Source for org.jfree.formula.function.text.ExactFunction

   1: /**
   2:  * =========================================
   3:  * LibFormula : a free Java formula library
   4:  * =========================================
   5:  *
   6:  * Project Info:  http://reporting.pentaho.org/libformula/
   7:  *
   8:  * (C) Copyright 2006-2007, by Pentaho Corporation and Contributors.
   9:  *
  10:  * This library is free software; you can redistribute it and/or modify it under the terms
  11:  * of the GNU Lesser General Public License as published by the Free Software Foundation;
  12:  * either version 2.1 of the License, or (at your option) any later version.
  13:  *
  14:  * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
  15:  * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  16:  * See the GNU Lesser General Public License for more details.
  17:  *
  18:  * You should have received a copy of the GNU Lesser General Public License along with this
  19:  * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  20:  * Boston, MA 02111-1307, USA.
  21:  *
  22:  * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
  23:  * in the United States and other countries.]
  24:  *
  25:  *
  26:  * ------------
  27:  * $Id: ExactFunction.java,v 1.9 2007/05/08 09:47:09 taqua Exp $
  28:  * ------------
  29:  * (C) Copyright 2006-2007, by Pentaho Corporation.
  30:  */
  31: package org.jfree.formula.function.text;
  32: 
  33: import org.jfree.formula.EvaluationException;
  34: import org.jfree.formula.FormulaContext;
  35: import org.jfree.formula.LibFormulaErrorValue;
  36: import org.jfree.formula.function.Function;
  37: import org.jfree.formula.function.ParameterCallback;
  38: import org.jfree.formula.lvalues.TypeValuePair;
  39: import org.jfree.formula.typing.Type;
  40: import org.jfree.formula.typing.TypeRegistry;
  41: import org.jfree.formula.typing.TypeConversionException;
  42: import org.jfree.formula.typing.coretypes.LogicalType;
  43: 
  44: /**
  45:  * This function reports if two given text values are exactly equal using a case-sensitive comparison.
  46:  *
  47:  * @author Cedric Pronzato
  48:  *
  49:  */
  50: public class ExactFunction implements Function
  51: {
  52:   private static final TypeValuePair RETURN_FALSE = new TypeValuePair(LogicalType.TYPE, Boolean.FALSE);
  53:   private static final TypeValuePair RETURN_TRUE = new TypeValuePair(LogicalType.TYPE, Boolean.TRUE);
  54: 
  55:   public ExactFunction()
  56:   {
  57:   }
  58: 
  59:   public TypeValuePair evaluate(FormulaContext context, ParameterCallback parameters) throws EvaluationException
  60:   {
  61:     final int parameterCount = parameters.getParameterCount();
  62:     if (parameterCount != 2)
  63:     {
  64:       throw new EvaluationException(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
  65:     }
  66:     final TypeRegistry typeRegistry = context.getTypeRegistry();
  67: 
  68:     final Type textType1 = parameters.getType(0);
  69:     final Object textValue1 = parameters.getValue(0);
  70:     final Type textType2 = parameters.getType(1);
  71:     final Object textValue2 = parameters.getValue(1);
  72: 
  73: 
  74:     // Numerical comparisons ignore "trivial" differences that
  75:     // depend only on numeric precision of finite numbers.
  76: 
  77:     // This fixes the common rounding errors, that are encountered when computing "((1/3) * 3)", which results
  78:     // in 0.99999 and not 1, as expected.
  79:     try
  80:     {
  81:       final Number number1 = typeRegistry.convertToNumber(textType1, textValue1);
  82:       final Number number2 = typeRegistry.convertToNumber(textType2, textValue2);
  83: 
  84:       final double delta = Math.abs(Math.abs(number1.doubleValue()) - Math.abs(number2.doubleValue()));
  85:       if(delta < 0.00005)
  86:       {
  87:         return RETURN_TRUE;
  88:       }
  89:       return RETURN_FALSE;
  90:     }
  91:     catch(TypeConversionException tce)
  92:     {
  93:       // Ignore, try to compare them as strings ..
  94:     }
  95: 
  96:     final String text1 = typeRegistry.convertToText(textType1, textValue1);
  97:     final String text2 = typeRegistry.convertToText(textType2, textValue2);
  98:     if(text1 == null || text2 == null)
  99:     {
 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: