add: calculator example to x-tba

x-tba/foundations/calc/05-switch/main.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	// lesson: switch
+
+	if len(os.Args) != 4 {
+		fmt.Println("Usage: calc <number1> <operator> <number2>")
+		return
+	}
+
+	a, err := strconv.ParseFloat(os.Args[1], 64)
+	if err != nil {
+		fmt.Println("Please provide a valid number")
+		return
+	}
+
+	b, err := strconv.ParseFloat(os.Args[3], 64)
+	if err != nil {
+		fmt.Println("Please provide a valid number")
+		return
+	}
+
+	var (
+		op  = os.Args[2]
+		res float64
+	)
+
+	switch op {
+	case "+":
+		res = a + b
+	case "-":
+		res = a - b
+	case "*":
+		res = a * b
+	case "/":
+		res = a / b
+	}
+
+	fmt.Printf("%v %v %v = %v\n", a, op, b, res)
+}