Merge pull request #113 from invenia/mz/subtraction

implement faster subtraction

Author: mzgubic

Project.toml

@@ -1,7 +1,7 @@
 name = "BlockDiagonals"
 uuid = "0a1fb500-61f7-11e9-3c65-f5ef3456f9f0"
 authors = ["Invenia Technical Computing Corporation"]
-version = "0.1.35"
+version = "0.1.36"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"

src/base_maths.jl

@@ -66,6 +66,8 @@ end
 ## Subtraction
 Base.:-(B::BlockDiagonal) = BlockDiagonal(.-(blocks(B)))
 Base.:-(M::AbstractMatrix, B::BlockDiagonal) =  M + -B
+Base.:-(B::BlockDiagonal, M::AbstractMatrix) =  -M + B
+Base.:-(B::BlockDiagonal, B2::BlockDiagonal) =  B + (-B2)
 
 ## Multiplication
 Base.:*(n::Number, B::BlockDiagonal) = B * n

test/base_maths.jl

@@ -76,6 +76,8 @@ using Test
 
         @test -b1 == -Matrix(b1)
         @test b1 - b1 == Matrix(b1) - Matrix(b1)
+        @test Matrix(b1) - b2 == Matrix(b1) - Matrix(b2)
+        @test b1 - Matrix(b2) == Matrix(b1) - Matrix(b2)
     end
 
     @testset "Multiplication" begin