Replacing QString().sprintf with arg calls for double

[Johan Borkhuis]

Hello,

I am trying to update my code from using sprintf to arg, as sprintf is deprecated and asprintf is not advised for new code.
But I am getting some issues with converting doubles to strings. With arg you can specify precision and a fillchar, but with doubles this fillchar is also applied to the front

This is my example code:

int main(int argc, char *argv[]) {
  QTextStream output(stdout);

  output << QString().sprintf("%12.6lf", 123.456) << endl;
  output << QString("%1").arg(123.456, 12, 'f', 6, QLatin1Char('0')) << endl;

  return 0;
}

This results in the following output:

  123.456000
00123.456000

Is it possible to change this behaviour of QString(..).arg(..)?

Regards,
Johan

[mpergand]

@Johan-Borkhuis

qDebug()<<QString("%1").arg(123.456, 12, 'f', 6, QLatin1Char(' '));
qDebug()<<QString::asprintf("% 12.6lf", 123.456);
"  123.456000"
"  123.456000"

or

qDebug()<<QString("%1").arg(123.456, 12, 'f', 6, QLatin1Char('0'));
qDebug()<<QString::asprintf("%012.6lf", 123.456);
"00123.456000"
"00123.456000"

[Christian Ehrlicher]

This post is deleted!

[JonB]

@mpergand said in Replacing QString().sprintf with arg calls for double:

qDebug()<<QString("%1").arg(123.456, 12, 'f', 6, QLatin1Char(' '));

This is what the OP wants. I believe [can't test] u' ' is the default so can presumably be omitted:

QString("%1").arg(123.456, 12, 'f', 6);

?

[mpergand]

@JonB said in Replacing QString().sprintf with arg calls for double:

' ' is the default so can presumably be omitted:

Yes but "ça va mieux en le disant" :)

[JonB]

@mpergand Yep, it was for my own understanding that it is the default behaviour.

[Johan Borkhuis]

Thank you all for this. I was expecting that I needed the '0' fillchar to fill at the end as well, but I was clearly wrong there. This helped me a lot.