1 files changed, 95 insertions, 0 deletions
diff --git a/src/lib/sort.go b/src/lib/sort.go
new file mode 100644
index 000000000..72b0ddd47
--- /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]; }