001    /**
002     * =========================================
003     * LibFormula : a free Java formula library
004     * =========================================
005     *
006     * Project Info:  http://reporting.pentaho.org/libformula/
007     *
008     * (C) Copyright 2006-2007, by Pentaho Corporation and Contributors.
009     *
010     * This library is free software; you can redistribute it and/or modify it under the terms
011     * of the GNU Lesser General Public License as published by the Free Software Foundation;
012     * either version 2.1 of the License, or (at your option) any later version.
013     *
014     * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
015     * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
016     * See the GNU Lesser General Public License for more details.
017     *
018     * You should have received a copy of the GNU Lesser General Public License along with this
019     * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
020     * Boston, MA 02111-1307, USA.
021     *
022     * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
023     * in the United States and other countries.]
024     *
025     *
026     * ------------
027     * $Id: ContextLookup.java 2716 2007-04-01 13:51:58Z taqua $
028     * ------------
029     * (C) Copyright 2006-2007, by Pentaho Corporation.
030     */
031    package org.jfree.formula.lvalues;
032    
033    import org.jfree.formula.typing.Type;
034    import org.jfree.formula.FormulaContext;
035    import org.jfree.formula.EvaluationException;
036    
037    /**
038     * A reference that queries the datarow.
039     *
040     * @author Thomas Morgner
041     */
042    public class ContextLookup extends AbstractLValue
043    {
044      private String name;
045    
046      public ContextLookup(final String name)
047      {
048        this.name = name;
049      }
050    
051      public TypeValuePair evaluate() throws EvaluationException
052      {
053        final FormulaContext context = getContext();
054        final Object value = context.resolveReference(name);
055        final Type type = context.resolveReferenceType(name);
056        return new TypeValuePair(type, value);
057      }
058    
059    
060      public String toString()
061      {
062        return "[" +  name + "]";
063      }
064    
065      /**
066       * Checks, whether the LValue is constant. Constant lvalues always return the
067       * same value.
068       *
069       * @return
070       */
071      public boolean isConstant()
072      {
073        return false;
074      }
075    
076      public String getName()
077      {
078        return name;
079      }
080    }