Scala, pattern matching, strings

Question

Is there way to match strings in scala like this:

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

where left and right are have type String?

Answer 1

You can achieve your goal by matching on regular expressions.

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")
}