Output of std.format for float difference between DMD and GDC

[BoraxMan]

On Wednesday, 4 December 2019 at 09:41:58 UTC, BoraxMan wrote:
> I have noted that DMD and GDC provide a different output to the 
> following line of code.
>
> writeln(format("$%-12,3.2f",66543.22));
>
> DMD outputs
>
> $66,543.22
>
> GDC outputs
>
> $66,543.22 ,
>
> As you can see, GDC puts a superflous comma at the end.  The 
> goal of this line is to convert a float to a monetary 
> representation, therefore DMD is what I want and GDC not.
>
> The question is, is the line of code in error?  If not, does 
> this mean there is a bug with GDC's libphobos?
>
> Regards,
> Dennis

I figured it out, its my lack of experience in D.

format("$%-*,3.2f",x.dig,x);

where x is the floating point value works as expected.