Re: compute ISBN-10, char-to-int?

[Perry Smith]

> On Sep 9, 2019, at 12:47 PM, Emanuel Berg via Users list for the GNU Emacs 
> text editor <help-gnu-emacs@gnu.org> wrote:
> 
> Stefan Monnier wrote:
> 
>> (- c ?0) and (+ n ?0) work not just with
>> Unicode code points, but with code points in
>> any character set that is sane enough to put
>> the digits from 0 to 9 consecutively in this
>> order. That's the case in ASCII, EBCDIC, and
>> all other charsets I know.
> 
> EBCDIC = Extended Binary-Coded Decimal Interchange Code
> 
> http://www.barrcentral.com/help/3270/appendix_b._ascii_and_ebcdic_tables.htm?sa=X&ved=2ahUKEwiTptvPpcTkAhWqpIsKHVtRCRgQ9QF6BAgLEAI
> 
> Seems to have something to do with IBM...

IBM has the concept of “code pages”… I think that concept is not unique to IBM. 
 Examples would be all of the ISO-8859-nn code pages where there is one (more 
or less) for each country or region.  (And then you get into terminal specific 
code pages and all sorts of fun mental illnesses).

I wrote a web app talking to an old IBM system and to my shock… EBCDIC also has 
code pages — roughly one per region or country.

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