【Go Time】Go語言裏的條件語句else、switch

if語句判斷

1. if裏的條件能夠賦值

2. if的條件裏賦值的變量做用域就在這個if語句裏

   if contents, err := ioutil.ReadFile(filename); err != nil {
       fmt.Println(err)
   } else {
       fmt.Printf("%s\n", contents)
   }
   
   // 這裏會報錯。contents 做用域不一樣
   // fmt.Printf("%s\n", contents)

switch語句

1. switch語句中，每一個case會自動break
2. switch後面能夠沒有表達式

func eval(a, b int, op string) int {
    var result int
    
    switch op {
        case "+":
           result = a + b
        case "-":
           result = a -b
        case "*":
           result = a * b
        case "/":
           result = a / b
        default:
           panic("unsupported operator:" + op)
    }

    return result
}

func grade(score int) string {
    var g := ""
    switch {
        case score < 0 || score > 100
           panic(fmt.Sprintf("Wrong score: %d", score))
        case score < 60:
           g = "F" // 或者 return "F"
        case score < 80:
           g = "C"
        case score < 90:
           g = "B"
        case score <= 100:
           g = "A"
    }
    return g
}