reader.rs

use std::io::buffered::BufferedReader;
use std::io::fs::File;

fn main() {
    let pairs = read_int_pairs();
    for &(a,b) in pairs.iter() {
        println!("{:4.4d}, {:4.4d}", a, b);
    }
}

fn read_int_pairs() -> ~[(int,int)] {
    let mut pairs = ~[];

    let args = std::os::args();
// Path is a little strange in that it takes a generic by-value, rather than by reference
    let path = match args.get_opt(1) {
        Some(f) => f,
        None => fail!("No input file parameter found!")
    };

    let mut reader = BufferedReader::new(File::open(&Path::new(path.as_slice())));
    for line in reader.lines() {
//    while !reader.eof() {

        // 1. Read a line of input.
//        let line = reader.read_line().unwrap();

        // 2. Split the line into fields ("words").
        let fields = line.words().to_owned_vec();

        // 3. Match the vector of fields against a vector pattern.
        match fields {

            // 4. When the line had two fields:
            [a, b] => {

                // 5. Try parsing both fields as ints.
                match (from_str::<int>(a), from_str::<int>(b)) {

                    // 6. If parsing succeeded for both, push both.
                    (Some(a), Some(b)) => pairs.push((a,b)),

                    // 7. Ignore non-int fields.
                    _ => ()
                }
            }

            // 8. Ignore lines that don't have 2 fields.
            _ => ()
        }
    }

    pairs
}