Add (col/row)support for Inv(Triangular) (#332)

Author: DanielVandH

Project.toml

@@ -1,6 +1,6 @@
 name = "LazyArrays"
 uuid = "5078a376-72f3-5289-bfd5-ec5146d43c02"
-version = "2.1.2"
+version = "2.1.3"
 
 [deps]
 ArrayLayouts = "4c555306-a7a7-4459-81d9-ec55ddd5c99a"

ext/LazyArraysBandedMatricesExt.jl

@@ -87,6 +87,16 @@ function rowsupport(::AbstractInvLayout{<:AbstractBandedLayout}, A, k)
     1:n
 end
 
+function colsupport(lay::AbstractInvLayout{<:TriangularLayout}, A, j)
+    B, = arguments(lay, A)
+    return colsupport(B, j)
+end
+
+function rowsupport(lay::AbstractInvLayout{<:TriangularLayout}, A, k)
+    B, = arguments(lay, A)
+    return rowsupport(B, k)
+end
+
 isbanded(K::Kron{<:Any,2}) = all(isbanded, K.args)
 
 function bandwidths(K::Kron{<:Any,2})

test/bandedtests.jl

@@ -890,4 +890,20 @@ LinearAlgebra.lmul!(β::Number, A::PseudoBandedMatrix) = (lmul!(β, A.data); A)
     end
 end
 
+@testset "Issue #329" begin
+    for op in (UpperTriangular, UnitUpperTriangular)
+        A = UpperTriangular(ApplyArray(inv, rand(5, 5)))
+        B = inv(A)
+        @test colsupport.(Ref(B), 1:5) == Base.OneTo.(1:5)
+        @test rowsupport.(Ref(B), 1:5) == range.(1:5, 5)
+    end 
+
+    for op in (LowerTriangular, UnitLowerTriangular)
+        A = LowerTriangular(ApplyArray(inv, rand(15, 15)))
+        B = inv(A)
+        @test colsupport.(Ref(B), 1:15) == range.(1:15, 15)
+        @test rowsupport.(Ref(B), 1:15) == Base.OneTo.(1:15)
+    end
+end
+
 end # module