Go語言中的控制語句

// code_004_process_control project main.go
package main

import (
    "fmt"
    "time"
)

func main() {
    //if語句
    if a := 3; a > 3 {
        fmt.Println("a >3")
    } else if a == 3 {
        fmt.Println("a==3")
    } else {
        fmt.Println("error")
    }

    fmt.Println("\n============\n")
    //switch語句1
    switch score := 90; score {
    case 80, 90, 100:
        fmt.Println("優秀")
    case 50, 60, 70:
        fmt.Println("及格")
    default:
        fmt.Println("差")
    }
    //switch語句2
    var score int = 90
    switch score {
    case 80, 90, 100:
        fmt.Println("優秀")
    case 50, 60, 70:
        fmt.Println("及格")
    default:
        fmt.Println("差")
    }
    //switch語句3
    switch s3 := 90; {
    case s3 >= 90:
        fmt.Println("優秀")
    case s3 >= 80:
        fmt.Println("良好")
    default:
        fmt.Println("一般")
    }

    fmt.Println("\n============\n")
    //最簡單的無限循環
    for {
        time.Sleep(3 * time.Second)
        fmt.Println("for循環結束")
        break
    } //相當于python中while True: java中的for(;;){}

    //for循環
    var i, sum int
    for i = 1; i <= 100; i++ {
        fmt.Printf("i=%d\n", i) //Printf()格式化輸出，Println()無法格式化
        sum += i
    }
    fmt.Println("sum =", sum)

    //for ... range...
    s := "abc"
    for i := range s { //支持str/array/slice/map--->>只能獲取到index的值
        fmt.Printf("%c\n", s[i])
    }
    for _, c := range s { //忽略index
        fmt.Printf("%c\n", c)
    }
    for i, c := range s {
        fmt.Printf("第%d個值為:%c\n", i, c)
    }

    //for ... break 或者continue
    for i := 0; i < 5; i++ {
        if i == 2 {
            fmt.Printf("i== 2時 跳出本次循環")
            break
        }
        fmt.Println(i)
    }
    for i := 0; i < 5; i++ {
        if 2 == i {
            fmt.Println("哈哈，你看不到我,你真2")
            continue
        }
        fmt.Println(i)
    } //備注：break 可以用for、switch、select,而continue僅能用于for循環

    //goto,用goto跳轉到必須在當前函數內定義的標簽:
    fmt.Println("\n============\n")
    for i := 0; i < 5; i++ {
        for {
            fmt.Println(i)
            goto LABEL //跳轉到標簽LABEL,從標簽處，執行代碼
        }
    }
    fmt.Println("Let's see goto LABEL!!!")

LABEL:
    fmt.Println("it is over")

}