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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 extends Application{
import grammars._
val head = phrase(term)
println(extractResult(head(new lexical.Scanner("1"))))
println(extractResult(head(new lexical.Scanner("1+2"))))
println(extractResult(head(new lexical.Scanner("9-4"))))
println(extractResult(head(new lexical.Scanner("9*9"))))
println(extractResult(head(new lexical.Scanner("8/2"))))
println(extractResult(head(new lexical.Scanner("4*9-0/7+9-8*1"))))
println(extractResult(head(new lexical.Scanner("(1+2)*3"))))
}
object grammars extends StandardTokenParsers with PackratParsers{
def extractResult(r : ParseResult[_]) = r match{
case Success(a,_) => a
case Failure(a,_) => a
case Error(a,_) => a
}
lexical.delimiters ++= List("+","-","*","/","(",")")
lexical.reserved ++= List("Hello","World")
/****
* term = term + fact | term - fact | fact
* fact = fact * num | fact / num | num
*/
val term: PackratParser[Int] = (term~("+"~>fact) ^^ {case x~y => x+y}
|term~("-"~>fact) ^^ {case x~y => x-y}
|fact)
val fact: PackratParser[Int] = (fact~("*"~>numericLit) ^^ {case x~y => x*y.toInt}
|fact~("/"~>numericLit) ^^ {case x~y => x/y.toInt}
|"("~>term<~")"
|numericLit ^^ {_.toInt})
}
|
