Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

RFC: prevent mapslices from mutating the original array #17266

Merged
merged 1 commit into from
Jul 5, 2016
Merged

RFC: prevent mapslices from mutating the original array #17266

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 4 additions & 1 deletion NEWS.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -84,7 +84,9 @@ Breaking changes
If a reshaped copy is needed, use `copy(reshape(a))` or `copy!` to a new array of
the desired shape ([#4211]).

* `mapslices` will always pass a view, so passing mutating functions will mutate the underlying array ([#16260])
* `mapslices` now re-uses temporary storage. Recipient functions
that expect input slices to be persistent should copy data to
other storage ([#17266]).

* Local variables and arguments are represented in lowered code as numbered `Slot`
objects instead of as symbols ([#15609]).
Expand Down Expand Up @@ -279,3 +281,4 @@ Deprecated or removed
[#16481]: https://github.com/JuliaLang/julia/issues/16481
[#16731]: https://github.com/JuliaLang/julia/issues/16731
[#16972]: https://github.com/JuliaLang/julia/issues/16972
[#17266]: https://github.com/JuliaLang/julia/issues/17266
6 changes: 4 additions & 2 deletions base/abstractarray.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1417,7 +1417,8 @@ function mapslices(f, A::AbstractArray, dims::AbstractVector)
idx[d] = Colon()
end

r1 = f(view(A, idx...))
Aslice = A[idx...]
r1 = f(Aslice)

# determine result size and allocate
Rsize = copy(dimsA)
Expand Down Expand Up @@ -1449,7 +1450,8 @@ function mapslices(f, A::AbstractArray, dims::AbstractVector)
for i in 1:nidx
idx[otherdims[i]] = ridx[otherdims[i]] = I.I[i]
end
R[ridx...] = f(view(A, idx...))
_unsafe_getindex!(Aslice, A, idx...)
R[ridx...] = f(Aslice)
end
end

Expand Down
3 changes: 1 addition & 2 deletions base/statistics.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -492,8 +492,7 @@ end
median!{T}(v::AbstractArray{T}) = median!(vec(v))
median{T}(v::AbstractArray{T}) = median!(copy!(Array(T, length(v)), v))

median!{T}(v::AbstractArray{T}, region) = mapslices(median!, v, region)
median{T}(v::AbstractArray{T}, region) = median!(copy(v), region)
median{T}(v::AbstractArray{T}, region) = mapslices(median!, v, region)

# for now, use the R/S definition of quantile; may want variants later
# see ?quantile in R -- this is type 7
Expand Down
6 changes: 6 additions & 0 deletions test/arrayops.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -843,6 +843,12 @@ let
n3a = mapslices(x-> ones(1,6), c, [2,3])
@test size(n1a) == (1,6,4) && size(n2a) == (1,3,6) && size(n3a) == (2,1,6)
@test size(n1) == (6,1,4) && size(n2) == (6,3,1) && size(n3) == (2,6,1)

# mutating functions
o = ones(3, 4)
m = mapslices(x->fill!(x, 0), o, 2)
@test m == zeros(3, 4)
@test o == ones(3, 4)
end


Expand Down