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: TFunction.java 3521 2007-10-16 10:55:14Z tmorgner $
028     * ------------
029     * (C) Copyright 2006-2007, by Pentaho Corporation.
030     */
031    package org.jfree.formula.function.text;
032    
033    import org.jfree.formula.EvaluationException;
034    import org.jfree.formula.FormulaContext;
035    import org.jfree.formula.LibFormulaErrorValue;
036    import org.jfree.formula.function.Function;
037    import org.jfree.formula.function.ParameterCallback;
038    import org.jfree.formula.lvalues.TypeValuePair;
039    import org.jfree.formula.typing.Type;
040    import org.jfree.formula.typing.coretypes.TextType;
041    
042    /**
043     * This function returns the given text value or a zero lenght string for non text type.
044     *
045     * @author Cedric Pronzato
046     *
047     */
048    public class TFunction implements Function
049    {
050      private static final TypeValuePair EMPTY_STRING = new TypeValuePair(TextType.TYPE, "");
051    
052      public TFunction()
053      {
054      }
055    
056      public TypeValuePair evaluate(final FormulaContext context, final ParameterCallback parameters) throws EvaluationException
057      {
058        final int parameterCount = parameters.getParameterCount();
059        if (parameterCount < 1)
060        {
061          throw new EvaluationException(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
062        }
063        final Type type1 = parameters.getType(0);
064        final Object value1 = parameters.getValue(0);
065    
066        if(type1 instanceof TextType || value1 instanceof String)
067        {
068          return new TypeValuePair(TextType.TYPE, value1);
069        }
070        else
071        {
072          return EMPTY_STRING;
073        }
074      }
075    
076      public String getCanonicalName()
077      {
078        return "T";
079      }
080    
081    }