diff -r e66bd5c563eb -r b5b5583a3a08 progs/mllex.scala --- a/progs/mllex.scala Mon Jul 27 11:02:48 2020 +0100 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,109 +0,0 @@ -:load matcher.scala - - -// some regular expressions -val KEYWORDS = ALTS(List("#", "(", ")", ",", "->", "...", ":", ":>", ";", "=", - "=>", "[", "]", "_", "{", "|", "}", "abstype", "and", "andalso", "as", - "case", "datatype", "do", "else", "end", "eqtype", "exception", "fn", - "fun", "functor", "handle", "if", "in", "include", "infix", "infixr", - "let", "local", "nonfix", "of", "op", "open", "orelse", "raise", "rec", - "sharing", "sig", "signature", "struct", "structure", "then", "type", - "val", "where", "while", "with", "withtype")) - -val DIGITS = RANGE("0123456789") -val NONZERODIGITS = RANGE("123456789") - -val POSITIVES = ALT(SEQ(NONZERODIGITS, STAR(DIGITS)), "0") -val INTEGERS = ALT(SEQ("~", POSITIVES), POSITIVES) - -val ALL = ALTS(KEYWORDS, INTEGERS) - -val COMMENT = SEQS("/*", NOT(SEGS(STAR(ALL), "*/", STAR(ALL))), "*/") - - - -val LPAREN = CHAR('(') -val RPAREN = CHAR(')') -val WHITESPACE = PLUS(RANGE(" \n".toList)) -val OPS = RANGE("+-*".toList) - -// for classifying the strings that have been recognised -abstract class Token -case object T_WHITESPACE extends Token -case object T_NUM extends Token -case class T_OP(s: String) extends Token -case object T_LPAREN extends Token -case object T_RPAREN extends Token -case class T_NT(s: String, rhs: List[Token]) extends Token - -def tokenizer(rs: List[Rule[Token]], s: String) : List[Token] = - tokenize(rs, s.toList).filterNot(_ match { - case T_WHITESPACE => true - case _ => false - }) - - - -// lexing rules for arithmetic expressions -val lexing_rules: List[Rule[Token]]= - List((NUMBER, (s) => T_NUM), - (WHITESPACE, (s) => T_WHITESPACE), - (LPAREN, (s) => T_LPAREN), - (RPAREN, (s) => T_RPAREN), - (OPS, (s) => T_OP(s.mkString))) - -tokenize_file(Nil, "nominal_library.ML") - - - - -type Grammar = List[(String, List[Token])] - -// grammar for arithmetic expressions -val grammar = - List ("E" -> List(T_NUM), - "E" -> List(T_NT("E", Nil), T_OP("+"), T_NT("E", Nil)), - "E" -> List(T_NT("E", Nil), T_OP("-"), T_NT("E", Nil)), - "E" -> List(T_NT("E", Nil), T_OP("*"), T_NT("E", Nil)), - "E" -> List(T_LPAREN, T_NT("E", Nil), T_RPAREN)) - -def startsWith[A](ts1: List[A], ts2: List[A]) : Boolean = (ts1, ts2) match { - case (_, Nil) => true - case (T_NT(e, _)::ts1,T_NT(f, _)::ts2) => (e == f) && startsWith(ts1, ts2) - case (t1::ts1, t2::ts2) => (t1 == t2) && startsWith(ts1, ts2) - case _ => false -} - -def chop[A](ts1: List[A], prefix: List[A], ts2: List[A]) : Option[(List[A], List[A])] = - ts1 match { - case Nil => None - case t::ts => - if (startsWith(ts1, prefix)) Some(ts2.reverse, ts1.drop(prefix.length)) - else chop(ts, prefix, t::ts2) - } - -// examples -chop(List(1,2,3,4,5,6,7,8,9), List(4,5), Nil) -chop(List(1,2,3,4,5,6,7,8,9), List(3,5), Nil) - -def replace[A](ts: List[A], out: List[A], in: List [A]) = - chop(ts, out, Nil) match { - case None => None - case Some((before, after)) => Some(before ::: in ::: after) - } - -def parse1(g: Grammar, ts: List[Token]) : Boolean = ts match { - case List(T_NT("E", tree)) => { println(tree); true } - case _ => { - val tss = for ((lhs, rhs) <- g) yield replace(ts, rhs, List(T_NT(lhs, rhs))) - tss.flatten.exists(parse1(g, _)) - } -} - - -println() ; parse1(grammar, tokenizer(lexing_rules, "2 + 3 * 4 + 1")) -println() ; parse1(grammar, tokenizer(lexing_rules, "(2 + 3) * (4 + 1)")) -println() ; parse1(grammar, tokenizer(lexing_rules, "(2 + 3) * 4 (4 + 1)")) - - -