Restore ± special cases (#227)

Author: dlfivefifty

Project.toml

@@ -1,6 +1,6 @@
 name = "FillArrays"
 uuid = "1a297f60-69ca-5386-bcde-b61e274b549b"
-version = "0.13.10"
+version = "0.13.11"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

src/fillalgebra.jl

@@ -212,6 +212,11 @@ function dot(u::AbstractVector{T}, D::Diagonal{U,<:Zeros}, v::AbstractVector{V})
 end
 
 # Addition and Subtraction
++(a::AbstractFill) = a
+-(a::Zeros) = a
+-(a::AbstractFill) = Fill(-getindex_value(a), size(a))
+
+
 function +(a::Zeros{T}, b::Zeros{V}) where {T, V} # for disambiguity
     promote_shape(a,b)
     return elconvert(promote_op(+,T,V),a)

test/runtests.jl

@@ -613,6 +613,14 @@ end
         @test zero(Ones(10,10)) == Zeros(10,10)
         @test zero(Fill(0.5, 10, 10)) == Zeros(10,10)
     end
+
+    @testset "Matrix ±" begin
+        x = Fill([1,2], 5)
+        z = Zeros{SVector{2,Int}}(5)
+        @test +(z) ≡ -(z) ≡ z
+        @test +(x) == x
+        @test -(x) == Fill(-[1,2], 5)
+    end
 end
 
 @testset "maximum/minimum/svd/sort" begin