Quadcap Embeddable Database

com/quadcap/sql/Expression.java

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package com.quadcap.sql;

/* Copyright 1999 - 2003 Quadcap Software.  All rights reserved.
 *
 * This software is distributed under the Quadcap Free Software License.
 * This software may be used or modified for any purpose, personal or
 * commercial.  Open Source redistributions are permitted.  Commercial
 * redistribution of larger works derived from, or works which bundle
 * this software requires a "Commercial Redistribution License"; see
 * http://www.quadcap.com/purchase.
 *
 * Redistributions qualify as "Open Source" under  one of the following terms:
 *   
 *    Redistributions are made at no charge beyond the reasonable cost of
 *    materials and delivery.
 *
 *    Redistributions are accompanied by a copy of the Source Code or by an
 *    irrevocable offer to provide a copy of the Source Code for up to three
 *    years at the cost of materials and delivery.  Such redistributions
 *    must allow further use, modification, and redistribution of the Source
 *    Code under substantially the same terms as this license.
 *
 * Redistributions of source code must retain the copyright notices as they
 * appear in each source code file, these license terms, and the
 * disclaimer/limitation of liability set forth as paragraph 6 below.
 *
 * Redistributions in binary form must reproduce this Copyright Notice,
 * these license terms, and the disclaimer/limitation of liability set
 * forth as paragraph 6 below, in the documentation and/or other materials
 * provided with the distribution.
 *
 * The Software is provided on an "AS IS" basis.  No warranty is
 * provided that the Software is free of defects, or fit for a
 * particular purpose.  
 *
 * Limitation of Liability. Quadcap Software shall not be liable
 * for any damages suffered by the Licensee or any third party resulting
 * from use of the Software.
 */

import java.io.IOException;

import java.util.Enumeration;
import java.util.Vector;

import java.sql.SQLException;

import com.quadcap.sql.types.Op;
import com.quadcap.sql.types.Type;
import com.quadcap.sql.types.Value;

import com.quadcap.util.Debug;

/**
 * Base class for all expression types.
 *
 * @author Stan Bailes
 */

public abstract class Expression {
    /**
     * Returns zero if this is a scalar expression, one if it's a vector
     * type and 2 if it's a table/cursor type.
     */
    public abstract int rank();

    /**
     * Return the expression's type if known
     */
    public abstract Type getType(Session session, Cursor cursor)
        throws SQLException;

    /**
     * If this is a scalar, return its value
     */
    public Value getValue(Session session, Cursor cursor)
        throws SQLException
    {
        return null;
    }

    /**
     * If this is a vector, return the value
     */
    public Row getValues(Session session, Cursor cursor) throws SQLException {
        if (rank() == 0) {
            Value v = getValue(session, cursor);
            Row row = new Row(1);
            row.set(1, v);
            return row;
        } else {
            throw new SQLException("getValues, rank = " + rank(), "Q0000");
        }
    }

    /**
     * If this is a cursor, return the value
     */
    public Cursor getCursor(Session session, Cursor cursor)
        throws SQLException
    {
        return null;
    }

    /**
     * Negate the logical value of the expression
     */
    public void invert() throws antlr.RecognitionException {
        throw new antlr.RecognitionException("Error, not a boolean expression");
    }

    /**
     * Give a visitor access to the parse tree.
     */
    public void visitSubExpressions(ExpressionVisitor v) {}


    public String getName() { return null; }

    abstract public String toString();
    
}