Re: [Caml-list] Default methods for module signatures

[Yotam Barnoy <yotambarnoy@gmail.com>]

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Very nice proposal. I'm not crazy about the word 'virtual' since it doesn't
really mean anything (and has been brutally abused in C++), but that's
obviously a minor nitpick. Any reason this patch wasn't picked up?

-Yotam


On Wed, Feb 5, 2014 at 3:29 PM, Alain Frisch <alain@frisch.fr> wrote:

> I proposed (13 years ago...) a small patch to support optional fields in
> modules.  This would help achieving the desired effect. See:
>
> http://alain.frisch.fr/info/patch-option-announce
> http://alain.frisch.fr/info/patch-option
>
> -- Alain
>
>
>
> On 2/5/2014 7:49 PM, Yotam Barnoy wrote:
>
>> Hello List
>>
>> I would like the following feature, and I'm not enough of an expert in
>> module-fu to know if something like this is doable.
>>
>> Suppose I have a module signature of
>>
>> module type Monad = sig
>>    type 'a m
>>    val return : 'a -> 'a m
>>    val (>>=) : 'a m -> ('a -> 'b m) -> 'b m
>>    val (>>) : 'a m -> 'b m -> 'b m
>> end
>>
>> I would like to have a default implementation for (>>), since a simple
>> default implementation is
>>
>> let (>>) m f = m >>= fun _ -> f
>>
>> Alternatively, I would like to include this from some DefaultMonad
>> module, but have the (>>=) referred to in the function be my newly
>> defined (>>=) implementation (ie. late binding). Is there currently any
>> way to do this? If not, would there be a way to implement a partial
>> default implementation built into or associated with a module signature?
>> Something like
>>
>> module type Monad = sig... default struct... end
>>
>> Haskell has this available as part of the semantics of their typeclass
>> system, and I think it would be really handy to have (if there isn't
>> already a way to do it currently).
>>
>> -Yotam
>>
>>
>>
>
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