22 Aug
                
                    2016
                
            
            
                22 Aug
                
                '16
                
            
            
            
        
    
                4:50 p.m.
            
        What about an UNSUPPORTED-FUNCTIONALITY ERROR subclass? I was thinking of putting it in UIOP, and exported, for the use of cases where a particular implementation doesn't support an operation. This might make it much easier to handle implementations that don't support all operations, PARTICULARLY in test cases. Best, r