Method next

edit/src/main.rs:120–130

(&self, cursor: Cursor)

    }

    fn next(&self, cursor: Cursor) -> Option<Cursor> {
        if cursor.piece == self.pieces.len() {
            return None; // End of the file
        }
        if cursor.pos == self.pieces[cursor.piece].len() - 1 {
            return Some(Cursor{piece: cursor.piece + 1,
                               pos: 0});
        }
        Some(Cursor{piece: cursor.piece,
                    pos: cursor.pos + 1})
    }

    fn previous(&self, cursor: Cursor) -> Option<Cursor> {
        if cursor.pos == 0 {