code: function(root,new$,old,caret) {
  	var k = new$.length;
  	var i = k;
  	var last = new$[k - 1];
  	
  	
  	if (k == old.length && new$[0] === old[0]) {
  		// running through to compare
  		while (i--){
  			if (new$[i] !== old[i]) { break; };
  		};
  	};
  	
  	if (i == -1) {
  		return last && last._slot_ || last || caret;
  	} else {
  		return reconcileCollectionChanges(root,new$,old,caret);
  	};
  }
docs: expects a flat non-sparse array of nodes in both new and old, always