GET_INFO(DEFINED_KEY)

     For an overview of the GET_INFO built-in, see the HELP topic GET_INFO.

     When parameter1 is DEFINED_KEY, the GET_INFO built-in takes a third
     parameter.  The parameter is a string that is the name of the key map
     or key map list to be searched.

     The following strings can be used for parameter2 when parameter1 is the
     keyword DEFINED_KEY:

       Parameter 2       | Return Value (Parameter 1 is keyword DEFINED_KEY)
      -------------------+------------------------------------------------+
       "first"           | Keyname   - First key defined in the specified
                         |             key map or key-map list
                         | 0         - If no keys are defined
       "last"            | Keyname   - Last key defined in the specified
                         |             key map or key-map list
                         | 0         - If no keys are defined
       "next"            | Keyname   - Next key defined in the specified
                         |             key map or key-map list
                         | 0         - If no keys are defined
       "previous"        | Keyname   - Previous key defined in the specified
                         |             key map or key-map list
                         | 0         - If no keys are defined
      -------------------+------------------------------------------------+

      Use string constant "first", before using "next". Use "last" before
      using "previous".