Rust code shared from the playground

playground.rs

/// Retrieve a list of new files to be copied to the DMS.
pub fn added_files<'a>(local: &'a BTreeSet<LibraryFile>, dms: &'a BTreeSet<LibraryFile>) ->
        Vec<&'a LibraryFile> {
    local.difference(dms).collect()
}

/// Retrieve a list of new files to be copied to the DMS.
pub fn added_files<'a>(local: &'a BTreeSet<LibraryFile>, dms: &'a BTreeSet<LibraryFile>) ->
        Box<Iterator<Item=&'a LibraryFile>> {
    Box::new(local.difference(dms)) as Box<Iterator<Item=&'a LibraryFile>>
}