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Scala example source code file (ContentModelParser.scala)

This example Scala source code file (ContentModelParser.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Scala tags/keywords

alt, any, choice, empty, letter, name, name, pcdata, pcdata, regexp, rparen, rparen, star, star

The Scala ContentModelParser.scala source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2002-2011, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://www.scala-lang.org/           **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */


package scala.xml
package dtd

/** Parser for regexps (content models in DTD element declarations) */

object ContentModelParser extends Scanner { // a bit too permissive concerning #PCDATA
  import ContentModel._

  /** parses the argument to a regexp */
  def parse(s: String): ContentModel = { initScanner(s); contentspec }

  def accept(tok: Int) = {
    if (token != tok) {
      if ((tok == STAR) && (token == END))                  // common mistake
        sys.error("in DTDs, \n"+
              "mixed content models must be like (#PCDATA|Name|Name|...)*");
      else
        sys.error("expected "+token2string(tok)+
              ", got unexpected token:"+token2string(token));
    }
    nextToken
  }

  // s [ '+' | '*' | '?' ]
  def maybeSuffix(s: RegExp) = token match {	
    case STAR => nextToken; Star(s) 
    case PLUS => nextToken; Sequ(s, Star(s)) 
    case OPT  => nextToken; Alt(Eps, s)
    case _    => s
  }

  // contentspec ::= EMPTY | ANY | (#PCDATA) | "(#PCDATA|"regexp)

  def contentspec: ContentModel = token match {

    case NAME => value match {
      case "ANY"   => ANY 
      case "EMPTY" => EMPTY
      case _       => sys.error("expected ANY, EMPTY or '(' instead of " + value );
    }
    case LPAREN => 

      nextToken; 
      sOpt;
      if (token != TOKEN_PCDATA)
        ELEMENTS(regexp);
      else {
        nextToken;
        token match {
        case RPAREN =>
          PCDATA
        case CHOICE =>
          val res = MIXED(choiceRest(Eps));
          sOpt;
          accept( RPAREN );
          accept( STAR );
          res
        case _ =>
          sys.error("unexpected token:" + token2string(token) );
        }
      }

    case _ =>
      sys.error("unexpected token:" + token2string(token) );
    }
  //                                  sopt ::= S?
  def sOpt() = if( token == S ) nextToken;

  //                      (' S? mixed ::= '#PCDATA' S? ')'
  //                                    | '#PCDATA' (S? '|' S? atom)* S? ')*'

  //       '(' S? regexp ::= cp S? [seqRest|choiceRest] ')' [ '+' | '*' | '?' ]
  def regexp: RegExp = {
    val p = particle;
    sOpt;
    maybeSuffix(token match {
      case RPAREN  => nextToken; p
      case CHOICE  => val q = choiceRest( p );accept( RPAREN ); q
      case COMMA   => val q = seqRest( p );   accept( RPAREN ); q
    })
  }

  //                                             seqRest ::= (',' S? cp S?)+
  def seqRest(p: RegExp) = { 
    var k = List(p);
    while( token == COMMA ) {
      nextToken;
      sOpt;
      k = particle::k;
      sOpt;
    }
    Sequ( k.reverse:_* )
  }

  //                                          choiceRest ::= ('|' S? cp S?)+
  def choiceRest( p:RegExp ) = { 
    var k = List( p );
    while( token == CHOICE ) {
      nextToken;
      sOpt;
      k = particle::k;
      sOpt;
    }
    Alt( k.reverse:_* )
  }

  //                                  particle ::=  '(' S? regexp
  //                                             |  name [ '+' | '*' | '?' ]
  def particle = token match {
    case LPAREN => nextToken; sOpt; regexp; 
    case NAME   => val a = Letter(ElemName(value)); nextToken; maybeSuffix(a)
    case _      => sys.error("expected '(' or Name, got:"+token2string(token));
  }

  //                                     atom ::= name
  def atom = token match {
    case NAME   => val a = Letter(ElemName(value)); nextToken; a
    case _      => sys.error("expected Name, got:"+token2string(token));
  }
}

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