flatten_results.rs

trait FlattenResultsIterator: Itertools {
    fn flatten_results<A, E, I>(&mut self) -> Result<Box<Iterator<Item=I>>, E>
        where Self: Sized + Iterator<Item=Result<A, E>>,
              A: 'static + IntoIterator<Item=I>,
              I: 'static,
    {
        self.fold_results(
            Box::new(iter::empty::<I>()) as Box<Iterator<Item=I>>,
            |accum, it| Box::new(accum.chain(it)) as Box<Iterator<Item=I>>)
    }
}