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Scala example source code file (StdLexical.scala)
The Scala StdLexical.scala source code/* __ *\ ** ________ ___ / / ___ Scala API ** ** / __/ __// _ | / / / _ | (c) 2006-2011, LAMP/EPFL ** ** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ ** ** /____/\___/_/ |_/____/_/ | | ** ** |/ ** \* */ package scala.util.parsing package combinator package lexical import token._ import input.CharArrayReader.EofCh import collection.mutable.HashSet /** <p> * This component provides a standard lexical parser for a simple, Scala-like language. * It parses keywords and identifiers, numeric literals (integers), strings, and delimiters. * </p> * <p> * To distinguish between identifiers and keywords, it uses a set of reserved identifiers: * every string contained in `reserved' is returned as a keyword token. * (Note that "=>" is hard-coded as a keyword.) * Additionally, the kinds of delimiters can be specified by the `delimiters' set. * </p> * <p> * Usually this component is used to break character-based input into bigger tokens, * which are then passed to a token-parser {@see TokenParsers}. * </p> * * @author Martin Odersky, Iulian Dragos, Adriaan Moors */ class StdLexical extends Lexical with StdTokens { // see `token' in `Scanners' def token: Parser[Token] = ( identChar ~ rep( identChar | digit ) ^^ { case first ~ rest => processIdent(first :: rest mkString "") } | digit ~ rep( digit ) ^^ { case first ~ rest => NumericLit(first :: rest mkString "") } | '\'' ~ rep( chrExcept('\'', '\n', EofCh) ) ~ '\'' ^^ { case '\'' ~ chars ~ '\'' => StringLit(chars mkString "") } | '\"' ~ rep( chrExcept('\"', '\n', EofCh) ) ~ '\"' ^^ { case '\"' ~ chars ~ '\"' => StringLit(chars mkString "") } | EofCh ^^^ EOF | '\'' ~> failure("unclosed string literal") | '\"' ~> failure("unclosed string literal") | delim | failure("illegal character") ) // legal identifier chars other than digits def identChar = letter | elem('_') // see `whitespace in `Scanners' def whitespace: Parser[Any] = rep( whitespaceChar | '/' ~ '*' ~ comment | '/' ~ '/' ~ rep( chrExcept(EofCh, '\n') ) | '/' ~ '*' ~ failure("unclosed comment") ) protected def comment: Parser[Any] = ( '*' ~ '/' ^^ { case _ => ' ' } | chrExcept(EofCh) ~ comment ) /** The set of reserved identifiers: these will be returned as `Keyword's */ val reserved = new HashSet[String] /** The set of delimiters (ordering does not matter) */ val delimiters = new HashSet[String] protected def processIdent(name: String) = if (reserved contains name) Keyword(name) else Identifier(name) private lazy val _delim: Parser[Token] = { // construct parser for delimiters by |'ing together the parsers for the individual delimiters, // starting with the longest one -- otherwise a delimiter D will never be matched if there is // another delimiter that is a prefix of D def parseDelim(s: String): Parser[Token] = accept(s.toList) ^^ { x => Keyword(s) } val d = new Array[String](delimiters.size) delimiters.copyToArray(d, 0) scala.util.Sorting.quickSort(d) (d.toList map parseDelim).foldRight(failure("no matching delimiter"): Parser[Token])((x, y) => y | x) } protected def delim: Parser[Token] = _delim } Other Scala examples (source code examples)Here is a short list of links related to this Scala StdLexical.scala source code file: |
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