char-set-adjoin!

[procedure] char-set-adjoin cset char1 ...

[procedure] char-set-adjoin! cset char1 ...

SRFI-14: Returns a character set that contains all characters in cset and characters given as char1 .... char-set-adjoin always creates a new character set. char-set-adjoin! may modify cset.

See also char-set-delete, char-set-delete!.