Support empty Hcat (#353)

Author: dlfivefifty

Project.toml

@@ -1,6 +1,6 @@
 name = "LazyArrays"
 uuid = "5078a376-72f3-5289-bfd5-ec5146d43c02"
-version = "2.2.3"
+version = "2.2.4"
 
 [deps]
 ArrayLayouts = "4c555306-a7a7-4459-81d9-ec55ddd5c99a"

src/lazyconcat.jl

@@ -129,11 +129,13 @@ reverse(f::Vcat{<:Any,1}) = Vcat((reverse(itr) for itr in reverse(f.args))...)
 const Hcat{T,I<:Tuple} = ApplyArray{T,2,typeof(hcat),I}
 
 Hcat(A...) = ApplyArray(hcat, A...)
+Hcat() = Hcat{Any}()
 Hcat{T}(A...) where T = ApplyArray{T}(hcat, A...)
 
 @inline applied_eltype(::typeof(hcat), args...) = promote_type(map(eltype,args)...)
 @inline applied_ndims(::typeof(hcat), args...) = 2
 @inline applied_size(::typeof(hcat), args...) = (size(args[1],1), +(map(a -> size(a,2), args)...))
+@inline applied_size(::typeof(hcat)) = (0,0)
 
 @inline hcat_getindex(f, k, j::Integer) = hcat_getindex_recursive(f, (k, j), f.args...)
 

test/concattests.jl

@@ -647,6 +647,11 @@ import LazyArrays: MemoryLayout, DenseColumnMajor, materialize!, call, paddeddat
         A = Applied(hvcat, 2, A, B, C, D)
         @test A[1,2] == M[1,2]
     end
+
+    @testset "1 arg Vcat/Hcat" begin
+        @test Array(Hcat()) == Array{Any}(undef,0,0)
+        @test rowsupport(Hcat(Vcat(Zeros(3,1))),1:2) == colsupport(Vcat(Hcat(Zeros(1,3))),1:2)
+    end
 end
 
 end # module