Zero dimensional BlockIndex (#431)

* Zero dimensional `BlockIndex`

---------

Co-authored-by: Sheehan Olver <[email protected]>

Author: mtfishman

Project.toml

@@ -1,6 +1,6 @@
 name = "BlockArrays"
 uuid = "8e7c35d0-a365-5155-bbbb-fb81a777f24e"
-version = "1.1.1"
+version = "1.2.0"
 
 [deps]
 ArrayLayouts = "4c555306-a7a7-4459-81d9-ec55ddd5c99a"

src/blockindices.jl

@@ -52,11 +52,10 @@ last(b::Block) = b
 iterate(x::Block) = (x, nothing)
 iterate(x::Block, ::Any) = nothing
 isempty(x::Block) = false
-broadcastable(x::Block) = x
+broadcastable(x::Block) = Ref(x)
 ndims(::Type{<:Block}) = 0
 ndims(::Block) = 0
 eltype(::Type{B}) where B<:Block = B
-getindex(B::Block, ::CartesianIndex{0}) = B
 
 # The following code is taken from CartesianIndex
 @inline (+)(index::Block{N}) where {N} = Block{N}(map(+, index.n))
@@ -147,10 +146,12 @@ struct BlockIndex{N,TI<:Tuple{Vararg{Integer,N}},Tα<:Tuple{Vararg{Integer,N}}}
 end
 
 @inline BlockIndex(a::NTuple{N,Block{1}}, b::Tuple) where N = BlockIndex(Int.(a), b)
+@inline BlockIndex(::Tuple{}, b::Tuple{}) = BlockIndex{0,Tuple{},Tuple{}}((), ())
 
 @inline BlockIndex(a::Integer, b::Integer) = BlockIndex((a,), (b,))
 @inline BlockIndex(a::Tuple, b::Integer) = BlockIndex(a, (b,))
 @inline BlockIndex(a::Integer, b::Tuple) = BlockIndex((a,), b)
+@inline BlockIndex() = BlockIndex((), ())
 
 @inline BlockIndex(a::Block, b::Tuple) = BlockIndex(a.n, b)
 @inline BlockIndex(a::Block, b::Integer) = BlockIndex(a, (b,))
@@ -202,7 +203,7 @@ BlockIndexRange(block::Block{N}, inds::Vararg{AbstractUnitRange{<:Integer},N}) w
 
 block(R::BlockIndexRange) = R.block
 
-getindex(::Block{0}) = Block()
+getindex(::Block{0}) = BlockIndex()
 getindex(B::Block{N}, inds::Vararg{Integer,N}) where N = BlockIndex(B,inds)
 getindex(B::Block{N}, inds::Vararg{AbstractUnitRange{<:Integer},N}) where N = BlockIndexRange(B,inds)
 getindex(B::Block{1}, inds::Colon) = B

test/test_blockarrays.jl

@@ -333,7 +333,7 @@ end
             @test size(ret) == ()
             @test all(iszero, ret)
             @test ret[Block()] == zeros()
-            @test ret[Block()[]] == zeros()
+            @test ret[Block()[]] == 0
             @test ret[] == 0
             @test view(ret, Block()) == zeros()
             @test Array(ret) == zeros()
@@ -360,7 +360,7 @@ end
             @test all(iszero, ret)
             @test ret[] == 0
             @test ret[Block()] == zeros()
-            @test ret[Block()[]] == zeros()
+            @test ret[Block()[]] == 0
             @test Array(ret) == zeros()
             ret[] = 1
             @test ret[] == 1

test/test_blockindices.jl

@@ -84,6 +84,7 @@ import BlockArrays: BlockIndex, BlockIndexRange, BlockSlice
     end
 
     @testset "BlockIndex" begin
+        @test Block()[] == BlockIndex()
         @test Block(1)[1] == BlockIndex((1,),(1,))
         @test Block(1)[1:2] == BlockIndexRange(Block(1),(1:2,))
         @test Block(1,1)[1,1] == BlockIndex((1,1),(1,1)) == BlockIndex((1,1),(1,))