Question

I am working with big_int type. I looked in the OCaml’s library Pervasives.

For example: in Int32

let t = 5l
Printf.printf "%ld" t

How can I define t and which %?d if I want to declare it is an big_int?

Answer 1

Below is a toplevel session. The #load directive would become a command-line link option if you used the compiler:

# #load "nums.cma" ;;
# let t = Big_int.big_int_of_int 5 ;;
val t : Big_int.big_int = <abstr>
# Printf.printf "%s" (Big_int.string_of_big_int t) ;;
5- : unit = ()

For numbers that do not fit in a native int, use Big_int.big_int_of_string. Example: Big_int.big_int_of_string "99999999999999999999999".

The complete list of functions is here.

Finally, the Big_int module is quite old and clumsy. The interface dates back to caml-light, in which the module system was rudimentary. This is the reason why each function name redundantly repeats “big_int…”. If you are choosing a big integer library now, I would recommend Zarith, which is modern and efficient. The drawback of Zarith is that it is a separate download (for now).