Function: map-charset-chars

Call FUNCTION for all characters in CHARSET.
FUNCTION is called with an argument RANGE and the optional 3rd
argument ARG.

RANGE is a cons (FROM . TO), where FROM and TO indicate a range of
characters contained in CHARSET.

The optional 4th and 5th arguments FROM-CODE and TO-CODE specify the
range of code points (in CHARSET) of target characters.

(fn FUNCTION CHARSET &optional ARG FROM-CODE TO-CODE)