go typeswitch1 源码
golang typeswitch1 代码
文件路径：/test/typeswitch1.go
// 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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