1 files changed, 42 insertions, 0 deletions
diff --git a/doc/progs/json2.go b/doc/progs/json2.go
new file mode 100644
index 000000000..6089ae671
--- /dev/null
+++ b/doc/progs/json2.go
@@ -0,0 +1,42 @@
+// Copyright 2012 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 main
+
+import (
+	"fmt"
+	"math"
+)
+
+func InterfaceExample() {
+	var i interface{}
+	i = "a string"
+	i = 2011
+	i = 2.777
+
+	// STOP OMIT
+
+	r := i.(float64)
+	fmt.Println("the circle's area", math.Pi*r*r)
+
+	// STOP OMIT
+
+	switch v := i.(type) {
+	case int:
+		fmt.Println("twice i is", v*2)
+	case float64:
+		fmt.Println("the reciprocal of i is", 1/v)
+	case string:
+		h := len(v) / 2
+		fmt.Println("i swapped by halves is", v[h:]+v[:h])
+	default:
+		// i isn't one of the types above
+	}
+
+	// STOP OMIT
+}
+
+func main() {
+	InterfaceExample()
+}