{"id":44764,"date":"2023-10-03T07:56:38","date_gmt":"2023-12-24T22:32:28","guid":{"rendered":"https:\/\/www.silicloud.com\/zh\/blog\/44764-2\/"},"modified":"2024-05-04T02:37:29","modified_gmt":"2024-05-03T18:37:29","slug":"44764-2","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/zh\/blog\/44764-2\/","title":{"rendered":""},"content":{"rendered":"

Go AdventCalendar2016\u306e9\u65e5\u76ee(2016\/12\/09)\u306e\u8a18\u4e8b\u3067\u3059\u3002
\n\u524d\u306e\u8a18\u4e8b\u306f massa142\u3055\u3093\u306e\u300cHacker News\u3092\u4e00\u89a7\u8868\u793a\u3057\u3066\u304f\u308c\u308bCLI\u30c4\u30fc\u30eb\u3092\u66f8\u3044\u305f\u300d\u3067\u3057\u305f\u3002<\/p>\n

\u306f\u3058\u3081\u306b<\/h1>\n

\u3061\u3087\u3063\u3068\u30de\u30a4\u30ca\u30fc\u306aGolang\u306e\u8a00\u8a9e\u4ed5\u69d8\u3067\u3042\u308b\u3001iota\u306b\u3064\u3044\u3066\u7d39\u4ecb\u3057\u307e\u3059\u3002
\n\u7d50\u69cb\u5165\u9580\u66f8\u3068\u304b\u306b\u3082\u66f8\u3044\u3066\u3042\u308b\u3093\u3067\u3059\u304c\u3001\u8aad\u307f\u98db\u3070\u3057\u304c\u3061\u306a\u3093\u3067\u3059\u3088\u306d\u3002
\n\u7279\u306b\u65b0\u898f\u6027\u304c\u3042\u308b\u5185\u5bb9\u3067\u306f\u306a\u3044\u306e\u3067\u3001\u30bf\u30a4\u30c8\u30eb\u3067\u3082\u3046\u77e5\u3063\u3066\u308b\u308f\uff01\u3068\u3044\u3046\u65b9\u306f\u305d\u3063\u9589\u3058\u3057\u3066\u3082\u3089\u3063\u3066\u5927\u4e08\u592b\u3067\u3059\u3002<\/p>\n

iota\u3068\u306f<\/h1>\n

iota\u306f\u3001\u5b9a\u6570\u5ba3\u8a00(const)\u306e\u5185\u3067\u306e\u65e2\u5b9a\u3055\u308c\u305f\u8b58\u5225\u5b50\u3067\u3059\u3002
\n\u578b\u306a\u3057\u306e\u6574\u6570\u306e\u9023\u756a\u3092\u751f\u6210\u3057\u307e\u3059\u3002\u5177\u4f53\u4f8b\u3092\u898b\u307e\u3057\u3087\u3046\u3002<\/p>\n

package<\/span> main<\/span>\r\n\r\nimport<\/span> \"fmt\"<\/span>\r\n\r\nconst<\/span> (<\/span>\r\n    zero<\/span>  =<\/span> iota<\/span>\r\n    one<\/span>   =<\/span> iota<\/span>\r\n    two<\/span>   =<\/span> iota<\/span>\r\n    three<\/span> =<\/span> iota<\/span>\r\n)<\/span>\r\n\r\nfunc<\/span> main<\/span>()<\/span> {<\/span>\r\n    fmt<\/span>.<\/span>Printf<\/span>(<\/span>\"zero:%v<\/span>\\n<\/span>\"<\/span>,<\/span> zero<\/span>)<\/span>\r\n    fmt<\/span>.<\/span>Printf<\/span>(<\/span>\"one:%v<\/span>\\n<\/span>\"<\/span>,<\/span> one<\/span>)<\/span>\r\n    fmt<\/span>.<\/span>Printf<\/span>(<\/span>\"two:%v<\/span>\\n<\/span>\"<\/span>,<\/span> two<\/span>)<\/span>\r\n    fmt<\/span>.<\/span>Printf<\/span>(<\/span>\"three:%v<\/span>\\n<\/span>\"<\/span>,<\/span> three<\/span>)<\/span>\r\n}<\/span>\r\n\r\n<\/code><\/pre>\n
https:\/\/play.golang.org\/p\/9uycXahdRE
\n\u7d50\u679c\u306f\u3053\u3046\u3067\u3059\u3002<\/p>\n
zero:0
\none:1
\ntwo:2
\nthree:3<\/p><\/blockquote>\n
\u6700\u521d\u306e1\u3064\u306e\u307f\u8a2d\u5b9a\u3057\u3066\u304a\u3051\u3070\u3001\u3042\u3068\u306f\u7701\u7565\u3059\u308b\u3053\u3068\u304c\u53ef\u80fd\u3067\u3059\u3002
\n\uff08\u3061\u306a\u307f\u306b\u3053\u308c\u306fiota\u306b\u9650\u3089\u305a\u3001\u5b9a\u7fa9\u3059\u308b\u5024\u3092\u7701\u7565\u3059\u308b\u3068\u3001\u76f4\u524d\u306b\u5b9a\u7fa9\u3055\u308c\u305f\u3082\u306e\u304c\u6d41\u7528\u3055\u308c\u307e\u3059\u3002\uff09<\/p>\n
package main\r\n\r\nimport \"fmt\"\r\n\r\nconst (\r\n    zero  = iota\r\n    one\r\n    two\r\n    three\r\n)\r\n\r\nfunc main() {\r\n    fmt.Printf(\"zero:%v\\n\", zero)\r\n    fmt.Printf(\"one:%v\\n\", one)\r\n    fmt.Printf(\"two:%v\\n\", two)\r\n    fmt.Printf(\"three:%v\\n\", three)\r\n}\r\n\r\n<\/code><\/pre>\n
ConstSpec\u6bce\u306b\u30a4\u30f3\u30af\u30ea\u30e1\u30f3\u30c8\u3055\u308c\u3001\u6b21\u306e\u4e88\u7d04\u8a9econst\u304c\u73fe\u308c\u305f\u3089\u30ea\u30bb\u30c3\u30c8\u3055\u308c\u307e\u3059\u3002<\/p>\n
const<\/span> (<\/span>\r\n    zero<\/span> =<\/span> iota<\/span> \/\/ 0<\/span>\r\n    one<\/span>  =<\/span> iota<\/span> \/\/ 1<\/span>\r\n)<\/span>\r\nconst<\/span> (<\/span>\r\n    two<\/span>   =<\/span> iota<\/span> \/\/ 0<\/span>\r\n    three<\/span> =<\/span> iota<\/span> \/\/ 1<\/span>\r\n)<\/span>\r\n<\/code><\/pre>\n
\u307e\u305f\u3001const\u306e\u4e2d\u3067\u3042\u308c\u3070\u3001\u5f0f\u306e\u306a\u304b\u3067\u5229\u7528\u3059\u308b\u3053\u3068\u3082\u3067\u304d\u307e\u3059\u3002<\/p>\n
const<\/span> (<\/span>\r\n    zero<\/span>  =<\/span> iota<\/span> *<\/span> iota<\/span> \/\/ 0<\/span>\r\n    one<\/span>                 \/\/ 1<\/span>\r\n    two<\/span>                 \/\/ 4<\/span>\r\n    three<\/span>               \/\/ 9<\/span>\r\n)<\/span>\r\n<\/code><\/pre>\n
const<\/span> (<\/span>\r\n    zero<\/span>  =<\/span> iota<\/span> !=<\/span> 1<\/span> \/\/ true<\/span>\r\n    one<\/span>               \/\/ false<\/span>\r\n    two<\/span>               \/\/ true<\/span>\r\n    three<\/span>             \/\/ true<\/span>\r\n)<\/span>\r\n<\/code><\/pre>\n
\u4ed6\u306e\u5b9a\u7fa9\u3068\u6df7\u5728\u3057\u3066\u3082\u3001ConstSpec\u306e\u305f\u3073\u306b\u30a4\u30f3\u30af\u30ea\u30e1\u30f3\u30c8\u3057\u3066\u3044\u307e\u3059\u3002<\/p>\n
const<\/span> (<\/span>\r\n    zero<\/span>  =<\/span> \"zero\"<\/span> \/\/ zero<\/span>\r\n    one<\/span>   =<\/span> iota<\/span>   \/\/ 1<\/span>\r\n    two<\/span>   =<\/span> \"\u5f10\"<\/span>    \/\/ \u5f10<\/span>\r\n    three<\/span> =<\/span> iota<\/span>   \/\/ 3<\/span>\r\n)<\/span>\r\n<\/code><\/pre>\n
\u307e\u305f\u3001const\u5185\u3067\u5148\u306biota\u3092\u8a2d\u5b9a\u3059\u308b\u3068\u7d50\u69cb\u9762\u767d\u304b\u3063\u305f\u3067\u3059\u3002iota\u306e\u6a5f\u80fd\u3067\u306f\u306a\u304f\u3001\u5b9a\u6570\u304c\u512a\u5148\u3055\u308c\u307e\u3057\u305f\u3002<\/p>\n
const<\/span> (<\/span>\r\n    iota<\/span>  =<\/span> \"iota\"<\/span> \/\/ iota<\/span>\r\n    zero<\/span>  =<\/span> iota<\/span>   \/\/ iota<\/span>\r\n    one<\/span>            \/\/ iota<\/span>\r\n    two<\/span>            \/\/ iota<\/span>\r\n    three<\/span>          \/\/ iota<\/span>\r\n)<\/span>\r\n<\/code><\/pre>\n
\u578b\u306a\u3057\u306e\u6574\u6570\u306a\u306e\u3067const\u3067\u4f7f\u7528\u3057\u305f\u5b9a\u6570\u3092TypeOf\u3059\u308b\u3068int\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n
package<\/span> main<\/span>\r\n\r\nimport<\/span> (<\/span>\r\n    \"fmt\"<\/span>\r\n    \"reflect\"<\/span>\r\n)<\/span>\r\n\r\nconst<\/span> (<\/span>\r\n    zero<\/span> =<\/span> iota<\/span>\r\n)<\/span>\r\n\r\nfunc<\/span> main<\/span>()<\/span> {<\/span>\r\n    fmt<\/span>.<\/span>Printf<\/span>(<\/span>\"zero type:%v<\/span>\\n<\/span>\"<\/span>,<\/span> reflect<\/span>.<\/span>TypeOf<\/span>(<\/span>zero<\/span>))<\/span>\r\n}<\/span>\r\n<\/code><\/pre>\n
\u3067\u3059\u306e\u3067\u3001\u3053\u306e\u3088\u3046\u306a\u5b9a\u7fa9\u3092\u3059\u308b\u3068\u5909\u63db\u3067\u304d\u306a\u3044\u306e\u3067\u30b3\u30f3\u30d1\u30a4\u30eb\u30a8\u30e9\u30fc\u3068\u306a\u308a\u307e\u3059\u3002<\/p>\n
const<\/span>(<\/span>\r\n    zero<\/span> string<\/span> =<\/span> iota<\/span>\r\n)<\/span>\r\n<\/code><\/pre>\n
…\/main.go:6: cannot convert 0 to type string<\/p><\/blockquote>\n
Github\u3067\u306f\u3053\u3046\u3044\u3046\u611f\u3058\u3067\u4f7f\u308f\u308c\u3066\u305f\u3088<\/h1>\n
\u8efd\u304f\u898b\u305f\u611f\u3058\u5358\u7d14\u306b\u30d5\u30e9\u30b0\u7684\u306a\u3082\u306e\u3092const\u3059\u308b\u30bd\u30fc\u30b9\u304c\u6b86\u3069\u3060\u3063\u305f\u3093\u3067\u3059\u304c\u3001<\/p>\n
type<\/span> ByteSize<\/span> float64<\/span>\r\n\r\nconst<\/span> (<\/span>\r\n    _<\/span>           =<\/span> iota<\/span> \/\/ ignore first value by assigning to blank identifier<\/span>\r\n    KB<\/span> ByteSize<\/span> =<\/span> 1<\/span> <<<\/span> (<\/span>10<\/span> *<\/span> iota<\/span>)<\/span>\r\n    MB<\/span>\r\n    GB<\/span>\r\n    TB<\/span>\r\n    PB<\/span>\r\n    EB<\/span>\r\n    ZB<\/span>\r\n    YB<\/span>\r\n)<\/span>\r\n<\/code><\/pre>\n
https:\/\/github.com\/golang\/go\/blob\/964639cc338db650ccadeafb7424bc8ebb2c0f6c\/doc\/progs\/eff_bytesize.go
\n\u3053\u306e\u30bd\u30fc\u30b9\u306f\u30b7\u30d5\u30c8\u6f14\u7b97\u5b50\u3067ByteSize\u578b\u306e\u5024\u4f5c\u3063\u3066\u3066\u9762\u767d\u304b\u3063\u305f\u3067\u3059\u3002<\/p>\n
\u304a\u308f\u308a\u306b<\/h1>\n
\u3068\u3044\u3046\u308f\u3051\u3067\u3001iota\u5217\u6319\u5b50\u306e\u3054\u7d39\u4ecb\u3067\u3057\u305f\u3002<\/p>\n
\u3072\u3089\u3081\u304d\u6b21\u7b2c\u3067\u697d\u3057\u304f\u4f7f\u3048\u305d\u3046\u306a\u306e\u3067\u3001\u3053\u3046\u3044\u3046\u3068\u3053\u3067\u4f7f\u3046\u3068\u4fbf\u5229\u3001\u3053\u3046\u3044\u3046\u611f\u3058\u3067\u4f7f\u3063\u3066\u308b\u3068\u3053\u3042\u3063\u305f\u3001\u306a\u3069\u3042\u3063\u305f\u3089\u6559\u3048\u3066\u3044\u305f\u3060\u3051\u308b\u3068\u3046\u308c\u3057\u3044\u3067\u3059\u3002<\/p>\n
\u53c2\u8003\u6587\u732e<\/h1>\n
Iota \u00b7 golang\/go Wiki
\nhttps:\/\/github.com\/golang\/go\/wiki\/Iota<\/p>\n
The Go Programming Language Specification – Iota
\nhttps:\/\/golang.org\/ref\/spec#Iota<\/p>\n
Yosssi’s blog – Go\u8a00\u8a9e\u306e\u8b58\u5225\u5b50iota\u306b\u3064\u3044\u3066
\n