the terminal bell, obeying the setting of 'bell-style'.

 -- Function: int rl_alphabetic (int c)
     Return 1 if C is an alphabetic character.

 -- Function: void rl_display_match_list (char **matches, int len, int
          max)
     A convenience function for displaying a list of strings in columnar
     format on Readline's output stream.  'matches' is the list of
     strings, in argv format, such as a list of completion matches.
     'len' is the number of strings in 'matches', and 'max' is the
     length of the longest string in 'matches'.  This function uses the
     setting of 'print-completions-horizontally' to select how the
     matches are displayed (*note Readline Init File Syntax::).  When
     displaying completions, this function sets the number of columns
     used for display to the value of 'completion-display-width', the
     value of the environment variable 'COLUMNS', or the screen width,
     in that order.

   The following are implemented as macros, defined in 'chardefs.h'.
Applications should refrain from using them.

 -- Function: int _rl_uppercase_p (int c)
     Return 1 if C is an uppercase alphabetic character.

 -- Function: int _rl_lowercase_p (int c)
     Return 1 if C is a lowercase alphabetic character.

 -- Function: int _rl_digit_p (int c)
     Return 1 if C is a numeric character.

 -- Function: int _rl_to_upper (int c)
     If C is a lowercase alphabetic character, return the corresponding
     uppercase character.

 -- Function: int _rl_to_lower (int c)
     If C is an uppercase alphabetic character, return the corresponding
     lowercase character.

 -- Function: int _rl_digit_value (int c)
     If C is a number, return the value it represents.