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Asked: 2026-05-26T02:46:01+00:00

I’ve done some searching around and apparently there used to be a Bignum module

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I’ve done some searching around and apparently there used to be a Bignum module in the standard library according to this But at this point I don’t see anything in the standard library.

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  1. Editorial Team

    There is no bignum module in the core OCaml distribution. The official recommendation is to use the third-party Zarith library, specifically its Z module.

    If you’ve installed OCaml as part of your operating system distribution, see if it has a package for Zarith. For example, on Debian, Ubuntu and derivatives, it’s libzarith-ocaml-dev. If Zarith isn’t available through your operating system, install it with OPAM:

    opam install zarith

    When building your application, compile with one of

    ocamlc -I +zarith zarith.cma …
ocamlopt -I +zarith zarith.cmxa …
ocamlfind <COMMAND> -package zarith -linkpkg …

    To use Zarith in the toplevel:

    ocaml -I +zarith zarith.cma zarith_top.cma

    Older versions of Ocaml had a bignum module in the standard distribution (but not in the standard library: it didn’t require separate installation, but had to be linked explicitly). It was the nums library, and its main module Num. Since OCaml 4.06, the nums library is distributed separately.

    Technically, there is no bignum module in the standard library, because the standard library in Ocaml terminology is the default library that programs are compiled against, and there’s no bignum module in that. Nor is there a Bignum library — because the bignum library is called nums, and its main module is called Num. It has been part of the standard Ocaml distribution since before Ocaml was called Ocaml, and still is.

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