package main
 
import (
	"fmt"
)
 
const (
	opAdd      = "add"
	opSubtract = "subtract"
	opMultiply = "multiply"
	opDivide   = "divide"
	opExit     = "exit"
)
 
var result float64
 
func add(a, b float64) {
	result = a + b
}
func multiply(a, b float64) {
	result = a * b
}
func subtract(a, b float64) {
	result = a - b
}
func divide(a, b float64) {
	result = a / b
}
 
func main() {
	var x float64
	var y float64

	//TODO: implement according to README.md 

	//the following code just demonstrates how to use fmt.Scan

		for {
		fmt.Print("What would you like to do? (add|subtract|divide|multiply|exit)")
		var str string
		fmt.Scan(&str)
		if str == opExit {
			break
		} else {
 
			fmt.Print("Please enter a float: ")
			fmt.Scan(&x)
 
			fmt.Print("Please enter a float: ")
			fmt.Scan(&y)
 
			switch str {
			case opAdd:
				add(x, y)
				fmt.Println(result)
			case opMultiply:
				multiply(x, y)
				fmt.Println(result)
			case opDivide:
				if y == 0 {
					fmt.Println("Division by 0 is not possible")
					continue
				}
				divide(x, y)
				fmt.Println(result)
			case opSubtract:
				subtract(x, y)
				fmt.Println(result)
			default:
				fmt.Println("Unknown operation")
			}
		}
	}
}