extern crate rayon;


use std::error::Error;
use rayon::iter::{IntoParallelRefIterator, ParallelIterator};

fn long_computation(x: u32) -> Result<u32, Box<Error>> {
    match x {
        4 => Err(Error::),
        _ => Ok(42)
    }
}

fn main() {

    let xs = vec![1, 2, 3, 4, 5, 6];

    let results : Vec<Result<u32, Box<Error>>> = xs
        .par_iter()
        .map(|&x| Ok(long_computation(x)? + 1))
        .collect();

}