Why is stdin.byLine.writeln so slow?

[monarch_dodra via Digitalmars-d-learn]

On Friday, 13 June 2014 at 22:25:25 UTC, H. S. Teoh via 
Digitalmars-d-learn wrote:
In C/C++,
> you'd have
> to manually write nested loops to print out the data, which may 
> involve
> manually calling accessor methods, manually counting them, 
> perhaps
> storing intermediate output fragments in temporary buffers,
> encapsulating all this jazz in a throwaway function so that you 
> can use
> it at multiple strategic points (in D you just copy-n-paste the 
> single
> line above), etc..  Pure lose.
>
> T

In C++, I usually use copy/transform:

*std::copy(begin(), end(), std::ostream_iterator<T>(std::cout, 
"\n")) = "\n";
or
*std::tranform(begin(), end(), 
std::ostream_iterator<T>(std::cout, "\n"), [](???){???}) = "\n";

It's a bit verbose, and looks like ass to the non-initiated, but 
once you are used to it, it's quite convenient. It's just 
something that grows on you. You can stack on a "foreach" if you 
need more "depth".

foreach(begin(), end(), [](R& r){
   *std::copy(r.begin(), r.end(), 
std::ostream_iterator<T>(std::cout, "\n")) = "\n";
});

Though arguably, that's just a loop in disguise :)