Re: (format "Hello %1$S%2$s" 'world "!")

[Noam Postavsky <npostavs@users.sourceforge.net>]

On Sun, Jul 2, 2017 at 12:32 PM, Clément Pit-Claudel
<cpitclaudel@gmail.com> wrote:
>> Why would we need a new function since %n$ would be an error for the old format anyway?
>
> This in itself is a good reason to have a new function.  A new function lets you migrate existing code, including plugins, to the new syntax, and load the polyfill in older Emacsen.  A new syntax that causes errors in old Emacsen isn't usable by anyone outside of Emacs core, for fear of compatibility problems.

We can still give a new name I suppose.

> The ones I'm familiar with use $1, {1}, or similar syntax,

What's the equivalent of %1$d in that syntax? Or is it just strings?

> but I've never seen %1$s :/

It's a POSIX extension to C's printf [1,2], also used by Java [3] and perl [4].

[1]: http://pubs.opengroup.org/onlinepubs/9699919799/functions/printf.html
[2]: https://en.wikipedia.org/wiki/Printf_format_string
[3]: https://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html
[4]: https://perldoc.perl.org/functions/sprintf.html