code: function _cycle_p(node, stack){
  	var ret = false;
  
  	var id = node.id();
  	each(stack,
  	     function(item){
  		 if( item == id ){
  		     ret = true;
  		 }
  	     });
  
  	return ret;
      }
docs: Detect a cycle by seeing if the ID in question appears in the search history stack. TODO/BUG: make this less hyper-dumb and/or slow.