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: IsBlankFunction.java 3521 2007-10-16 10:55:14Z tmorgner $
028     * ------------
029     * (C) Copyright 2006-2007, by Pentaho Corporation.
030     */
031    
032    package org.jfree.formula.function.information;
033    
034    import org.jfree.formula.EvaluationException;
035    import org.jfree.formula.FormulaContext;
036    import org.jfree.formula.LibFormulaErrorValue;
037    import org.jfree.formula.function.Function;
038    import org.jfree.formula.function.ParameterCallback;
039    import org.jfree.formula.lvalues.ContextLookup;
040    import org.jfree.formula.lvalues.LValue;
041    import org.jfree.formula.lvalues.TypeValuePair;
042    import org.jfree.formula.typing.coretypes.LogicalType;
043    
044    /**
045     * Document me!
046     * 
047     * @author : Thomas Morgner
048     */
049    public class IsBlankFunction implements Function
050    {
051      private static final TypeValuePair RETURN_FALSE = new TypeValuePair(
052          LogicalType.TYPE, Boolean.FALSE);
053    
054      private static final TypeValuePair RETURN_TRUE = new TypeValuePair(
055          LogicalType.TYPE, Boolean.TRUE);
056    
057      public IsBlankFunction()
058      {
059      }
060    
061      public String getCanonicalName()
062      {
063        return "ISBLANK";
064      }
065    
066      public TypeValuePair evaluate(final FormulaContext context,
067          final ParameterCallback parameters) throws EvaluationException
068      {
069        final int parameterCount = parameters.getParameterCount();
070        if (parameterCount < 1)
071        {
072          throw new EvaluationException(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
073        }
074        final Object value = parameters.getValue(0);
075    
076        final LValue raw = parameters.getRaw(0);
077        if (raw instanceof ContextLookup)
078        {
079          if (value == null)
080          {
081            return RETURN_TRUE;
082          }
083        }
084    
085        return RETURN_FALSE;
086      }
087    }