# HG changeset patch # User Christian Urban # Date 1349949498 -3600 # Node ID 774007c4b1b337cf06a3cb9dc6b5f60c66020cce # Parent f63ba92a7d7860fdb990fb0040db1fb5c5b6cb2d tuned diff -r f63ba92a7d78 -r 774007c4b1b3 regexp.scala --- a/regexp.scala Wed Oct 10 14:08:49 2012 +0100 +++ b/regexp.scala Thu Oct 11 10:58:18 2012 +0100 @@ -9,9 +9,13 @@ case class STAR(r: Rexp) extends Rexp // some convenience for typing in regular expressions -implicit def string2rexp(s : String) : Rexp = { - s.foldRight (EMPTY: Rexp) ( (c, r) => SEQ(CHAR(c), r) ) +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) + // for example println(STAR("abc")) @@ -99,3 +103,4 @@ println(matcher("cab" ,"cab")) println(matcher(STAR("a"),"aaa")) + diff -r f63ba92a7d78 -r 774007c4b1b3 regexp2.scala --- a/regexp2.scala Wed Oct 10 14:08:49 2012 +0100 +++ b/regexp2.scala Thu Oct 11 10:58:18 2012 +0100 @@ -1,4 +1,5 @@ -// regular expressions + +// regular expressions including NOT abstract class Rexp case object NULL extends Rexp @@ -32,15 +33,15 @@ } // tests whether a regular expression -// recognises nothing -def zeroable (r: Rexp) : Boolean = r match { +// cannot recognise more +def no_more (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) => if (nullable(r1)) (zeroable(r1) && zeroable(r2)) else zeroable(r1) + 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) => !(zeroable(r)) + case NOT(r) => !(no_more(r)) } @@ -57,15 +58,6 @@ 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 @@ -83,66 +75,49 @@ 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 DIGIT = RANGE("0123456789".toList) +val NONZERODIGIT = RANGE("123456789".toList) -val IDENT = SEQ(LETTER, STAR(ALT(LETTER,DIGITS))) -val NUMBER = ALT(SEQ(NONZERODIGITS, STAR(DIGITS)), "0") +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, DIGITS), WHITESPACE) - +val ALL = ALT(ALT(LETTER, DIGIT), WHITESPACE) 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, WHITESPACES) +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 (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 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 lex_one (regs: List[Rexp], s: List[Char]) : (List[Char], List[Char]) = { +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 lex_all (regs: List[Rexp], s: List[Char]) : List[String] = s match { +def tokenize (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) + case _ => one_string(regs, s) match { + case (rest, s) => s.mkString :: tokenize(regs, rest) } } -val regs: List[Rexp]= List("if", "then", "else", "+", IDENT, NUMBER, WHITESPACES) - -println(lex_all(regs, "if true then 42 else +".toList)) -println(lex_all(regs, "ifff if 34 34".toList)) -println(lex_all(regs, "ifff +if+ 34 34".toList)) -println(lex_all(regs, "1+x+3+4+foo".toList)) -println(lex_all(regs, "ifff $ if 34".toList)) - +//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 $ diff -r f63ba92a7d78 -r 774007c4b1b3 regexp3.scala --- a/regexp3.scala Wed Oct 10 14:08:49 2012 +0100 +++ b/regexp3.scala Thu Oct 11 10:58:18 2012 +0100 @@ -1,4 +1,5 @@ -// regular expressions + +// regular expressions including NOT abstract class Rexp case object NULL extends Rexp @@ -26,22 +27,21 @@ case EMPTY => true case CHAR(_) => false case ALT(r1, r2) => nullable(r1) || nullable(r2) - case SEQ(r1, r2) => if (nullable(r1)) (zeroable(r1) && zeroable(r2)) else zeroable(r1) + 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 { +// cannot recognise more +def no_more (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) => if (nullable(r1)) (zeroable(r1) && zeroable(r2)) else zeroable(r1) - //case SEQ(r1, r2) => zeroable(r1) || zeroable(r2) + 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) => !(zeroable(r)) + case NOT(r) => !(no_more(r)) } @@ -58,16 +58,6 @@ 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 { @@ -76,71 +66,38 @@ case c::s => ALT(CHAR(c), RANGE(s)) } -//one or more +// one or more def PLUS(r: Rexp) = SEQ(r, STAR(r)) - -//some regular expressions +// 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 DIGIT = RANGE("0123456789".toList) +val NONZERODIGIT = RANGE("123456789".toList) -val IDENT = SEQ(LETTER, STAR(ALT(LETTER,DIGITS))) -val NUMBER = ALT(SEQ(NONZERODIGITS, STAR(DIGITS)), "0") +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, DIGITS), WHITESPACE) - +val ALL = ALT(ALT(LETTER, DIGIT), WHITESPACE) val COMMENT = SEQ(SEQ("/*", NOT(SEQ(SEQ(STAR(ALL), "*/"), STAR(ALL)))), "*/") + +// for classifying the strings that have been recognised abstract class Token case object T_WHITESPACE extends Token +case object T_COMMENT extends Token case class T_IDENT(s: String) extends Token case class T_OP(s: String) extends Token case class T_NUM(n: Int) extends Token case class T_KEYWORD(s: String) extends Token -case object T_COMMENT extends Token - - -// an example list of rules -type Rule = (Rexp, List[Char] => Token) - -val rules: List[Rule]= - List(("if", (s) => T_KEYWORD(s.mkString)), - ("then", (s) => T_KEYWORD(s.mkString)), - ("else", (s) => T_KEYWORD(s.mkString)), - ("+", (s) => T_OP(s.mkString)), - (IDENT, (s) => T_IDENT(s.mkString)), - (NUMBER, (s) => T_NUM(s.mkString.toInt)), - (WHITESPACES, (s) => T_WHITESPACE)) -def error (s: String) = throw new IllegalArgumentException ("Could not lex " + s) - -def munch(r: Rexp, action: List[Char] => Token, s: List[Char], t: List[Char]) : Option[(List[Char], Token)] = - s match { - case Nil if (nullable(r)) => Some(Nil, action(t)) - case Nil => None - case c::s if (zeroable(der (c, r)) && nullable(r)) => Some(c::s, action(t)) - case c::s if (zeroable(der (c, r))) => None - case c::s => munch(der (c, r), action, s, t ::: List(c)) - } - -def lex_one (rs: List[Rule], s: List[Char]) : (List[Char], Token) = { - val somes = rs.map { (r) => munch(r._1, r._2, s, Nil) } .flatten - if (somes == Nil) error(s.mkString) else (somes sortBy (_._1.length) head) -} - -def lex_all (rs: List[Rule], s: List[Char]) : List[Token] = s match { - case Nil => Nil - case _ => lex_one(rs, s) match { - case (rest, t) => t :: lex_all(rs, rest) - } -} +// an example list of syntactic rules +type Rule = (Rexp, List[Char] => Token) val rules: List[Rule]= List(("if", (s) => T_KEYWORD(s.mkString)), @@ -152,25 +109,34 @@ (WHITESPACES, (s) => T_WHITESPACE), (COMMENT, (s) => T_COMMENT)) -println(lex_all(rules, "/*ifff if */ hhjj /*34 */".toList)) +def error (s: String) = throw new IllegalArgumentException ("Cannot tokenize: " + s) -munch(COMMENT, (s) => T_COMMENT , "/*ifff if */ hhjj /*34 */".toList, Nil) -val COMMENT2 = NOT(SEQ(SEQ(STAR(ALL), "*/"), STAR(ALL))) - -der('/', COMMENT) -zeroable(der('/', COMMENT)) -zeroable(der('a', COMMENT2)) +def munch(r: Rexp, action: List[Char] => Token, s: List[Char], t: List[Char]) : Option[(List[Char], Token)] = + s match { + case Nil if (nullable(r)) => Some(Nil, action(t)) + case Nil => None + case c::s if (no_more(der (c, r)) && nullable(r)) => Some(c::s, action(t)) + case c::s if (no_more(der (c, r))) => None + case c::s => munch(der (c, r), action, s, t ::: List(c)) + } -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) +def one_token (rs: List[Rule], s: List[Char]) : (List[Char], Token) = { + val somes = rs.map { (r) => munch(r._1, r._2, s, Nil) } .flatten + if (somes == Nil) error(s.mkString) else (somes sortBy (_._1.length) head) +} -println(lex_all(rules, "/* if true then */ then 42 else +".toList)) -println(lex_all(rules, "if true then then 42 else +".toList)) -println(lex_all(rules, "ifff if 34 34".toList)) -println(lex_all(rules, "ifff $ if 34".toList)) +def tokenize (rs: List[Rule], s: List[Char]) : List[Token] = s match { + case Nil => Nil + case _ => one_token(rs, s) match { + case (rest, token) => token :: tokenize(rs, rest) + } +} - +//examples +println(tokenize(rules, "if true then then 42 else +".toList)) +println(tokenize(rules, "if+true+then+then+42+else +".toList)) +println(tokenize(rules, "ifff if 34 34".toList)) +println(tokenize(rules, "/*ifff if */ hhjj /*34 */".toList)) +println(tokenize(rules, "/* if true then */ then 42 else +".toList)) +//println(tokenize(rules, "ifff $ if 34".toList)) // causes an error because of the symbol $