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

   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: LeftFunction.java 2752 2007-04-10 14:10:41Z taqua $
  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.coretypes.TextType;
  42: 
  43: /**
  44:  * This function returns a selected number of text characters from the left.<br/>
  45:  * This function depends on <code>MidFunction</code>.
  46:  *
  47:  * @see MidFunction
  48:  *
  49:  * @author Cedric Pronzato
  50:  *
  51:  */
  52: public class LeftFunction implements Function
  53: {
  54:   public LeftFunction()
  55:   {
  56:   }
  57: 
  58:   public TypeValuePair evaluate(final FormulaContext context,
  59:                                 final ParameterCallback parameters) throws EvaluationException
  60:   {
  61:     final int parameterCount = parameters.getParameterCount();
  62:     if (parameterCount < 1 || parameterCount > 2)
  63:     {
  64:       throw new EvaluationException(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
  65:     }
  66:     final TypeRegistry typeRegistry = context.getTypeRegistry();
  67: 
  68:     final Type textType = parameters.getType(0);
  69:     final Object textValue = parameters.getValue(0);
  70: 
  71:     final String text = typeRegistry.convertToText(textType, textValue);
  72:     final int length;
  73:     if(parameterCount == 2)
  74:     {
  75:       final Type lengthType = parameters.getType(1);
  76:       final Object lengthValue = parameters.getValue(1);
  77:       final Number lengthConv = typeRegistry.convertToNumber(lengthType, lengthValue);
  78:       if(lengthConv.doubleValue() < 0)
  79:       {
  80:         throw new EvaluationException(LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
  81:       }
  82: 
  83:       length = lengthConv.intValue();
  84:     }
  85:     else
  86:     {
  87:       length = 1;
  88:     }
  89: 
  90:     if(text == null)
  91:     {
  92:       throw new EvaluationException(LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
  93:     }
  94: 
  95:     // Note that MID(T;1;Length) produces the same results as LEFT(T;Length).
  96:     final MidFunction function = new MidFunction();
  97:     return new TypeValuePair(TextType.TYPE, function.process(text, new Integer(1), new Integer(length)));
  98:   }
  99: 
 100:   public String getCanonicalName()
 101:   {
 102:     return "LEFT";
 103:   }
 104: