From a0ac7d1f39ff431bbaadf73d83379b004baa5695 Mon Sep 17 00:00:00 2001
From: Milan Bouchet-Valat <nalimilan@club.fr>
Date: Mon, 31 Jul 2017 16:13:07 +0200
Subject: [PATCH] Make partialsort!() and partialsortperm!() return a view
 rather than a copy

Returning a copy (partially) defeats the purpose of these functions, which is
to avoid allocations.
---
 base/sort.jl | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/base/sort.jl b/base/sort.jl
index cf173218e14abf..ede1e1e032bce1 100644
--- a/base/sort.jl
+++ b/base/sort.jl
@@ -85,7 +85,12 @@ issorted(itr;
 function partialsort!(v::AbstractVector, k::Union{Int,OrdinalRange}, o::Ordering)
     inds = indices(v, 1)
     sort!(v, first(inds), last(inds), PartialQuickSort(k), o)
-    v[k]
+
+    if k isa Integer
+        return v[k]
+    else
+        return view(v, k)
+    end
 end
 
 """
@@ -704,7 +709,12 @@ function partialsortperm!(ix::AbstractVector{<:Integer}, v::AbstractVector,
 
     # do partial quicksort
     sort!(ix, PartialQuickSort(k), Perm(ord(lt, by, rev, order), v))
-    return ix[k]
+
+    if k isa Integer
+        return ix[k]
+    else
+        return view(ix, k)
+    end
 end
 
 ## sortperm: the permutation to sort an array ##