From d4cfe28885317c16a4db0ffde30f30a79b063da8 Mon Sep 17 00:00:00 2001
From: Miek Gieben <miek@miek.nl>
Date: Fri, 1 Feb 2013 08:44:45 -0800
Subject: [PATCH] sort: add Reverse as a function
This updates: https://golang.org/cl/6909059/
Fixes #4511.
R=minux.ma, rsc
CC=golang-dev
https://golang.org/cl/6932054
---
src/pkg/sort/example_test.go | 7 +++++++
src/pkg/sort/sort.go | 16 ++++++++++++++++
src/pkg/sort/sort_test.go | 17 +++++++++++++++++
3 files changed, 40 insertions(+)
diff --git a/src/pkg/sort/example_test.go b/src/pkg/sort/example_test.go
index f57d02546f7..f7372bec375 100644
--- a/src/pkg/sort/example_test.go
+++ b/src/pkg/sort/example_test.go
@@ -15,3 +15,10 @@ func ExampleInts() {
fmt.Println(s)
// Output: [1 2 3 4 5 6]
}
+
+func ExampleReverse() {
+ s := []int{5, 2, 6, 3, 1, 4} // unsorted
+ sort.Sort(sort.Reverse(sort.IntSlice(s)))
+ fmt.Println(s)
+ // Output: [6 5 4 3 2 1]
+}
diff --git a/src/pkg/sort/sort.go b/src/pkg/sort/sort.go
index 62a4d55e798..3f7a99730c8 100644
--- a/src/pkg/sort/sort.go
+++ b/src/pkg/sort/sort.go
@@ -197,6 +197,22 @@ func Sort(data Interface) {
quickSort(data, 0, n, maxDepth)
}
+type reverse struct {
+ // This embedded Interface permits Reverse to use the methods of
+ // another Interface implementation.
+ Interface
+}
+
+// Less returns the opposite of the embedded implementation's Less method.
+func (r reverse) Less(i, j int) bool {
+ return r.Interface.Less(j, i)
+}
+
+// Reverse returns the reverse order for data.
+func Reverse(data Interface) Interface {
+ return &reverse{data}
+}
+
// IsSorted reports whether data is sorted.
func IsSorted(data Interface) bool {
n := data.Len()
diff --git a/src/pkg/sort/sort_test.go b/src/pkg/sort/sort_test.go
index ee8a9d0e849..439a3d5399e 100644
--- a/src/pkg/sort/sort_test.go
+++ b/src/pkg/sort/sort_test.go
@@ -92,6 +92,23 @@ func TestSortLarge_Random(t *testing.T) {
}
}
+func TestReverseSortIntSlice(t *testing.T) {
+ data := ints
+ data1 := ints
+ a := IntSlice(data[0:])
+ Sort(a)
+ r := IntSlice(data1[0:])
+ Sort(Reverse(r))
+ for i := 0; i < len(data); i++ {
+ if a[i] != r[len(data)-1-i] {
+ t.Errorf("reverse sort didn't sort")
+ }
+ if i > len(data)/2 {
+ break
+ }
+ }
+}
+
func BenchmarkSortString1K(b *testing.B) {
b.StopTimer()
for i := 0; i < b.N; i++ {
--
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