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From n.@apache.org
Subject cvs commit: httpd-2.0/docs/manual/mod mod_include.html.en mod_include.xml
Date Thu, 28 Aug 2003 15:37:17 GMT
nd          2003/08/28 08:37:17

  Modified:    docs/manual/mod mod_include.html.en mod_include.xml
  Log:
  add information about the == operator, && / || priorities and
  expression optimization/debugging
  
  Revision  Changes    Path
  1.28      +34 -4     httpd-2.0/docs/manual/mod/mod_include.html.en
  
  Index: mod_include.html.en
  ===================================================================
  RCS file: /home/cvs/httpd-2.0/docs/manual/mod/mod_include.html.en,v
  retrieving revision 1.27
  retrieving revision 1.28
  diff -u -r1.27 -r1.28
  --- mod_include.html.en	30 Jun 2003 01:16:32 -0000	1.27
  +++ mod_include.html.en	28 Aug 2003 15:37:16 -0000	1.28
  @@ -507,6 +507,7 @@
         <dd>true if <var>string</var> is not empty</dd>
   
         <dt><code><var>string1</var> = <var>string2</var><br
/>
  +      <var>string1</var> == <var>string2</var><br />
         <var>string1</var> != <var>string2</var></code></dt>
         
         <dd><p>Compare <var>string1</var> with <var>string2</var>.
If
  @@ -514,11 +515,12 @@
         then it is treated as a regular expression. Regular expressions are
         implemented by the <a href="http://www.pcre.org">PCRE</a> engine and
         have the same syntax as those in <a href="http://www.perl.com">perl
  -      5</a>.</p>
  +      5</a>. Note that <code>==</code> is just an alias for <code>=</code>
  +      and behaves exactly the same way.</p>
   
  -      <p>If you are matching positive (<code>=</code>), you can capture
  -      grouped parts of the regular expression. The captured parts are
  -      stored in the special variables <code>$1</code> ..
  +      <p>If you are matching positive (<code>=</code> or <code>==</code>),
you
  +      can capture grouped parts of the regular expression. The captured parts
  +      are stored in the special variables <code>$1</code> ..
         <code>$9</code>.</p>
   
         <div class="example"><h3>Example</h3><p><code>
  @@ -566,6 +568,10 @@
         &lt;!--#if expr="($a = test1) &amp;&amp; ($b = test2)" --&gt;
       </code></p></div>
   
  +    <p>The boolean operators <code>&amp;&amp;</code> and <code>||</code>
  +    share the same priority. So if you want to bind such an operator more
  +    tightly, you should use parentheses.</p>
  +
       <p>Anything that's not recognized as a variable or an operator
       is treated as a string. Strings can also be quoted:
       <code>'string'</code>. Unquoted strings can't contain whitespace
  @@ -578,6 +584,30 @@
         and<br />
         <br />
         <code>'<var>string1</var>&nbsp;&nbsp;&nbsp;&nbsp;<var>string2</var>'</code>
results in <code><var>string1</var>&nbsp;&nbsp;&nbsp;&nbsp;<var>string2</var></code>.</p></div>
  +
  +    <div class="note"><h3>Optimization of Boolean Expressions</h3>
  +      <p>If the expressions become more complex and slow down processing
  +      significantly, you can try to optimize them according to the
  +      evaluation rules:</p>
  +      <ul>
  +      <li>Expressions are evaluated from left to right</li>
  +      <li>Binary boolean operators (<code>&amp;&amp;</code> and
<code>||</code>)
  +          are short circuited whereever possible. In conclusion with the rule
  +          above that means, <code class="module"><a href="../mod/mod_include.html">mod_include</a></code>
evaluates at first
  +          the left expression. If the left result if sufficient to determine
  +          the end result, processing stops here. Otherwise it evaluates the
  +          right side and computes the end result from both left and right
  +          results.</li>
  +      <li>Short circuit evaluation is turned off as long as there are regular
  +          expressions to deal with. These must be evaluated to fill in the
  +          backreference variables (<code>$1</code> .. <code>$9</code>).</li>
  +      </ul>
  +      <p>If you want to look how a particular expression is handled, you can
  +      recompile <code class="module"><a href="../mod/mod_include.html">mod_include</a></code>
using the
  +      <code>-DDEBUG_INCLUDE</code> compiler option. This inserts for every
  +      parsed expression tokenizer information, the parse tree and how it is
  +      evaluated into the output sent to the client.</p>
  +    </div>
   </div>
   <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif"
/></a></div>
   <div class="directive-section"><h2><a name="SSIEndTag" id="SSIEndTag">SSIEndTag</a>
<a name="ssiendtag" id="ssiendtag">Directive</a></h2>
  
  
  
  1.24      +34 -4     httpd-2.0/docs/manual/mod/mod_include.xml
  
  Index: mod_include.xml
  ===================================================================
  RCS file: /home/cvs/httpd-2.0/docs/manual/mod/mod_include.xml,v
  retrieving revision 1.23
  retrieving revision 1.24
  diff -u -r1.23 -r1.24
  --- mod_include.xml	30 Jun 2003 01:07:23 -0000	1.23
  +++ mod_include.xml	28 Aug 2003 15:37:17 -0000	1.24
  @@ -474,6 +474,7 @@
         <dd>true if <var>string</var> is not empty</dd>
   
         <dt><code><var>string1</var> = <var>string2</var><br
/>
  +      <var>string1</var> == <var>string2</var><br />
         <var>string1</var> != <var>string2</var></code></dt>
         
         <dd><p>Compare <var>string1</var> with <var>string2</var>.
If
  @@ -481,11 +482,12 @@
         then it is treated as a regular expression. Regular expressions are
         implemented by the <a href="http://www.pcre.org">PCRE</a> engine and
         have the same syntax as those in <a href="http://www.perl.com">perl
  -      5</a>.</p>
  +      5</a>. Note that <code>==</code> is just an alias for <code>=</code>
  +      and behaves exactly the same way.</p>
   
  -      <p>If you are matching positive (<code>=</code>), you can capture
  -      grouped parts of the regular expression. The captured parts are
  -      stored in the special variables <code>$1</code> ..
  +      <p>If you are matching positive (<code>=</code> or <code>==</code>),
you
  +      can capture grouped parts of the regular expression. The captured parts
  +      are stored in the special variables <code>$1</code> ..
         <code>$9</code>.</p>
   
         <example><title>Example</title>
  @@ -533,6 +535,10 @@
         &lt;!--#if expr="($a = test1) &amp;&amp; ($b = test2)" --&gt;
       </example>
   
  +    <p>The boolean operators <code>&amp;&amp;</code> and <code>||</code>
  +    share the same priority. So if you want to bind such an operator more
  +    tightly, you should use parentheses.</p>
  +
       <p>Anything that's not recognized as a variable or an operator
       is treated as a string. Strings can also be quoted:
       <code>'string'</code>. Unquoted strings can't contain whitespace
  @@ -551,6 +557,30 @@
         >string2</var>'</code> results in <code><var
         >string1</var>&nbsp;&nbsp;&nbsp;&nbsp;<var>string2</var></code>.</p>
       </example>
  +
  +    <note><title>Optimization of Boolean Expressions</title>
  +      <p>If the expressions become more complex and slow down processing
  +      significantly, you can try to optimize them according to the
  +      evaluation rules:</p>
  +      <ul>
  +      <li>Expressions are evaluated from left to right</li>
  +      <li>Binary boolean operators (<code>&amp;&amp;</code> and
<code>||</code>)
  +          are short circuited whereever possible. In conclusion with the rule
  +          above that means, <module>mod_include</module> evaluates at first
  +          the left expression. If the left result if sufficient to determine
  +          the end result, processing stops here. Otherwise it evaluates the
  +          right side and computes the end result from both left and right
  +          results.</li>
  +      <li>Short circuit evaluation is turned off as long as there are regular
  +          expressions to deal with. These must be evaluated to fill in the
  +          backreference variables (<code>$1</code> .. <code>$9</code>).</li>
  +      </ul>
  +      <p>If you want to look how a particular expression is handled, you can
  +      recompile <module>mod_include</module> using the
  +      <code>-DDEBUG_INCLUDE</code> compiler option. This inserts for every
  +      parsed expression tokenizer information, the parse tree and how it is
  +      evaluated into the output sent to the client.</p>
  +    </note>
   </section>
   
   <directivesynopsis>
  
  
  

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