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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package javax.xml.xpath;

import java.util.List;

/**
 * XPathFunction provides access to XPath functions.
 *
 * Functions are identified by QName and arity in XPath.
 *
 * @author  Norman Walsh
 * @author  Jeff Suttor
 * @since 1.5
 */
public interface XPathFunction {
  /**
   * Evaluate the function with the specified arguments.
   *
   * To the greatest extent possible, side-effects should be avoided in the
   * definition of extension functions. The implementation evaluating an
   * XPath expression is under no obligation to call extension functions in
   * any particular order or any particular number of times.
   *
   * @param args The arguments, null is a valid value.
   *
   * @return The result of evaluating the XPath function as an Object.
   *
   * @throws XPathFunctionException If args cannot be evaluated with this XPath function.
   */
  public Object evaluate(List args)
    throws XPathFunctionException;
}