ExsltMath


1   /*
2    * Copyright 1999-2004 The Apache Software Foundation.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  /*
17   * $Id: ExsltMath.java,v 1.12 2004/02/11 17:56:36 minchau Exp $
18   */
19  package org.apache.xalan.lib;
20  
21  import org.apache.xpath.NodeSet;
22  
23  import org.w3c.dom.Node  ;
24  import org.w3c.dom.NodeList  ;
25  
26  /**
27   * This class contains EXSLT math extension functions.
28   * It is accessed by specifying a namespace URI as follows:
29   * <pre>
30   *    xmlns:math="http://exslt.org/math"
31   * </pre>
32   * 
33   * The documentation for each function has been copied from the relevant
34   * EXSLT Implementer page.
35   * 
36   * @see <a HREF="http://www.exslt.org/">EXSLT</a>
37  
38   * @xsl.usage general
39   */
40  public class ExsltMath extends ExsltBase
41  {
42    // Constants
43    private static String   PI = "3.1415926535897932384626433832795028841971693993751";
44    private static String   E  = "2.71828182845904523536028747135266249775724709369996";
45    private static String   SQRRT2 = "1.41421356237309504880168872420969807856967187537694";
46    private static String   LN2 = "0.69314718055994530941723212145817656807550013436025";
47    private static String   LN10 = "2.302585092994046";
48    private static String   LOG2E = "1.4426950408889633";
49    private static String   SQRT1_2 = "0.7071067811865476";
50      
51    /**
52     * The math:max function returns the maximum value of the nodes passed as the argument. 
53     * The maximum value is defined as follows. The node set passed as an argument is sorted 
54     * in descending order as it would be by xsl:sort with a data type of number. The maximum 
55     * is the result of converting the string value of the first node in this sorted list to 
56     * a number using the number function. 
57     * <p>
58     * If the node set is empty, or if the result of converting the string values of any of the 
59     * nodes to a number is NaN, then NaN is returned.
60     * 
61     * @param nl The NodeList for the node-set to be evaluated.
62     * 
63     * @return the maximum value found, NaN if any node cannot be converted to a number.
64     * 
65     * @see <a HREF="http://www.exslt.org/">EXSLT</a>
66     */
67    public static double max (NodeList   nl)
68    {
69      if (nl == null || nl.getLength() == 0)
70        return Double.NaN;
71        
72      double m = - Double.MAX_VALUE;
73      for (int i = 0; i < nl.getLength(); i++)
74      {
75        Node   n = nl.item(i);
76        double d = toNumber(n);
77        if (Double.isNaN(d))
78          return Double.NaN;
79        else if (d > m)
80          m = d;
81      }
82      
83      return m;   
84    }
85  
86    /**
87     * The math:min function returns the minimum value of the nodes passed as the argument. 
88     * The minimum value is defined as follows. The node set passed as an argument is sorted 
89     * in ascending order as it would be by xsl:sort with a data type of number. The minimum 
90     * is the result of converting the string value of the first node in this sorted list to 
91     * a number using the number function. 
92     * <p>
93     * If the node set is empty, or if the result of converting the string values of any of 
94     * the nodes to a number is NaN, then NaN is returned.
95     * 
96     * @param nl The NodeList for the node-set to be evaluated.
97     * 
98     * @return the minimum value found, NaN if any node cannot be converted to a number.
99     * 
100    * @see <a HREF="http://www.exslt.org/">EXSLT</a>
101    */
102   public static double min (NodeList   nl)
103   {
104     if (nl == null || nl.getLength() == 0)
105       return Double.NaN;
106 
107     double m = Double.MAX_VALUE;
108     for (int i = 0; i < nl.getLength(); i++)
109     {
110       Node   n = nl.item(i);
111       double d = toNumber(n);
112       if (Double.isNaN(d))
113         return Double.NaN;
114       else if (d < m)
115         m = d;
116     }
117     
118     return m;
119   }
120   
121   /**
122    * The math:highest function returns the nodes in the node set whose value is the maximum 
123    * value for the node set. The maximum value for the node set is the same as the value as 
124    * calculated by math:max. A node has this maximum value if the result of converting its 
125    * string value to a number as if by the number function is equal to the maximum value, 
126    * where the equality comparison is defined as a numerical comparison using the = operator.
127    * <p>
128    * If any of the nodes in the node set has a non-numeric value, the math:max function will 
129    * return NaN. The definition numeric comparisons entails that NaN != NaN. Therefore if any 
130    * of the nodes in the node set has a non-numeric value, math:highest will return an empty 
131    * node set. 
132    * 
133    * @param nl The NodeList for the node-set to be evaluated.
134    * 
135    * @return node-set with nodes containing the maximum value found, an empty node-set
136    * if any node cannot be converted to a number.
137    */
138   public static NodeList   highest (NodeList   nl)
139   {        
140     double maxValue = max(nl);
141 
142     NodeSet highNodes = new NodeSet();
143     highNodes.setShouldCacheNodes(true);    
144     
145     if (Double.isNaN(maxValue))
146       return highNodes;  // empty Nodeset
147     
148     for (int i = 0; i < nl.getLength(); i++)
149     {
150       Node   n = nl.item(i);
151       double d = toNumber(n); 
152       if (d == maxValue)
153         highNodes.addElement(n);
154     }
155     return highNodes;
156   }
157   
158   /**
159    * The math:lowest function returns the nodes in the node set whose value is the minimum value 
160    * for the node set. The minimum value for the node set is the same as the value as calculated 
161    * by math:min. A node has this minimum value if the result of converting its string value to 
162    * a number as if by the number function is equal to the minimum value, where the equality 
163    * comparison is defined as a numerical comparison using the = operator.
164    * <p>
165    * If any of the nodes in the node set has a non-numeric value, the math:min function will return 
166    * NaN. The definition numeric comparisons entails that NaN != NaN. Therefore if any of the nodes 
167    * in the node set has a non-numeric value, math:lowest will return an empty node set.
168    * 
169    * @param nl The NodeList for the node-set to be evaluated.
170    * 
171    * @return node-set with nodes containing the minimum value found, an empty node-set
172    * if any node cannot be converted to a number.
173    * 
174    */
175   public static NodeList   lowest (NodeList   nl)
176   {
177     double minValue = min(nl);
178 
179     NodeSet lowNodes = new NodeSet();
180     lowNodes.setShouldCacheNodes(true);
181     
182     if (Double.isNaN(minValue))
183       return lowNodes;  // empty Nodeset
184     
185     for (int i = 0; i < nl.getLength(); i++)
186     {
187       Node   n = nl.item(i);
188       double d = toNumber(n); 
189       if (d == minValue)
190         lowNodes.addElement(n);
191     }
192     return lowNodes;
193   }
194   
195   /**
196    * The math:abs function returns the absolute value of a number.
197    *
198    * @param num A number
199    * @return The absolute value of the number
200    */
201    public static double abs(double num)
202    {
203      return Math.abs(num);
204    }
205 
206   /**
207    * The math:acos function returns the arccosine value of a number.
208    *
209    * @param num A number
210    * @return The arccosine value of the number
211    */
212    public static double acos(double num)
213    {
214      return Math.acos(num);
215    }
216 
217   /**
218    * The math:asin function returns the arcsine value of a number. 
219    *
220    * @param num A number
221    * @return The arcsine value of the number
222    */
223    public static double asin(double num)
224    {
225      return Math.asin(num);
226    }
227 
228   /**
229    * The math:atan function returns the arctangent value of a number. 
230    *
231    * @param num A number
232    * @return The arctangent value of the number
233    */
234    public static double atan(double num)
235    {
236      return Math.atan(num);
237    }
238   
239   /**
240    * The math:atan2 function returns the angle ( in radians ) from the X axis to a point (y,x). 
241    *
242    * @param num1 The X axis value
243    * @param num2 The Y axis value
244    * @return The angle (in radians) from the X axis to a point (y,x)
245    */
246    public static double atan2(double num1, double num2)
247    {
248      return Math.atan2(num1, num2);
249    }
250 
251   /**
252    * The math:cos function returns cosine of the passed argument. 
253    *
254    * @param num A number
255    * @return The cosine value of the number
256    */
257    public static double cos(double num)
258    {
259      return Math.cos(num);
260    }
261 
262   /**
263    * The math:exp function returns e (the base of natural logarithms) raised to a power. 
264    *
265    * @param num A number
266    * @return The value of e raised to the given power
267    */
268    public static double exp(double num)
269    {
270      return Math.exp(num);
271    }
272 
273   /**
274    * The math:log function returns the natural logarithm of a number. 
275    *
276    * @param num A number
277    * @return The natural logarithm of the number
278    */
279    public static double log(double num)
280    {
281      return Math.log(num);
282    }
283 
284   /**
285    * The math:power function returns the value of a base expression taken to a specified power. 
286    *
287    * @param num1 The base
288    * @param num2 The power
289    * @return The value of the base expression taken to the specified power
290    */
291    public static double power(double num1, double num2)
292    {
293      return Math.pow(num1, num2);
294    }
295 
296   /**
297    * The math:random function returns a random number from 0 to 1. 
298    *
299    * @return A random double from 0 to 1
300    */
301    public static double random()
302    {
303      return Math.random();
304    }
305 
306   /**
307    * The math:sin function returns the sine of the number. 
308    *
309    * @param num A number
310    * @return The sine value of the number
311    */
312    public static double sin(double num)
313    {
314      return Math.sin(num);
315    }
316 
317   /**
318    * The math:sqrt function returns the square root of a number. 
319    *
320    * @param num A number
321    * @return The square root of the number
322    */
323    public static double sqrt(double num)
324    {
325      return Math.sqrt(num);
326    }
327 
328   /**
329    * The math:tan function returns the tangent of the number passed as an argument. 
330    *
331    * @param num A number
332    * @return The tangent value of the number
333    */
334    public static double tan(double num)
335    {
336      return Math.tan(num);
337    }
338 
339   /**
340    * The math:constant function returns the specified constant to a set precision. 
341    * The possible constants are:
342    * <pre>
343    *  PI
344    *  E
345    *  SQRRT2
346    *  LN2
347    *  LN10
348    *  LOG2E
349    *  SQRT1_2
350    * </pre>
351    * @param name The name of the constant
352    * @param precision The precision
353    * @return The value of the specified constant to the given precision
354    */
355    public static double constant(String   name, double precision)
356    {
357      String   value = null;
358      if (name.equals("PI"))
359        value = PI;
360      else if (name.equals("E"))
361        value = E;
362      else if (name.equals("SQRRT2"))
363        value = SQRRT2;
364      else if (name.equals("LN2"))
365        value = LN2;
366      else if (name.equals("LN10"))
367        value = LN10;
368      else if (name.equals("LOG2E"))
369        value = LOG2E;
370      else if (name.equals("SQRT1_2"))
371        value = SQRT1_2;
372      
373      if (value != null)
374      {
375        int bits = new Double  (precision).intValue();
376        
377        if (bits <= value.length())
378          value = value.substring(0, bits);
379          
380        return new Double  (value).doubleValue();
381      }
382      else
383        return Double.NaN;
384             
385    }
386       
387 }
388
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