text: /**
   * The selector css3 module provides support for css3 selectors.
   * @module dom
   * @submodule selector-css3
   * @for Selector
   */
  
  /*
      an+b = get every _a_th node starting at the _b_th
      0n+b = no repeat ("0" and "n" may both be omitted (together) , e.g. "0n+1" or "1", not "0+1"), return only the _b_th element
      1n+b =  get every element starting from b ("1" may may be omitted, e.g. "1n+0" or "n+0" or "n")
      an+0 = get every _a_th element, "0" may be omitted 
  */
  
  Y.Selector._reNth = /^(?:([\-]?\d*)(n){1}|(odd|even)$)*([\-+]?\d*)$/;
  
  Y.Selector._getNth = function(node, expr, tag, reverse) {
      Y.Selector._reNth.test(expr);
      var a = parseInt(RegExp.$1, 10), // include every _a_ elements (zero means no repeat, just first _a_)
          n = RegExp.$2, // "n"
          oddeven = RegExp.$3, // "odd" or "even"
          b = parseInt(RegExp.$4, 10) || 0, // start scan from element _b_
          result = [],
          siblings = Y.Selector._children(node.parentNode, tag),
          op;
  
      if (oddeven) {
          a = 2; // always every other
          op = '+';
          n = 'n';
          b = (oddeven === 'odd') ? 1 : 0;
      } else if ( isNaN(a) ) {
          a = (n) ? 1 : 0; // start from the first or no repeat
      }
  
      if (a === 0) { // just the first
          if (reverse) {
              b = siblings.length - b + 1; 
          }
  
          if (siblings[b - 1] === node) {
              return true;
          } else {
              return false;
          }
  
      } else if (a < 0) {
          reverse = !!reverse;
          a = Math.abs(a);
      }
  
      if (!reverse) {
          for (var i = b - 1, len = siblings.length; i < len; i += a) {
              if ( i >= 0 && siblings[i] === node ) {
                  return true;
              }
          }
      } else {
          for (var i = siblings.length - b, len = siblings.length; i >= 0; i -= a) {
              if ( i < len && siblings[i] === node ) {
                  return true;
              }
          }
      }
      return false;
  };
  
  Y.mix(Y.Selector.pseudos, {
      'root': function(node) {
          return node === node.ownerDocument.documentElement;
      },
  
      'nth-child': function(node, expr) {
          return Y.Selector._getNth(node, expr);
      },
  
      'nth-last-child': function(node, expr) {
          return Y.Selector._getNth(node, expr, null, true);
      },
  
      'nth-of-type': function(node, expr) {
          return Y.Selector._getNth(node, expr, node.tagName);
      },
       
      'nth-last-of-type': function(node, expr) {
          return Y.Selector._getNth(node, expr, node.tagName, true);
      },
       
      'last-child': function(node) {
          var children = Y.Selector._children(node.parentNode);
          return children[children.length - 1] === node;
      },
  
      'first-of-type': function(node) {
          return Y.Selector._children(node.parentNode, node.tagName)[0] === node;
      },
       
      'last-of-type': function(node) {
          var children = Y.Selector._children(node.parentNode, node.tagName);
          return children[children.length - 1] === node;
      },
       
      'only-child': function(node) {
          var children = Y.Selector._children(node.parentNode);
          return children.length === 1 && children[0] === node;
      },
  
      'only-of-type': function(node) {
          var children = Y.Selector._children(node.parentNode, node.tagName);
          return children.length === 1 && children[0] === node;
      },
  
      'empty': function(node) {
          return node.childNodes.length === 0;
      },
  
      'not': function(node, expr) {
          return !Y.Selector.test(node, expr);
      },
  
      'contains': function(node, expr) {
          var text = node.innerText || node.textContent || '';
          return text.indexOf(expr) > -1;
      },
  
      'checked': function(node) {
          return (node.checked === true || node.selected === true);
      },
  
      enabled: function(node) {
          return (node.disabled !== undefined && !node.disabled);
      },
  
      disabled: function(node) {
          return (node.disabled);
      }
  });
  
  Y.mix(Y.Selector.operators, {
      '^=': '^{val}', // Match starts with value
      '$=': '{val}$', // Match ends with value
      '*=': '{val}' // Match contains value as substring 
  });
  
  Y.Selector.combinators['~'] = {
      axis: 'previousSibling'
  };
  