[Zababa]

Standard ML and OCaml have both sum types (like in Rust) and exceptions. I feel like both have their value, and both are important. A nice thing is that you can match on exceptions:

    match number_of_lines_of_a_file() with
    | x -> x
    [ exception File_not_found -> 0

This makes it really easy to create alternative versions of functions, using exceptions or option types:

    match number_of_lines_of_a_file_opt() with
    | Some x -> x
    | None -> raise File_not_found

    match number_of_lines_of_a_file_exc() with
    | x -> Some x
    | exception File_not_found -> None