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Source file test/typeswitch1.go

Documentation: test

  // run
  
  // 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.
  
  // Test simple type switches on basic types.
  
  package main
  
  import "fmt"
  
  const (
  	a = iota
  	b
  	c
  	d
  	e
  )
  
  var x = []int{1, 2, 3}
  
  func f(x int, len *byte) {
  	*len = byte(x)
  }
  
  func whatis(x interface{}) string {
  	switch xx := x.(type) {
  	default:
  		return fmt.Sprint("default ", xx)
  	case int, int8, int16, int32:
  		return fmt.Sprint("signed ", xx)
  	case int64:
  		return fmt.Sprint("signed64 ", int64(xx))
  	case uint, uint8, uint16, uint32:
  		return fmt.Sprint("unsigned ", xx)
  	case uint64:
  		return fmt.Sprint("unsigned64 ", uint64(xx))
  	case nil:
  		return fmt.Sprint("nil ", xx)
  	}
  	panic("not reached")
  }
  
  func whatis1(x interface{}) string {
  	xx := x
  	switch xx.(type) {
  	default:
  		return fmt.Sprint("default ", xx)
  	case int, int8, int16, int32:
  		return fmt.Sprint("signed ", xx)
  	case int64:
  		return fmt.Sprint("signed64 ", xx.(int64))
  	case uint, uint8, uint16, uint32:
  		return fmt.Sprint("unsigned ", xx)
  	case uint64:
  		return fmt.Sprint("unsigned64 ", xx.(uint64))
  	case nil:
  		return fmt.Sprint("nil ", xx)
  	}
  	panic("not reached")
  }
  
  func check(x interface{}, s string) {
  	w := whatis(x)
  	if w != s {
  		fmt.Println("whatis", x, "=>", w, "!=", s)
  		panic("fail")
  	}
  
  	w = whatis1(x)
  	if w != s {
  		fmt.Println("whatis1", x, "=>", w, "!=", s)
  		panic("fail")
  	}
  }
  
  func main() {
  	check(1, "signed 1")
  	check(uint(1), "unsigned 1")
  	check(int64(1), "signed64 1")
  	check(uint64(1), "unsigned64 1")
  	check(1.5, "default 1.5")
  	check(nil, "nil <nil>")
  }
  

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