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 */
021package csheets.core.formula;
022
023import csheets.core.IllegalValueTypeException;
024import csheets.core.Value;
025
026/**
027 * A function that can be used in a formula.
028 * @author Einar Pehrson
029 */
030public 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}