ammonite log

amm.scala

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Welcome to the Ammonite Repl 1.3.2
(Scala 2.12.7 Java 1.8.0_212)
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@ import $ivy.`org.scala-lang.modules::scala-parser-combinators:1.1.2`
import $ivy.$

@ {
    sealed trait Expr
    case class Term(term: String) extends Expr
    case class And(x: Expr, y: Expr) extends Expr
    case class Or(x: Expr, y: Expr) extends Expr

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

  object Parsing extends RegexParsers with PackratParsers {

    override val skipWhitespace = false

    val validIdentifiers = List("aaa", "bbb", "ccc", "ddd")

    lazy val term: PackratParser[Term] = """\s*""".r ~> """\w+""".r flatMap { identifier =>
      if (validIdentifiers.contains(identifier))
        success(Term(identifier))
      else
        err(s"expected one of: $validIdentifiers")
    }

    lazy val and: PackratParser[And] =
      expr ~ """\s+and\s+""".r ~ (term | parensExpr) ^^ { case e1 ~ _ ~ e2 => And(e1, e2) }

    lazy val or: PackratParser[Or] =
      expr ~ """\s+or\s+""".r ~ (term | parensExpr) ^^ { case e1 ~ _ ~ e2 => Or(e1, e2) }

    lazy val parensExpr: PackratParser[Expr] = """\s*\(""".r ~> expr <~ """\s*\)""".r

    lazy val expr: PackratParser[Expr] =
      term ||| and ||| or ||| parensExpr

    lazy val root: PackratParser[Expr] =
      phrase(expr)

    def parseExpr(input: String): ParseResult[Expr] =
      parse(root, new PackratReader(new CharSequenceReader(input)))
  }
  }
defined trait Expr
defined class Term
defined class And
defined class Or
import scala.util.parsing.combinator.{PackratParsers, RegexParsers}

import scala.util.parsing.input.CharSequenceReader


defined object Parsing

@ println(Parsing.parseExpr("aaa and invalidIdentifier"))
[1.4] failure: end of input expected

aaa and invalidIdentifier
   ^