/**
* =========================================
* LibFormula : a free Java formula library
* =========================================
*
* Project Info: http://reporting.pentaho.org/libformula/
*
* (C) Copyright 2006-2007, by Pentaho Corporation and Contributors.
*
* This library is free software; you can redistribute it and/or modify it under the terms
* of the GNU Lesser General Public License as published by the Free Software Foundation;
* either version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License along with this
* library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, MA 02111-1307, USA.
*
* [Java is a trademark or registered trademark of Sun Microsystems, Inc.
* in the United States and other countries.]
*
*
* ------------
* $Id: LeftFunction.java,v 1.6 2007/04/10 14:10:41 taqua Exp $
* ------------
* (C) Copyright 2006-2007, by Pentaho Corporation.
*/
package org.jfree.formula.function.text;
import org.jfree.formula.EvaluationException;
import org.jfree.formula.FormulaContext;
import org.jfree.formula.LibFormulaErrorValue;
import org.jfree.formula.function.Function;
import org.jfree.formula.function.ParameterCallback;
import org.jfree.formula.lvalues.TypeValuePair;
import org.jfree.formula.typing.Type;
import org.jfree.formula.typing.TypeRegistry;
import org.jfree.formula.typing.coretypes.TextType;
/**
* This function returns a selected number of text characters from the left.<br/>
* This function depends on <code>MidFunction</code>.
*
* @see MidFunction
*
* @author Cedric Pronzato
*
*/
public class LeftFunction implements Function
{
public LeftFunction()
{
}
public TypeValuePair evaluate(final FormulaContext context,
final ParameterCallback parameters) throws EvaluationException
{
final int parameterCount = parameters.getParameterCount();
if (parameterCount < 1 || parameterCount > 2)
{
throw new EvaluationException(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
}
final TypeRegistry typeRegistry = context.getTypeRegistry();
final Type textType = parameters.getType(0);
final Object textValue = parameters.getValue(0);
final String text = typeRegistry.convertToText(textType, textValue);
final int length;
if(parameterCount == 2)
{
final Type lengthType = parameters.getType(1);
final Object lengthValue = parameters.getValue(1);
final Number lengthConv = typeRegistry.convertToNumber(lengthType, lengthValue);
if(lengthConv.doubleValue() < 0)
{
throw new EvaluationException(LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
}
length = lengthConv.intValue();
}
else
{
length = 1;
}
if(text == null)
{
throw new EvaluationException(LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
}
// Note that MID(T;1;Length) produces the same results as LEFT(T;Length).
final MidFunction function = new MidFunction();
return new TypeValuePair(TextType.TYPE, function.process(text, new Integer(1), new Integer(length)));
}
public String getCanonicalName()
{
return "LEFT";
}
}