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// $Id$
package scala.util.regexp ;
/** basic regular expressions */
trait Base {
type _regexpT <: RegExp;
abstract class RegExp {
val isNullable:Boolean;
}
/** Alt( R,R,R* ) */
case class Alt(rs: _regexpT*) extends RegExp {
// check rs \in R,R,R*
// @todo: flattening
if({ val it = rs.elements; !it.hasNext || {it.next; !it.hasNext }})
throw new SyntaxError("need at least 2 branches in Alt");
final val isNullable = {
val it = rs.elements;
while( it.hasNext && it.next.isNullable ) {}
!it.hasNext
}
}
case class Sequ(rs: _regexpT*) extends RegExp {
// @todo: flattening
// check rs \in R,R*
if({ val it = rs.elements; !it.hasNext })
throw new SyntaxError("need at least 1 item in Sequ");
final val isNullable = {
val it = rs.elements;
while( it.hasNext && it.next.isNullable ) {}
!it.hasNext
}
}
case class Star(r: _regexpT) extends RegExp {
final val isNullable = true;
}
case object Eps extends RegExp {
final val isNullable = true;
override def toString() = "Eps";
}
/** this class can be used to add meta information to regexps */
class Meta( r1: _regexpT ) extends RegExp {
final val isNullable = r1.isNullable;
def r = r1;
}
final def mkSequ(rs: _regexpT *): RegExp =
if(!rs.elements.hasNext)
Eps
else
Sequ(rs:_*);
}
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