Source for org.jfree.formula.function.math.EvenFunction

   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: EvenFunction.java,v 1.1 2007/05/18 14:36:57 mimil Exp $
  28:  * ------------
  29:  * (C) Copyright 2006-2007, by Pentaho Corporation.
  30:  */
  31: package org.jfree.formula.function.math;
  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.coretypes.NumberType;
  41: 
  42: /**
  43:  * This function returns the rounding of a number up to the nearest even
  44:  * integer.
  45:  * 
  46:  * @author Cedric Pronzato
  47:  * 
  48:  */
  49: public class EvenFunction implements Function
  50: {
  51: 
  52:   public EvenFunction()
  53:   {
  54:   }
  55: 
  56:   public TypeValuePair evaluate(FormulaContext context,
  57:       ParameterCallback parameters) throws EvaluationException
  58:   {
  59:     final int parameterCount = parameters.getParameterCount();
  60:     if (parameterCount < 1)
  61:     {
  62:       throw new EvaluationException(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
  63:     }
  64:     final Type type1 = parameters.getType(0);
  65:     final Object value1 = parameters.getValue(0);
  66:     final Number result = context.getTypeRegistry().convertToNumber(type1,
  67:         value1);
  68: 
  69:     final int intValue = result.intValue();
  70:     Integer ret = null;
  71: 
  72:     int test = intValue;
  73:     if (intValue < 0)
  74:     {
  75:       test = intValue * -1;
  76:     }
  77: 
  78:     if (test % 2 == 0) // even
  79:     {
  80:       if (intValue == 0)
  81:       {
  82:         if (result.doubleValue() < 0)
  83:         {
  84:           ret = new Integer(-2);
  85:         }
  86:         else if (result.doubleValue() > 0)
  87:         {
  88:           ret = new Integer(2);
  89:         }
  90:         else
  91:         {
  92:           ret = new Integer(0);
  93:         }
  94:       }
  95:       else
  96:       {
  97:         ret = new Integer(intValue);
  98:       }
  99:     }
 100:     else
 101:     // odd
 102:     {
 103:       if (result.doubleValue() < 0)
 104:       {
 105:         ret = new Integer(intValue - 1);
 106:       }
 107:       else
 108:       {
 109:         ret = new Integer(intValue + 1);
 110:       }
 111:     }
 112: 
 113:     return new TypeValuePair(NumberType.GENERIC_NUMBER, ret);
 114:   }
 115: 
 116:   public String getCanonicalName()
 117:   {
 118:     return "EVEN";
 119:   }
 120: 
 121: }