Localized number output with format ~h

[Ludovic Courtès]

Hello Guilers!

Our beloved ‘format’ now supports locale-dependent number output, using
the new ~h format specifier:

    ~h
          Localized number(1).  Parameters: WIDTH, DECIMALS, PADCHAR.

          Like ~f, output an exact or floating point number, but do so
          according to the current locale, or according to the given
          locale object when the `:' modifier is used (*note
          `number->locale-string': Number Input and Output.).

               (format #t "~h" 12345.5678)  ; with "C" as the current locale
               -| 12345.5678

               (format #t "~14,,'*:h" 12345.5678
                       (make-locale LC_ALL "en_US"))
               -| ***12,345.5678

               (format #t "~,2:h" 12345.5678
                       (make-locale LC_NUMERIC "fr_FR"))
               -| 12 345,56

The difference with ~f is that it doesn’t have the SCALE and
OVERFLOWCHAR parameters (it would be doable but seems overkill to me),
and it supports the ‘:’ modifier to specify a locale object.

I would appreciate comments on the interface, since it will basically be
around forever.

Also, if you’re aware of other Schemes that have a ‘format’-like
procedure that supports localized number output, it may be a good idea
to try to choose an interface close to theirs (like using a whatever
letter they use instead of ~h.)

Thanks!

Ludo’.