base/sort: add sort! for multidimensional arrays (#28902)

base/sort.jl

@@ -938,6 +938,8 @@ Sort a multidimensional array `A` along the given dimension.
 See [`sort!`](@ref) for a description of possible
 keyword arguments.
 
+To sort slices of an array, refer to [`sortslices`](@ref).
+
 # Examples
 ```jldoctest
 julia> A = [4 3; 1 2]
@@ -987,6 +989,53 @@ end
     Av
 end
 
+"""
+    sort!(A; dims::Integer, alg::Algorithm=defalg(v), lt=isless, by=identity, rev::Bool=false, order::Ordering=Forward)
+
+Sort the multidimensional array `A` along dimension `dims`.
+See [`sort!`](@ref) for a description of possible keyword arguments.
+
+To sort slices of an array, refer to [`sortslices`](@ref).
+
+# Examples
+```jldoctest
+julia> A = [4 3; 1 2]
+2×2 Array{Int64,2}:
+ 4  3
+ 1  2
+
+julia> sort!(A, dims = 1); A
+2×2 Array{Int64,2}:
+ 1  2
+ 4  3
+
+julia> sort!(A, dims = 2); A
+2×2 Array{Int64,2}:
+ 1  2
+ 3  4
+```
+"""
+function sort!(A::AbstractArray;
+               dims::Integer,
+               alg::Algorithm=defalg(A),
+               lt=isless,
+               by=identity,
+               rev::Union{Bool,Nothing}=nothing,
+               order::Ordering=Forward)
+    ordr = ord(lt, by, rev, order)
+    nd = ndims(A)
+    k = dims
+
+    1 <= k <= nd || throw(ArgumentError("dimension out of range"))
+
+    remdims = ntuple(i -> i == k ? 1 : size(A, i), nd)
+    for idx in CartesianIndices(remdims)
+        Av = view(A, ntuple(i -> i == k ? Colon() : idx[i], nd)...)
+        sort!(Av, alg, ordr)
+    end
+    A
+end
+
 ## fast clever sorting for floats ##
 
 module Float

test/arrayops.jl

@@ -1199,11 +1199,13 @@ end
     @test issorted(as[:,1])
     @test issorted(as[:,2])
     @test issorted(as[:,3])
+    @test sort!(copy(a), dims=1) == as
 
     as = sort(a, dims=2)
     @test issorted(as[1,:])
     @test issorted(as[2,:])
     @test issorted(as[3,:])
+    @test sort!(copy(a), dims=2) == as
 
     local b = rand(21,21,2)
 
@@ -1212,15 +1214,18 @@ end
         @test issorted(bs[:,i,1])
         @test issorted(bs[:,i,2])
     end
+    @test sort!(copy(b), dims=1) == bs
 
     bs = sort(b, dims=2)
     for i in 1:21
         @test issorted(bs[i,:,1])
         @test issorted(bs[i,:,2])
     end
+    @test sort!(copy(b), dims=2) == bs
 
     bs = sort(b, dims=3)
     @test all(bs[:,:,1] .<= bs[:,:,2])
+    @test sort!(copy(b), dims=3) == bs
 end
 
 @testset "higher dimensional sortslices" begin