parsers.scala

import scala.util.parsing.combinator.{ Parsers, RegexParsers }
import scala.util.parsing.input.{ CharSequenceReader, Reader }

object ParsingExample extends Parsers {
  override type Elem = Char

  object Delimiter extends Parser[String] {
    def apply(reader: Input): ParseResult[String] = {
      if (reader atEnd) {
        Failure("end of string", reader)
      } else if (reader.first != '-') {
        Failure("no separator found", reader)
      } else {
        Success(reader.first, reader.rest)
      }
    }
  }

  val DigitSequence = Parser { reader =>
    if (reader atEnd) {
      Failure("end of string", reader)
    } else if (!reader.first.isDigit) {
      Failure("no digits found", reader)
    } else {
      var digits = reader.first.toString
      var rest = reader.rest
      while (!rest.atEnd && rest.first.isDigit) {
        digits += rest.first
        rest = rest.rest
      }
      Success(digits, rest)
    }
  }

  case class RolodexCard(pre: String, post: String)

  val PhoneNumber = DigitSequence ~ Delimiter ~ DigitSequence map {
    case pre ~ _ ~ post => RolodexCard(pre, post)
  }
}

object RegexParsingExample extends RegexParsers {
  case class RolodexCard(pre: String, post: String)

  val DigitSequence = """\d+""".r
  val Delimiter = "-"
  val PhoneNumber = DigitSequence ~ Delimiter ~ DigitSequence map {
    case pre ~ _ ~ post => RolodexCard(pre, post)
  }
}