composition of functions of Result<T,E>

semi_monad_function_of_result_type.rs

use std::io;
use std::io::prelude::*;

fn main() {
    loop {
        let r = get_input("Enter the first number: ")
                    .and_then(|x| get_input("Enter the second number: ")
                        .and_then(|y| get_input("Enter the third number: ")
                            .and_then(|z| Ok(x + y + z))));

        if r.is_ok() {
            println!("The result is {}.", r.unwrap());
            break;
        }
    }
}

fn get_input(msg: &str) -> Result<i32, io::Error> {
    let mut buffer = String::new();
    print!("{}", msg);
    io::stdout().flush().unwrap();
    let stdin = io::stdin();
    let mut handle = stdin.lock();
    handle.read_line(&mut buffer).and_then(|_| {
        buffer
            .trim()
            .parse::<i32>()
            .map_err(|e| io::Error::new(io::ErrorKind::Other, e))
    })
}