// $Id: BooleanFunction.java 96 2005-02-28 21:07:29Z blindsey $

package com.jclark.xsl.expr;

import com.jclark.xsl.om.*;

/**
 * a single argument XPath function which casts its
 * argument to a boolean
 * Function: boolean boolean(object) 
 *
 *   <p>The boolean function converts its argument to a boolean as follows:</p>
 *<ul>
 *   <li>    a number is true if and only if it is neither 
 *        positive or negative zero nor NaN</li>
 *
 *   <li>    a node-set is true if and only if it is non-empty</li>
 *
 *   <li>    a string is true if and only if its length is non-zero</li>
 *
 *   <li>    an object of a type other than the four basic types 
 *           is converted to a boolean in a way that is
 *           dependent on that type</li>
 *</ul>
 */
class BooleanFunction extends Function1 
{
    ConvertibleExpr makeCallExpr(ConvertibleExpr e) throws ParseException 
    {
        // ConvertibleExprs know how to cast themselves to booleans
        return e.makeBooleanExpr();
    }
}