json2.go

     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
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