val ints_of_string : ?sep:string -> string -> int list
(** [nums_from_string ?sep s] takes a string of integers separated by [sep] and
    gives back a list of the integers. By default [sep] is " " *)

val distance1 : int -> int -> int
(** [distance1 a b] returns the absolute difference between [a] and [b]. *)

val strings_of_file : string -> string list
(** [strings_from_file fname] returns a list of strings from the file [fname].
    Each string represents a line from the file. *)

val main : (string -> 'a) -> (('b -> string) * ('a -> 'b)) list -> unit
(** [main prep parts] executes an advent of code problem. [prep fname] should be
    a function that returns the input from [fname]. Each elemet of [parts] is a
    pair of functions. The first converts the output to a string (for example
    [string_of_int]). The second executes the given part. Output is given as if
    done by: [print_string ( prep fname |> snd |> fst )] *)