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.lang;
022    
023    import csheets.core.IllegalValueTypeException;
024    import csheets.core.Value;
025    import csheets.core.formula.Expression;
026    import csheets.core.formula.UnaryOperator;
027    
028    /**
029     * A negator (negative sign).
030     * @author Einar Pehrson
031     */
032    public class Negator implements UnaryOperator {
033    
034            /** The unique version identifier used for serialization */
035            private static final long serialVersionUID = 1008038195417799885L;
036    
037            /**
038             * Creates a new negator.
039             */
040            public Negator() {}
041    
042            /**
043             * Returns the negation of the operand's value.
044             * @return the negation of the operand's value
045             * @throws IllegalValueTypeException if the value of the operand is not numeric
046             */
047            public Value applyTo(Expression operand) throws IllegalValueTypeException {
048                    return new Value(-operand.evaluate().toNumber().doubleValue());
049            }
050    
051            public String getIdentifier() {
052                    return "-";
053            }
054    
055            public boolean isPrefix() {
056                    return true;
057            }
058    
059            public Value.Type getOperandValueType() {
060                    return Value.Type.NUMERIC;
061            }
062    
063            public String toString() {
064                    return getIdentifier();
065            }
066    }