SetExpression.java #2

/*
// $Id: //guest/julian_hyde/saffron/src/main/openjava/ptree/SetExpression.java#2 $
// Saffron preprocessor and data engine
// Copyright (C) 2002 Julian Hyde <julian.hyde@mail.com>
// 
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library General Public
// License as published by the Free Software Foundation; either
// version 2 of the License, or (at your option) any later version.
// 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Library General Public License for more details.
// 
// You should have received a copy of the GNU Library General Public
// License along with this library; if not, write to the
// Free Software Foundation, Inc., 59 Temple Place - Suite 330,
// Boston, MA  02111-1307, USA.
// 
// See the COPYING file located in the top-level-directory of
// the archive of this library for complete text of license.
*/

package openjava.ptree;
import openjava.mop.*;
import java.util.Vector;

/**
 * A <code>SetExpression</code> is an expression which consists of a set of
 * rows.  (Other expressions, such as variable references, may have set types
 * also.)
 */
public abstract class SetExpression extends NonLeaf
	implements Expression
{
    private OJClass rowType;

    // implement Expression
    public synchronized OJClass getRowType(Environment env)
    {
	if (rowType == null) {
	    try {
		rowType = deriveRowType(env);
	    } catch (Exception e) {
		System.err.println(
		    "unexpected exception : " + e.toString() );
	    }
	}
	return rowType;
    }

    protected abstract OJClass deriveRowType(Environment env)
	throws Exception;

    // implement Expression
    public OJClass getType(Environment env)
    {
	OJClass rowType = getRowType(env);
	return OJClass.arrayOf(rowType);
//  	try {
//  	    return OJClass.forName(rowType.getName() + "[]");
//  	} catch (OJClassNotFoundException e) {
//  	    throw Toolbox.newInternal(e);
//  	}
    }

    public Expression[] flatten()
    {
	return flatten(this);
    }

    public static Expression[] flatten(Expression expression)
    {
	Vector v = new Vector();
	if (expression != null) {
	    flattenRecurse(expression, v);
	}
	Expression[] expressions = new Expression[v.size()];
	v.copyInto(expressions);
	return expressions;
    }

    private static void flattenRecurse(Expression expression, Vector v)
    {
	if (expression instanceof JoinExpression) {
	    JoinExpression join = (JoinExpression) expression;
	    flattenRecurse(join.getLeft(), v);
	    flattenRecurse(join.getRight(), v);
	} else {
	    v.addElement(expression);
	}
    }
};

// End SetExpression.java