My question is, how do I output the current List size with List.concat without affecting the incoming input? Look forward to your advice. Thank you!
Perhaps my description is not clear, please allow me to use error code roughly to show my intention.
Map.to_alist subtrees
|> List.rev
|> List.map ~f:(fun subtree → subtree_to_table options subtrees subtree group_table) |> let a_list = List.concat in printf “%d\n” (List.length a_list); List.concat
|> fun ls → (ls, group_table)