diff -r 47f86885d481 -r e85600529ca5 regexp2.scala
--- a/regexp2.scala	Sun Dec 23 00:38:56 2012 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,123 +0,0 @@
-
-// regular expressions including NOT
-abstract class Rexp
-
-case object NULL extends Rexp
-case object EMPTY extends Rexp
-case class CHAR(c: Char) extends Rexp
-case class ALT(r1: Rexp, r2: Rexp) extends Rexp
-case class SEQ(r1: Rexp, r2: Rexp) extends Rexp
-case class STAR(r: Rexp) extends Rexp
-case class NOT(r: Rexp) extends Rexp
-
-
-// some convenience for typing in regular expressions
-def charlist2rexp(s : List[Char]) : Rexp = s match {
-  case Nil => EMPTY
-  case c::Nil => CHAR(c)
-  case c::s => SEQ(CHAR(c), charlist2rexp(s))
-}
-implicit def string2rexp(s : String) : Rexp = charlist2rexp(s.toList)
-
-
-// nullable function: tests whether the regular 
-// expression can recognise the empty string
-def nullable (r: Rexp) : Boolean = r match {
-  case NULL => false
-  case EMPTY => true
-  case CHAR(_) => false
-  case ALT(r1, r2) => nullable(r1) || nullable(r2)
-  case SEQ(r1, r2) => nullable(r1) && nullable(r2)
-  case STAR(_) => true
-  case NOT(r) => !(nullable(r))
-}
-
-// tests whether a regular expression 
-// cannot recognise more
-def no_more (r: Rexp) : Boolean = r match {
-  case NULL => true
-  case EMPTY => false
-  case CHAR(_) => false
-  case ALT(r1, r2) => no_more(r1) && no_more(r2)
-  case SEQ(r1, r2) => if (nullable(r1)) (no_more(r1) && no_more(r2)) else no_more(r1)
-  case STAR(_) => false
-  case NOT(r) => !(no_more(r))
-}
-
-
-// derivative of a regular expression w.r.t. a character
-def der (c: Char, r: Rexp) : Rexp = r match {
-  case NULL => NULL
-  case EMPTY => NULL
-  case CHAR(d) => if (c == d) EMPTY else NULL
-  case ALT(r1, r2) => ALT(der(c, r1), der(c, r2))
-  case SEQ(r1, r2) => 
-    if (nullable(r1)) ALT(SEQ(der(c, r1), r2), der(c, r2))
-    else SEQ(der(c, r1), r2)
-  case STAR(r) => SEQ(der(c, r), STAR(r))
-  case NOT(r) => NOT(der (c, r))
-}
-
-
-// regular expression for specifying 
-// ranges of characters
-def RANGE(s : List[Char]) : Rexp = s match {
-  case Nil => NULL
-  case c::Nil => CHAR(c)
-  case c::s => ALT(CHAR(c), RANGE(s))
-}
-
-//one or more
-def PLUS(r: Rexp) = SEQ(r, STAR(r))
-
-
-//some regular expressions
-val LOWERCASE = RANGE("abcdefghijklmnopqrstuvwxyz".toList)
-val UPPERCASE = RANGE("ABCDEFGHIJKLMNOPQRSTUVWXYZ".toList)
-val LETTER = ALT(LOWERCASE, UPPERCASE)
-val DIGIT = RANGE("0123456789".toList)
-val NONZERODIGIT = RANGE("123456789".toList)
-
-val IDENT = SEQ(LETTER, STAR(ALT(LETTER,DIGIT)))
-val NUMBER = ALT(SEQ(NONZERODIGIT, STAR(DIGIT)), "0")
-val WHITESPACE = RANGE(" \n".toList)
-val WHITESPACES = PLUS(WHITESPACE)
-
-val ALL = ALT(ALT(LETTER, DIGIT), WHITESPACE)
-val COMMENT = SEQ(SEQ("/*", NOT(SEQ(SEQ(STAR(ALL), "*/"), STAR(ALL)))), "*/")
-
-
-// an example list of regular expressions
-val regs: List[Rexp]=  List("if", "then", "else", "+", IDENT, NUMBER, WHITESPACES, COMMENT) 
-
-
-def error (s: String) = throw new IllegalArgumentException ("Could not lex " + s)
-
-def munch(r: Rexp, s: List[Char], t: List[Char]) : Option[(List[Char], List[Char])] = 
-  s match {
-    case Nil if (nullable(r)) => Some(Nil, t)
-    case Nil => None
-    case c::s if (no_more(der (c, r)) && nullable(r)) => Some(c::s, t)
-    case c::s if (no_more(der (c, r))) => None
-    case c::s => munch(der (c, r), s, t ::: List(c))
-  }
-
-def one_string (regs: List[Rexp], s: List[Char]) : (List[Char], List[Char]) = {
- val somes = regs.map { munch(_, s, Nil) } .flatten
- if (somes == Nil) error(s.mkString) else (somes sortBy (_._1.length) head)
-}
-
-def tokenize (regs: List[Rexp], s: List[Char]) : List[String] = s match {
-  case Nil => Nil
-  case _ => one_string(regs, s) match {
-    case (rest, s) => s.mkString :: tokenize(regs, rest) 
-  }
-}
-
-//examples
-println(tokenize(regs, "if true then then 42 else +".toList))
-println(tokenize(regs, "if+true+then+then+42+else +".toList))
-println(tokenize(regs, "ifff if     34 34".toList))
-println(tokenize(regs, "/*ifff if */ hhjj /*34 */".toList))
-println(tokenize(regs, "/* if true then */ then 42 else +".toList))
-//println(tokenize(regs, "ifff $ if 34".toList)) // causes an error because of the symbol $