Add function nestedview and example

Author: oschulz

src/array_of_similar_arrays.jl

@@ -51,6 +51,17 @@ The following type aliases are defined:
 
 `VectorOfSimilarArrays` supports `push!()`, etc., provided the underlying
 array supports resizing of it's last dimension (e.g. an `ElasticArray`).
+
+The nested array can also be created using the function [`nestedview`](@doc)
+and the wrapped flat array can be accessed using [`flatview`](@ref)
+afterwards:
+
+```julia
+    A_flat = rand(2,3,4,5,6)
+    A_nested = nestedview(A_flat, 2)
+    A_nested isa AbstractArray{<:AbstractArray{T,2},3} where T
+    flatview(A_nested) === A_flat
+```
 """
 struct ArrayOfSimilarArrays{
     T, M, N, L,

src/functions.jl

@@ -42,11 +42,25 @@ will fall back to `Base.Iterators.flatten`.
 function flatview end
 export flatview
 
-flatview(A::AbstractArray) = A
+@inline flatview(A::AbstractArray) = A
 
-flatview(A::AbstractArray{<:AbstractArray}) = Base.Iterators.flatten(A)
+@inline flatview(A::AbstractArray{<:AbstractArray}) = Base.Iterators.flatten(A)
 
 
+"""
+    nestedview(A::AbstractArray{T,M+N}, M::Integer)
+
+AbstractArray{<:AbstractArray{T,M},N}
+
+View array `A` in as an `M`-dimensional array of `N`-dimensional arrays by
+wrapping it into an [`ArrayOfSimilarArrays`](@ref).
+"""
+function nestedview end
+export nestedview
+
+@inline nestedview(A::AbstractArray{T,L}, M::Integer) where {T,L} =
+    ArrayOfSimilarArrays{T,M}(A)
+
 
 """
     innersize(A:AbstractArray{<:AbstractArray}, [dim])

test/array_of_similar_arrays.jl

@@ -109,4 +109,11 @@ using UnsafeArrays
         test_from_nested(VectorOfSimilarVectors{Float32}, VectorOfSimilarVectors{Float32,Array{Float32,2}}, Val(1), Val(1))
         test_from_nested(VectorOfSimilarVectors, VectorOfSimilarVectors{Float64,Array{Float64,2}}, Val(1), Val(1))
     end
+
+    @testset "examples" begin
+        A_flat = rand(2,3,4,5,6)
+        A_nested = nestedview(A_flat, 2)
+        A_nested isa AbstractArray{<:AbstractArray{T,2},3} where T
+        flatview(A_nested) === A_flat
+    end
 end