diff -r 47f86885d481 -r e85600529ca5 parser2a.scala
--- a/parser2a.scala	Sun Dec 23 00:38:56 2012 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,105 +0,0 @@
-// Parser combinators including semantic actions
-// parses lists of tokens
-//
-// Needs
-//    :load matcher.scala
-
-// some regular expressions
-val LETTER = RANGE("abcdefghijklmnopqrstuvwxyz")
-val ID = PLUS(LETTER)
-
-val DIGIT = RANGE("0123456789")
-val NONZERODIGIT = RANGE("123456789")
-val NUMBER = ALT(SEQ(NONZERODIGIT, STAR(DIGIT)), "0")
-
-val LPAREN = CHAR('(')
-val RPAREN = CHAR(')')
-
-val WHITESPACE = PLUS(RANGE(" \n"))
-val OPS = RANGE("+-*")
-
-// for classifying the strings that have been recognised
-abstract class Token
-
-case object T_WHITESPACE extends Token
-case class T_NUM(s: String) extends Token
-case class T_ID(s: String) extends Token
-case class T_OP(s: String) extends Token
-case object T_LPAREN extends Token
-case object T_RPAREN extends Token
-case object T_IF extends Token
-case object T_THEN extends Token
-case object T_ELSE extends Token
-
-// lexing rules for arithmetic expressions
-val lexing_rules: List[Rule[Token]]= 
-  List(("if", (s) => T_IF),
-       ("then", (s) => T_THEN),
-       ("else", (s) => T_ELSE),
-       (NUMBER, (s) => T_NUM(s.mkString)),
-       (ID, (s) => T_ID(s.mkString)),
-       (WHITESPACE, (s) => T_WHITESPACE),
-       (LPAREN, (s) => T_LPAREN),
-       (RPAREN, (s) => T_RPAREN),
-       (OPS, (s) => T_OP(s.mkString)))
-
-val Tok = Tokenizer(lexing_rules, List(T_WHITESPACE))
-
-// parser combinators with return type T
-abstract class Parser[T] {
-  def parse(ts: List[Token]): Set[(T, List[Token])]
-
-  def parse_all(ts: List[Token]) : Set[T] =
-    for ((head, tail) <- parse(ts); if (tail == Nil)) yield head
-
-  def || (right : => Parser[T]) : Parser[T] = new AltParser(this, right)
-  def ==>[S] (f: => T => S) : Parser [S] = new FunParser(this, f)
-  def ~[S] (right : => Parser[S]) : Parser[(T, S)] = new SeqParser(this, right)
-  def ~>[S] (right : => Parser[S]) : Parser[S] = this ~ right ==> (x => x._2)
-  def <~[S] (right : => Parser[S]) : Parser[T] = this ~ right ==> (x => x._1)
-
-}
-
-class SeqParser[T, S](p: => Parser[T], q: => Parser[S]) extends Parser[(T, S)] {
-  def parse(sb: List[Token]) = 
-    for ((head1, tail1) <- p.parse(sb); 
-         (head2, tail2) <- q.parse(tail1)) yield ((head1, head2), tail2)
-}
-
-class AltParser[T](p: => Parser[T], q: => Parser[T]) extends Parser[T] {
-  def parse (sb: List[Token]) = p.parse(sb) ++ q.parse(sb)   
-}
-
-class FunParser[T, S](p: => Parser[T], f: T => S) extends Parser[S] {
-  def parse (sb: List[Token]) = 
-    for ((head, tail) <- p.parse(sb)) yield (f(head), tail)
-}
-
-
-case class TokParser(tok: Token) extends Parser[Token] {
-  def parse(ts: List[Token]) = ts match {
-    case t::ts if (t == tok) => Set((t, ts)) 
-    case _ => Set ()
-  }
-}
-
-implicit def token2tparser(t: Token) = TokParser(t)
-
-case object NumParser extends Parser[Int] {
-  def parse(ts: List[Token]) = ts match {
-    case T_NUM(s)::ts => Set((s.toInt, ts)) 
-    case _ => Set ()
-  }
-}
-
-lazy val E: Parser[Int] = (T ~ T_OP("+") ~ E) ==> { case ((x, y), z) => x + z } || T  
-lazy val T: Parser[Int] = (F ~ T_OP("*") ~ T) ==> { case ((x, y), z) => x * z } || F
-lazy val F: Parser[Int] = (T_LPAREN ~> E <~ T_RPAREN) || NumParser
-   
-println(E.parse_all(Tok.fromString("1 + 2 + 3")))
-println(E.parse_all(Tok.fromString("1 + 2 * 3")))
-println(E.parse_all(Tok.fromString("(1 + 2) * 3")))
-
-// Excercise: implement minus 
-println(E.parse_all(Tok.fromString("(1 - 2) * 3")))
-println(E.parse_all(Tok.fromString("(1 + 2) * - 3")))