Basic Calculator

calculator.kt

fun main(args: Array<String>) {
    println("Basic Calculator")

    val firstNumber: Number?
    val secondNumber: Number?
    val operation: String?

    while (true) {
        print("Input first Number: ")
        val input = readln()
        if (input.isBlank()) continue

        firstNumber = input.toIntOrNull() ?: input.toDoubleOrNull() ?: continue
        break
    }

    while (true) {
        print("Input second Number: ")
        val input = readln()
        if (input.isBlank()) continue

        secondNumber = input.toIntOrNull() ?: input.toDoubleOrNull() ?: continue
        break
    }

    while (true) {
        print("Input operation: ")
        val input = readln()
        if (input == "*" || input == "+" || input == "-" || input == "/") {
            operation = input
            break
        }
    }

    when (operation) {
        "*" -> when {
            firstNumber is Double && secondNumber is Double -> {
                printResult(firstNumber * secondNumber)
            }

            firstNumber is Double -> {
                printResult(firstNumber * secondNumber as Int)
            }

            secondNumber is Double -> {
                printResult(firstNumber as Int * secondNumber)
            }

            else -> {
                printResult(firstNumber as Int * secondNumber as Int)
            }
        }

        "+" -> when {
            firstNumber is Double && secondNumber is Double -> {
                printResult(firstNumber + secondNumber)
            }

            firstNumber is Double -> {
                printResult(firstNumber + secondNumber as Int)
            }

            secondNumber is Double -> {
                printResult(firstNumber as Int + secondNumber)
            }

            else -> {
                printResult(firstNumber as Int + secondNumber as Int)
            }
        }

        "-" -> when {
            firstNumber is Double && secondNumber is Double -> {
                printResult(firstNumber - secondNumber)
            }

            firstNumber is Double -> {
                printResult(firstNumber - secondNumber as Int)
            }

            secondNumber is Double -> {
                printResult(firstNumber as Int - secondNumber)
            }

            else -> {
                printResult(firstNumber as Int - secondNumber as Int)
            }
        }

        "/" -> when {
            firstNumber is Double && secondNumber is Double -> {
                printResult(firstNumber / secondNumber)
            }

            firstNumber is Double -> {
                printResult(firstNumber / secondNumber as Int)
            }

            secondNumber is Double -> {
                printResult(firstNumber as Int / secondNumber)
            }

            else -> {
                printResult(firstNumber as Int / secondNumber as Int)
            }
        }

        else -> throw Exception("Something went wrong")
    }
}

fun printResult(result: Number) {
    println("Result is $result")
}