Re: [Caml-list] Default value in module

[Yotam Barnoy <yotambarnoy@gmail.com>]

The easiest thing to do is to create a prototype module with the value
you want, and to include that module (include Foo) in any module you
want to have that basic structure. You can even have as many prototype
modules as you want, so the system is extremely flexible.

On Tue, Sep 12, 2017 at 4:00 PM, Paul A. Steckler <steck@stecksoft.com> wrote:
> I found myself wanting to define several modules that implement a
> module type, where all the implementations but one use the same value
> of an item in the type. Essentially, I wanted a default value in the
> module type, which I can override if needed. Maybe there's a way to do
> this already.
>
> If not, the type could look like:
> --
> module type Foo =
> sig
>   val ?x : int = 42
>  end
> --
>
> and instances could be:
>
> --
> module Bar1 : Foo =
> struct
>   let x = 17
> end
>
> module Bar2 : Foo =
> struct
> end
> --
>
> Is this a reasonable idea?
>
> More precisely, I wanted to take an existing module type, add an item
> to it, and then edit just the instance with the non-default value. As
> it was, I had to edit all the instances. I could have used the class
> system to do something similar, but that would have required changing
> even more code.
>
> -- Paul
>
> --
> Caml-list mailing list.  Subscription management and archives:
> https://sympa.inria.fr/sympa/arc/caml-list
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs