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Source file test/typeswitch.go

Documentation: test

     1  // run
     2  
     3  // Copyright 2009 The Go Authors. All rights reserved.
     4  // Use of this source code is governed by a BSD-style
     5  // license that can be found in the LICENSE file.
     6  
     7  // Test simple type switches, including chans, maps etc.
     8  
     9  package main
    10  
    11  import "os"
    12  
    13  const (
    14  	Bool = iota
    15  	Int
    16  	Float
    17  	String
    18  	Struct
    19  	Chan
    20  	Array
    21  	Map
    22  	Func
    23  	Last
    24  )
    25  
    26  type S struct {
    27  	a int
    28  }
    29  
    30  var s S = S{1234}
    31  
    32  var c = make(chan int)
    33  
    34  var a = []int{0, 1, 2, 3}
    35  
    36  var m = make(map[string]int)
    37  
    38  func assert(b bool, s string) {
    39  	if !b {
    40  		println(s)
    41  		os.Exit(1)
    42  	}
    43  }
    44  
    45  func f(i int) interface{} {
    46  	switch i {
    47  	case Bool:
    48  		return true
    49  	case Int:
    50  		return 7
    51  	case Float:
    52  		return 7.4
    53  	case String:
    54  		return "hello"
    55  	case Struct:
    56  		return s
    57  	case Chan:
    58  		return c
    59  	case Array:
    60  		return a
    61  	case Map:
    62  		return m
    63  	case Func:
    64  		return f
    65  	}
    66  	panic("bad type number")
    67  }
    68  
    69  func main() {
    70  	for i := Bool; i < Last; i++ {
    71  		switch x := f(i).(type) {
    72  		case bool:
    73  			assert(x == true && i == Bool, "bool")
    74  		case int:
    75  			assert(x == 7 && i == Int, "int")
    76  		case float64:
    77  			assert(x == 7.4 && i == Float, "float64")
    78  		case string:
    79  			assert(x == "hello" && i == String, "string")
    80  		case S:
    81  			assert(x.a == 1234 && i == Struct, "struct")
    82  		case chan int:
    83  			assert(x == c && i == Chan, "chan")
    84  		case []int:
    85  			assert(x[3] == 3 && i == Array, "array")
    86  		case map[string]int:
    87  			assert(x != nil && i == Map, "map")
    88  		case func(i int) interface{}:
    89  			assert(x != nil && i == Func, "fun")
    90  		default:
    91  			assert(false, "unknown")
    92  		}
    93  	}
    94  
    95  	// boolean switch (has had bugs in past; worth writing down)
    96  	switch {
    97  	case true:
    98  		assert(true, "switch 2 bool")
    99  	default:
   100  		assert(false, "switch 2 unknown")
   101  	}
   102  
   103  	switch true {
   104  	case true:
   105  		assert(true, "switch 3 bool")
   106  	default:
   107  		assert(false, "switch 3 unknown")
   108  	}
   109  
   110  	switch false {
   111  	case false:
   112  		assert(true, "switch 4 bool")
   113  	default:
   114  		assert(false, "switch 4 unknown")
   115  	}
   116  }
   117  

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