1 // Copyright 2012 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package main 6 7 import ( 8 "fmt" 9 "math" 10 ) 11 12 func InterfaceExample() { 13 var i interface{} 14 i = "a string" 15 i = 2011 16 i = 2.777 17 18 // STOP OMIT 19 20 r := i.(float64) 21 fmt.Println("the circle's area", math.Pi*r*r) 22 23 // STOP OMIT 24 25 switch v := i.(type) { 26 case int: 27 fmt.Println("twice i is", v*2) 28 case float64: 29 fmt.Println("the reciprocal of i is", 1/v) 30 case string: 31 h := len(v) / 2 32 fmt.Println("i swapped by halves is", v[h:]+v[:h]) 33 default: 34 // i isn't one of the types above 35 } 36 37 // STOP OMIT 38 } 39 40 func main() { 41 InterfaceExample() 42 } 43
