001    /*
002     * Copyright (c) 2005 Einar Pehrson <einar@pehrson.nu>.
003     *
004     * This file is part of
005     * CleanSheets - a spreadsheet application for the Java platform.
006     *
007     * CleanSheets is free software; you can redistribute it and/or modify
008     * it under the terms of the GNU General Public License as published by
009     * the Free Software Foundation; either version 2 of the License, or
010     * (at your option) any later version.
011     *
012     * CleanSheets is distributed in the hope that it will be useful,
013     * but WITHOUT ANY WARRANTY; without even the implied warranty of
014     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
015     * GNU General Public License for more details.
016     *
017     * You should have received a copy of the GNU General Public License
018     * along with CleanSheets; if not, write to the Free Software
019     * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
020     */
021    package csheets.core.formula;
022    
023    import csheets.core.IllegalValueTypeException;
024    import csheets.core.Value;
025    
026    /**
027     * A function that can be used in a formula.
028     * @author Einar Pehrson
029     */
030    public interface Function {
031    
032            /**
033             * Returns the operator's string identirifer.
034             * @return a string representation of the operator.
035             */
036            public String getIdentifier();
037    
038            /**
039             * Invokes the function using the given arguments and returns the result.
040             * @return the result of the operation
041             */
042            public Value applyTo(Expression[] args) throws IllegalValueTypeException;
043    
044            /**
045             * Returns the parameters of the function.
046             * @return the parameters of the function
047             */
048            public FunctionParameter[] getParameters();
049    
050            /**
051             * Returns whether the function accepts a variable number of arguments,
052             * i.e. whether the function's parameter list is unbounded.
053             * @return true if the function accepts a variable number of arguments
054             */
055            public boolean isVarArg();
056    }