230: Mainline

Here is a look at the four calls involved when the recursive_power_of_2 function is set to work on 3:

Arguments      |     ^      Returned values 
            3  |     |  8   
               v     | 
           *-------------* 
           | First call  | 
           *-------------* 
            2  |     ^  4  
               v     | 
           *-------------* 
           | Second call | 
           *-------------* 
            1  |     ^  2  
               v     | 
           *-------------* 
           | Third call  | 
           *-------------* 
            0  |     ^  1  
               v     | 
           *-------------* 
           | Fourth call | 
           *-------------*