Add fallback for +(::BlockDiagonal,::Diagonal) when blocks are not …

…square (#120)

* Add fallback to `+(::BlockDiagonal,::Diagonal)` for nonsquare blocks

* Add tests

* Bump version

Project.toml

@@ -1,7 +1,7 @@
 name = "BlockDiagonals"
 uuid = "0a1fb500-61f7-11e9-3c65-f5ef3456f9f0"
 authors = ["Invenia Technical Computing Corporation"]
-version = "0.1.37"
+version = "0.1.38"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"

src/base_maths.jl

@@ -42,8 +42,11 @@ function Base.:+(B::BlockDiagonal, M::StridedMatrix)
  return A
 end
 
-function Base.:+(B::BlockDiagonal, M::Diagonal)::BlockDiagonal
+function Base.:+(B::BlockDiagonal, M::Diagonal)
  size(B) == size(M) || throw(DimensionMismatch("dimensions must match"))
+ if !all(is_square, blocks(B))
+ return Matrix(B) + M # Fallback on the generic Base method
+ end
  A = copy(B)
  d = diag(M)
  row = 1

test/base_maths.jl

@@ -19,6 +19,8 @@ using Test
  b64 = BlockDiagonal([rand(rng, 2, 2), rand(rng, 2, 2)])
  b32 = BlockDiagonal([rand(rng, Float32, 2, 2), rand(rng, Float32, 2, 2)])
 
+ bns = BlockDiagonal([rand(rng, N1, N2), rand(rng, N2, N3), rand(rng, N3, N1)])
+
  @testset "Addition" begin
  @testset "BlockDiagonal + BlockDiagonal" begin
  @test b1 + b1 isa BlockDiagonal
@@ -58,6 +60,15 @@ using Test
  @test D + b1 isa BlockDiagonal
  @test D + b1 == D + Matrix(b1)
  @test_throws DimensionMismatch D′ + b1
+
+ # Non-square blocks
+ @test D + bns isa Matrix
+ @test D + bns == D + Matrix(bns)
+ @test_throws DimensionMismatch D′ + bns
+
+ @test bns + D isa Matrix
+ @test bns + D == D + Matrix(bns)
+ @test_throws DimensionMismatch bns + D′
  end
 
  @testset "BlockDiagonal + UniformScaling" begin
@@ -69,11 +80,11 @@ using Test
  @test 5I + b1 == 5I + Matrix(b1)
  end
  end # Addition
- 
+
  @testset "Subtraction" begin
  @test -b1 isa BlockDiagonal
  @test b1 - b1 isa BlockDiagonal
- 
+
  @test -b1 == -Matrix(b1)
  @test b1 - b1 == Matrix(b1) - Matrix(b1)
  @test Matrix(b1) - b2 == Matrix(b1) - Matrix(b2)