diff -r e85600529ca5 -r 4794759139ea scala/regexp4.scala
--- a/scala/regexp4.scala Sat Jun 15 09:11:11 2013 -0400
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,168 +0,0 @@
-// regular expressions
-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
-// recognises nothing
-def zeroable (r: Rexp) : Boolean = r match {
- case NULL => true
- case EMPTY => false
- case CHAR(_) => false
- case ALT(r1, r2) => zeroable(r1) && zeroable(r2)
- case SEQ(r1, r2) => zeroable(r1) || zeroable(r2)
- case STAR(_) => false
- case NOT(r) => !(zeroable(r))
-}
-
-def starts_with (r: Rexp, c: Char) : Boolean = r match {
- case NULL => false
- case EMPTY => false
- case CHAR(d) => (c == d)
- case ALT(r1, r2) => starts_with(r1, c) || starts_with(r2, c)
- case SEQ(r1, r2) => if (nullable(r1)) (starts_with(r1, c) || starts_with(r2, c))
- else starts_with(r1, c)
- case STAR(r) => starts_with(r, c)
- case NOT(r) => !(starts_with(r, c))
-}
-
-// 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))
-}
-
-// derivative w.r.t. a string (iterates der)
-def ders (s: List[Char], r: Rexp) : Rexp = s match {
- case Nil => r
- case c::s => ders(s, der(c, r))
-}
-
-// main matcher function
-def matcher(r: Rexp, s: String) : Boolean = nullable(ders(s.toList, 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 DIGITS = RANGE("0123456789".toList)
-val NONZERODIGITS = RANGE("123456789".toList)
-
-val IDENT = SEQ(LETTER, STAR(ALT(LETTER,DIGITS)))
-val NUMBER = ALT(SEQ(NONZERODIGITS, STAR(DIGITS)), "0")
-val WHITESPACE = RANGE(" \n".toList)
-val SYMBOLS = RANGE("/*".toList)
-
-val ALL = ALT(ALT(ALT(LETTER, DIGITS), WHITESPACE), SYMBOLS)
-
-val COMMENT = SEQ(SEQ("/*", NOT(SEQ(SEQ(STAR(ALL), "*/"), STAR(ALL)))), "*/")
-
-println(matcher(NUMBER, "0"))
-println(matcher(NUMBER, "01"))
-println(matcher(NUMBER, "123450"))
-
-println(matcher(SEQ(STAR("a"), STAR("b")), "bbaaa"))
-println(matcher(ALT(STAR("a"), STAR("b")), ""))
-println(matcher("abc", ""))
-println(matcher(STAR(ALT(EMPTY, "a")), ""))
-println(matcher(STAR(EMPTY), "a"))
-println(matcher("cab","cab"))
-println(matcher(STAR("a"),"aaa"))
-println(matcher("cab" ,"cab"))
-println(matcher(STAR("a"),"aaa"))
-
-println(matcher(COMMENT, "/* */"))
-println(matcher(COMMENT, "/* foobar comment */"))
-println(matcher(COMMENT, "/* test */ test */"))
-
-// an example list of regular expressions
-val regs: List[Rexp]= List("if", "then", "else", "+", IDENT, NUMBER, COMMENT, WHITESPACE)
-
-
-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])] =
- if (zeroable(r)) None else s match {
- case Nil => if (nullable(r)) Some(Nil, t) else None
- case c::s if (zeroable(der (c, r)) && nullable(r)) => Some(c::s, t)
- //case c::s if (zeroable(der (c, r))) => None
- case c::s => munch(der (c, r), s, t ::: List(c))
-}
-
-
-def lex_one (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 lex_all (regs: List[Rexp], s: List[Char]) : List[String] = s match {
- case Nil => Nil
- case _ => lex_one(regs, s) match {
- case (rest, s) => s.mkString :: lex_all(regs, rest)
- }
-}
-
-
-
-starts_with(der('/', COMMENT), '*')
-
-munch(COMMENT, "/*ifff if 34 */".toList, Nil)
-val COMMENT2 = NOT(SEQ(SEQ(STAR(ALL), "*/"), STAR(ALL)))
-
-der('a', COMMENT2)
-zeroable(der('a', COMMENT2))
-
-matcher(COMMENT2, "ifff if 34")
-munch(COMMENT2, "ifff if 34".toList, Nil)
-starts_with(COMMENT2, 'i')
-lex_all(regs, "ifff if 34".toList)
-lex_all(regs, "ifff $ if 34".toList)
-