import com.sun.org.apache.xpath.internal.operations.Minus; //导入依赖的package包/类
/**
 * Visit a predicate within a location path.  Note that there isn't a
 * proper unique component for predicates, and that the expression will
 * be called also for whatever type Expression is.
 *
 * @param owner The owner of the expression, to which the expression can
 *              be reset if rewriting takes place.
 * @param pred The predicate object.
 * @return true if the sub expressions should be traversed.
 */
public boolean visitPredicate(ExpressionOwner owner, Expression pred)
{
  m_predDepth++;

  if(m_predDepth == 1)
  {
    if((pred instanceof Variable) ||
       (pred instanceof XNumber) ||
       (pred instanceof Div) ||
       (pred instanceof Plus) ||
       (pred instanceof Minus) ||
       (pred instanceof Mod) ||
       (pred instanceof Quo) ||
       (pred instanceof Mult) ||
       (pred instanceof com.sun.org.apache.xpath.internal.operations.Number) ||
       (pred instanceof Function))
        m_hasPositionalPred = true;
    else
      pred.callVisitors(owner, this);
  }

  m_predDepth--;

  // Don't go have the caller go any further down the subtree.
  return false;
}
 

import com.sun.org.apache.xpath.internal.operations.Minus; //导入依赖的package包/类
/**
 * Compile a '-' operation.
 *
 * @param opPos The current position in the m_opMap array.
 *
 * @return reference to {@link com.sun.org.apache.xpath.internal.operations.Minus} instance.
 *
 * @throws TransformerException if a error occurs creating the Expression.
 */
protected Expression minus(int opPos) throws TransformerException
{
  return compileOperation(new Minus(), opPos);
}