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: Function.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;
032    
033    import java.io.Serializable;
034    
035    import org.jfree.formula.lvalues.TypeValuePair;
036    import org.jfree.formula.FormulaContext;
037    import org.jfree.formula.EvaluationException;
038    import org.jfree.formula.typing.TypeConversionException;
039    
040    /**
041     * A function is an arbitary computation. A return value type is not available
042     * unless the function has been evaluated.
043     *
044     * Functions must be stateless, that means: Calling the same function with
045     * exactly the same parameters must always result in the same computed value.
046     *
047     * @author Thomas Morgner
048     */
049    public interface Function extends Serializable
050    {
051      public String getCanonicalName();
052      public TypeValuePair evaluate (FormulaContext context,
053                                     ParameterCallback parameters)
054          throws EvaluationException, TypeConversionException;
055    }