Add promotion for matrix * vector and vector * matrix

Nemocas · Feb 18, 2023 · 5b8af02 · 5b8af02
1 parent 8441a3a
commit 5b8af02
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diff --git a/src/Matrix.jl b/src/Matrix.jl
@@ -975,6 +975,31 @@ end
 
 ==(x::MatElem, y::MatElem) = ==(promote(x, y)...)
 
+# matrix * vec and vec * matrx
+function Base.promote(x::MatrixElem{S},
+                      y::Vector{T}) where {S <: NCRingElement,
+                                               T <: NCRingElement}
+   U = promote_rule_sym(S, T)
+   if U === S
+      return x, map(base_ring(x), y)
+   elseif U === T && length(y) != 0
+      return change_base_ring(parent(y[1]), x), y
+   else
+      error("Cannot promote to common type")
+   end
+end
+
+function Base.promote(x::Vector{S},
+                      y::MatrixElem{T}) where {S <: NCRingElement,
+                                               T <: NCRingElement}
+   yy, xx = promote(y, x)
+   return xx, yy
+end
+
+*(x::MatrixElem, y::Vector) = *(promote(x, y)...)
+
+*(x::Vector, y::MatrixElem) = *(promote(x, y)...)
+
 function Base.promote(x::MatElem{S}, y::T) where {S <: NCRingElement, T <: NCRingElement}
    U = promote_rule_sym(S, T)
    if U === S

diff --git a/test/generic/Matrix-test.jl b/test/generic/Matrix-test.jl
@@ -1334,6 +1334,23 @@ end
 
    @test one(F) == R[1 0; 0 1]
    @test R[1 0; 0 1] == one(R)
+
+   # vector * matrix
+   m = [1 2; 3 4]
+   F = ResidueField(ZZ, 3)
+   R, t = PolynomialRing(F, "t")
+   A = matrix(R, m)
+   B = matrix(F, m)
+   v = [one(F), 2*one(F)]
+   vv = [one(R), 2*one(R)]
+   @test (@inferred A * v) == A * vv
+   @test (@inferred v * A) == vv * A
+
+   @test (@inferred B * vv) == A * vv
+   @test (@inferred vv * B) == vv * A
+
+   @test_throws ErrorException A * Rational{BigInt}[1 ,2]
+   @test_throws ErrorException Rational{BigInt}[1 ,2] * A
 end
 
 @testset "Generic.Mat.permutation" begin

diff --git a/test/generic/MatrixAlgebra-test.jl b/test/generic/MatrixAlgebra-test.jl
@@ -348,6 +348,23 @@ end
 
    @test one(F) == R[1 0; 0 1]
    @test R[1 0; 0 1] == one(R)
+
+   # vector * matrix
+   m = [1 2; 3 4]
+   F = ResidueField(ZZ, 3)
+   R, t = PolynomialRing(F, "t")
+   A = MatrixAlgebra(R, 2)(m)
+   B = MatrixAlgebra(F, 2)(m)
+   v = [one(F), 2*one(F)]
+   vv = [one(R), 2*one(R)]
+   @test (@inferred A * v) == A * vv
+   @test (@inferred v * A) == vv * A
+
+   @test (@inferred B * vv) == A * vv
+   @test (@inferred vv * B) == vv * A
+
+   @test_throws ErrorException A * Rational{BigInt}[1 ,2]
+   @test_throws ErrorException Rational{BigInt}[1 ,2] * A
 end
 
 @testset "Generic.MatAlg.permutation" begin