deref_iter.rs

fn is_printable_ascii(c: u8) -> bool {
    c >= 0x20u8 && c < 0x7fu8
}

fn main() {
    // why temporary variable needed?
    // error: borrowed value does not live long enough
    let test_data: ~[u8] = std::io::File::open(&Path::new("test_data")).read_to_end();
    let _test_data_filtered: ~[u8] = test_data.iter()
        // why double deref?
        // error: mismatched types: expected `u8` but found `&&u8` (expected u8 but found &-ptr)
        .filter(|c| is_printable_ascii(**c))
         // why this is needed?
         // error: mismatched types: expected `~[u8]` but found `~[&u8]` (expected u8 but found &-ptr)
        .map(|x| *x)
        .to_owned_vec();
}