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package examples.parsing
import scala.util.parsing.combinator1.syntactical.StandardTokenParsers
object ArithmeticParsers extends StandardTokenParsers {
lexical.delimiters ++= List("(", ")", "+", "-", "*", "/")
def expr: Parser[Any] = term ~ rep("+" ~ term | "-" ~ term)
def term = factor ~ rep("*" ~ factor | "/" ~ factor)
def factor: Parser[Any] = "(" ~ expr ~ ")" | numericLit
def main(args: Array[String]) {
val tokens = new lexical.Scanner(args(0))
println(args(0))
println(phrase(expr)(tokens))
}
}
object ArithmeticParsers1 extends StandardTokenParsers {
lexical.delimiters ++= List("(", ")", "+", "-", "*", "/")
val reduceList: Int ~ List[String ~ Int] => Int = {
case i ~ ps => (i /: ps)(reduce)
}
def reduce(x: Int, r: String ~ Int) = (r: @unchecked) match {
case "+" ~ y => x + y
case "-" ~ y => x - y
case "*" ~ y => x * y
case "/" ~ y => x / y
}
def expr : Parser[Int] = term ~ rep ("+" ~ term | "-" ~ term) ^^ reduceList
def term : Parser[Int] = factor ~ rep ("*" ~ factor | "/" ~ factor) ^^ reduceList
def factor: Parser[Int] = "(" ~> expr <~ ")" | numericLit ^^ (_.toInt)
def main(args: Array[String]) {
val tokens = new lexical.Scanner(args(0))
println(args(0))
println(phrase(expr)(tokens))
}
}
class Expr
case class BinOp(op: String, l: Expr, r: Expr) extends Expr
case class Num(n: Int) extends Expr
object ArithmeticParsers2 extends StandardTokenParsers {
lexical.delimiters ++= List("(", ")", "+", "-", "*", "/")
val reduceList: Expr ~ List[String ~ Expr] => Expr = {
case i ~ ps => (i /: ps)(reduce)
}
def reduce(l: Expr, r: String ~ Expr) = BinOp(r._1, l, r._2)
def mkNum(s: String) = Num(s.toInt)
def expr : Parser[Expr] = term ~ rep ("+" ~ term | "-" ~ term) ^^ reduceList
def term : Parser[Expr] = factor ~ rep ("*" ~ factor | "/" ~ factor) ^^ reduceList
def factor: Parser[Expr] = "(" ~> expr <~ ")" | numericLit ^^ ((s: String) => Num(s.toInt))
def main(args: Array[String]) {
val parse = phrase(expr)
val tokens = new lexical.Scanner(args(0))
println(args(0))
println(parse(tokens))
}
}
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