From 4ce40cc06f87a4faf4bddca19d05552005ed60b2 Mon Sep 17 00:00:00 2001
From: Michael Abbott <32575566+mcabbott@users.noreply.github.com>
Date: Wed, 15 Dec 2021 11:07:05 -0500
Subject: [PATCH] docstring comment about eachslice

---
 base/abstractarray.jl | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/base/abstractarray.jl b/base/abstractarray.jl
index 923b3b29a48b26..80fd51b4be4ed0 100644
--- a/base/abstractarray.jl
+++ b/base/abstractarray.jl
@@ -2770,6 +2770,11 @@ julia> map(g, eachslice(A, dims=2))
 julia> mapslices(sum, A; dims=(1,3)) == sum(A; dims=(1,3))
 true
 ```
+
+Notice that in `eachslice(A; dims=2)`, the specified dimension is the
+one *without* a colon in the slice. This is `view(A,:,i,:)`, whereas
+`mapslices(f, A; dims=(1,3))` uses `A[:,i,:]`. The function `f` may mutate
+values in the slice without affecting `A`.
 """
 function mapslices(f, A::AbstractArray; dims)
     isempty(dims) && return map(f, A)