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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: