OCaml: Print a long int list 10 elements per row - printf

Question

I'm working with really long lists of integers and need a way of printing them 10 to a row. This is what I've got so far and now I'm stuck:
open Printf
let print_list list = List.iter (printf "%d ") list;;
(* Remove first n elements from list *)
let rec remove n list =
if n== 0 then list
else match list with
| [] -> []
| hd::tl -> remove (n-1) tl;;
(* Remove and return first n elements from a list *)
let rec take n list =
match n with
| 0 -> []
| _ -> List.hd list :: take (n-1) (List.tl list);;
let rec print_rows list =
if List.length list > 10 then
begin
let l = take 10 list;
print_list l;
print_endline " ";
print_rows (remove 5 list)
end else print_list list;;
I'm sure there is a better way recursively with matching patterns, but I can't figure this out. Help!

Answer 1

Here's a function that does something close to what you want. It doesn't do anything fancy, it just counts the number of ints printed so far and inserts endlines at the right times.
let printby10 intlist =
let iprint count n =
Printf.printf "%d " n;
if count mod 10 = 9 then Printf.printf "\n";
count + 1
in
ignore (List.fold_left iprint 0 intlist)
This code leaves an incomplete line if the number of ints isn't a multiple of 10. Maybe you would want to fix that up.

Answer 2

Another (but very close to that of #Jeffrey Scofield) approach would be to use the standard function List.iteri, which provides the current element's index:
let print_by_rows n_per_row =
List.iteri (fun i x ->
print_int x;
if (i + 1) mod n_per_row <> 0 then print_string " "
else print_newline ())
A test:
μ> print_by_rows 10 (Array.to_list (Array.make 20 42));;
42 42 42 42 42 42 42 42 42 42
42 42 42 42 42 42 42 42 42 42
- : unit = ()
And one more:
μ> print_by_rows 5 (Array.to_list (Array.make 20 42));;
42 42 42 42 42
42 42 42 42 42
42 42 42 42 42
42 42 42 42 42
- : unit = ()