5.2 常數

建議閱讀官方文件：

特別值得留意的是關鍵字 iota，它能夠讓編譯器產生特定運算規則的常數值。以下是一些範例。

Example 1

const (
    Sunday =  0         // 0
    Monday =  iota + 1  // 1 (iota = 0)
    Tuesday             // 2 (iota = 1)
    Wednesday           // 3 (iota = 2)
    Thursday            // 4 (iota = 3)
    Friday              // 5 (iota = 4)
    Saturday            // 6 (iota = 5)
)

Example 2

const (
    Black      = iota + 1       // 1 = 0+1  (iota = 0)
    Red                         // 2 = 1+1  (iota = 1)
    Yellow                      // 3 = 2+1  (iota = 2)
    Green      = iota + 2       // 5 = 3+2  (iota = 3)
    Blue                        // 6 = 4+2  (iota = 4)
    Pink, Gray = iota, iota + 1 // 5, 6     (iota = 5)
    Brown      = iota + 3       // 9 = 6+3  (iota = 6)
    White                       // 10 = 7+3 (iota = 7)
)

Try it: https://go.dev/play/p/F-XPYY3g2Hm

Example 3

定義常數時，也可以使用自訂型別。

package main

import "fmt"

type language = string
type MyString string

const (
    EN language = "English"
    ZH          = "Chinese"
)

func main() {
    var lang language = "English"
    var str MyString = "Hello"
    fmt.Printf("Type of lang: %T\n", lang)
    fmt.Printf("Type of str: %T\n", str)

    fmt.Printf("Type of const EN: %T\n", EN)
}

執行結果：

Type of lang: string
Type of str: main.MyString
Type of const EN: string

Try it: https://go.dev/play/p/u2V08y0BmHq

先這樣，也許有空時會再更新。 我的其他站點：

Last modified: 2024-10-15