Re: printf issue with thousands separator

[Dr . Jürgen Sauermann]

Hi Christian,

thanks for the info. The problem is, though, that calling setlocale()
in GNU APL is problematic since I cannot possibly know beforehand
what the locale of the user will be. And I cannot know all peculiarities
of all possible locales. In our case the thousands separator comes
after every 3 digits, but rumour has it that, for example, China has
 a different scheme where the grouping size varies along the number.

For these and other reasons (serious portability concerns on different
platforms) I removed support for locales in GNU APL 1.2 (around 2014).

Since then GNU APL relies on the C standard which says that the default
locale for all C programs is "C" and, as a consequence, GNU APL runs
under the C locale.

Unfortunately the C locale has no thousands separator:

#include <stdio.h>
#include <locale.h>

int
main(int argc, char *argv[])
{
   setlocale (LC_NUMERIC, "C.UTF-8");

   printf("%'f\n", 555555.66);
}

which prints:

555555.660000

I believe that using the C locale is arguably better than e.g. reading
the environment variables related to locales because it makes the
behaviour of GNU APL more predictable across different platforms.

I find it somewhat inconsistent if a programmer can explicitly request
the output of the thousands separators with the ' flag and that glibc
may then not follow suit because of the locale.

Best Regards,
Jürgen

 

On 7/6/22 1:33 AM, Christian Robert wrote:

Jürgen,

#include <stdio.h>
#include <locale.h>

int
main(int argc, char *argv[])
{
   setlocale (LC_NUMERIC, "en_US.utf8");

   printf("%'f\n", 555555.66);
}

print:

555,555.660000


my 2 cents...

Xtian.


On 2022-07-05 12:40, Dr. Jürgen Sauermann wrote:

Hi Martin,

I believe I understood your problem now. As far as *⎕FIO* is concerned it should be fixed
in *SVN 1579*:

*      "%'.2f" ⎕FIO.sprintf 1234567.89**
**1,234,567.89**
*

There could be a misunderstanding as to how 'Format by example' works (and that misunderstanding
might also be caused by my testcases). What the APL2 calls a left or right "decorator" is not intended
as an arbitrary string in the printf() fashion, but something that is directly attached (and possibly
suppressed) to a number. In most cases the left decorator is either the minus sign or the overbar and
the right decorator is not used. The rare exceptions where the right decorator is used are:

1. negative numbers printed in parentheses instead of a minus sign. Sometimes used in bookkeeping.
2. output of negative numbers in a different color (typically red) using VT100 escape sequences as
left and right decorators.

In the examples that you apparently tried there were 2 left decorators (one being the $
and the other being the minus sign) and Format by example simply does not allow that.

The problem with ⎕FIO was actually caused by glibc which apparently ignores  the ' flag even
if the locale tells otherwise, On my machine (and in plain C):

*int
main(int argc, char *argv[])
{
    printf("%'f\n", 555555.66);
}
*
prints:

*555555.660000*

I did already pass the ' flag to *sprintf() *in glibc but glibc then simply ignored it.

Best Regards,
Jürgen



On 7/5/22 10:08 AM, Martin Michel wrote:

Hi Jürgen,

thanks for your quick reply.

I will look into adding support for the thousands separator (but not supporting the
locales nonsense). That is, the thousands separator will always be comma and not
e.g. full-stop like in some countries and comma in others.

That would be great and I fully agree, locales support would be too much
of a requirement.

BTW format by example should have done the job (see the APL2 language
reference page 140):


       "5,555.50" ⍕ 1234.56
1,234.56

Well, I tried this but it only works for the simpler cases. I could
manage to format figures with the currency symbol on the right side but
the format by examples falls short if I want it on the left, combined
with negative numbers and also rounding (e.g. no decimal point in
example spec).

So this works:

       ' -1,555,555.40 $' ⍕ 123456.789 ¯987654.12
      123,456.79 $   -987,654.12 $

But I have not found anything which would give me these results:

     $ +123,457   $ -987,654

As far as I have understood IBM APL2 Language Reference this is not
possible with format by example. I would be happy if you can convince me
otherwise, then I would indeed not need ⎕FIO.

Kind regards,
Martin