You need a parser for the printed representation of your type. There are
many sources of information on parsing in OCaml, for example:
https://realworldocaml.org/v1/en/html/parsing-with-ocamllex-and-menhir.html,
https://caml.inria.fr/pub/docs/oreilly-book/html/book-ora103.html; if you
have a copy of "The Functional Approach To Programming" parsing is covered
there also.  As a shortcut, you _may_ be able to use sexp-lib to
automagically create a parser for you; sexp-lib is covered in
https://realworldocaml.org/v1/en/html/data-serialization-with-s-expressions.html
.

-- 
Best,
Zhenya

On Thu, Jun 29, 2017 at 11:24 AM, Umair Siddique <umair.hvg@gmail.com>
wrote:

> Hi all,
>
> Can someone indicate me the best way to read custom type from a file or
> from command line.
>
> for example, type abc = Awsome | Great ;;
>
> I want to read it from a file or command line
>
>
> Thanks
>
> Uma
>