OCaml open only certain values/types from module

Question

Does OCaml have an equivalent (possibly involving a camlp4 directive) of

from module import value1, value2 in Python or

use Module qw[value1 value2]; in Perl ?

I'd like to be able to write something like

open Ctypes (@->), string;; or open Ctypes ((@->), string);;

instead of

let (@->) = Ctypes.(@->);;
let string = Ctypes.string;;

Answer 1

The closest is:

let value1, value2 = Module.(value1, value2) 

For this very reason, open statements are most of the time evil (especially at the top level).

Answer 2

I'm afraid there is no such partial module opening like what you described.

• If your modules have no naming conflict, then it's simple enough to just use open Ctypes

• Otherwise, you can shorten the module name by

  module CT = Ctypes
  
  (* and then just call CT.some_function instead of Ctypes.some_function *)
  

• Your solutions is quite a neat one, but be careful that the name string may override the primitive type string of OCaml.

  let (@->) = Ctypes.(@->);;
  let string = Ctypes.string;;  (* override the type string *)