Solution: calculator STDIN switch

---

examples/calc-stdin-switch/calc_stdin_switch.go

package main

import (
    "fmt"
    "os"
    "strconv"
)

func main() {
    var aStr string
    var bStr string
    var operator string
    var a float64
    var b float64
    var err error
    var result float64

    fmt.Print("a: ")
    fmt.Scan(&aStr)
    a, err = strconv.ParseFloat(aStr, 64)
    if err != nil {
        fmt.Printf("The value '%v' could not be converted to a floating point number. %v\n", aStr, err)
        os.Exit(1)
    }

    fmt.Print("op: ")
    fmt.Scan(&operator)

    fmt.Print("b: ")
    fmt.Scan(&bStr)
    b, err = strconv.ParseFloat(bStr, 64)
    if err != nil {
        fmt.Printf("The value '%v' could not be converted to a floating point number. %v\n", bStr, err)
        os.Exit(1)

    }

    switch operator {
    case "+":
        result = a + b
    case "-":
        result = a - b
    case "*":
        result = a * b
    case "/":
        result = a / b
    default:
        fmt.Printf("Unhandled operator: '%v'\n", operator)
        os.Exit(1)
    }
    fmt.Printf("%v %v %v = %v\n", a, operator, b, result)

}