The following works as expected but the format string will end hard-coded:

import std.stdio;
import std.format;

void main (

) {

int intAmount = 1234567;

writeln(format("%,d", intAmount)); /// eg: 1,234,567

}

I tried something like:

import std.stdio;
import std.format;
import core.stdc.locale;

void main (

) {

setlocale(LC_ALL, "");

int intAmount = 1234567;

writeln(format("%`d", intAmount)); /// please, note the backtick instead of ,

}

... to no avail :(

On Tuesday, 25 May 2021 at 22:37:25 UTC, someone wrote:

From the documentation of formattedWrite:

So the syntax you want is:

writeln(format("%,?d", '`', intAmount));

On Tuesday, 25 May 2021 at 23:41:39 UTC, Paul Backus wrote:

writeln(format("%,?d", '`', intAmount));

Thanks for your reply, but no, let me clarify:

I do not want 123`456`789 or whatever else custom delimiter.

I just want to output what is already set in the LC_ALL locale environment variable which in my case results in 123,456,789 which of course I can mimic hard-coding it, but the idea is ... quite the opposite.

The ` (backtick) I used in my example was from another example I found somewhere on the net saying that, when you use the backtick character after issuing a setlocale() call, you'll get the output accordingly to the LC_ALL variable. Needless to say I am not sure whether this is correct or not because the documentation I came across is confusing to say the least; furthermore, someone saying not every implementation is compatible with this behavior and someone else claiming it works for POSIX or the reverse I do not remember correctly right now.

I do not need to use std.format.format().

I can welcome any other function in the standard library to achieve this.

On Wednesday, 26 May 2021 at 00:18:29 UTC, someone wrote:

In that case, you will want to use the C library functions from core.stdc.stdio.

On Wednesday, 26 May 2021 at 00:40:30 UTC, Paul Backus wrote:

import core.stdc.stdio;
import core.stdc.locale;

import std.stdio;

void main (

) {

   core.stdc.locale.setlocale(LC_ALL, "");

   int intAmount = 1234567;

   core.stdc.stdio.printf("%'d", intAmount); /// Deprecation: format specifier `"%'"` is invalid ... but it works: 1,234,567 as specified in my locale :)

}

But I can't use writeln() formatted with the ' character to get on what's defined on my locale.

PS: Previously I stated the backtick, I was wrong, the format specifier to get what's on the locale is the single quote, sorry for that.

On Saturday, 29 May 2021 at 02:26:57 UTC, someone wrote:

   core.stdc.stdio.printf("%'d", intAmount); /// Deprecation: format specifier `"%'"` is invalid ... but it works: 1,234,567 as specified in my locale :)

D warns for format specifiers that do not conform to the C99 standard, and the ' flag character is not part of C99. GCC gives a similar warning with -Wall -pedantic:

$ gcc -Wall -pedantic -o example example.c
example.c: In function ‘main’:
example.c:5:9: warning: ISO C does not support the ''' printf flag [-Wformat=]
  printf("%'d\n", 123456789);
         ^~~~~~~

On Saturday, 29 May 2021 at 02:59:43 UTC, Paul Backus wrote:

Crystal clear !