string - Scala、模式匹配、字符串

Question

有没有办法像这样匹配scala中的字符串:

  def matcher(arg: String) : Expr = {
    case left :: '*' :: right => new Binary("*", left, right)
    case left :: '+' :: right => new Binary("+", left, right)
  }

哪里的 left 和 right 是 String 类型？

Answer 1

您可以通过匹配正则表达式来实现您的目标。

trait Expr

case class Binary(op: String, leftOperand: String, rightOperand: String) extends Expr

val mulPattern = "(\\d*)\\*(\\d*)".r
val addPattern = "(\\d*)\\+(\\d*)".r

def matcher(arg: String) : Expr = {
  arg match {
    case mulPattern(left, right) => new Binary("*", left, right)
    case addPattern(left, right) => new Binary("+", left, right)
  }
}

def main(args: Array[String]): Unit = {
  println(matcher("1+2")) // Binary("+", "1", "2")
  println(matcher("3*4")) // Binary("*", "3", "4")
}