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    1   /*
    2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/SumFunction.java,v 1.10 2005/06/28 13:44:45 elharo Exp $
    3    * $Revision: 1.10 $
    4    * $Date: 2005/06/28 13:44:45 $
    5    *
    6    * ====================================================================
    7    *
    8    * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
    9    * All rights reserved.
    10   *
    11   * Redistribution and use in source and binary forms, with or without
    12   * modification, are permitted provided that the following conditions
    13   * are met:
    14   *
    15   * 1. Redistributions of source code must retain the above copyright
    16   *    notice, this list of conditions, and the following disclaimer.
    17   *
    18   * 2. Redistributions in binary form must reproduce the above copyright
    19   *    notice, this list of conditions, and the disclaimer that follows
    20   *    these conditions in the documentation and/or other materials
    21   *    provided with the distribution.
    22   *
    23   * 3. The name "Jaxen" must not be used to endorse or promote products
    24   *    derived from this software without prior written permission.  For
    25   *    written permission, please contact license@jaxen.org.
    26   *
    27   * 4. Products derived from this software may not be called "Jaxen", nor
    28   *    may "Jaxen" appear in their name, without prior written permission
    29   *    from the Jaxen Project Management (pm@jaxen.org).
    30   *
    31   * In addition, we request (but do not require) that you include in the
    32   * end-user documentation provided with the redistribution and/or in the
    33   * software itself an acknowledgement equivalent to the following:
    34   *     "This product includes software developed by the
    35   *      Jaxen Project <http://www.jaxen.org/>."
    36   * Alternatively, the acknowledgment may be graphical using the logos
    37   * available at http://www.jaxen.org/
    38   *
    39   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
    40   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
    41   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    42   * DISCLAIMED.  IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
    43   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    44   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    45   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
    46   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
    47   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    48   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
    49   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    50   * SUCH DAMAGE.
    51   *
    52   * ====================================================================
    53   * This software consists of voluntary contributions made by many
    54   * individuals on behalf of the Jaxen Project and was originally
    55   * created by bob mcwhirter <bob@werken.com> and
    56   * James Strachan <jstrachan@apache.org>.  For more information on the
    57   * Jaxen Project, please see <http://www.jaxen.org/>.
    58   *
    59   * $Id: SumFunction.java,v 1.10 2005/06/28 13:44:45 elharo Exp $
    60   */
    61
    62
    63  package org.jaxen.function;
    64
    65  import java.util.Iterator;
    66  import java.util.List;
    67
    68  import org.jaxen.Context;
    69  import org.jaxen.Function;
    70  import org.jaxen.FunctionCallException;
    71  import org.jaxen.Navigator;
    72
    73  /***
    74   * <p><b>4.4</b> <code><i>number</i> sum(<i>node-set</i>)</code> </p>
    75   *
    76   * <blockquote src="http://www.w3.org/TR/xpath#function-sum">
    77   * The sum function returns the sum, for each node in the argument node-set,
    78   * of the result of converting the string-values of the node to a number.
    79   * </blockquote>
    80   *
    81   * @author bob mcwhirter (bob @ werken.com)
    82   * @see <a href="http://www.w3.org/TR/xpath#function-sum" target="_top">Section 4.4 of the XPath Specification</a>
    83   */
    84  public class SumFunction implements Function
    85  {
    86
    87      /***
    88       * Create a new <code>SumFunction</code> object.
    89       */
    90      public SumFunction() {}
    91
    92      /*** Returns the sum of its arguments.
    93       *
    94       * @param context the context at the point in the
    95       *         expression when the function is called
    96       * @param args a list that contains exactly one item, also a <code>List</code>
    97       *
    98       * @return a <code>Double</code> containing the sum of the items in <code>args.get(0)</code>
    99       *
    100      * @throws FunctionCallException if <code>args</code> has more or less than one item;
    101      *     or if the first argument is not a <code>List</code>
    102      */
    103     public Object call(Context context,
    104                        List args) throws FunctionCallException
    105     {
    106
    107         if (args.size() == 1)
    108         {
    109             return evaluate( args.get(0),
    110                              context.getNavigator() );
    111         }
    112
    113         throw new FunctionCallException( "sum() requires one argument." );
    114     }
    115
    116     /***
    117      * Returns the sum of the items in a list.
    118      * If necessary, each item in the list is first converted to a <code>Double</code>
    119      * as if by the XPath <code>number()</code> function.
    120      *
    121      * @param obj a <code>List</code> of numbers to be summed
    122      * @param nav ignored
    123      *
    124      * @return the sum of the list
    125      *
    126      * @throws FunctionCallException if <code>obj</code> is not a <code>List</code>
    127      */
    128     public static Double evaluate(Object obj,
    129                                   Navigator nav) throws FunctionCallException
    130     {
    131         double sum  = 0;
    132
    133         if (obj instanceof List)
    134         {
    135             Iterator nodeIter = ((List)obj).iterator();
    136             while ( nodeIter.hasNext() )
    137             {
    138                 double term = NumberFunction.evaluate( nodeIter.next(),
    139                                                 nav ).doubleValue();
    140                 sum += term;
    141             }
    142         }
    143         else
    144         {
    145             throw new FunctionCallException("The argument to the sum function must be a node-set");
    146         }
    147
    148         return new Double(sum);
    149     }
    150
    151 }