18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package com.sun.tools.internal.xjc.reader.gbind;
  27 
  28 import java.util.Set;
  29 
  30 /**
  31  * This builds content models.
  32  *
  33  * @author Kohsuke Kawaguchi
  34  */
  35 public abstract class Expression {
  36 
  37     /**
  38      * Computes <tt>LAST(exp)</tt>
  39      */
  40     abstract ElementSet lastSet();
  41 
  42     /**
  43      * True of <tt>\epsilon \in L(exp)</tt>
  44      */
  45     abstract boolean isNullable();
  46 
  47     /**
  48      * Builds up a DAG among {@link Element}s in this expression.
  49      */
  50     abstract void buildDAG(ElementSet incoming);
  51 
  52     /**
  53      * {@link Expression} that represents epsilon, the length-0 string.
  54      */
  55     public static final Expression EPSILON = new Expression() {
  56         ElementSet lastSet() {
  57             return ElementSet.EMPTY_SET;
  58         }
  59 
  60         boolean isNullable() {
  61             return true;
  62         }
  63 

  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package com.sun.tools.internal.xjc.reader.gbind;
  27 
  28 import java.util.Set;
  29 
  30 /**
  31  * This builds content models.
  32  *
  33  * @author Kohsuke Kawaguchi
  34  */
  35 public abstract class Expression {
  36 
  37     /**
  38      * Computes {@code LAST(exp)}
  39      */
  40     abstract ElementSet lastSet();
  41 
  42     /**
  43      * True of {@code \epsilon \in L(exp)}
  44      */
  45     abstract boolean isNullable();
  46 
  47     /**
  48      * Builds up a DAG among {@link Element}s in this expression.
  49      */
  50     abstract void buildDAG(ElementSet incoming);
  51 
  52     /**
  53      * {@link Expression} that represents epsilon, the length-0 string.
  54      */
  55     public static final Expression EPSILON = new Expression() {
  56         ElementSet lastSet() {
  57             return ElementSet.EMPTY_SET;
  58         }
  59 
  60         boolean isNullable() {
  61             return true;
  62         }
  63