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: LeftFunction.java 2752 2007-04-10 14:10:41Z taqua $
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.coretypes.TextType;
042
043 /**
044 * This function returns a selected number of text characters from the left.<br/>
045 * This function depends on <code>MidFunction</code>.
046 *
047 * @see MidFunction
048 *
049 * @author Cedric Pronzato
050 *
051 */
052 public class LeftFunction implements Function
053 {
054 public LeftFunction()
055 {
056 }
057
058 public TypeValuePair evaluate(final FormulaContext context,
059 final ParameterCallback parameters) throws EvaluationException
060 {
061 final int parameterCount = parameters.getParameterCount();
062 if (parameterCount < 1 || parameterCount > 2)
063 {
064 throw new EvaluationException(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
065 }
066 final TypeRegistry typeRegistry = context.getTypeRegistry();
067
068 final Type textType = parameters.getType(0);
069 final Object textValue = parameters.getValue(0);
070
071 final String text = typeRegistry.convertToText(textType, textValue);
072 final int length;
073 if(parameterCount == 2)
074 {
075 final Type lengthType = parameters.getType(1);
076 final Object lengthValue = parameters.getValue(1);
077 final Number lengthConv = typeRegistry.convertToNumber(lengthType, lengthValue);
078 if(lengthConv.doubleValue() < 0)
079 {
080 throw new EvaluationException(LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
081 }
082
083 length = lengthConv.intValue();
084 }
085 else
086 {
087 length = 1;
088 }
089
090 if(text == null)
091 {
092 throw new EvaluationException(LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
093 }
094
095 // Note that MID(T;1;Length) produces the same results as LEFT(T;Length).
096 final MidFunction function = new MidFunction();
097 return new TypeValuePair(TextType.TYPE, function.process(text, new Integer(1), new Integer(length)));
098 }
099
100 public String getCanonicalName()
101 {
102 return "LEFT";
103 }
104
105 }