Fwd: Formatted output with locale

[Vladimir Zhbanov <vzhbanov@gmail.com>]

Martin,
I'm sorry for the private reply, my fault :-(
Forward to the list.

---------- Forwarded message ----------
From: Vladimir Zhbanov <vzhbanov@gmail.com>
Date: Mon, 14 Nov 2016 09:03:19 +0300
Subject: Re: Formatted output with locale
To: dev@famic.de

Hi Martin,

On 11/13/16, dev@famic.de <dev@famic.de> wrote:
> Hi there,
> I have problems to get a proper formatting using the (ice-9 format)
> module. In my code, I need to deal with monetary figures, but I fail
> to get the correct format for my German locale.
> Let's say I have one hundred thousand Euros. The correct format to output
> this in de_DE.utf-8 would be
> 100.000,00 EUR
> (with 2 decimals)
>
> Now I tried:
> (setlocale LC_ALL "de_DE.UTF-8")
> (use-modules (ice-9 format))
> (define a 100000.00)
> (format #t "~12,2h EUR~%" a)
> (format #t "~,,12$ EUR~%" a)
> (format #t "~12,2f EUR~%" a)
>
> But this is what Guile gives to me:
>    100.000,0 EUR
>    100000.00 EUR
>    100000.00 EUR
>
> None is correct. What did I miss?
> -Martin

Looking at the `format' code for option `h' I see the procedure
`number->locale-string' is used.

OK, let's do some experiments:

scheme@(guile-user)> (setlocale LC_ALL)
$2 = "ru_RU.UTF-8"
scheme@(guile-user)> ,use (ice-9 i18n)
scheme@(guile-user)> (number->locale-string 10.0 5)
$3 = "10,0"
scheme@(guile-user)> (number->locale-string .00003 2)
$4 = "3,0e"
scheme@(guile-user)> (number->locale-string .00003 1)
$5 = "3,0"
scheme@(guile-user)> (number->locale-string .00003 3)
$6 = "3,0e-"
scheme@(guile-user)> (number->locale-string .0 3)
$7 = "-0,0"
scheme@(guile-user)> (number->locale-string .0 10)
$8 = "-0,0"
scheme@(guile-user)> (number->locale-string .0 1)
$9 = "-0,0"

Now for the procedure monetary-amount->locale-string:

scheme@(guile-user)> (monetary-amount->locale-string .0 #t)
$10 = "-0.0 RUB "
scheme@(guile-user)> (monetary-amount->locale-string 100000.0 #t)
$11 = "100\xa0000.0 RUB "
scheme@(guile-user)> (monetary-amount->locale-string .00003 #t)
$12 = "3.0e RUB "

And my guile version:

scheme@(guile-user)> (version)
$13 = "2.0.11"


It seems `number->locale-string' is broken. If I do, e.g.
  (number->locale-string .00003 10)
it yields
  "3,0e-5"

If the last arg decreases, it just trims the number of
characters after comma, which is wrong in this case.

Output for zero is funny, too.

Regards,
  Vladimir