时间戳

首页 > 解决方案 > 如何创建数字之间的操作？

android - 如何创建数字之间的操作？

问题描述

在第一次我尝试在 kotlin 中创建操作代码时，我的意思是当我在终端中运行代码并输入第一个数字123456时，当我按下+操作符时，代码将其读取为字符串选项，它将变为123456+.

底线是：我想创建可以计算两个数字的运算符 kotlin 代码，当我按+或-或或/或数字时*，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、四和五。

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)

}

标签： androidkotlin

解决方案

今天早上我有一些时间。对于某人来说，这可能是一个很好的问候世界，所以就这样吧。

要读取输入并从中建立状态，您将需要：

  • 从用户那里读取每个新参数的循环
  • 一种跟踪您已阅读的输入的方法。这实际上是一个小型状态机。我已经使用一个enum和一个when表达式实现了我的。

它在这里（可能不完全是您正在寻找的东西，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()
                }
            }
        }
    }
}

推荐阅读