加減乘除求餘都是很簡單的數學計算，直接上程式碼

package main

import "fmt"

func main() {
    demo61()
}

func demo61() {
    var ret float32
    //ret = getResult(5, 3, "+")
    //fmt.Println("ret=", ret)
    //ret = getResult(5, 3, "-")
    //fmt.Println("ret=", ret)
    //ret = getResult(5, 3, "*")
    //fmt.Println("ret=", ret)
 


    ret = getResult2(5, 3, "/")
    fmt.Println("ret=", ret)
    ret = getResult2(5, 3, "%")
    fmt.Println("ret=", ret)
}

//if-elseif-else結構
func getResult(a float32, b float32, operator string) (ret float32) {
    /*
    單分支
    if operator=="+"{
        ret = a+b
    }
    */

    /*
    //雙分支
    if operator=="+"{
        ret = a+b
    }else {
        fmt.Printf("不支援的操作符：%s\n",operator)
    }
    */
 


    //多分支
    if operator == "+" {
        ret = a + b
    } else if operator == "-" {
        ret = a - b
    } else if operator == "*" {
        ret = a * b
    } else if operator == "/" {
        ret = a / b
    } else if operator == "%" {
        ret = float32(int(a) % int(b))
    } else {
        fmt.Printf("不支援的操作符：%s\n"
 
, operator)
    }

    return
}

//switch-case-default結構
func getResult2(a float32, b float32, operator string) (ret float32) {
    //判斷operator的取值
    switch operator {

    //情形1,2,3...
    case "+":
        ret = a + b
    case "-":
        ret = a - b
    case "*":
        ret = a * b
    case "/":
        ret = a / b
    case "%":
        ret = float32(int(a) % int(b))

    //如果不符合上述任何一種情形
    default:
        fmt.Printf("不支援的操作符:%s\n", operator)
    }
    return
}