view of RangeCumSum with OneTo (#142)

* view of RangeCumSum with OneTo

* propagate inbounds

* forward to getindex

* test type of view of RangeCumsum

Author: jishnub

src/ArrayLayouts.jl

@@ -9,7 +9,7 @@ using Base: AbstractCartesianIndex, OneTo, RangeIndex, ReinterpretArray, Reshape
 
 import Base: axes, size, length, eltype, ndims, first, last, diff, isempty, union, sort!,
                 ==, *, +, -, /, \, copy, copyto!, similar, getproperty, getindex, strides,
-                reverse, unsafe_convert, convert
+                reverse, unsafe_convert, convert, view
 
 using Base.Broadcast: Broadcasted
 

src/cumsum.jl

@@ -26,6 +26,8 @@ end
 
 Base.@propagate_inbounds getindex(c::RangeCumsum, kr::OneTo) = RangeCumsum(c.range[kr])
 
+Base.@propagate_inbounds view(c::RangeCumsum, kr::OneTo) = c[kr]
+
 first(r::RangeCumsum) = first(r.range)
 last(r::RangeCumsum) = sum(r.range)
 diff(r::RangeCumsum) = r.range[2:end]

test/test_cumsum.jl

@@ -6,6 +6,8 @@ using ArrayLayouts, Test
         @test r == r
         @test r .+ 1 == cumsum(r.range) .+ 1
         @test r[Base.OneTo(3)] == r[1:3]
+        @test @view(r[Base.OneTo(3)]) === r[Base.OneTo(3)] == r[1:3]
+        @test @view(r[Base.OneTo(3)]) isa RangeCumsum
         @test last(r) == r[end]
         @test diff(r) == diff(Vector(r))
         @test first(r) == r[1]