Define arithmetic operations on Symmetric/Hermitian with Number

Author: ararslan

base/linalg/symmetric.jl

@@ -108,21 +108,14 @@ end
 end
 
 function setindex!(A::Symmetric, v, i::Integer, j::Integer)
-    if (A.uplo == 'U' && i >= j) || (A.uplo == 'L' && i <= j)
-        setindex!(A.data, v, i, j)
-    else
-        setindex!(A.data, v, j, i)
-    end
+    i == j || throw(ArgumentError("Cannot set a non-diagonal index in a symmetric matrix"))
+    setindex!(A.data, v, i, j)
 end
 
 function setindex!(A::Hermitian, v, i::Integer, j::Integer)
-    if i == j && !isreal(v)
-        throw(ArgumentError("Cannot set a nonreal value to the diagonal in a Hermitian matrix"))
-    elseif (A.uplo == 'U' && i >= j) || (A.uplo == 'L' && i <= j)
-        setindex!(A.data, v, i, j)
-    else
-        setindex!(A.data, v, j, i)
-    end
+    i == j || throw(ArgumentError("Cannot set a non-diagonal index in a Hermitian matrix"))
+    isreal(v) || throw(ArgumentError("Cannot set a nonreal value to the diagonal in a Hermitian matrix"))
+    setindex!(A.data, v, i, j)
 end
 
 similar{T}(A::Symmetric, ::Type{T}) = Symmetric(similar(A.data, T))
@@ -255,6 +248,10 @@ A_mul_B!{T<:BlasComplex,S<:StridedMatrix}(C::StridedMatrix{T}, A::StridedMatrix{
 *(A::HermOrSym, B::HermOrSym) = full(A)*full(B)
 *(A::StridedMatrix, B::HermOrSym) = A*full(B)
 
+for T in (:Symmetric, :Hermitian), op in (:+, :-, :*, :/)
+    @eval ($op)(A::$T, x::Number) = ($T)(($op)(A.data, x), Symbol(A.uplo))
+end
+
 bkfact(A::HermOrSym) = bkfact(A.data, Symbol(A.uplo), issymmetric(A))
 factorize(A::HermOrSym) = bkfact(A)
 

test/linalg/symmetric.jl

@@ -266,10 +266,16 @@ let X = sparse([1 -1; -1 1])
 
         W[1,1] = 4
         @test W == T(sparse([4 -1; -1 1]))
+        @test_throws ArgumentError (W[1,2] = 2)
 
         @test Y + I == T(sparse([2 -1; -1 2]))
         @test Y - I == T(sparse([0 -1; -1 0]))
+        @test Y * I == Y
+
         @test Y + 1 == T(sparse([2 0; 0 2]))
+        @test Y - 1 == T(sparse([0 -2; -2 0]))
+        @test Y * 2 == T(sparse([2 -2; -2 2]))
+        @test Y / 1 == Y
     end
 
     @test_throws ArgumentError Hermitian(X) + 2im*I