfSimilarArrays{T,M}) where {T,M}
+    size_inner, size_outer = split_tuple(size(A.data), Val{M}())
     empty_size_outer = map(x -> zero(x), size_outer)
+    (size_inner..., empty_size_outer...)
+end
 
+function Base.empty(A::VectorOfSimilarArrays{T,M}, ::Type{<:AbstractArray{U}}) where {T,M,U}
+    new_data_size = _empty_data_size(A)
     # ToDo: Don't use similar if data is an ElasticArray?
-    VectorOfSimilarArrays{T,M}(similar(data, U, size_inner..., empty_size_outer...))
+    VectorOfSimilarArrays{T,M}(similar(A.data, U, new_data_size...))
 end
 
-Base.empty(A::VectorOfSimilarArrays{T,M}) where {T,M} = empty(A, Array{T})
+function Base.empty!(A::VectorOfSimilarArrays{T,M}) where {T,M}
+    resize!(A.data, _empty_data_size(A))
+    A
+end
 
 
 

src/vector_of_arrays.jl

@@ -379,13 +379,20 @@ 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)
+function Base.empty(A::VectorOfArrays{T,N}, ::Type{<:DenseArray{U,N}}) where {T,N,U}
+    empty_data = empty(A.data, U)
     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 Base.empty!(A::VectorOfArrays)
+    empty!(A.data)
+    resize!(A.elem_ptr, 1)
+    empty!(A.kernel_size)
+    A
+end
+
 
 function Adapt.adapt_structure(to, A::VectorOfArrays)
     VectorOfArrays(

test/array_of_similar_arrays.jl

@@ -248,6 +248,13 @@ using StatsBase: cov2cor
         B = ArrayOfSimilarArrays(A)
         @test typeof(@inferred empty(B)) == typeof(B)
         @test empty(A) == empty(B)
+
+        C = VectorOfSimilarArrays{Float64,2}(ElasticArray(B.data))
+        @test @inferred(empty(C)) == empty(A)
+        @test @inferred(empty!(deepcopy(C))) == empty(A)
+        @test @inferred(empty(C)) == @inferred(empty!(deepcopy(C)))
+        @test append!(empty(C), C) == A
+        @test append!(empty!(deepcopy(C)), C) == A
     end
 
     @testset "stats" begin

test/vector_of_arrays.jl

@@ -217,7 +217,11 @@ using ArraysOfArrays: full_consistency_checks, append_elemptr!, element_ptr
         B = VectorOfArrays(A);
 
         @test typeof(@inferred empty(B)) == typeof(B)
-        @test empty(A) == empty(B)
+        @test @inferred(empty(B)) == empty(A)
+        @test @inferred(empty!(deepcopy(B))) == empty(A)
+        @test @inferred(empty(B)) == @inferred(empty!(deepcopy(B)))
+        @test append!(empty(B), B) == A
+        @test append!(empty!(deepcopy(B)), B) == A
     end