| <chr> | (<mag>) | C | 
| alpha? | (x|<chr> => <log>) | G | 
|  | returns true iff x is one of the ASCII upper or
  lowercase characters. |  | 
| digit? | (x|<chr> => <log>) | G | 
|  | returns true iff x is one of the ten ASCII numeric characters. |  | 
| lower? | (x|<chr> => <log>) | G | 
|  | returns true iff x is one of the ASCII lowercase characters. |  | 
| upper? | (x|<chr> => <log>) | G | 
|  | returns true iff x is one of the ASCII uppercase characters. |  | 
| to-digit | (x|<chr> => <int>) | G | 
|  | converts ascii representation of digit to an integer one. |  | 
| to-lower | (x|<chr> => <chr>) | G | 
|  | returns lowercase version of uppercase alphabetic 
  characters otherwise returns x. |  | 
| to-upper | (x|<chr> => <chr>) | G | 
|  | returns uppercase version of lowercase alphabetic 
  characters otherwise returns x. |  | 
|  |