How is std.regex.replaceAllInto more efficient?

[Dmitry Olshansky via Digitalmars-d]

On 17-Oct-2015 13:06, Shriramana Sharma wrote:
> Dmitry Olshansky wrote:
>
>> Feel free to improve on the examples, I'd gladly pull such patches.
>
> How about this, using the "comifying" regex from the replaceAll example:
>
>      auto re = ctRegex!(`(?<=\d)(?=(\d\d\d)+\b)`, "g");
>      auto sink = appender!(char [])();
>      foreach (line; stdin.byLine())
>      {
>          sink.clear();
>          replaceAllInto(sink, line, re, ",");
>          writeln(sink.data());
>      }
>

My problem with it is writeln/byLine b/c it can't be unittested. 
Documented unit-tests as examples are gold.

On the other hand you can post it to list of example shown on the first 
page of dlang.org because I think it's kind of cool.

Also a variation of this example can be put in std.regex synopsis.

-- 
Dmitry Olshansky