Generalize indexing a BandSlice (#337)

* Reindex for BandSlice

* generalize BandSlice indexing

* version bump to v0.17.16

* specialize only for AbstractRange indices

It's ok to be conservative here

Author: jishnub

Project.toml

@@ -1,6 +1,6 @@
 name = "BandedMatrices"
 uuid = "aae01518-5342-5314-be14-df237901396f"
-version = "0.17.15"
+version = "0.17.16"
 
 [deps]
 ArrayLayouts = "4c555306-a7a7-4459-81d9-ec55ddd5c99a"

src/generic/Band.jl

@@ -211,7 +211,7 @@ for f in (:indices, :unsafe_indices, :axes1, :first, :last, :size, :length,
     @eval $f(S::BandSlice) = $f(S.indices)
 end
 
-getindex(S::BandSlice, i::Int) = getindex(S.indices, i)
+getindex(S::BandSlice, i::Union{Int, AbstractRange}) = getindex(S.indices, i)
 show(io::IO, r::BandSlice) = print(io, "BandSlice(", r.band, ", ", r.indices, ")")
 
 to_index(::Band) = throw(ArgumentError("Block must be converted by to_indices(...)"))

test/test_indexing.jl

@@ -670,6 +670,14 @@ import BandedMatrices: rowstart, rowstop, colstart, colstop,
         end
     end
 
+    @testset "views of band views" begin
+        A = BandedMatrix(0=>1:4, 1=>(1:3) .+ 5, -1=>(1:3) .+ 10)
+        v = @view A[band(1)]
+        w = view(v, 2:3)
+        @test w == [7,8]
+        @test parentindices(w) isa Tuple{AbstractRange}
+    end
+
     @testset "other special indexing" begin
         @testset "all elements" begin
             a = BandedMatrix(Ones(3, 3), (1, 1))