[Caml-list] adding a function to an already existing module

[Caml-list] adding a function to an already existing module

[Francois Berenger]

Hello,

Let's say I want to add a function to the List module
of the std lib.

I'd like to do this without having to change list.ml
in the std lib.

And, my function need to have access to everything available
in list.ml (constructors, type names, etc.).

Is this possible and how to do this?

For example, I want to create MyList, and this module
is the exact List module plus some functions of my own.
Then, some of my code would use MyList instead of List.

Thanks a lot,
F.

PS: a full copy-paste of list.ml is considered cheating ;)

Re: [Caml-list] adding a function to an already existing module

[Siraaj Khandkar]

module MyList = struct
    include List

   let foo l = bar l
end


On Jan 11, 2013, at 0:07, Francois Berenger <berenger@riken.jp> wrote:

> Hello,
> 
> Let's say I want to add a function to the List module
> of the std lib.
> 
> I'd like to do this without having to change list.ml
> in the std lib.
> 
> And, my function need to have access to everything available
> in list.ml (constructors, type names, etc.).
> 
> Is this possible and how to do this?
> 
> For example, I want to create MyList, and this module
> is the exact List module plus some functions of my own.
> Then, some of my code would use MyList instead of List.
> 
> Thanks a lot,
> F.
> 
> PS: a full copy-paste of list.ml is considered cheating ;)
> 
> -- 
> 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

Re: [Caml-list] adding a function to an already existing module

[Francois Berenger]

On 01/11/2013 02:14 PM, Siraaj Khandkar wrote:
> module MyList = struct
>      include List
>
>     let foo l = bar l
> end

Not exactly, because:

module MyList = struct
   include List
   let expose_length_aux = length_aux (* stupid example *)
end

gives:
Error: Unbound value length_aux

While length_aux is available to code from list.ml.

> On Jan 11, 2013, at 0:07, Francois Berenger <berenger@riken.jp> wrote:
>
>> Hello,
>>
>> Let's say I want to add a function to the List module
>> of the std lib.
>>
>> I'd like to do this without having to change list.ml
>> in the std lib.
>>
>> And, my function need to have access to everything available
>> in list.ml (constructors, type names, etc.).
>>
>> Is this possible and how to do this?
>>
>> For example, I want to create MyList, and this module
>> is the exact List module plus some functions of my own.
>> Then, some of my code would use MyList instead of List.
>>
>> Thanks a lot,
>> F.
>>
>> PS: a full copy-paste of list.ml is considered cheating ;)
>>
>> --
>> 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

Re: [Caml-list] adding a function to an already existing module

[Siraaj Khandkar]

On Jan 11, 2013, at 0:26, Francois Berenger <berenger@riken.jp> wrote:

> On 01/11/2013 02:14 PM, Siraaj Khandkar wrote:
>> module MyList = struct
>>     include List
>> 
>>    let foo l = bar l
>> end
> 
> Not exactly, because:
> 
> module MyList = struct
>  include List
>  let expose_length_aux = length_aux (* stupid example *)
> end
> 
> gives:
> Error: Unbound value length_aux
> 
> While length_aux is available to code from list.ml.

Oh, I didn't realize you really did mean "everything"! :)

Not much you can do if the interface doesn't expose it though, it's kind of the point. Copying and moding list.ml does seem like the only way to get _exactly_ what you want then.



> 
>> On Jan 11, 2013, at 0:07, Francois Berenger <berenger@riken.jp> wrote:
>> 
>>> Hello,
>>> 
>>> Let's say I want to add a function to the List module
>>> of the std lib.
>>> 
>>> I'd like to do this without having to change list.ml
>>> in the std lib.
>>> 
>>> And, my function need to have access to everything available
>>> in list.ml (constructors, type names, etc.).
>>> 
>>> Is this possible and how to do this?
>>> 
>>> For example, I want to create MyList, and this module
>>> is the exact List module plus some functions of my own.
>>> Then, some of my code would use MyList instead of List.
>>> 
>>> Thanks a lot,
>>> F.
>>> 
>>> PS: a full copy-paste of list.ml is considered cheating ;)
>>> 
>>> --
>>> 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
> 
> 
> -- 
> 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