Re: RFC: locale-sensitive Emacs functions

[Paul Eggert <eggert@cs.ucla.edu>]

Gdobbins wrote:
> In Common Lisp, such directives use : rather than ', but more importantly they also take arguments to specify the grouping and the separation character.

The ' flag is the only printf flag that the POSIX printf function supports but 
the Emacs 'format' function does not. When I looked into this a while ago I 
remember concluding that I was glad I didn't have to write code to support the ' 
flag, as it would require messing with the LC_NUMERIC locale setting (currently 
hardwired to "C" for other good reasons) and would make for some work redoing 
carefully-calculated output buffer sizes internal to 'format', not to mention 
the character set conversion that would be required.

For what it's worth, the Common Lisp approach cannot handle the Indian numbering 
system, which has a comma every two digits except that the last grouping 
contains three digits (e.g., "12,34,56,789"). This is something that POSIX can do.