What is the correct way in D to format a string like sprintf? I need to pad a number with zeroes. I tried to use std.format.format and std.string.format, but had some strange results.

On Tue, 16 Aug 2011 09:23:26 -0400, teo <teo.ubuntu@yahoo.com> wrote:

> What is the correct way in D to format a string like sprintf? I need to
> pad a number with zeroes. I tried to use std.format.format and
> std.string.format, but had some strange results.

I think maybe std.string.format?  I realize looking at the docs it's *woefully* underdocumented, but I think it works just like writefln or std.format.format but without the need for an output range.

-Steve

teo:

> What is the correct way in D to format a string like sprintf? I need to pad a number with zeroes. I tried to use std.format.format and std.string.format, but had some strange results.

Why don't you show one or more complete runnable examples that show your strange results? Both if there are bugs in Phobos to report in Bugzilla, or if you are using it badly, it's useful to know it.

Bye,
bearophile

On Tue, 16 Aug 2011 09:32:47 -0400, Steven Schveighoffer <schveiguy@yahoo.com> wrote:

> On Tue, 16 Aug 2011 09:23:26 -0400, teo <teo.ubuntu@yahoo.com> wrote:
>
>> What is the correct way in D to format a string like sprintf? I need to
>> pad a number with zeroes. I tried to use std.format.format and
>> std.string.format, but had some strange results.
>
> I think maybe std.string.format?  I realize looking at the docs it's *woefully* underdocumented, but I think it works just like writefln or std.format.format but without the need for an output range.

bleh, disregard that.  I only read that you tried std.format.format, I didn't realize you already tried std.string.format.

I agree with bearophile, post your "strange results"

-Steve

Is this what you're after?

import std.string;
void main()
{
    auto str = format("%.4s", 4);
    assert(str == "0004");
}

On Tue, 16 Aug 2011 09:51:41 -0400, bearophile wrote:

> teo:
> 
>> What is the correct way in D to format a string like sprintf? I need to pad a number with zeroes. I tried to use std.format.format and std.string.format, but had some strange results.
> 
> Why don't you show one or more complete runnable examples that show your strange results? Both if there are bugs in Phobos to report in Bugzilla, or if you are using it badly, it's useful to know it.
> 
> Bye,
> bearophile


Please ignore my post. It is all my fault. std.string.format is working as expected (at least in my case).

On Tue, 16 Aug 2011 13:23:26 +0000, teo wrote:

> What is the correct way in D to format a string like sprintf? I need to pad a number with zeroes. I tried to use std.format.format and std.string.format, but had some strange results.

You can go ahead and use the normal std.format to accomplish this task. This particular implementation is not very efficient, due to the immutable nature of strings, and the fact that I'm adding one character at a time.

If you do this operation a lot, you might want to make a version that works with pointers instead.


import std.stdio;
import std.format;

void sprintf(ref string s, ...) {
    void putc(dchar c) {
        s ~= c;
    }
    std.format.doFormat(&putc, _arguments, _argptr);
}

void main() {
    string testString;
    // Remember the format string:
    //   % - begins format
    //   0 - use leading '0's
    //   6 - we want 6 total chars printed (includes one for decimal)
    //   . - indicate precision (numbers after decimal)
    //   2 - do not show anything less than 1 cent
    sprintf(testString, "Your change %s is $%06.2f.", "Bob", 12.3456);
    // Output:  "Your change Bob is $012.35."
    writeln(testString);
}