Fix negation of SymTridiagonal (fixes JuliaLang#36680) (JuliaLang#36681)

simeonschaub · Aug 11, 2020 · 869440d · 869440d
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commit 869440d
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diff --git a/stdlib/LinearAlgebra/src/tridiag.jl b/stdlib/LinearAlgebra/src/tridiag.jl
@@ -204,6 +204,7 @@ end
 
 +(A::SymTridiagonal, B::SymTridiagonal) = SymTridiagonal(A.dv+B.dv, A.ev+B.ev)
 -(A::SymTridiagonal, B::SymTridiagonal) = SymTridiagonal(A.dv-B.dv, A.ev-B.ev)
+-(A::SymTridiagonal) = SymTridiagonal(-A.dv, -A.ev)
 *(A::SymTridiagonal, B::Number) = SymTridiagonal(A.dv*B, A.ev*B)
 *(B::Number, A::SymTridiagonal) = A*B
 /(A::SymTridiagonal, B::Number) = SymTridiagonal(A.dv/B, A.ev/B)

diff --git a/stdlib/LinearAlgebra/test/tridiag.jl b/stdlib/LinearAlgebra/test/tridiag.jl
@@ -294,6 +294,11 @@ end
  @test_throws DimensionMismatch LinearAlgebra.mul!(Cnm,B,Cnn)
  end
  end
+ @testset "Negation" begin
+ mA = -A
+ @test mA isa mat_type
+ @test -mA == A
+ end
  if mat_type == SymTridiagonal
  @testset "Tridiagonal/SymTridiagonal mixing ops" begin
  B = convert(Tridiagonal{elty}, A)