code: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements. See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership. The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the  "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /*
   * $Id$
   */
  package org.apache.xalan.lib;
  
  import org.apache.xpath.NodeSet;
  
  import org.w3c.dom.Node;
  import org.w3c.dom.NodeList;
  
  /**
   * This class contains EXSLT math extension functions.
   * It is accessed by specifying a namespace URI as follows:
   * <pre>
   *    xmlns:math="http://exslt.org/math"
   * </pre>
   * 
   * The documentation for each function has been copied from the relevant
   * EXSLT Implementer page.
   * 
   * @see <a href="http://www.exslt.org/">EXSLT</a>
  
   * @xsl.usage general
   */
  public class ExsltMath extends ExsltBase
  {
    // Constants
    private static String PI = "3.1415926535897932384626433832795028841971693993751";
    private static String E  = "2.71828182845904523536028747135266249775724709369996";
    private static String SQRRT2 = "1.41421356237309504880168872420969807856967187537694";
    private static String LN2 = "0.69314718055994530941723212145817656807550013436025";
    private static String LN10 = "2.302585092994046";
    private static String LOG2E = "1.4426950408889633";
    private static String SQRT1_2 = "0.7071067811865476";
  	
    /**
     * The math:max function returns the maximum value of the nodes passed as the argument. 
     * The maximum value is defined as follows. The node set passed as an argument is sorted 
     * in descending order as it would be by xsl:sort with a data type of number. The maximum 
     * is the result of converting the string value of the first node in this sorted list to 
     * a number using the number function. 
     * <p>
     * If the node set is empty, or if the result of converting the string values of any of the 
     * nodes to a number is NaN, then NaN is returned.
     * 
     * @param nl The NodeList for the node-set to be evaluated.
     * 
     * @return the maximum value found, NaN if any node cannot be converted to a number.
     * 
     * @see <a href="http://www.exslt.org/">EXSLT</a>
     */
    public static double max (NodeList nl)
    {
      if (nl == null || nl.getLength() == 0)
        return Double.NaN;
        
      double m = - Double.MAX_VALUE;
      for (int i = 0; i < nl.getLength(); i++)
      {
        Node n = nl.item(i);
        double d = toNumber(n);
        if (Double.isNaN(d))
          return Double.NaN;
        else if (d > m)
          m = d;
      }
    	
      return m;  	
    }
  
    /**
     * The math:min function returns the minimum value of the nodes passed as the argument. 
     * The minimum value is defined as follows. The node set passed as an argument is sorted 
     * in ascending order as it would be by xsl:sort with a data type of number. The minimum 
     * is the result of converting the string value of the first node in this sorted list to 
     * a number using the number function. 
     * <p>
     * If the node set is empty, or if the result of converting the string values of any of 
     * the nodes to a number is NaN, then NaN is returned.
     * 
     * @param nl The NodeList for the node-set to be evaluated.
     * 
     * @return the minimum value found, NaN if any node cannot be converted to a number.
     * 
     * @see <a href="http://www.exslt.org/">EXSLT</a>
     */
    public static double min (NodeList nl)
    {
      if (nl == null || nl.getLength() == 0)
        return Double.NaN;
  
      double m = Double.MAX_VALUE;
      for (int i = 0; i < nl.getLength(); i++)
      {
        Node n = nl.item(i);
        double d = toNumber(n);
        if (Double.isNaN(d))
          return Double.NaN;
        else if (d < m)
          m = d;
      }
      
      return m;
    }
    
    /**
     * The math:highest function returns the nodes in the node set whose value is the maximum 
     * value for the node set. The maximum value for the node set is the same as the value as 
     * calculated by math:max. A node has this maximum value if the result of converting its 
     * string value to a number as if by the number function is equal to the maximum value, 
     * where the equality comparison is defined as a numerical comparison using the = operator.
     * <p>
     * If any of the nodes in the node set has a non-numeric value, the math:max function will 
     * return NaN. The definition numeric comparisons entails that NaN != NaN. Therefore if any 
     * of the nodes in the node set has a non-numeric value, math:highest will return an empty 
     * node set. 
     * 
     * @param nl The NodeList for the node-set to be evaluated.
     * 
     * @return node-set with nodes containing the maximum value found, an empty node-set
     * if any node cannot be converted to a number.
     */
    public static NodeList highest (NodeList nl)
    {        
      double maxValue = max(nl);
  
      NodeSet highNodes = new NodeSet();
      highNodes.setShouldCacheNodes(true);    
      
      if (Double.isNaN(maxValue))
        return highNodes;  // empty Nodeset
      
      for (int i = 0; i < nl.getLength(); i++)
      {
        Node n = nl.item(i);
        double d = toNumber(n); 
        if (d == maxValue)
          highNodes.addElement(n);
      }
      return highNodes;
    }
    
    /**
     * The math:lowest function returns the nodes in the node set whose value is the minimum value 
     * for the node set. The minimum value for the node set is the same as the value as calculated 
     * by math:min. A node has this minimum value if the result of converting its string value to 
     * a number as if by the number function is equal to the minimum value, where the equality 
     * comparison is defined as a numerical comparison using the = operator.
     * <p>
     * If any of the nodes in the node set has a non-numeric value, the math:min function will return 
     * NaN. The definition numeric comparisons entails that NaN != NaN. Therefore if any of the nodes 
     * in the node set has a non-numeric value, math:lowest will return an empty node set.
     * 
     * @param nl The NodeList for the node-set to be evaluated.
     * 
     * @return node-set with nodes containing the minimum value found, an empty node-set
     * if any node cannot be converted to a number.
     * 
     */
    public static NodeList lowest (NodeList nl)
    {
      double minValue = min(nl);
  
      NodeSet lowNodes = new NodeSet();
      lowNodes.setShouldCacheNodes(true);
      
      if (Double.isNaN(minValue))
        return lowNodes;  // empty Nodeset
      
      for (int i = 0; i < nl.getLength(); i++)
      {
        Node n = nl.item(i);
        double d = toNumber(n); 
        if (d == minValue)
          lowNodes.addElement(n);
      }
      return lowNodes;
    }
    
    /**
     * The math:abs function returns the absolute value of a number.
     *
     * @param num A number
     * @return The absolute value of the number
     */
     public static double abs(double num)
     {
       return Math.abs(num);
     }
  
    /**
     * The math:acos function returns the arccosine value of a number.
     *
     * @param num A number
     * @return The arccosine value of the number
     */
     public static double acos(double num)
     {
       return Math.acos(num);
     }
  
    /**
     * The math:asin function returns the arcsine value of a number. 
     *
     * @param num A number
     * @return The arcsine value of the number
     */
     public static double asin(double num)
     {
       return Math.asin(num);
     }
  
    /**
     * The math:atan function returns the arctangent value of a number. 
     *
     * @param num A number
     * @return The arctangent value of the number
     */
     public static double atan(double num)
     {
       return Math.atan(num);
     }
    
    /**
     * The math:atan2 function returns the angle ( in radians ) from the X axis to a point (y,x). 
     *
     * @param num1 The X axis value
     * @param num2 The Y axis value
     * @return The angle (in radians) from the X axis to a point (y,x)
     */
     public static double atan2(double num1, double num2)
     {
       return Math.atan2(num1, num2);
     }
  
    /**
     * The math:cos function returns cosine of the passed argument. 
     *
     * @param num A number
     * @return The cosine value of the number
     */
     public static double cos(double num)
     {
       return Math.cos(num);
     }
  
    /**
     * The math:exp function returns e (the base of natural logarithms) raised to a power. 
     *
     * @param num A number
     * @return The value of e raised to the given power
     */
     public static double exp(double num)
     {
       return Math.exp(num);
     }
  
    /**
     * The math:log function returns the natural logarithm of a number. 
     *
     * @param num A number
     * @return The natural logarithm of the number
     */
     public static double log(double num)
     {
       return Math.log(num);
     }
  
    /**
     * The math:power function returns the value of a base expression taken to a specified power. 
     *
     * @param num1 The base
     * @param num2 The power
     * @return The value of the base expression taken to the specified power
     */
     public static double power(double num1, double num2)
     {
       return Math.pow(num1, num2);
     }
  
    /**
     * The math:random function returns a random number from 0 to 1. 
     *
     * @return A random double from 0 to 1
     */
     public static double random()
     {
       return Math.random();
     }
  
    /**
     * The math:sin function returns the sine of the number. 
     *
     * @param num A number
     * @return The sine value of the number
     */
     public static double sin(double num)
     {
       return Math.sin(num);
     }
  
    /**
     * The math:sqrt function returns the square root of a number. 
     *
     * @param num A number
     * @return The square root of the number
     */
     public static double sqrt(double num)
     {
       return Math.sqrt(num);
     }
  
    /**
     * The math:tan function returns the tangent of the number passed as an argument. 
     *
     * @param num A number
     * @return The tangent value of the number
     */
     public static double tan(double num)
     {
       return Math.tan(num);
     }
  
    /**
     * The math:constant function returns the specified constant to a set precision. 
     * The possible constants are:
     * <pre>
     *  PI
     *  E
     *  SQRRT2
     *  LN2
     *  LN10
     *  LOG2E
     *  SQRT1_2
     * </pre>
     * @param name The name of the constant
     * @param precision The precision
     * @return The value of the specified constant to the given precision
     */
     public static double constant(String name, double precision)
     {
       String value = null;
       if (name.equals("PI"))
         value = PI;
       else if (name.equals("E"))
         value = E;
       else if (name.equals("SQRRT2"))
         value = SQRRT2;
       else if (name.equals("LN2"))
         value = LN2;
       else if (name.equals("LN10"))
         value = LN10;
       else if (name.equals("LOG2E"))
         value = LOG2E;
       else if (name.equals("SQRT1_2"))
         value = SQRT1_2;
       
       if (value != null)
       {
         int bits = new Double(precision).intValue();
         
         if (bits <= value.length())
           value = value.substring(0, bits);
           
         return new Double(value).doubleValue();
       }
       else
         return Double.NaN;
              
     }
        
  }
  