Scala example source code file (packrat3.scala)

This example Scala source code file (packrat3.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

list, nosuccess, packratparser, packratparser, packratparsers, packratreader, packratreader, parser, parser, some, standardtokenparsers, success, test, unit

The Scala packrat3.scala source code

import scala.util.parsing.combinator._

import scala.util.parsing.combinator.syntactical.StandardTokenParsers
import scala.util.parsing.input._
import scala.util.parsing.syntax._

import scala.collection.mutable.HashMap

object Test {
  def main(args: Array[String]): Unit = {
    import grammars3._

    val head = phrase(AnBnCn)

    println(extractResult(head(new lexical.Scanner("a b c"))))
    println(extractResult(head(new lexical.Scanner("a a b b c c"))))
    println(extractResult(head(new lexical.Scanner("a a a b b b c c c"))))
    println(extractResult(head(new lexical.Scanner("a a a a b b b b c c c c"))))

    println(extractResult(AnBnCn(new PackratReader(new lexical.Scanner("a a a b b b b c c c c")))))
    println(extractResult(AnBnCn(new PackratReader(new lexical.Scanner("a a a a b b b c c c c")))))
    println(extractResult(AnBnCn(new PackratReader(new lexical.Scanner("a a a a b b b b c c c")))))
  }
}

object grammars3 extends StandardTokenParsers with PackratParsers {
  
  def extractResult(r: ParseResult[_]) = r match {
    case Success(a,_) => a
    case NoSuccess(a,_) => a
  }
  

  lexical.reserved ++= List("a","b", "c")
  val a: PackratParser[Any] = memo("a")
  val b: PackratParser[Any] = memo("b")
  val c: PackratParser[Any] = memo("c")

  val AnBnCn: PackratParser[Any] = 
    guard(repMany1(a,b) ~ not(b)) ~ rep1(a) ~ repMany1(b,c)// ^^{case x~y => x:::y}


  private def repMany[T](p: => Parser[T], q: => Parser[T]): Parser[List[T]] = 
  ( p~repMany(p,q)~q ^^ {case x~xs~y => x::xs:::(y::Nil)}
   | success(Nil)
  )

  def repMany1[T](p: => Parser[T], q: => Parser[T]): Parser[List[T]] = 
   p~opt(repMany(p,q))~q ^^ {case x~Some(xs)~y => x::xs:::(y::Nil)}

}