Questions regarding char-table-range RANGE arg

[Federico Tedin]

Hi everyone,

I was trying to understand better how char tables work but I got stuck 
at the following:

In the docs for `char-table-range' 
(https://www.gnu.org/software/emacs/manual/html_node/elisp/Char_002dTables.html), 
it is mentioned
that it is possible to specify (from . to) as the value for RANGE. This 
already seemed a bit unexpected for me, as the function
is supposed to retrieve a single value from the char table - how could 
it do it for a range, where potentially many different values
could be defined? I did some tests:

(setq tt (make-char-table nil))

(set-char-table-range tt (cons 10 20) "foo")
(set-char-table-range tt (cons 21 25) "bar")

(char-table-range tt (cons 5 15)) ; includes some "foo" values?
  -> nil ; no

(char-table-range tt (cons 10 15)) ; includes some "foo" values?
  -> "foo" ; yes, makes sense

(char-table-range tt (cons 15 22)) ; includes some "foo" and "bar" values?
  -> "foo" ; ok, only the first range was considered

(char-table-range tt (cons 15 0)) ; what if I set `to' to a nonsensical 
value?
  -> "foo"

(char-table-range tt (cons 15 99999)) ; or this one
  -> "foo"

(char-table-range tt (cons 26 30)) ; should return nil
  -> nil ; ok

So from my tests it seems like only `from' is considered? Similar to the 
case where RANGE is just a character. I was hoping someone
with a better understanding of character tables could maybe explain the 
behaviour observed above. It is possible it could me just
missinterpreting the documentation (I am trying to keep a more end-user 
perspective for this, i.e. not look at the Emacs source code
and only use documentation). I did try looking also into 
chartab-tests.el though but could not find more information there.

Thanks!