develop interfaces through cats

sort
2,3,5

R=gri
DELTA=648  (647 added, 0 deleted, 1 changed)
OCL=15315
CL=15352

1 files changed, 72 insertions, 0 deletions

diff --git a/doc/progs/sort.go b/doc/progs/sort.go
new file mode 100644
index 000000000..db0d8b16e
--- /dev/null
+++ b/doc/progs/sort.go
@@ -0,0 +1,72 @@
+// 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);
+}
+
+export func Sort(data SortInterface) {
+	// Bubble sort for brevity
+	for i := 0; i < data.len(); i++ {
+		for j := i; j < data.len(); j++ {
+			if data.less(j, i) {
+				data.swap(i, j)
+			}
+		}
+	}
+}
+
+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
+
+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]; }
+
+
+// Convenience wrappers for common cases
+
+export func SortInts(a *[]int)        { Sort(&IntArray{a}); }
+export func SortFloats(a *[]float)    { Sort(&FloatArray{a}); }
+export func SortStrings(a *[]string)  { Sort(&StringArray{a}); }
+
+
+export func IntsAreSorted(a *[]int) bool       { return IsSorted(&IntArray{a}); }
+export func FloatsAreSorted(a *[]float) bool   { return IsSorted(&FloatArray{a}); }
+export func StringsAreSorted(a *[]string) bool { return IsSorted(&StringArray{a}); }