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: IsEvenFunction.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.information;
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.TypeRegistry;
041    import org.jfree.formula.typing.coretypes.LogicalType;
042    
043    /**
044     * This function retruns true if the given value is an even number.
045     * 
046     * @author Cedric Pronzato
047     * 
048     */
049    public class IsEvenFunction implements Function
050    {
051      private static final TypeValuePair RETURN_TRUE = new TypeValuePair(
052          LogicalType.TYPE, Boolean.TRUE);
053    
054      private static final TypeValuePair RETURN_FALSE = new TypeValuePair(
055          LogicalType.TYPE, Boolean.FALSE);
056    
057      public IsEvenFunction()
058      {
059      }
060    
061      public TypeValuePair evaluate(final FormulaContext context,
062          final ParameterCallback parameters) throws EvaluationException
063      {
064        final int parameterCount = parameters.getParameterCount();
065        if (parameterCount < 1)
066        {
067          throw new EvaluationException(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
068        }
069    
070        final Type type1 = parameters.getType(0);
071        final Object value = parameters.getValue(0);
072    
073        final TypeRegistry typeRegistry = context.getTypeRegistry();
074        final Number number = typeRegistry.convertToNumber(type1, value);
075    
076        if (number == null)
077        {
078          throw new EvaluationException(
079              LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
080        }
081    
082        int intValue = number.intValue();
083        if (intValue < 0)
084        {
085          intValue *= -1;
086        }
087    
088        if (intValue % 2 == 0)
089        {
090          return RETURN_TRUE;
091        }
092    
093        return RETURN_FALSE;
094      }
095    
096      public String getCanonicalName()
097      {
098        return "ISEVEN";
099      }
100    
101    }