/**
  * Initializes the $comparators field.
  * 
  * @since 1.5.3
  */
 protected static function initializeComparators()
 {
     global $smwgQComparators, $smwStrictComparators;
     static $initialized = false;
     if ($initialized) {
         return;
     }
     $initialized = true;
     // Note: Comparators that contain other comparators at the beginning of the string need to be at beginning of the array.
     $comparators = array('!~' => SMW_CMP_NLKE, '<<' => SMW_CMP_LESS, '>>' => SMW_CMP_GRTR, '<' => $smwStrictComparators ? SMW_CMP_LESS : SMW_CMP_LEQ, '>' => $smwStrictComparators ? SMW_CMP_GRTR : SMW_CMP_GEQ, '≤' => SMW_CMP_LEQ, '≥' => SMW_CMP_GEQ, '!' => SMW_CMP_NEQ, '~' => SMW_CMP_LIKE);
     $allowedComparators = explode('|', $smwgQComparators);
     // Remove the comparators that are not allowed.
     foreach ($comparators as $string => $comparator) {
         if (!in_array($string, $allowedComparators)) {
             unset($comparators[$string]);
         }
     }
     self::$comparators = $comparators;
 }