From 18852cf6d3f23a4fbcf2756836eb929283126827 Mon Sep 17 00:00:00 2001
From: Robert Griesemer <gri@golang.org>
Date: Mon, 8 Sep 2008 18:43:42 -0700
Subject: [PATCH] - added sort package and test case

R=r
OCL=14975
CL=14975
---
 src/lib/make.bash |  2 +-
 src/lib/sort.go   | 95 +++++++++++++++++++++++++++++++++++++++++++++++
 test/sorting.go   | 62 +++++++++++++++++++++++++++++++
 3 files changed, 158 insertions(+), 1 deletion(-)
 create mode 100644 src/lib/sort.go
 create mode 100644 test/sorting.go

diff --git a/src/lib/make.bash b/src/lib/make.bash
index f0f545f251..a9be5938b8 100755
--- a/src/lib/make.bash
+++ b/src/lib/make.bash
@@ -7,7 +7,7 @@
 echo; echo; echo %%%% making lib %%%%; echo
 
 rm -f *.6
-for i in fmt.go flag.go container/vector.go
+for i in fmt.go flag.go container/vector.go sort.go
 do
 	base=$(basename $i .go)
 	echo 6g -o $GOROOT/pkg/$base.6 $i
diff --git a/src/lib/sort.go b/src/lib/sort.go
new file mode 100644
index 0000000000..72b0ddd47a
--- /dev/null
+++ b/src/lib/sort.go
@@ -0,0 +1,95 @@
+// 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
+
+export type SortInterface interface {
+	len() int;
+	less(i, j int) bool;
+	swap(i, j int);
+}
+
+
+func Pivot(data SortInterface, a, b int) int {
+	// if we have at least 10 elements, find a better median
+	// by selecting the median of 3 elements and putting it
+	// at position a
+	if b - a >= 10 {
+		m0 := (a + b) / 2;
+		m1 := a;
+		m2 := b - 1;
+		// 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); }
+		// "m0 <= m1 <= m2"
+	}
+	
+	m := a;
+	for i := a + 1; i < b; i++ {
+		if data.less(i, a) {
+			m++;
+			data.swap(i, m);
+		}
+	}
+	data.swap(a, m);
+	
+	return m;
+}
+
+
+func Quicksort(data SortInterface, a, b int) {
+	if a + 1 < b {
+		m := Pivot(data, a, b);
+		Quicksort(data, 0, m);
+		Quicksort(data, m + 1, b);
+	}
+}
+
+
+export func Sort(data SortInterface) {
+	Quicksort(data, 0, data.len());
+}
+
+
+export func IsSorted(data SortInterface) 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
+// TODO: Once we can associate methods with all types, this can be simplified
+//       since we cann associate the methods with the arrays directly.
+
+export type IntArray struct {
+	data *[]int;
+}
+
+func (p *IntArray) len() int            { return len(p.data); }
+func (p *IntArray) less(i, j int) bool  { return p.data[i] < p.data[j]; }
+func (p *IntArray) swap(i, j int)       { p.data[i], p.data[j] = p.data[j], p.data[i]; }
+
+
+export type FloatArray struct {
+	data *[]float;
+}
+
+func (p *FloatArray) len() int            { return len(p.data); }
+func (p *FloatArray) less(i, j int) bool  { return p.data[i] < p.data[j]; }
+func (p *FloatArray) swap(i, j int)       { p.data[i], p.data[j] = p.data[j], p.data[i]; }
+
+
+export type StringArray struct {
+	data *[]string;
+}
+
+func (p *StringArray) len() int            { return len(p.data); }
+func (p *StringArray) less(i, j int) bool  { return p.data[i] < p.data[j]; }
+func (p *StringArray) swap(i, j int)       { p.data[i], p.data[j] = p.data[j], p.data[i]; }
diff --git a/test/sorting.go b/test/sorting.go
new file mode 100644
index 0000000000..1619d83acc
--- /dev/null
+++ b/test/sorting.go
@@ -0,0 +1,62 @@
+// 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.
+
+// $G $F.go && $L $F.$A && ./$A.out
+
+package main
+
+import Sort "sort"
+
+func main() {
+	{	data := []int{74, 59, 238, -784, 9845, 959, 905, 0, 0, 42, 7586, -5467984, 7586};
+		a := Sort.IntArray(&data);
+		
+		Sort.Sort(&a);
+
+		/*
+		for i := 0; i < len(data); i++ {
+			print(data[i], " ");
+		}
+		print("\n");
+		*/
+		
+		if !Sort.IsSorted(&a) {
+			panic();
+		}
+	}
+
+	{	data := []float{74.3, 59.0, 238.2, -784.0, 2.3, 9845.768, -959.7485, 905, 7.8, 7.8};
+		a := Sort.FloatArray(&data);
+		
+		Sort.Sort(&a);
+
+		/*
+		for i := 0; i < len(data); i++ {
+			print(data[i], " ");
+		}
+		print("\n");
+		*/
+		
+		if !Sort.IsSorted(&a) {
+			panic();
+		}
+	}
+
+	{	data := []string{"", "Hello", "foo", "bar", "foo", "f00", "%*&^*&^&", "***"};
+		a := Sort.StringArray(&data);
+		
+		Sort.Sort(&a);
+
+		/*
+		for i := 0; i < len(data); i++ {
+			print(data[i], " ");
+		}
+		print("\n");
+		*/
+		
+		if !Sort.IsSorted(&a) {
+			panic();
+		}
+	}
+}
-- 
2.48.1