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 }