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               <div id="css-table">
  <div id="col-1">
   <ul>
    <li><a href="#col-1-tab-1">Example 8</a></li>
   </ul>
   <div id="col-1-tab-1">
    <article>
    <b>nested HTML comments:</b><br>
    <textarea class="input" id="html-nested">
<!-- empty comment -->
<!-- nested comments
  <div>
    <!-- blah blah comment -->
    <p>blah blah</p>
    <!-- blat blat comment -->
    <p>blat blat</p>
  </div>
-->
<!-- empty comment -->
<!-- more nested comments
  <div>
    <!-- interior nesting
      <!-- foo foo comment -->
      <p>foo foo </p>
    -->
    <!-- bar bar comment -->
    <p>bar bar</p>
  </div>
-->
<!-- empty comment -->
</textarea>
    <button id="translate" >translate</button> <button id="revert" >revert</button>
    </article>
   </div>
  </div>
  <div id="col-2">
   <ul>
    <li><a href="#col-2-tab-1">discussion</a></li>
   </ul>
   <div id="col-2-tab-1">
    <article>
    <b>discussion:</b><br>
    <p>
    This example illustrates several unique features of <b>apg-exp</b>.
    <ul>
    <li><b>recursion:</b> <a href="https://codepen.io/apg-exp/pen/RaJbaj">Example 6</a> covers the basics on recursion.
    Here it is used to find nested HTML comments.
    The panel at right shows the two recursive pattern syntaxes used.</li>
    <li><b>global mode:</b> This lets us iterate over all occurrences of nested comments in the sample HTML.</li>
    <li><b>the result.rules object:</b> The result.rules object facilitates locating and working
    with the named sub-phrases within the matched phrase.</li>
    </ul>
    </p>
    <p>
    How it works.
    <ul>
    <li><b>the translate button:</b>
    <ul><li>
    Calls the function <code>translate()</code> which iterates over all HTML comments, whether nested or not.
    </li><li>
    For each comment, calls <code>translateComment()</code> which converts any inner, nested comments
    from <span class="nowrap"><code>&lt;!-- --&gt;</code></span> to <span class="nowrap"><code>&lt;!~~ ~~&gt;</code></span>.
    The conversion is done "in place" in a copy of the input string character code array.
    </li></ul>
    </li> 
    <li><b>the revert button:</b>
    <ul><li>
    Calls the function <code>revert()</code> which iterates over all converted HTML comments, whether nested or not.
    </li><li>
    For each converted comment, calls <code>revertComment()</code> which converts all translated comments
    from <span class="nowrap"><code>&lt;!~~ ~~&gt;</code></span> back to <span class="nowrap"><code>&lt;!-- --&gt;</code></span>.
    The conversion is done "in place" in a copy of the input string character code array.
    </li></ul>
    </li>
    </ul>
    </p>
    </article>
   </div>
  </div>
  <div id="col-3">
   <ul>
    <li><a href="#col-3-tab-1">patterns</a></li>
   </ul>
   <div id="col-3-tab-1">
    <article>
    <b>nested pattern syntax:</b><br>
    <textarea class="input" id="nested-pattern" disabled>
</textarea>
    <p>
    <b>revert pattern syntax:</b><br>
    <textarea class="input" id="revert-pattern" disabled>
</textarea>
    </p>
    </article>
   </div>
  </div>
 </div>

            
          
!
            
              /* Pen-specific styles */
* {
  box-sizing: border-box;
}

body {
  color: #000;
  font-size: .8rem;
  line-height: 150%;
}

h1 {
  font-size: 1.75rem;
  margin: 0 0 0.75rem 0;
  font-family: 'Open Sans', sans-serif;
  font-weight: 700;
}

h2 {
  font-family: 'Open Sans', sans-serif;
  font-weight: 700;
}

article {
  font-family: 'Open Sans', sans-serif;
  font-weight: 400;
}

b {
  font-family: 'Open Sans', sans-serif;
  font-weight: 700;
}

i {
  font-family: 'Open Sans', sans-serif;
  font-style: italic;
}

textarea {
  width: 100%;
}

button {
  font-size: 1em;
  cursor: pointer;
  cursor: hand;
  margin: 0px 0px 2px 0px;
  width: 6em;
}

p.title {
  margin: 0px 0px 3px 0px;
}

a.link {
  color: #4284B0;
}

a.link:visited {
  color: #9c4be7;
}

/* Pattern styles */
#css-table {
	display: table;
	width: 100%;
}

#col-1 {
	display: table-cell;
	width: 30%;
	border: 1px solid #4284B0;
}

#col-2 {
	display: table-cell;
	width: 40%;
	border-width: 1px 0px;
	border-style: solid;
	border-color: #4284B0;
}

#col-3 {
	display: table-cell;
	width: 30%;
	border: 1px solid #4284B0;
}

textarea.input {
	font-size: .9rem;
	font-family: monospace;
	height: 20rem;
}
textarea#nested-pattern, textarea#revert-pattern {
  height: 8rem;
}

span.nowrap{
	white-space: nowrap;
}

            
          
!
            
              var strings = {};
var exp = {};
var $translate, $revert, $htmlNested;

// convert array of character codes to string
var arrayToString = function(array){
  var string = "";
  for(var i = 0; i < array.length; i += 1){
    string += String.fromCharCode(array[i]);
  }
  return string;
}

// convert a string to an array of character codes
var stringToArray = function(string){
  var array = [];
  for(var i = 0; i < string.length; i += 1){
    array.push(string.charCodeAt(i));
  }
  return array;
}

// replace all but the first <!-- with <!~~ and all but the last --> with ~~> 
var translateComment = function(input, result){
  for(var i = 1; i < result.rules["L"].length; i += 1){
    var beg = result.rules["L"][i].index;
    // replace "-" (45) with "~" (126)
    input[beg+2] = 126;
    input[beg+3] = 126;
  }
  for(var i = 0; i < result.rules["L"].length-1; i += 1){
    var beg = result.rules["R"][i].index;
    // replace "-" (45) with "~" (126)
    input[beg] = 126;
    input[beg+1] = 126;
  }
}

// replace all <!~~ with <!-- and all ~~> with -->
var revertComment = function(input, result){
  for(var i = 0; i < result.rules["L"].length; i += 1){
    var beg = result.rules["L"][i].index;
    // replace "~" (126) with "-" (45) 
    input[beg+2] = 45;
    input[beg+3] = 45;
    beg = result.rules["R"][i].index;
    input[beg] = 45;
    input[beg+1] = 45;
  }
}

// translate interior nested HTML comments to <!~~ ~~>
var translate = function(){
  var str = $htmlNested.val();
  var result = exp.nested.exec(str);
  var input = result ? stringToArray(str) : [];
  while(result){
    translateComment(input, result);
    result = exp.nested.exec(str);
  }
  if(input.length > 0){
    $htmlNested.val(arrayToString(input));
  }
}

// revert <!~~ ~~> to <!-- --> for all levels of nesting
var revert = function(){
  var str = $htmlNested.val();
  var result = exp.revert.exec(str);
  var input = result ? stringToArray(str) : [];
  while(result){
    revertComment(input, result);
    result = exp.revert.exec(str);
  }
  if(input.length > 0){
    $htmlNested.val(arrayToString(input));
  }
}
$(document).ready(function() {
  // nested comment pattern syntax
  strings.nested = '';
  strings.nested += 'P    = L text 1*(P text) R / L text R\n';
  strings.nested += 'L    = "<!--"\n';
  strings.nested += 'R    = "-->"\n';
  strings.nested += 'text = *(!L !R any)\n';
  strings.nested += 'any  = %d32-126 / %d9-10 / %d13\n';
  
  // nested, converted comment pattern syntax
  strings.revert = '';
  strings.revert += 'P    = L text 1*(P text) R / L text R\n';
  strings.revert += 'L    = "<!~~"\n';
  strings.revert += 'R    = "~~>"\n';
  strings.revert += 'text = *(!L !R any)\n';
  strings.revert += 'any  = %d32-126 / %d9-10 / %d13\n';

  // global mode for iterating over all occurrences
  exp.nested = new ApgExp(strings.nested, "g");
  exp.revert = new ApgExp(strings.revert, "g");
  
  // the jQuery objects
  $translate = $("#translate");
  $translate.click(translate);
  $revert = $("#revert")
  $revert.click(revert);
  $htmlNested = $("#html-nested")

  // page setup
  $("#nested-pattern").val(strings.nested);
  $("#revert-pattern").val(strings.revert);
  $("#col-1").tabs();
  $("#col-2").tabs();
  $("#col-3").tabs();
});

            
          
!
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