fold                    Efficient fold / reduce / accumulate / combine
                        of a vector
future_imap             Apply a function to each element of a vector,
                        and its index via futures
future_invoke_map       Invoke functions via futures
future_map              Apply a function to each element of a vector
                        via futures
future_map2             Map over multiple inputs simultaneously via
                        futures
future_modify           Modify elements selectively via futures
future_options          'future' specific options
