Redundancy in OCaml type declaration (ml/mli)

Question

I\'m trying to understand a specific thing about ocaml modules and their compilation:

am I forced to redeclare types already declared in a .mli inside t

Answer 1

In general, yes, you are required to duplicate the types.

You can work around this, however, with Camlp4 and the pa_macro syntax extension (findlib package: camlp4.macro). It defines, among other things, and INCLUDE construct. You can use it to factor the common type definitions out into a separate file and include that file in both the .ml and .mli files. I haven't seen this done in a deployed OCaml project, however, so I don't know that it would qualify as recommended practice, but it is possible.

The literate programming solution, however, is cleaner IMO.