build: move package sources from src/pkg to src

Preparation was in CL 134570043.
This CL contains only the effect of 'hg mv src/pkg/* src'.
For more about the move, see golang.org/s/go14nopkg.

10 files changed, 1681 insertions, 0 deletions

diff --git a/src/sort/example_interface_test.go b/src/sort/example_interface_test.go
new file mode 100644
index 000000000..442204ea9
--- /dev/null
+++ b/src/sort/example_interface_test.go
@@ -0,0 +1,44 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sort_test
+
+import (
+	"fmt"
+	"sort"
+)
+
+type Person struct {
+	Name string
+	Age  int
+}
+
+func (p Person) String() string {
+	return fmt.Sprintf("%s: %d", p.Name, p.Age)
+}
+
+// ByAge implements sort.Interface for []Person based on
+// the Age field.
+type ByAge []Person
+
+func (a ByAge) Len() int           { return len(a) }
+func (a ByAge) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
+func (a ByAge) Less(i, j int) bool { return a[i].Age < a[j].Age }
+
+func Example() {
+	people := []Person{
+		{"Bob", 31},
+		{"John", 42},
+		{"Michael", 17},
+		{"Jenny", 26},
+	}
+
+	fmt.Println(people)
+	sort.Sort(ByAge(people))
+	fmt.Println(people)
+
+	// Output:
+	// [Bob: 31 John: 42 Michael: 17 Jenny: 26]
+	// [Michael: 17 Jenny: 26 Bob: 31 John: 42]
+}
diff --git a/src/sort/example_keys_test.go b/src/sort/example_keys_test.go
new file mode 100644
index 000000000..a8e47e492
--- /dev/null
+++ b/src/sort/example_keys_test.go
@@ -0,0 +1,96 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sort_test
+
+import (
+	"fmt"
+	"sort"
+)
+
+// A couple of type definitions to make the units clear.
+type earthMass float64
+type au float64
+
+// A Planet defines the properties of a solar system object.
+type Planet struct {
+	name     string
+	mass     earthMass
+	distance au
+}
+
+// By is the type of a "less" function that defines the ordering of its Planet arguments.
+type By func(p1, p2 *Planet) bool
+
+// Sort is a method on the function type, By, that sorts the argument slice according to the function.
+func (by By) Sort(planets []Planet) {
+	ps := &planetSorter{
+		planets: planets,
+		by:      by, // The Sort method's receiver is the function (closure) that defines the sort order.
+	}
+	sort.Sort(ps)
+}
+
+// planetSorter joins a By function and a slice of Planets to be sorted.
+type planetSorter struct {
+	planets []Planet
+	by      func(p1, p2 *Planet) bool // Closure used in the Less method.
+}
+
+// Len is part of sort.Interface.
+func (s *planetSorter) Len() int {
+	return len(s.planets)
+}
+
+// Swap is part of sort.Interface.
+func (s *planetSorter) Swap(i, j int) {
+	s.planets[i], s.planets[j] = s.planets[j], s.planets[i]
+}
+
+// Less is part of sort.Interface. It is implemented by calling the "by" closure in the sorter.
+func (s *planetSorter) Less(i, j int) bool {
+	return s.by(&s.planets[i], &s.planets[j])
+}
+
+var planets = []Planet{
+	{"Mercury", 0.055, 0.4},
+	{"Venus", 0.815, 0.7},
+	{"Earth", 1.0, 1.0},
+	{"Mars", 0.107, 1.5},
+}
+
+// ExampleSortKeys demonstrates a technique for sorting a struct type using programmable sort criteria.
+func Example_sortKeys() {
+	// Closures that order the Planet structure.
+	name := func(p1, p2 *Planet) bool {
+		return p1.name < p2.name
+	}
+	mass := func(p1, p2 *Planet) bool {
+		return p1.mass < p2.mass
+	}
+	distance := func(p1, p2 *Planet) bool {
+		return p1.distance < p2.distance
+	}
+	decreasingDistance := func(p1, p2 *Planet) bool {
+		return !distance(p1, p2)
+	}
+
+	// Sort the planets by the various criteria.
+	By(name).Sort(planets)
+	fmt.Println("By name:", planets)
+
+	By(mass).Sort(planets)
+	fmt.Println("By mass:", planets)
+
+	By(distance).Sort(planets)
+	fmt.Println("By distance:", planets)
+
+	By(decreasingDistance).Sort(planets)
+	fmt.Println("By decreasing distance:", planets)
+
+	// Output: By name: [{Earth 1 1} {Mars 0.107 1.5} {Mercury 0.055 0.4} {Venus 0.815 0.7}]
+	// By mass: [{Mercury 0.055 0.4} {Mars 0.107 1.5} {Venus 0.815 0.7} {Earth 1 1}]
+	// By distance: [{Mercury 0.055 0.4} {Venus 0.815 0.7} {Earth 1 1} {Mars 0.107 1.5}]
+	// By decreasing distance: [{Mars 0.107 1.5} {Earth 1 1} {Venus 0.815 0.7} {Mercury 0.055 0.4}]
+}
diff --git a/src/sort/example_multi_test.go b/src/sort/example_multi_test.go
new file mode 100644
index 000000000..ac316540f
--- /dev/null
+++ b/src/sort/example_multi_test.go
@@ -0,0 +1,131 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sort_test
+
+import (
+	"fmt"
+	"sort"
+)
+
+// A Change is a record of source code changes, recording user, language, and delta size.
+type Change struct {
+	user     string
+	language string
+	lines    int
+}
+
+type lessFunc func(p1, p2 *Change) bool
+
+// multiSorter implements the Sort interface, sorting the changes within.
+type multiSorter struct {
+	changes []Change
+	less    []lessFunc
+}
+
+// Sort sorts the argument slice according to the less functions passed to OrderedBy.
+func (ms *multiSorter) Sort(changes []Change) {
+	ms.changes = changes
+	sort.Sort(ms)
+}
+
+// OrderedBy returns a Sorter that sorts using the less functions, in order.
+// Call its Sort method to sort the data.
+func OrderedBy(less ...lessFunc) *multiSorter {
+	return &multiSorter{
+		less: less,
+	}
+}
+
+// Len is part of sort.Interface.
+func (ms *multiSorter) Len() int {
+	return len(ms.changes)
+}
+
+// Swap is part of sort.Interface.
+func (ms *multiSorter) Swap(i, j int) {
+	ms.changes[i], ms.changes[j] = ms.changes[j], ms.changes[i]
+}
+
+// Less is part of sort.Interface. It is implemented by looping along the
+// less functions until it finds a comparison that is either Less or
+// !Less. Note that it can call the less functions twice per call. We
+// could change the functions to return -1, 0, 1 and reduce the
+// number of calls for greater efficiency: an exercise for the reader.
+func (ms *multiSorter) Less(i, j int) bool {
+	p, q := &ms.changes[i], &ms.changes[j]
+	// Try all but the last comparison.
+	var k int
+	for k = 0; k < len(ms.less)-1; k++ {
+		less := ms.less[k]
+		switch {
+		case less(p, q):
+			// p < q, so we have a decision.
+			return true
+		case less(q, p):
+			// p > q, so we have a decision.
+			return false
+		}
+		// p == q; try the next comparison.
+	}
+	// All comparisons to here said "equal", so just return whatever
+	// the final comparison reports.
+	return ms.less[k](p, q)
+}
+
+var changes = []Change{
+	{"gri", "Go", 100},
+	{"ken", "C", 150},
+	{"glenda", "Go", 200},
+	{"rsc", "Go", 200},
+	{"r", "Go", 100},
+	{"ken", "Go", 200},
+	{"dmr", "C", 100},
+	{"r", "C", 150},
+	{"gri", "Smalltalk", 80},
+}
+
+// ExampleMultiKeys demonstrates a technique for sorting a struct type using different
+// sets of multiple fields in the comparison. We chain together "Less" functions, each of
+// which compares a single field.
+func Example_sortMultiKeys() {
+	// Closures that order the Change structure.
+	user := func(c1, c2 *Change) bool {
+		return c1.user < c2.user
+	}
+	language := func(c1, c2 *Change) bool {
+		return c1.language < c2.language
+	}
+	increasingLines := func(c1, c2 *Change) bool {
+		return c1.lines < c2.lines
+	}
+	decreasingLines := func(c1, c2 *Change) bool {
+		return c1.lines > c2.lines // Note: > orders downwards.
+	}
+
+	// Simple use: Sort by user.
+	OrderedBy(user).Sort(changes)
+	fmt.Println("By user:", changes)
+
+	// More examples.
+	OrderedBy(user, increasingLines).Sort(changes)
+	fmt.Println("By user,<lines:", changes)
+
+	OrderedBy(user, decreasingLines).Sort(changes)
+	fmt.Println("By user,>lines:", changes)
+
+	OrderedBy(language, increasingLines).Sort(changes)
+	fmt.Println("By language,<lines:", changes)
+
+	OrderedBy(language, increasingLines, user).Sort(changes)
+	fmt.Println("By language,<lines,user:", changes)
+
+	// Output:
+	// By user: [{dmr C 100} {glenda Go 200} {gri Smalltalk 80} {gri Go 100} {ken Go 200} {ken C 150} {r Go 100} {r C 150} {rsc Go 200}]
+	// By user,<lines: [{dmr C 100} {glenda Go 200} {gri Smalltalk 80} {gri Go 100} {ken C 150} {ken Go 200} {r Go 100} {r C 150} {rsc Go 200}]
+	// By user,>lines: [{dmr C 100} {glenda Go 200} {gri Go 100} {gri Smalltalk 80} {ken Go 200} {ken C 150} {r C 150} {r Go 100} {rsc Go 200}]
+	// By language,<lines: [{dmr C 100} {ken C 150} {r C 150} {gri Go 100} {r Go 100} {ken Go 200} {glenda Go 200} {rsc Go 200} {gri Smalltalk 80}]
+	// By language,<lines,user: [{dmr C 100} {ken C 150} {r C 150} {gri Go 100} {r Go 100} {glenda Go 200} {ken Go 200} {rsc Go 200} {gri Smalltalk 80}]
+
+}
diff --git a/src/sort/example_test.go b/src/sort/example_test.go
new file mode 100644
index 000000000..f7372bec3
--- /dev/null
+++ b/src/sort/example_test.go
@@ -0,0 +1,24 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sort_test
+
+import (
+	"fmt"
+	"sort"
+)
+
+func ExampleInts() {
+	s := []int{5, 2, 6, 3, 1, 4} // unsorted
+	sort.Ints(s)
+	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/sort/example_wrapper_test.go b/src/sort/example_wrapper_test.go
new file mode 100644
index 000000000..cf6d74cf7
--- /dev/null
+++ b/src/sort/example_wrapper_test.go
@@ -0,0 +1,77 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sort_test
+
+import (
+	"fmt"
+	"sort"
+)
+
+type Grams int
+
+func (g Grams) String() string { return fmt.Sprintf("%dg", int(g)) }
+
+type Organ struct {
+	Name   string
+	Weight Grams
+}
+
+type Organs []*Organ
+
+func (s Organs) Len() int      { return len(s) }
+func (s Organs) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+
+// ByName implements sort.Interface by providing Less and using the Len and
+// Swap methods of the embedded Organs value.
+type ByName struct{ Organs }
+
+func (s ByName) Less(i, j int) bool { return s.Organs[i].Name < s.Organs[j].Name }
+
+// ByWeight implements sort.Interface by providing Less and using the Len and
+// Swap methods of the embedded Organs value.
+type ByWeight struct{ Organs }
+
+func (s ByWeight) Less(i, j int) bool { return s.Organs[i].Weight < s.Organs[j].Weight }
+
+func Example_sortWrapper() {
+	s := []*Organ{
+		{"brain", 1340},
+		{"heart", 290},
+		{"liver", 1494},
+		{"pancreas", 131},
+		{"prostate", 62},
+		{"spleen", 162},
+	}
+
+	sort.Sort(ByWeight{s})
+	fmt.Println("Organs by weight:")
+	printOrgans(s)
+
+	sort.Sort(ByName{s})
+	fmt.Println("Organs by name:")
+	printOrgans(s)
+
+	// Output:
+	// Organs by weight:
+	// prostate (62g)
+	// pancreas (131g)
+	// spleen   (162g)
+	// heart    (290g)
+	// brain    (1340g)
+	// liver    (1494g)
+	// Organs by name:
+	// brain    (1340g)
+	// heart    (290g)
+	// liver    (1494g)
+	// pancreas (131g)
+	// prostate (62g)
+	// spleen   (162g)
+}
+
+func printOrgans(s []*Organ) {
+	for _, o := range s {
+		fmt.Printf("%-8s (%v)\n", o.Name, o.Weight)
+	}
+}
diff --git a/src/sort/export_test.go b/src/sort/export_test.go
new file mode 100644
index 000000000..b6e30ceb5
--- /dev/null
+++ b/src/sort/export_test.go
@@ -0,0 +1,9 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sort
+
+func Heapsort(data Interface) {
+	heapSort(data, 0, data.Len())
+}
diff --git a/src/sort/search.go b/src/sort/search.go
new file mode 100644
index 000000000..8a2c1c33b
--- /dev/null
+++ b/src/sort/search.go
@@ -0,0 +1,112 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements binary search.
+
+package sort
+
+// Search uses binary search to find and return the smallest index i
+// in [0, n) at which f(i) is true, assuming that on the range [0, n),
+// f(i) == true implies f(i+1) == true.  That is, Search requires that
+// f is false for some (possibly empty) prefix of the input range [0, n)
+// and then true for the (possibly empty) remainder; Search returns
+// the first true index.  If there is no such index, Search returns n.
+// (Note that the "not found" return value is not -1 as in, for instance,
+// strings.Index).
+// Search calls f(i) only for i in the range [0, n).
+//
+// A common use of Search is to find the index i for a value x in
+// a sorted, indexable data structure such as an array or slice.
+// In this case, the argument f, typically a closure, captures the value
+// to be searched for, and how the data structure is indexed and
+// ordered.
+//
+// For instance, given a slice data sorted in ascending order,
+// the call Search(len(data), func(i int) bool { return data[i] >= 23 })
+// returns the smallest index i such that data[i] >= 23.  If the caller
+// wants to find whether 23 is in the slice, it must test data[i] == 23
+// separately.
+//
+// Searching data sorted in descending order would use the <=
+// operator instead of the >= operator.
+//
+// To complete the example above, the following code tries to find the value
+// x in an integer slice data sorted in ascending order:
+//
+//	x := 23
+//	i := sort.Search(len(data), func(i int) bool { return data[i] >= x })
+//	if i < len(data) && data[i] == x {
+//		// x is present at data[i]
+//	} else {
+//		// x is not present in data,
+//		// but i is the index where it would be inserted.
+//	}
+//
+// As a more whimsical example, this program guesses your number:
+//
+//	func GuessingGame() {
+//		var s string
+//		fmt.Printf("Pick an integer from 0 to 100.\n")
+//		answer := sort.Search(100, func(i int) bool {
+//			fmt.Printf("Is your number <= %d? ", i)
+//			fmt.Scanf("%s", &s)
+//			return s != "" && s[0] == 'y'
+//		})
+//		fmt.Printf("Your number is %d.\n", answer)
+//	}
+//
+func Search(n int, f func(int) bool) int {
+	// Define f(-1) == false and f(n) == true.
+	// Invariant: f(i-1) == false, f(j) == true.
+	i, j := 0, n
+	for i < j {
+		h := i + (j-i)/2 // avoid overflow when computing h
+		// i ≤ h < j
+		if !f(h) {
+			i = h + 1 // preserves f(i-1) == false
+		} else {
+			j = h // preserves f(j) == true
+		}
+	}
+	// i == j, f(i-1) == false, and f(j) (= f(i)) == true  =>  answer is i.
+	return i
+}
+
+// Convenience wrappers for common cases.
+
+// SearchInts searches for x in a sorted slice of ints and returns the index
+// as specified by Search. The return value is the index to insert x if x is
+// not present (it could be len(a)).
+// The slice must be sorted in ascending order.
+//
+func SearchInts(a []int, x int) int {
+	return Search(len(a), func(i int) bool { return a[i] >= x })
+}
+
+// SearchFloat64s searches for x in a sorted slice of float64s and returns the index
+// as specified by Search.  The return value is the index to insert x if x is not
+// present (it could be len(a)).
+// The slice must be sorted in ascending order.
+//
+func SearchFloat64s(a []float64, x float64) int {
+	return Search(len(a), func(i int) bool { return a[i] >= x })
+}
+
+// SearchStrings searches for x in a sorted slice of strings and returns the index
+// as specified by Search.  The return value is the index to insert x if x is not
+// present (it could be len(a)).
+// The slice must be sorted in ascending order.
+//
+func SearchStrings(a []string, x string) int {
+	return Search(len(a), func(i int) bool { return a[i] >= x })
+}
+
+// Search returns the result of applying SearchInts to the receiver and x.
+func (p IntSlice) Search(x int) int { return SearchInts(p, x) }
+
+// Search returns the result of applying SearchFloat64s to the receiver and x.
+func (p Float64Slice) Search(x float64) int { return SearchFloat64s(p, x) }
+
+// Search returns the result of applying SearchStrings to the receiver and x.
+func (p StringSlice) Search(x string) int { return SearchStrings(p, x) }
diff --git a/src/sort/search_test.go b/src/sort/search_test.go
new file mode 100644
index 000000000..29b8d62df
--- /dev/null
+++ b/src/sort/search_test.go
@@ -0,0 +1,161 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sort_test
+
+import (
+	"runtime"
+	. "sort"
+	"testing"
+)
+
+func f(a []int, x int) func(int) bool {
+	return func(i int) bool {
+		return a[i] >= x
+	}
+}
+
+var data = []int{0: -10, 1: -5, 2: 0, 3: 1, 4: 2, 5: 3, 6: 5, 7: 7, 8: 11, 9: 100, 10: 100, 11: 100, 12: 1000, 13: 10000}
+
+var tests = []struct {
+	name string
+	n    int
+	f    func(int) bool
+	i    int
+}{
+	{"empty", 0, nil, 0},
+	{"1 1", 1, func(i int) bool { return i >= 1 }, 1},
+	{"1 true", 1, func(i int) bool { return true }, 0},
+	{"1 false", 1, func(i int) bool { return false }, 1},
+	{"1e9 991", 1e9, func(i int) bool { return i >= 991 }, 991},
+	{"1e9 true", 1e9, func(i int) bool { return true }, 0},
+	{"1e9 false", 1e9, func(i int) bool { return false }, 1e9},
+	{"data -20", len(data), f(data, -20), 0},
+	{"data -10", len(data), f(data, -10), 0},
+	{"data -9", len(data), f(data, -9), 1},
+	{"data -6", len(data), f(data, -6), 1},
+	{"data -5", len(data), f(data, -5), 1},
+	{"data 3", len(data), f(data, 3), 5},
+	{"data 11", len(data), f(data, 11), 8},
+	{"data 99", len(data), f(data, 99), 9},
+	{"data 100", len(data), f(data, 100), 9},
+	{"data 101", len(data), f(data, 101), 12},
+	{"data 10000", len(data), f(data, 10000), 13},
+	{"data 10001", len(data), f(data, 10001), 14},
+	{"descending a", 7, func(i int) bool { return []int{99, 99, 59, 42, 7, 0, -1, -1}[i] <= 7 }, 4},
+	{"descending 7", 1e9, func(i int) bool { return 1e9-i <= 7 }, 1e9 - 7},
+	{"overflow", 2e9, func(i int) bool { return false }, 2e9},
+}
+
+func TestSearch(t *testing.T) {
+	for _, e := range tests {
+		i := Search(e.n, e.f)
+		if i != e.i {
+			t.Errorf("%s: expected index %d; got %d", e.name, e.i, i)
+		}
+	}
+}
+
+// log2 computes the binary logarithm of x, rounded up to the next integer.
+// (log2(0) == 0, log2(1) == 0, log2(2) == 1, log2(3) == 2, etc.)
+//
+func log2(x int) int {
+	n := 0
+	for p := 1; p < x; p += p {
+		// p == 2**n
+		n++
+	}
+	// p/2 < x <= p == 2**n
+	return n
+}
+
+func TestSearchEfficiency(t *testing.T) {
+	n := 100
+	step := 1
+	for exp := 2; exp < 10; exp++ {
+		// n == 10**exp
+		// step == 10**(exp-2)
+		max := log2(n)
+		for x := 0; x < n; x += step {
+			count := 0
+			i := Search(n, func(i int) bool { count++; return i >= x })
+			if i != x {
+				t.Errorf("n = %d: expected index %d; got %d", n, x, i)
+			}
+			if count > max {
+				t.Errorf("n = %d, x = %d: expected <= %d calls; got %d", n, x, max, count)
+			}
+		}
+		n *= 10
+		step *= 10
+	}
+}
+
+// Smoke tests for convenience wrappers - not comprehensive.
+
+var fdata = []float64{0: -3.14, 1: 0, 2: 1, 3: 2, 4: 1000.7}
+var sdata = []string{0: "f", 1: "foo", 2: "foobar", 3: "x"}
+
+var wrappertests = []struct {
+	name   string
+	result int
+	i      int
+}{
+	{"SearchInts", SearchInts(data, 11), 8},
+	{"SearchFloat64s", SearchFloat64s(fdata, 2.1), 4},
+	{"SearchStrings", SearchStrings(sdata, ""), 0},
+	{"IntSlice.Search", IntSlice(data).Search(0), 2},
+	{"Float64Slice.Search", Float64Slice(fdata).Search(2.0), 3},
+	{"StringSlice.Search", StringSlice(sdata).Search("x"), 3},
+}
+
+func TestSearchWrappers(t *testing.T) {
+	for _, e := range wrappertests {
+		if e.result != e.i {
+			t.Errorf("%s: expected index %d; got %d", e.name, e.i, e.result)
+		}
+	}
+}
+
+func runSearchWrappers() {
+	SearchInts(data, 11)
+	SearchFloat64s(fdata, 2.1)
+	SearchStrings(sdata, "")
+	IntSlice(data).Search(0)
+	Float64Slice(fdata).Search(2.0)
+	StringSlice(sdata).Search("x")
+}
+
+func TestSearchWrappersDontAlloc(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping malloc count in short mode")
+	}
+	if runtime.GOMAXPROCS(0) > 1 {
+		t.Skip("skipping; GOMAXPROCS>1")
+	}
+	allocs := testing.AllocsPerRun(100, runSearchWrappers)
+	if allocs != 0 {
+		t.Errorf("expected no allocs for runSearchWrappers, got %v", allocs)
+	}
+}
+
+func BenchmarkSearchWrappers(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		runSearchWrappers()
+	}
+}
+
+// Abstract exhaustive test: all sizes up to 100,
+// all possible return values.  If there are any small
+// corner cases, this test exercises them.
+func TestSearchExhaustive(t *testing.T) {
+	for size := 0; size <= 100; size++ {
+		for targ := 0; targ <= size; targ++ {
+			i := Search(size, func(i int) bool { return i >= targ })
+			if i != targ {
+				t.Errorf("Search(%d, %d) = %d", size, targ, i)
+			}
+		}
+	}
+}
diff --git a/src/sort/sort.go b/src/sort/sort.go
new file mode 100644
index 000000000..e980c295c
--- /dev/null
+++ b/src/sort/sort.go
@@ -0,0 +1,474 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package sort provides primitives for sorting slices and user-defined
+// collections.
+package sort
+
+// A type, typically a collection, that satisfies sort.Interface can be
+// sorted by the routines in this package.  The methods require that the
+// elements of the collection be enumerated by an integer index.
+type Interface interface {
+	// Len is the number of elements in the collection.
+	Len() int
+	// Less reports whether the element with
+	// index i should sort before the element with index j.
+	Less(i, j int) bool
+	// Swap swaps the elements with indexes i and j.
+	Swap(i, j int)
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+// Insertion sort
+func insertionSort(data Interface, a, b int) {
+	for i := a + 1; i < b; i++ {
+		for j := i; j > a && data.Less(j, j-1); j-- {
+			data.Swap(j, j-1)
+		}
+	}
+}
+
+// siftDown implements the heap property on data[lo, hi).
+// first is an offset into the array where the root of the heap lies.
+func siftDown(data Interface, lo, hi, first int) {
+	root := lo
+	for {
+		child := 2*root + 1
+		if child >= hi {
+			break
+		}
+		if child+1 < hi && data.Less(first+child, first+child+1) {
+			child++
+		}
+		if !data.Less(first+root, first+child) {
+			return
+		}
+		data.Swap(first+root, first+child)
+		root = child
+	}
+}
+
+func heapSort(data Interface, a, b int) {
+	first := a
+	lo := 0
+	hi := b - a
+
+	// Build heap with greatest element at top.
+	for i := (hi - 1) / 2; i >= 0; i-- {
+		siftDown(data, i, hi, first)
+	}
+
+	// Pop elements, largest first, into end of data.
+	for i := hi - 1; i >= 0; i-- {
+		data.Swap(first, first+i)
+		siftDown(data, lo, i, first)
+	}
+}
+
+// Quicksort, following Bentley and McIlroy,
+// ``Engineering a Sort Function,'' SP&E November 1993.
+
+// medianOfThree moves the median of the three values data[a], data[b], data[c] into data[a].
+func medianOfThree(data Interface, a, b, c int) {
+	m0 := b
+	m1 := a
+	m2 := c
+	// bubble sort on 3 elements
+	if data.Less(m1, m0) {
+		data.Swap(m1, m0)
+	}
+	if data.Less(m2, m1) {
+		data.Swap(m2, m1)
+	}
+	if data.Less(m1, m0) {
+		data.Swap(m1, m0)
+	}
+	// now data[m0] <= data[m1] <= data[m2]
+}
+
+func swapRange(data Interface, a, b, n int) {
+	for i := 0; i < n; i++ {
+		data.Swap(a+i, b+i)
+	}
+}
+
+func doPivot(data Interface, lo, hi int) (midlo, midhi int) {
+	m := lo + (hi-lo)/2 // Written like this to avoid integer overflow.
+	if hi-lo > 40 {
+		// Tukey's ``Ninther,'' median of three medians of three.
+		s := (hi - lo) / 8
+		medianOfThree(data, lo, lo+s, lo+2*s)
+		medianOfThree(data, m, m-s, m+s)
+		medianOfThree(data, hi-1, hi-1-s, hi-1-2*s)
+	}
+	medianOfThree(data, lo, m, hi-1)
+
+	// Invariants are:
+	//	data[lo] = pivot (set up by ChoosePivot)
+	//	data[lo <= i < a] = pivot
+	//	data[a <= i < b] < pivot
+	//	data[b <= i < c] is unexamined
+	//	data[c <= i < d] > pivot
+	//	data[d <= i < hi] = pivot
+	//
+	// Once b meets c, can swap the "= pivot" sections
+	// into the middle of the slice.
+	pivot := lo
+	a, b, c, d := lo+1, lo+1, hi, hi
+	for {
+		for b < c {
+			if data.Less(b, pivot) { // data[b] < pivot
+				b++
+			} else if !data.Less(pivot, b) { // data[b] = pivot
+				data.Swap(a, b)
+				a++
+				b++
+			} else {
+				break
+			}
+		}
+		for b < c {
+			if data.Less(pivot, c-1) { // data[c-1] > pivot
+				c--
+			} else if !data.Less(c-1, pivot) { // data[c-1] = pivot
+				data.Swap(c-1, d-1)
+				c--
+				d--
+			} else {
+				break
+			}
+		}
+		if b >= c {
+			break
+		}
+		// data[b] > pivot; data[c-1] < pivot
+		data.Swap(b, c-1)
+		b++
+		c--
+	}
+
+	n := min(b-a, a-lo)
+	swapRange(data, lo, b-n, n)
+
+	n = min(hi-d, d-c)
+	swapRange(data, c, hi-n, n)
+
+	return lo + b - a, hi - (d - c)
+}
+
+func quickSort(data Interface, a, b, maxDepth int) {
+	for b-a > 7 {
+		if maxDepth == 0 {
+			heapSort(data, a, b)
+			return
+		}
+		maxDepth--
+		mlo, mhi := doPivot(data, a, b)
+		// Avoiding recursion on the larger subproblem guarantees
+		// a stack depth of at most lg(b-a).
+		if mlo-a < b-mhi {
+			quickSort(data, a, mlo, maxDepth)
+			a = mhi // i.e., quickSort(data, mhi, b)
+		} else {
+			quickSort(data, mhi, b, maxDepth)
+			b = mlo // i.e., quickSort(data, a, mlo)
+		}
+	}
+	if b-a > 1 {
+		insertionSort(data, a, b)
+	}
+}
+
+// Sort sorts data.
+// It makes one call to data.Len to determine n, and O(n*log(n)) calls to
+// data.Less and data.Swap. The sort is not guaranteed to be stable.
+func Sort(data Interface) {
+	// Switch to heapsort if depth of 2*ceil(lg(n+1)) is reached.
+	n := data.Len()
+	maxDepth := 0
+	for i := n; i > 0; i >>= 1 {
+		maxDepth++
+	}
+	maxDepth *= 2
+	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()
+	for i := n - 1; i > 0; i-- {
+		if data.Less(i, i-1) {
+			return false
+		}
+	}
+	return true
+}
+
+// Convenience types for common cases
+
+// IntSlice attaches the methods of Interface to []int, sorting in increasing order.
+type IntSlice []int
+
+func (p IntSlice) Len() int           { return len(p) }
+func (p IntSlice) Less(i, j int) bool { return p[i] < p[j] }
+func (p IntSlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
+// Sort is a convenience method.
+func (p IntSlice) Sort() { Sort(p) }
+
+// Float64Slice attaches the methods of Interface to []float64, sorting in increasing order.
+type Float64Slice []float64
+
+func (p Float64Slice) Len() int           { return len(p) }
+func (p Float64Slice) Less(i, j int) bool { return p[i] < p[j] || isNaN(p[i]) && !isNaN(p[j]) }
+func (p Float64Slice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
+// isNaN is a copy of math.IsNaN to avoid a dependency on the math package.
+func isNaN(f float64) bool {
+	return f != f
+}
+
+// Sort is a convenience method.
+func (p Float64Slice) Sort() { Sort(p) }
+
+// StringSlice attaches the methods of Interface to []string, sorting in increasing order.
+type StringSlice []string
+
+func (p StringSlice) Len() int           { return len(p) }
+func (p StringSlice) Less(i, j int) bool { return p[i] < p[j] }
+func (p StringSlice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
+// Sort is a convenience method.
+func (p StringSlice) Sort() { Sort(p) }
+
+// Convenience wrappers for common cases
+
+// Ints sorts a slice of ints in increasing order.
+func Ints(a []int) { Sort(IntSlice(a)) }
+
+// Float64s sorts a slice of float64s in increasing order.
+func Float64s(a []float64) { Sort(Float64Slice(a)) }
+
+// Strings sorts a slice of strings in increasing order.
+func Strings(a []string) { Sort(StringSlice(a)) }
+
+// IntsAreSorted tests whether a slice of ints is sorted in increasing order.
+func IntsAreSorted(a []int) bool { return IsSorted(IntSlice(a)) }
+
+// Float64sAreSorted tests whether a slice of float64s is sorted in increasing order.
+func Float64sAreSorted(a []float64) bool { return IsSorted(Float64Slice(a)) }
+
+// StringsAreSorted tests whether a slice of strings is sorted in increasing order.
+func StringsAreSorted(a []string) bool { return IsSorted(StringSlice(a)) }
+
+// Notes on stable sorting:
+// The used algorithms are simple and provable correct on all input and use
+// only logarithmic additional stack space.  They perform well if compared
+// experimentally to other stable in-place sorting algorithms.
+//
+// Remarks on other algorithms evaluated:
+//  - GCC's 4.6.3 stable_sort with merge_without_buffer from libstdc++:
+//    Not faster.
+//  - GCC's __rotate for block rotations: Not faster.
+//  - "Practical in-place mergesort" from  Jyrki Katajainen, Tomi A. Pasanen
+//    and Jukka Teuhola; Nordic Journal of Computing 3,1 (1996), 27-40:
+//    The given algorithms are in-place, number of Swap and Assignments
+//    grow as n log n but the algorithm is not stable.
+//  - "Fast Stable In-Plcae Sorting with O(n) Data Moves" J.I. Munro and
+//    V. Raman in Algorithmica (1996) 16, 115-160:
+//    This algorithm either needs additional 2n bits or works only if there
+//    are enough different elements available to encode some permutations
+//    which have to be undone later (so not stable an any input).
+//  - All the optimal in-place sorting/merging algorithms I found are either
+//    unstable or rely on enough different elements in each step to encode the
+//    performed block rearrangements. See also "In-Place Merging Algorithms",
+//    Denham Coates-Evely, Department of Computer Science, Kings College,
+//    January 2004 and the reverences in there.
+//  - Often "optimal" algorithms are optimal in the number of assignments
+//    but Interface has only Swap as operation.
+
+// Stable sorts data while keeping the original order of equal elements.
+//
+// It makes one call to data.Len to determine n, O(n*log(n)) calls to
+// data.Less and O(n*log(n)*log(n)) calls to data.Swap.
+func Stable(data Interface) {
+	n := data.Len()
+	blockSize := 20
+	a, b := 0, blockSize
+	for b <= n {
+		insertionSort(data, a, b)
+		a = b
+		b += blockSize
+	}
+	insertionSort(data, a, n)
+
+	for blockSize < n {
+		a, b = 0, 2*blockSize
+		for b <= n {
+			symMerge(data, a, a+blockSize, b)
+			a = b
+			b += 2 * blockSize
+		}
+		symMerge(data, a, a+blockSize, n)
+		blockSize *= 2
+	}
+}
+
+// SymMerge merges the two sorted subsequences data[a:m] and data[m:b] using
+// the SymMerge algorithm from Pok-Son Kim and Arne Kutzner, "Stable Minimum
+// Storage Merging by Symmetric Comparisons", in Susanne Albers and Tomasz
+// Radzik, editors, Algorithms - ESA 2004, volume 3221 of Lecture Notes in
+// Computer Science, pages 714-723. Springer, 2004.
+//
+// Let M = m-a and N = b-n. Wolog M < N.
+// The recursion depth is bound by ceil(log(N+M)).
+// The algorithm needs O(M*log(N/M + 1)) calls to data.Less.
+// The algorithm needs O((M+N)*log(M)) calls to data.Swap.
+//
+// The paper gives O((M+N)*log(M)) as the number of assignments assuming a
+// rotation algorithm which uses O(M+N+gcd(M+N)) assignments. The argumentation
+// in the paper carries through for Swap operations, especially as the block
+// swapping rotate uses only O(M+N) Swaps.
+func symMerge(data Interface, a, m, b int) {
+	if a >= m || m >= b {
+		return
+	}
+
+	mid := a + (b-a)/2
+	n := mid + m
+	start := 0
+	if m > mid {
+		start = n - b
+		r, p := mid, n-1
+		for start < r {
+			c := start + (r-start)/2
+			if !data.Less(p-c, c) {
+				start = c + 1
+			} else {
+				r = c
+			}
+		}
+	} else {
+		start = a
+		r, p := m, n-1
+		for start < r {
+			c := start + (r-start)/2
+			if !data.Less(p-c, c) {
+				start = c + 1
+			} else {
+				r = c
+			}
+		}
+	}
+	end := n - start
+	rotate(data, start, m, end)
+	symMerge(data, a, start, mid)
+	symMerge(data, mid, end, b)
+}
+
+// Rotate two consecutives blocks u = data[a:m] and v = data[m:b] in data:
+// Data of the form 'x u v y' is changed to 'x v u y'.
+// Rotate performs at most b-a many calls to data.Swap.
+func rotate(data Interface, a, m, b int) {
+	i := m - a
+	if i == 0 {
+		return
+	}
+	j := b - m
+	if j == 0 {
+		return
+	}
+
+	if i == j {
+		swapRange(data, a, m, i)
+		return
+	}
+
+	p := a + i
+	for i != j {
+		if i > j {
+			swapRange(data, p-i, p, j)
+			i -= j
+		} else {
+			swapRange(data, p-i, p+j-i, i)
+			j -= i
+		}
+	}
+	swapRange(data, p-i, p, i)
+}
+
+/*
+Complexity of Stable Sorting
+
+
+Complexity of block swapping rotation
+
+Each Swap puts one new element into its correct, final position.
+Elements which reach their final position are no longer moved.
+Thus block swapping rotation needs |u|+|v| calls to Swaps.
+This is best possible as each element might need a move.
+
+Pay attention when comparing to other optimal algorithms which
+typically count the number of assignments instead of swaps:
+E.g. the optimal algorithm of Dudzinski and Dydek for in-place
+rotations uses O(u + v + gcd(u,v)) assignments which is
+better than our O(3 * (u+v)) as gcd(u,v) <= u.
+
+
+Stable sorting by SymMerge and BlockSwap rotations
+
+SymMerg complexity for same size input M = N:
+Calls to Less:  O(M*log(N/M+1)) = O(N*log(2)) = O(N)
+Calls to Swap:  O((M+N)*log(M)) = O(2*N*log(N)) = O(N*log(N))
+
+(The following argument does not fuzz over a missing -1 or
+other stuff which does not impact the final result).
+
+Let n = data.Len(). Assume n = 2^k.
+
+Plain merge sort performs log(n) = k iterations.
+On iteration i the algorithm merges 2^(k-i) blocks, each of size 2^i.
+
+Thus iteration i of merge sort performs:
+Calls to Less  O(2^(k-i) * 2^i) = O(2^k) = O(2^log(n)) = O(n)
+Calls to Swap  O(2^(k-i) * 2^i * log(2^i)) = O(2^k * i) = O(n*i)
+
+In total k = log(n) iterations are performed; so in total:
+Calls to Less O(log(n) * n)
+Calls to Swap O(n + 2*n + 3*n + ... + (k-1)*n + k*n)
+   = O((k/2) * k * n) = O(n * k^2) = O(n * log^2(n))
+
+
+Above results should generalize to arbitrary n = 2^k + p
+and should not be influenced by the initial insertion sort phase:
+Insertion sort is O(n^2) on Swap and Less, thus O(bs^2) per block of
+size bs at n/bs blocks:  O(bs*n) Swaps and Less during insertion sort.
+Merge sort iterations start at i = log(bs). With t = log(bs) constant:
+Calls to Less O((log(n)-t) * n + bs*n) = O(log(n)*n + (bs-t)*n)
+   = O(n * log(n))
+Calls to Swap O(n * log^2(n) - (t^2+t)/2*n) = O(n * log^2(n))
+
+*/
diff --git a/src/sort/sort_test.go b/src/sort/sort_test.go
new file mode 100644
index 000000000..6c36f30e0
--- /dev/null
+++ b/src/sort/sort_test.go
@@ -0,0 +1,553 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sort_test
+
+import (
+	"fmt"
+	"math"
+	"math/rand"
+	. "sort"
+	"strconv"
+	"testing"
+)
+
+var ints = [...]int{74, 59, 238, -784, 9845, 959, 905, 0, 0, 42, 7586, -5467984, 7586}
+var float64s = [...]float64{74.3, 59.0, math.Inf(1), 238.2, -784.0, 2.3, math.NaN(), math.NaN(), math.Inf(-1), 9845.768, -959.7485, 905, 7.8, 7.8}
+var strings = [...]string{"", "Hello", "foo", "bar", "foo", "f00", "%*&^*&^&", "***"}
+
+func TestSortIntSlice(t *testing.T) {
+	data := ints
+	a := IntSlice(data[0:])
+	Sort(a)
+	if !IsSorted(a) {
+		t.Errorf("sorted %v", ints)
+		t.Errorf("   got %v", data)
+	}
+}
+
+func TestSortFloat64Slice(t *testing.T) {
+	data := float64s
+	a := Float64Slice(data[0:])
+	Sort(a)
+	if !IsSorted(a) {
+		t.Errorf("sorted %v", float64s)
+		t.Errorf("   got %v", data)
+	}
+}
+
+func TestSortStringSlice(t *testing.T) {
+	data := strings
+	a := StringSlice(data[0:])
+	Sort(a)
+	if !IsSorted(a) {
+		t.Errorf("sorted %v", strings)
+		t.Errorf("   got %v", data)
+	}
+}
+
+func TestInts(t *testing.T) {
+	data := ints
+	Ints(data[0:])
+	if !IntsAreSorted(data[0:]) {
+		t.Errorf("sorted %v", ints)
+		t.Errorf("   got %v", data)
+	}
+}
+
+func TestFloat64s(t *testing.T) {
+	data := float64s
+	Float64s(data[0:])
+	if !Float64sAreSorted(data[0:]) {
+		t.Errorf("sorted %v", float64s)
+		t.Errorf("   got %v", data)
+	}
+}
+
+func TestStrings(t *testing.T) {
+	data := strings
+	Strings(data[0:])
+	if !StringsAreSorted(data[0:]) {
+		t.Errorf("sorted %v", strings)
+		t.Errorf("   got %v", data)
+	}
+}
+
+func TestSortLarge_Random(t *testing.T) {
+	n := 1000000
+	if testing.Short() {
+		n /= 100
+	}
+	data := make([]int, n)
+	for i := 0; i < len(data); i++ {
+		data[i] = rand.Intn(100)
+	}
+	if IntsAreSorted(data) {
+		t.Fatalf("terrible rand.rand")
+	}
+	Ints(data)
+	if !IntsAreSorted(data) {
+		t.Errorf("sort didn't sort - 1M ints")
+	}
+}
+
+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++ {
+		data := make([]string, 1<<10)
+		for i := 0; i < len(data); i++ {
+			data[i] = strconv.Itoa(i ^ 0x2cc)
+		}
+		b.StartTimer()
+		Strings(data)
+		b.StopTimer()
+	}
+}
+
+func BenchmarkStableString1K(b *testing.B) {
+	b.StopTimer()
+	for i := 0; i < b.N; i++ {
+		data := make([]string, 1<<10)
+		for i := 0; i < len(data); i++ {
+			data[i] = strconv.Itoa(i ^ 0x2cc)
+		}
+		b.StartTimer()
+		Stable(StringSlice(data))
+		b.StopTimer()
+	}
+}
+
+func BenchmarkSortInt1K(b *testing.B) {
+	b.StopTimer()
+	for i := 0; i < b.N; i++ {
+		data := make([]int, 1<<10)
+		for i := 0; i < len(data); i++ {
+			data[i] = i ^ 0x2cc
+		}
+		b.StartTimer()
+		Ints(data)
+		b.StopTimer()
+	}
+}
+
+func BenchmarkStableInt1K(b *testing.B) {
+	b.StopTimer()
+	for i := 0; i < b.N; i++ {
+		data := make([]int, 1<<10)
+		for i := 0; i < len(data); i++ {
+			data[i] = i ^ 0x2cc
+		}
+		b.StartTimer()
+		Stable(IntSlice(data))
+		b.StopTimer()
+	}
+}
+
+func BenchmarkSortInt64K(b *testing.B) {
+	b.StopTimer()
+	for i := 0; i < b.N; i++ {
+		data := make([]int, 1<<16)
+		for i := 0; i < len(data); i++ {
+			data[i] = i ^ 0xcccc
+		}
+		b.StartTimer()
+		Ints(data)
+		b.StopTimer()
+	}
+}
+
+func BenchmarkStableInt64K(b *testing.B) {
+	b.StopTimer()
+	for i := 0; i < b.N; i++ {
+		data := make([]int, 1<<16)
+		for i := 0; i < len(data); i++ {
+			data[i] = i ^ 0xcccc
+		}
+		b.StartTimer()
+		Stable(IntSlice(data))
+		b.StopTimer()
+	}
+}
+
+const (
+	_Sawtooth = iota
+	_Rand
+	_Stagger
+	_Plateau
+	_Shuffle
+	_NDist
+)
+
+const (
+	_Copy = iota
+	_Reverse
+	_ReverseFirstHalf
+	_ReverseSecondHalf
+	_Sorted
+	_Dither
+	_NMode
+)
+
+type testingData struct {
+	desc        string
+	t           *testing.T
+	data        []int
+	maxswap     int // number of swaps allowed
+	ncmp, nswap int
+}
+
+func (d *testingData) Len() int { return len(d.data) }
+func (d *testingData) Less(i, j int) bool {
+	d.ncmp++
+	return d.data[i] < d.data[j]
+}
+func (d *testingData) Swap(i, j int) {
+	if d.nswap >= d.maxswap {
+		d.t.Errorf("%s: used %d swaps sorting slice of %d", d.desc, d.nswap, len(d.data))
+		d.t.FailNow()
+	}
+	d.nswap++
+	d.data[i], d.data[j] = d.data[j], d.data[i]
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func lg(n int) int {
+	i := 0
+	for 1<<uint(i) < n {
+		i++
+	}
+	return i
+}
+
+func testBentleyMcIlroy(t *testing.T, sort func(Interface), maxswap func(int) int) {
+	sizes := []int{100, 1023, 1024, 1025}
+	if testing.Short() {
+		sizes = []int{100, 127, 128, 129}
+	}
+	dists := []string{"sawtooth", "rand", "stagger", "plateau", "shuffle"}
+	modes := []string{"copy", "reverse", "reverse1", "reverse2", "sort", "dither"}
+	var tmp1, tmp2 [1025]int
+	for _, n := range sizes {
+		for m := 1; m < 2*n; m *= 2 {
+			for dist := 0; dist < _NDist; dist++ {
+				j := 0
+				k := 1
+				data := tmp1[0:n]
+				for i := 0; i < n; i++ {
+					switch dist {
+					case _Sawtooth:
+						data[i] = i % m
+					case _Rand:
+						data[i] = rand.Intn(m)
+					case _Stagger:
+						data[i] = (i*m + i) % n
+					case _Plateau:
+						data[i] = min(i, m)
+					case _Shuffle:
+						if rand.Intn(m) != 0 {
+							j += 2
+							data[i] = j
+						} else {
+							k += 2
+							data[i] = k
+						}
+					}
+				}
+
+				mdata := tmp2[0:n]
+				for mode := 0; mode < _NMode; mode++ {
+					switch mode {
+					case _Copy:
+						for i := 0; i < n; i++ {
+							mdata[i] = data[i]
+						}
+					case _Reverse:
+						for i := 0; i < n; i++ {
+							mdata[i] = data[n-i-1]
+						}
+					case _ReverseFirstHalf:
+						for i := 0; i < n/2; i++ {
+							mdata[i] = data[n/2-i-1]
+						}
+						for i := n / 2; i < n; i++ {
+							mdata[i] = data[i]
+						}
+					case _ReverseSecondHalf:
+						for i := 0; i < n/2; i++ {
+							mdata[i] = data[i]
+						}
+						for i := n / 2; i < n; i++ {
+							mdata[i] = data[n-(i-n/2)-1]
+						}
+					case _Sorted:
+						for i := 0; i < n; i++ {
+							mdata[i] = data[i]
+						}
+						// Ints is known to be correct
+						// because mode Sort runs after mode _Copy.
+						Ints(mdata)
+					case _Dither:
+						for i := 0; i < n; i++ {
+							mdata[i] = data[i] + i%5
+						}
+					}
+
+					desc := fmt.Sprintf("n=%d m=%d dist=%s mode=%s", n, m, dists[dist], modes[mode])
+					d := &testingData{desc: desc, t: t, data: mdata[0:n], maxswap: maxswap(n)}
+					sort(d)
+					// Uncomment if you are trying to improve the number of compares/swaps.
+					//t.Logf("%s: ncmp=%d, nswp=%d", desc, d.ncmp, d.nswap)
+
+					// If we were testing C qsort, we'd have to make a copy
+					// of the slice and sort it ourselves and then compare
+					// x against it, to ensure that qsort was only permuting
+					// the data, not (for example) overwriting it with zeros.
+					//
+					// In go, we don't have to be so paranoid: since the only
+					// mutating method Sort can call is TestingData.swap,
+					// it suffices here just to check that the final slice is sorted.
+					if !IntsAreSorted(mdata) {
+						t.Errorf("%s: ints not sorted", desc)
+						t.Errorf("\t%v", mdata)
+						t.FailNow()
+					}
+				}
+			}
+		}
+	}
+}
+
+func TestSortBM(t *testing.T) {
+	testBentleyMcIlroy(t, Sort, func(n int) int { return n * lg(n) * 12 / 10 })
+}
+
+func TestHeapsortBM(t *testing.T) {
+	testBentleyMcIlroy(t, Heapsort, func(n int) int { return n * lg(n) * 12 / 10 })
+}
+
+func TestStableBM(t *testing.T) {
+	testBentleyMcIlroy(t, Stable, func(n int) int { return n * lg(n) * lg(n) / 3 })
+}
+
+// This is based on the "antiquicksort" implementation by M. Douglas McIlroy.
+// See http://www.cs.dartmouth.edu/~doug/mdmspe.pdf for more info.
+type adversaryTestingData struct {
+	data      []int
+	keys      map[int]int
+	candidate int
+}
+
+func (d *adversaryTestingData) Len() int { return len(d.data) }
+
+func (d *adversaryTestingData) Less(i, j int) bool {
+	if _, present := d.keys[i]; !present {
+		if _, present := d.keys[j]; !present {
+			if i == d.candidate {
+				d.keys[i] = len(d.keys)
+			} else {
+				d.keys[j] = len(d.keys)
+			}
+		}
+	}
+
+	if _, present := d.keys[i]; !present {
+		d.candidate = i
+		return false
+	}
+	if _, present := d.keys[j]; !present {
+		d.candidate = j
+		return true
+	}
+
+	return d.keys[i] >= d.keys[j]
+}
+
+func (d *adversaryTestingData) Swap(i, j int) {
+	d.data[i], d.data[j] = d.data[j], d.data[i]
+}
+
+func TestAdversary(t *testing.T) {
+	const size = 100
+	data := make([]int, size)
+	for i := 0; i < size; i++ {
+		data[i] = i
+	}
+
+	d := &adversaryTestingData{data, make(map[int]int), 0}
+	Sort(d) // This should degenerate to heapsort.
+}
+
+func TestStableInts(t *testing.T) {
+	data := ints
+	Stable(IntSlice(data[0:]))
+	if !IntsAreSorted(data[0:]) {
+		t.Errorf("nsorted %v\n   got %v", ints, data)
+	}
+}
+
+type intPairs []struct {
+	a, b int
+}
+
+// IntPairs compare on a only.
+func (d intPairs) Len() int           { return len(d) }
+func (d intPairs) Less(i, j int) bool { return d[i].a < d[j].a }
+func (d intPairs) Swap(i, j int)      { d[i], d[j] = d[j], d[i] }
+
+// Record initial order in B.
+func (d intPairs) initB() {
+	for i := range d {
+		d[i].b = i
+	}
+}
+
+// InOrder checks if a-equal elements were not reordered.
+func (d intPairs) inOrder() bool {
+	lastA, lastB := -1, 0
+	for i := 0; i < len(d); i++ {
+		if lastA != d[i].a {
+			lastA = d[i].a
+			lastB = d[i].b
+			continue
+		}
+		if d[i].b <= lastB {
+			return false
+		}
+		lastB = d[i].b
+	}
+	return true
+}
+
+func TestStability(t *testing.T) {
+	n, m := 100000, 1000
+	if testing.Short() {
+		n, m = 1000, 100
+	}
+	data := make(intPairs, n)
+
+	// random distribution
+	for i := 0; i < len(data); i++ {
+		data[i].a = rand.Intn(m)
+	}
+	if IsSorted(data) {
+		t.Fatalf("terrible rand.rand")
+	}
+	data.initB()
+	Stable(data)
+	if !IsSorted(data) {
+		t.Errorf("Stable didn't sort %d ints", n)
+	}
+	if !data.inOrder() {
+		t.Errorf("Stable wasn't stable on %d ints", n)
+	}
+
+	// already sorted
+	data.initB()
+	Stable(data)
+	if !IsSorted(data) {
+		t.Errorf("Stable shuffeled sorted %d ints (order)", n)
+	}
+	if !data.inOrder() {
+		t.Errorf("Stable shuffeled sorted %d ints (stability)", n)
+	}
+
+	// sorted reversed
+	for i := 0; i < len(data); i++ {
+		data[i].a = len(data) - i
+	}
+	data.initB()
+	Stable(data)
+	if !IsSorted(data) {
+		t.Errorf("Stable didn't sort %d ints", n)
+	}
+	if !data.inOrder() {
+		t.Errorf("Stable wasn't stable on %d ints", n)
+	}
+}
+
+var countOpsSizes = []int{1e2, 3e2, 1e3, 3e3, 1e4, 3e4, 1e5, 3e5, 1e6}
+
+func countOps(t *testing.T, algo func(Interface), name string) {
+	sizes := countOpsSizes
+	if testing.Short() {
+		sizes = sizes[:5]
+	}
+	if !testing.Verbose() {
+		t.Skip("Counting skipped as non-verbose mode.")
+	}
+	for _, n := range sizes {
+		td := testingData{
+			desc:    name,
+			t:       t,
+			data:    make([]int, n),
+			maxswap: 1<<31 - 1,
+		}
+		for i := 0; i < n; i++ {
+			td.data[i] = rand.Intn(n / 5)
+		}
+		algo(&td)
+		t.Logf("%s %8d elements: %11d Swap, %10d Less", name, n, td.nswap, td.ncmp)
+	}
+}
+
+func TestCountStableOps(t *testing.T) { countOps(t, Stable, "Stable") }
+func TestCountSortOps(t *testing.T)   { countOps(t, Sort, "Sort  ") }
+
+func bench(b *testing.B, size int, algo func(Interface), name string) {
+	b.StopTimer()
+	data := make(intPairs, size)
+	x := ^uint32(0)
+	for i := 0; i < b.N; i++ {
+		for n := size - 3; n <= size+3; n++ {
+			for i := 0; i < len(data); i++ {
+				x += x
+				x ^= 1
+				if int32(x) < 0 {
+					x ^= 0x88888eef
+				}
+				data[i].a = int(x % uint32(n/5))
+			}
+			data.initB()
+			b.StartTimer()
+			algo(data)
+			b.StopTimer()
+			if !IsSorted(data) {
+				b.Errorf("%s did not sort %d ints", name, n)
+			}
+			if name == "Stable" && !data.inOrder() {
+				b.Errorf("%s unstable on %d ints", name, n)
+			}
+		}
+	}
+}
+
+func BenchmarkSort1e2(b *testing.B)   { bench(b, 1e2, Sort, "Sort") }
+func BenchmarkStable1e2(b *testing.B) { bench(b, 1e2, Stable, "Stable") }
+func BenchmarkSort1e4(b *testing.B)   { bench(b, 1e4, Sort, "Sort") }
+func BenchmarkStable1e4(b *testing.B) { bench(b, 1e4, Stable, "Stable") }
+func BenchmarkSort1e6(b *testing.B)   { bench(b, 1e6, Sort, "Sort") }
+func BenchmarkStable1e6(b *testing.B) { bench(b, 1e6, Stable, "Stable") }