Test for scale and scale! to not assume commutivity. Issue #13690

test/linalg/generic.jl

@@ -1,7 +1,26 @@
 # This file is a part of Julia. License is MIT: http://julialang.org/license
 
+import Base: *
 using Base.Test
 
+# A custom Quaternion type with minimal defined interface and methods.
+# Used to test scale and scale! methods to show non-commutativity.
+immutable Quaternion{T<:Real} <: Number
+    s::T
+    v1::T
+    v2::T
+    v3::T
+    norm::Bool
+end
+Quaternion(s::Real, v1::Real, v2::Real, v3::Real, n::Bool = false) =
+    Quaternion( promote(s, v1, v2, v3)..., n)
+Quaternion(a::Vector) = Quaternion(0, a[1], a[2], a[3])
+(*)(q::Quaternion, w::Quaternion) = Quaternion(q.s*w.s - q.v1*w.v1 - q.v2*w.v2 - q.v3*w.v3,
+                                               q.s*w.v1 + q.v1*w.s + q.v2*w.v3 - q.v3*w.v2,
+                                               q.s*w.v2 - q.v1*w.v3 + q.v2*w.s + q.v3*w.v1,
+                                               q.s*w.v3 + q.v1*w.v2 - q.v2*w.v1 + q.v3*w.s,
+                                               q.norm && w.norm)
+
 debug = false
 
 srand(123)
@@ -119,6 +138,12 @@ b = randn(Base.LinAlg.SCAL_CUTOFF) # make sure we try BLAS path
 @test isequal(scale(BigFloat[1.0], 2.0im),     Complex{BigFloat}[2.0im])
 @test isequal(scale(BigFloat[1.0], 2.0f0im),   Complex{BigFloat}[2.0im])
 
+# test scale and scale! for non-commutative multiplication
+q = Quaternion([0.44567, 0.755871, 0.882548, 0.423612])
+qmat = []
+push!(qmat, Quaternion([0.015007, 0.355067, 0.418645, 0.318373]))
+@test scale!(q, copy(qmat)) != scale!(copy(qmat), q)
+
 # test ops on Numbers
 for elty in [Float32,Float64,Complex64,Complex128]
     a = rand(elty)