用scala语言写一段中缀表达式求值的代码

以下是使用Scala语言编写的中缀表达式求值代码：

import scala.collection.mutable.Stack

def evaluateExpression(expression: String): Int = {
  val operators = Stack[Char]()
  val operands = Stack[Int]()
  var i = 0

  while (i < expression.length) {
    val token = expression(i)
    if (token.isDigit) {
      var num = token.toString.toInt
      while (i + 1 < expression.length && expression(i + 1).isDigit) {
        num = num * 10 + expression(i + 1).toString.toInt
        i += 1
      }
      operands.push(num)
    } else if (token == '(') {
      operators.push(token)
    } else if (token == ')') {
      while (operators.top != '(') {
        val op = operators.pop()
        val op2 = operands.pop()
        val op1 = operands.pop()
        operands.push(applyOperator(op, op1, op2))
      }
      operators.pop()
    } else if (token == '+' || token == '-' || token == '*' || token == '/') {
      while (operators.nonEmpty && hasPrecedence(token, operators.top)) {
        val op = operators.pop()
        val op2 = operands.pop()
        val op1 = operands.pop()
        operands.push(applyOperator(op, op1, op2))
      }
      operators.push(token)
    }
    i += 1
  }

  while (operators.nonEmpty) {
    val op = operators.pop()
    val op2 = operands.pop()
    val op1 = operands.pop()
    operands.push(applyOperator(op, op1, op2))
  }

  operands.pop()
}

def applyOperator(operator: Char, operand1: Int, operand2: Int): Int = {
  operator match {
    case '+' => operand1 + operand2
    case '-' => operand1 - operand2
    case '*' => operand1 * operand2
    case '/' => operand1 / operand2
  }
}

def hasPrecedence(op1: Char, op2: Char): Boolean = {
  if (op2 == '(' || op2 == ')') false
  else if ((op1 == '*' || op1 == '/') && (op2 == '+' || op2 == '-')) false
  else true
}

val expression = "((4+3)*2-1)/5"
val result = evaluateExpression(expression)
println(s"The result of $expression is $result")

此代码使用堆栈（Stack）数据结构来解析中缀表达式。它遍历表达式中的每个字符，并根据它是数字，运算符或括号来执行不同的操作。它还使用applyOperator和hasPrecedence函数来执行操作并确定运算符的优先级。最终，该函数返回表达式的计算结果。