sliding

main.rs

use std::env::{args, args_os};
use std::io;
use std::io::Read;

/// $ seq 1 4 | sliding 
/// > 1 2
/// > 2 3
/// > 3 4
fn main() -> Result<(), io::Error> {
    let d = args().enumerate().find(|(_, x)| x == "-d").map_or_else(
        || " ".to_string(),
        |(i, _)| {
            args_os()
                .nth(i + 1)
                .expect("need value")
                .to_str()
                .unwrap()
                .to_string()
        },
    );
    let io = io::stdin();
    let mut handle = io.lock();

    let mut buff = String::new();
    handle.read_to_string(&mut buff)?;
    let iter = buff.lines().zip(buff.lines().skip(1));

    for x in iter {
        println!("{}{}{}", x.0, d, x.1);
    }
    Ok(())
}