/*

 * Copyright (c) 2004, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package sun.tools.jstat;

import java.util.*;

/**

 * A typesafe enumeration for describing mathematical operators.

 *

 * @author Brian Doherty

 * @since 1.5

 */

public abstract class Operator {

    private static int nextOrdinal = 0;

    private static HashMap<String, Operator> map = new HashMap<String, Operator>();

    private final String name;

    private final int ordinal = nextOrdinal++;

    private Operator(String name) {

        this.name = name;

        map.put(name, this);

    }

    protected abstract double eval(double x, double y);

    /* Operator '+' */

    public static final Operator PLUS = new Operator("+") {

        protected double eval(double x, double y) {

            return x + y;

        }

    };

    /* Operator '-' */

    public static final Operator MINUS = new Operator("-") {

        protected double eval(double x, double y) {

            return x - y;

        }

    };

    /* Operator '/' */

    public static final Operator DIVIDE = new Operator("/") {

        protected double eval(double x, double y) {

            if (y == 0) {

                return Double.NaN;

            }

            return x / y;

        }

    };

    /* Operator '*' */

    public static final Operator MULTIPLY = new Operator("*") {

        protected double eval(double x, double y) {

            return x * y;

        }

    };

    /**

     * Returns the string representation of this Operator object.

     *

     * @return  the string representation of this Operator object

     */

    public String toString() {

        return name;

    }

    /**

     * Maps a string to its corresponding Operator object.

     *

     * @param   s  an string to match against Operator objects.

     * @return     The Operator object matching the given string.

     */

    public static Operator toOperator(String s) {

        return map.get(s);

    }

    /**

     * Returns an enumeration of the keys for this enumerated type

     *

     * @param   s  an string to match against Operator objects.

     * @return     The Operator object matching the given string.

     */

    protected static Set<?> keySet() {

        return map.keySet();

    }

}