Meandering Thought

I've been playing around with recursive functions in actionscript for a bit now and yesterday came across this pretty cool one for reversing a string.  The code follows :  

 
function Reverse(s : String ) :  String {
	var tmp : String = null;
 
   if ( s.length == 1 )  return s;
   else
   {
	   var sLast 		: String = s.substr( s.length -1, s.length );
	   var sRemainder 	: String = s.substr( 0, s.length -1 );
	  tmp = sLast + Reverse( sRemainder );
	  return tmp;
   }
}
 
var str : String = "abcdef";
trace( Reverse( str ) );
 

This little diagram I drew out helped me understand what the execution stack looked like :