android - 如何创建数字之间的操作？

Question

首先我尝试在 kotlin 中创建操作代码，我的意思是当在终端中运行代码并输入第一个数字 123456 当我按下 + 运算符时代码读取它作为字符串选项，它将变为 123456+。

底线是:我想创建运算符 kotlin 代码可以计算两个数字，当我按 + 或 - 或 / or * 数字一的行必须干净才能输入数字二进行计算，因此输入数字三、四、五。

这是我的代码:

fun operation(arr: ArrayList<String?>?) {

    val joo = readLine()!!
    val loo = joo.removeSuffix("+")

    var soo = loo.toInt()
    arr!!.add(soo.toString())

    val voo = joo.lastIndex
    when(voo.toString()){
        "+" -> arr.last()!!.plus(soo)
    }

    println("${soo}")

    operation(arr)

}

Answer 1

今天早上我有时间。对于某些人来说，这可能是一个很好的问候世界，所以开始吧。

要读取输入并从中建立状态，您需要:

• 从用户那里读取每个新参数的循环
• 一种跟踪您已阅读输入的方法。这实际上是一个小状态机。我使用 enum 和 when 表达式实现了我的。

这就是(可能不完全是您要查找的内容，但应该让您了解可能的结构:

import java.util.*

// This gives us the states that our state machine can be in.
enum class State {
    WANT_FIRST_OPERAND,
    WANT_SECOND_OPERAND,
    WANT_OPERATOR
}

fun main() {
    val scanner = Scanner(System.`in`)
    var state = State.WANT_FIRST_OPERAND
    println("Ready to do some maths!")
    var firstOperand = 0.0
    var secondOperand: Double
    var operator = ""
    // This loop will keep asking the user for input and progress through the states of the state machine.
    loop@ while (true) {
        // This when block encapsulates the logic for each state of our state machine.
        when (state) {
            State.WANT_FIRST_OPERAND -> {
                println("Give me your first operand.")
                try {
                    firstOperand = scanner.nextDouble()
                    state = State.WANT_OPERATOR
                } catch (e: Exception) {
                    println("Sorry, that did not work, did you give me a number?")
                    scanner.nextLine()
                }
            }
            State.WANT_OPERATOR -> {
                println("Give me the operator. (+, -, /, *)")
                try {
                    operator = scanner.next("[-*+/]+").trim()
                    state = State.WANT_SECOND_OPERAND
                } catch (e: Exception) {
                    println("Sorry, that did not work.")
                    scanner.nextLine()
                }
            }
            State.WANT_SECOND_OPERAND -> {
                println("Give me your second operand.")
                try {
                    secondOperand = scanner.nextDouble()
                    val answer = when(operator){
                        "+" -> firstOperand + secondOperand
                        "-" -> firstOperand - secondOperand
                        "/" -> firstOperand / secondOperand // You want to do something if second operand is 0 here
                        "*" -> firstOperand * secondOperand
                        else -> {
                            println("Hmmm, something went wrong there I don't know $operator, try again")
                            state = State.WANT_OPERATOR
                            continue@loop
                        }
                    }
                    println("The Answer is $answer, lets do another one!")
                    state = State.WANT_FIRST_OPERAND
                } catch (e: Exception) {
                    println("Sorry, that did not work, did you give me a number?")
                    scanner.nextLine()
                }
            }
        }
    }
}