Russ Cox | 5d16d23 | 2009-09-09 00:18:16 -0700 | [diff] [blame] | 1 | // $G $D/$F.go && $L $F.$A && ./$A.out |
| 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 | package main |
| 8 | |
| 9 | import "fmt" |
| 10 | |
| 11 | const ( |
| 12 | a = iota; |
| 13 | b; |
| 14 | c; |
| 15 | d; |
| 16 | e; |
| 17 | ) |
| 18 | |
| 19 | var x = []int{1,2,3} |
| 20 | |
| 21 | func f(x int, len *byte) { |
| 22 | *len = byte(x); |
| 23 | } |
| 24 | |
| 25 | func whatis(x interface{}) string { |
| 26 | switch xx := x.(type) { |
| 27 | default: |
| 28 | return fmt.Sprint("default ", xx); |
| 29 | case int, int8, int16, int32: |
| 30 | return fmt.Sprint("signed ", xx); |
| 31 | case int64: |
| 32 | return fmt.Sprint("signed64 ", int64(xx)); |
| 33 | case uint, uint8, uint16, uint32: |
| 34 | return fmt.Sprint("unsigned ", xx); |
| 35 | case uint64: |
| 36 | return fmt.Sprint("unsigned64 ", uint64(xx)); |
| 37 | case nil: |
| 38 | return fmt.Sprint("nil ", xx); |
| 39 | } |
| 40 | panic("not reached"); |
| 41 | } |
| 42 | |
| 43 | func whatis1(x interface{}) string { |
| 44 | xx := x; |
| 45 | switch xx.(type) { |
| 46 | default: |
| 47 | return fmt.Sprint("default ", xx); |
| 48 | case int, int8, int16, int32: |
| 49 | return fmt.Sprint("signed ", xx); |
| 50 | case int64: |
| 51 | return fmt.Sprint("signed64 ", xx.(int64)); |
| 52 | case uint, uint8, uint16, uint32: |
| 53 | return fmt.Sprint("unsigned ", xx); |
| 54 | case uint64: |
| 55 | return fmt.Sprint("unsigned64 ", xx.(uint64)); |
| 56 | case nil: |
| 57 | return fmt.Sprint("nil ", xx); |
| 58 | } |
| 59 | panic("not reached"); |
| 60 | } |
| 61 | |
| 62 | func check(x interface{}, s string) { |
| 63 | w := whatis(x); |
| 64 | if w != s { |
| 65 | fmt.Println("whatis", x, "=>", w, "!=", s); |
| 66 | panic(); |
| 67 | } |
| 68 | |
| 69 | w = whatis1(x); |
| 70 | if w != s { |
| 71 | fmt.Println("whatis1", x, "=>", w, "!=", s); |
| 72 | panic(); |
| 73 | } |
| 74 | } |
| 75 | |
| 76 | func main() { |
| 77 | check(1, "signed 1"); |
| 78 | check(uint(1), "unsigned 1"); |
| 79 | check(int64(1), "signed64 1"); |
| 80 | check(uint64(1), "unsigned64 1"); |
| 81 | check(1.5, "default 1.5"); |
| 82 | check(nil, "nil <nil>"); |
| 83 | } |
| 84 | |