Overload copymutable_oftype and fillband! (#380)

* Overload copymutable_oftype and fillband!

* add tests

src/banded/BandedMatrix.jl

@@ -148,6 +148,16 @@ convert(::Type{DefaultBandedMatrix}, M::AbstractMatrix{T}) where T = convert(Def
 
 copy(B::BandedMatrix) = _BandedMatrix(copy(B.data), B.raxis, B.l, B.u)
 
+if isdefined(LinearAlgebra, :copymutable_oftype)
+    LinearAlgebra.copymutable_oftype(B::BandedMatrix, ::Type{S}) where S =
+        _BandedMatrix(LinearAlgebra.copymutable_oftype(B.data, S), B.raxis, B.l, B.u)
+
+    LinearAlgebra.copymutable_oftype(B::Adjoint{<:Any,<:BandedMatrix}, ::Type{S}) where S =
+        LinearAlgebra.copymutable_oftype(parent(B), S)'
+    LinearAlgebra.copymutable_oftype(B::Transpose{<:Any,<:BandedMatrix}, ::Type{S}) where S =
+        transpose(LinearAlgebra.copymutable_oftype(parent(B), S))
+end
+
 promote_rule(::Type{BandedMatrix{T1, C1}}, ::Type{BandedMatrix{T2, C2}}) where {T1,C1, T2,C2} =
     BandedMatrix{promote_type(T1,T2), promote_type(C1, C2)}
 
@@ -341,6 +351,9 @@ similar(bm::AbstractBandedMatrix, n::Integer, m::Integer, l::Integer, u::Integer
     similar(bm, eltype(bm), m, n, l, u)
 similar(bm::AbstractBandedMatrix, nm::Tuple{<:Integer,<:Integer}) = similar(bm, nm...)
 
+
+
+
 ## Abstract Array Interface
 
 axes(A::BandedMatrix) = (A.raxis, axes(A.data,2))
@@ -806,6 +819,11 @@ function fill!(A::BandedMatrix, x)
     A
 end
 
+function LinearAlgebra.fillband!(A::BandedMatrix{T}, x, l, u) where T
+    fill!(view(A.data, max(A.u+1-u,1):min(A.u+1-l,size(A.data,1)), :), x)
+    A
+end
+
 diag(A::BandedMatrix, k::Integer = 0) = A[band(k)]
 
 ## BandedSubBandedMatrix routines

test/test_banded.jl

@@ -505,4 +505,16 @@ Base.similar(::MyMatrix, ::Type{T}, m::Int, n::Int) where T = MyMatrix{T}(undef,
             @test @view(p[2:3]) == 2:3
         end
     end
+
+    if isdefined(LinearAlgebra, :copymutable_oftype)
+        @testset "copymutable_oftype" begin
+            B = _BandedMatrix((2:3)', 4, -2, 2)
+            @test LinearAlgebra.copymutable_oftype(B, Float64) == B
+            @test LinearAlgebra.copymutable_oftype(B, Float64) isa BandedMatrix{Float64}
+            @test LinearAlgebra.copymutable_oftype(B', Float64) == B'
+            @test LinearAlgebra.copymutable_oftype(B', Float64) isa Adjoint{Float64,<:BandedMatrix{Float64}}
+            @test LinearAlgebra.copymutable_oftype(transpose(B), Float64) == transpose(B)
+            @test LinearAlgebra.copymutable_oftype(transpose(B), Float64) isa Transpose{Float64,<:BandedMatrix{Float64}}
+        end
+    end
 end