Teach selectdim that its slices are slices (#531)

... as done in JuliaLang/julia#26655.
JuliaLang · Apr 11, 2018 · fa09434 · fa09434
1 parent 040ccc1
commit fa09434
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Showing 2 changed files with 8 additions and 1 deletion.
diff --git a/src/Compat.jl b/src/Compat.jl
@@ -1780,7 +1780,7 @@ end
 
 if !isdefined(Base, :selectdim) # 0.7.0-DEV.3976
     export selectdim
-    @inline selectdim(A::AbstractArray, d::Integer, i) = _selectdim(A, d, i, Base.setindex(axes(A), i, d))
+    @inline selectdim(A::AbstractArray, d::Integer, i) = _selectdim(A, d, i, Base.setindex(map(Base.Slice, axes(A)), i, d))
     @noinline function _selectdim(A, d, i, idxs)
         d >= 1 || throw(ArgumentError("dimension must be ≥ 1"))
         nd = ndims(A)

diff --git a/test/runtests.jl b/test/runtests.jl
@@ -1681,6 +1681,13 @@ let A = rand(5,5)
     @test selectdim(A, 2, 1:3) == A[:, 1:3]
     selectdim(A, 1, 3)[3] = 42
     @test A[3,3] == 42
+    if VERSION < v"0.7.0-DEV.3976" || VERSION >= v"0.7.0-DEV.4739"
+        # in the omitted version range, Julia's selectdim always gives IndexCartesian()
+        B = rand(4, 3, 2)
+        @test IndexStyle(selectdim(B, 1, 1)) == IndexStyle(view(B, 1, :, :)) == IndexLinear()
+        @test IndexStyle(selectdim(B, 2, 1)) == IndexStyle(view(B, :, 1, :)) == IndexCartesian()
+        @test IndexStyle(selectdim(B, 3, 1)) == IndexStyle(view(B, :, :, 1)) == IndexLinear()
+    end
 end
 
 nothing