Re: byLine(n)?

[Stanislav Blinov via Digitalmars-d-learn]

On Sunday, 11 June 2017 at 05:36:08 UTC, helxi wrote:
I was writing a program that reads and prints the first nth 
lines to the stdout:

import std.stdio;

void main(string[] args)
{
    import std.algorithm, std.range;
    import std.conv;
    stdin.byLine.take(args[1].to!ulong).each!writeln;
}

As far as I understand the stdin.byLine.take(args[1].to!ulong) 
part reads all the lines written in stdin.
What if I want to make byLine read only and only first nth line?

stdin.byLine(args[1].to!ulong).each!writeln;

Obviously the code above won't work. Is there any efficient 
workaround?

You need only the nth line? Then you'd need to `drop` the 
preceding ones:

void main(string[] args) {
    import std.algorithm, std.range, std.stdio, std.conv;
    stdin.byLine.drop(args[1].to!int-1).front.writeln;
}

Or if you need every nth line, combine `drop` and `stride`:

void main(string[] args) {
    import std.algorithm, std.range, std.stdio, std.conv;
    auto step = args[1].to!int;
    stdin.byLine.drop(step-1).stride(step).each!writeln;
}