Term_grammar.scala
changeset 92 e85600529ca5
parent 91 47f86885d481
child 93 4794759139ea
--- a/Term_grammar.scala	Sun Dec 23 00:38:56 2012 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,62 +0,0 @@
-//:load matcher.scala
-//:load parser3.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 lexed
-abstract class Token
-
-case object T_WHITESPACE extends Token
-case class T_NUM(s: String) extends Token
-case class T_OP(s: String) extends Token
-case object T_LPAREN extends Token
-case object T_RPAREN extends Token
-
-
-// lexing rules for arithmetic expressions
-val lexing_rules: List[Rule[Token]]= 
-  List((NUMBER, (s) => T_NUM(s.mkString)),
-       (WHITESPACE, (s) => T_WHITESPACE),
-       (LPAREN, (s) => T_LPAREN),
-       (RPAREN, (s) => T_RPAREN),
-       (OPS, (s) => T_OP(s.mkString)))
-
-val Tk = Tokenizer(lexing_rules, List(T_WHITESPACE))
-
-
-case class TokParser(tok: Token) extends Parser[List[Token], 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[List[Token], Int] {
-  def parse(ts: List[Token]) = ts match {
-    case T_NUM(s)::ts => Set((s.toInt, ts)) 
-    case _ => Set ()
-  }
-}
-
-lazy val E: Parser[List[Token], Int] = (T ~ T_OP("+") ~ E) ==> { case ((x, y), z) => x + z } || T  
-lazy val T: Parser[List[Token], Int] = (F ~ T_OP("*") ~ T) ==> { case ((x, y), z) => x * z } || F
-lazy val F: Parser[List[Token], Int] = (T_LPAREN ~> E <~ T_RPAREN) || NumParser
-   
-println(E.parse_all(Tk.fromString("1 + 2 + 3")))
-println(E.parse_all(Tk.fromString("1 + 2 * 3")))
-println(E.parse_all(Tk.fromString("(1 + 2) * 3")))
-println(E.parse_all(Tk.fromString("(14 + 2) * (3 + 2)")))
-