Re: RFC: String interpolation

[Paul Eggert]

On 12/13/2016 09:42 AM, Richard Stallman wrote:
> We have seen various proposals for what string interpolation should do.
> What spec does your patch implement?

It implements Lars's proposal here:

http://lists.gnu.org/archive/html/emacs-devel/2016-12/msg00504.html

His example:

(format "Altitude= %.2f%" (+ alt 100) ", direction = %.2f%" (- dir) ".")

might generate:

"Altitude= 400.57, direction = -240.93."

The idea is that if a format string's first conversion specifier is 
followed by "%" and end-of-string, the value to be formatted is followed 
by another format string that continues the first string. This is an 
extension to the current behavior of 'format', where the trailing "%" is 
an error.

Similar rules apply to other formatting functions like 'message'. For 
example, this code in org-clock.el:

      (message (concat "Clock stopped at %s after "
                       (org-minutes-to-clocksum-string (+ (* 60 h) m)) 
"%s")
               te (if remove " => LINE REMOVED" ""))

could be rewritten this way:

      (message "Clock stopped at %s%" te
               " after %s%" (org-minutes-to-clocksum-string (+ (* 60 h) 
m))
               "%s" (if remove " => LINE REMOVED" ""))