Overload lmul!/rmul! (#92)

* Overload lmul!/rmul!

* add comment

Author: dlfivefifty

Project.toml

@@ -1,6 +1,6 @@
 name = "FillArrays"
 uuid = "1a297f60-69ca-5386-bcde-b61e274b549b"
-version = "0.8.7"
+version = "0.8.8"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

src/FillArrays.jl

@@ -7,7 +7,7 @@ import Base: size, getindex, setindex!, IndexStyle, checkbounds, convert,
     copy, vec, setindex!, count, ==, reshape, _throw_dmrs, map, zero
 
 import LinearAlgebra: rank, svdvals!, tril, triu, tril!, triu!, diag, transpose, adjoint, fill!,
-    norm2, norm1, normInf, normMinusInf, normp
+    norm2, norm1, normInf, normMinusInf, normp, lmul!, rmul!
 
 import Base.Broadcast: broadcasted, DefaultArrayStyle, broadcast_shape
 

src/fillalgebra.jl

@@ -211,3 +211,24 @@ norm2(a::AbstractFill) = sqrt(length(a))*norm(getindex_value(a))
 normp(a::AbstractFill, p) = (length(a))^(1/p)*norm(getindex_value(a))
 normInf(a::AbstractFill) = norm(getindex_value(a))
 normMinusInf(a::AbstractFill) = norm(getindex_value(a))
+
+
+###
+# lmul!/rmul!
+###
+
+function lmul!(x::Number, z::AbstractFill)
+    λ = getindex_value(z)
+    # Following check ensures consistency w/ lmul!(x, Array(z))
+    # for, e.g., lmul!(NaN, z)
+    x*λ == λ || throw(ArgumentError("Cannot scale by $x"))
+    z
+end
+
+function rmul!(z::AbstractFill, x::Number)
+    λ = getindex_value(z)
+	# Following check ensures consistency w/ lmul!(x, Array(z))
+    # for, e.g., lmul!(NaN, z)
+    λ*x == λ || throw(ArgumentError("Cannot scale by $x"))
+    z
+end

test/runtests.jl

@@ -952,3 +952,17 @@ end
     @test reshape(Fill(2,2,3),Val(1)) ≡ Fill(2,6)
     @test reshape(Fill(2, 2), (2, )) ≡ Fill(2, 2)
 end
+
+@testset "lmul!/rmul!" begin
+    z = Zeros(1_000_000_000_000)
+    @test lmul!(2.0,z) === z
+    @test rmul!(z,2.0) === z
+    @test_throws ArgumentError lmul!(Inf,z)
+    @test_throws ArgumentError rmul!(z,Inf)
+
+    x = Fill([1,2],1_000_000_000_000)
+    @test lmul!(1.0,x) === x
+    @test rmul!(x,1.0) === x
+    @test_throws ArgumentError lmul!(2.0,x)
+    @test_throws ArgumentError rmul!(x,2.0)
+end