1// Copyright 2013 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// +build !go1.2
6
7package language
8
9import "sort"
10
11func sortStable(s sort.Interface) {
12	ss := stableSort{
13		s:   s,
14		pos: make([]int, s.Len()),
15	}
16	for i := range ss.pos {
17		ss.pos[i] = i
18	}
19	sort.Sort(&ss)
20}
21
22type stableSort struct {
23	s   sort.Interface
24	pos []int
25}
26
27func (s *stableSort) Len() int {
28	return len(s.pos)
29}
30
31func (s *stableSort) Less(i, j int) bool {
32	return s.s.Less(i, j) || !s.s.Less(j, i) && s.pos[i] < s.pos[j]
33}
34
35func (s *stableSort) Swap(i, j int) {
36	s.s.Swap(i, j)
37	s.pos[i], s.pos[j] = s.pos[j], s.pos[i]
38}
39