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: ExactFunction.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.TypeRegistry;
041    import org.jfree.formula.typing.TypeConversionException;
042    import org.jfree.formula.typing.coretypes.LogicalType;
043    
044    /**
045     * This function reports if two given text values are exactly equal using a case-sensitive comparison.
046     *
047     * @author Cedric Pronzato
048     *
049     */
050    public class ExactFunction implements Function
051    {
052      private static final TypeValuePair RETURN_FALSE = new TypeValuePair(LogicalType.TYPE, Boolean.FALSE);
053      private static final TypeValuePair RETURN_TRUE = new TypeValuePair(LogicalType.TYPE, Boolean.TRUE);
054    
055      public ExactFunction()
056      {
057      }
058    
059      public TypeValuePair evaluate(final FormulaContext context, final ParameterCallback parameters) throws EvaluationException
060      {
061        final int parameterCount = parameters.getParameterCount();
062        if (parameterCount != 2)
063        {
064          throw new EvaluationException(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
065        }
066        final TypeRegistry typeRegistry = context.getTypeRegistry();
067    
068        final Type textType1 = parameters.getType(0);
069        final Object textValue1 = parameters.getValue(0);
070        final Type textType2 = parameters.getType(1);
071        final Object textValue2 = parameters.getValue(1);
072    
073    
074        // Numerical comparisons ignore "trivial" differences that
075        // depend only on numeric precision of finite numbers.
076    
077        // This fixes the common rounding errors, that are encountered when computing "((1/3) * 3)", which results
078        // in 0.99999 and not 1, as expected.
079        try
080        {
081          final Number number1 = typeRegistry.convertToNumber(textType1, textValue1);
082          final Number number2 = typeRegistry.convertToNumber(textType2, textValue2);
083    
084          final double delta = Math.abs(Math.abs(number1.doubleValue()) - Math.abs(number2.doubleValue()));
085          if(delta < 0.00005)
086          {
087            return RETURN_TRUE;
088          }
089          return RETURN_FALSE;
090        }
091        catch(TypeConversionException tce)
092        {
093          // Ignore, try to compare them as strings ..
094        }
095    
096        final String text1 = typeRegistry.convertToText(textType1, textValue1);
097        final String text2 = typeRegistry.convertToText(textType2, textValue2);
098        if(text1 == null || text2 == null)
099        {
100          throw new EvaluationException(LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
101        }
102    
103        if (text1.equals(text2))
104        {
105          return RETURN_TRUE;
106        }
107        return RETURN_FALSE;
108      }
109    
110      public String getCanonicalName()
111      {
112        return "EXACT";
113      }
114    
115    }