ocaml-lib-devel

[Ocaml-lib-devel] Module Structure

[Nicolas C. <war...@fr...>]

Hi list,

I have been thinking for some time on the module structure for ExtLib
issues, and I think I found a quite reasonable comprise.
Ok, first of all, we we talk there only about modules which are extending
the StdLib ones, other "new" modules doesn't cause any problems.
But for the Stdlib one - let's take the example of ExtList - there is some
problems :

- some people would like to use ExtList as a replacement of List

For this first category of people, we can do the following :

-- file extList.mli ---
module List : sig ... end
--- eof ---

Like this theses people will only have to add an extra "open ExtList" in the
beginning of their files and then they can use the List standard functions
as well as the List extended ones within the same short and readable
namespace : List.

But !
- this we're modifying the specification of some functions, people with
existing running code would like to use only ExtList as an additionnal
library of functions, without overriding the current Stdlib ones.

Here's the answer :
--- file extLib.mli ---
module ExtList = ExtList.List
--- eof ---

So they only have to do an "open ExtLib" and then they can use extended
functions under the ExtList namespace.

Nicolas Cannasse

Re: [Ocaml-lib-devel] Module Structure

[fva <fv...@ts...>]

Nicolas Cannasse wrote:

>Hi list,
>
>I have been thinking for some time on the module structure for ExtLib
>issues, and I think I found a quite reasonable comprise.
>Ok, first of all, we we talk there only about modules which are extending
>the StdLib ones, other "new" modules doesn't cause any problems.
>But for the Stdlib one - let's take the example of ExtList - there is some
>problems :
>
>- some people would like to use ExtList as a replacement of List
>
>For this first category of people, we can do the following :
>
>-- file extList.mli ---
>module List : sig ... end
>--- eof ---
>
>Like this theses people will only have to add an extra "open ExtList" in the
>beginning of their files and then they can use the List standard functions
>as well as the List extended ones within the same short and readable
>namespace : List.
>
>But !
>- this we're modifying the specification of some functions, people with
>existing running code would like to use only ExtList as an additionnal
>library of functions, without overriding the current Stdlib ones.
>
>Here's the answer :
>--- file extLib.mli ---
>module ExtList = ExtList.List
>--- eof ---
>
>So they only have to do an "open ExtLib" and then they can use extended
>functions under the ExtList namespace.
>
>Nicolas Cannasse
>
How was that going...?

Vote +1 for this proposal...

Regards,

       Fran

Re: [Ocaml-lib-devel] Module Structure

[Manos R. <er...@cs...>]

This still does let one use all of ExtLib with a simple 
  open ExtLib

I think that 

    module ExtLib = struct
      module List = ExtList
      ...
    end

will solve this problem.

-- Manos

On Mon, Mar 17, 2003 at 05:23:57PM +0900, Nicolas Cannasse wrote:
> Hi list,
> 
> I have been thinking for some time on the module structure for ExtLib
> issues, and I think I found a quite reasonable comprise.
> Ok, first of all, we we talk there only about modules which are extending
> the StdLib ones, other "new" modules doesn't cause any problems.
> But for the Stdlib one - let's take the example of ExtList - there is some
> problems :
> 
> - some people would like to use ExtList as a replacement of List
> 
> For this first category of people, we can do the following :
> 
> -- file extList.mli ---
> module List : sig ... end
> --- eof ---
> 
> Like this theses people will only have to add an extra "open ExtList" in the
> beginning of their files and then they can use the List standard functions
> as well as the List extended ones within the same short and readable
> namespace : List.
> 
> But !
> - this we're modifying the specification of some functions, people with
> existing running code would like to use only ExtList as an additionnal
> library of functions, without overriding the current Stdlib ones.
> 
> Here's the answer :
> --- file extLib.mli ---
> module ExtList = ExtList.List
> --- eof ---
> 
> So they only have to do an "open ExtLib" and then they can use extended
> functions under the ExtList namespace.
> 
> Nicolas Cannasse
> 

Re: [Ocaml-lib-devel] Module Structure

[Nicolas C. <war...@fr...>]

> This still does let one use all of ExtLib with a simple
>   open ExtLib
>
> I think that
>
>     module ExtLib = struct
>       module List = ExtList
>       ...
>     end
>
> will solve this problem.

Perhaps, but I wonder then if you're doing
open ExtLib
are you linking with all the modules ExtList, ExtHashtbl, ExtString... even
if you're not using them ?

Nicolas Cannasse

Re: [Ocaml-lib-devel] Module Structure

[Nicolas C. <war...@fr...>]

> > This still does let one use all of ExtLib with a simple
> >   open ExtLib
> >
> > I think that
> >
> >     module ExtLib = struct
> >       module List = ExtList
> >       ...
> >     end
> >
> > will solve this problem.
>
> Perhaps, but I wonder then if you're doing
> open ExtLib
> are you linking with all the modules ExtList, ExtHashtbl, ExtString...
even
> if you're not using them ?

I have checked the following.
When you're doing "open ExtLib" it will really link all the modules declared
in extLib.ml, even if later the application does not use them. We have then
three choices :
- use my module structure proposal, that will cause the users which are
using ExtLib as an extension to link all the overidden modules
- use Manos Renieris one, that will cause the users which are using ExtLib
as an StdLib replacement to link all the overidden modules
- find another prefix keyword ( for exemple Std ) so there is no more ExtLib
module, but it can be use :

As a replacement of the List standard module :
        --- test.ml ---
        open StdList
        List.map f l
        --- stdList.mli ---
        module List : sig <...> end

As a extended library of functions :
        --- test.ml ---
        ExtList.map f l
        -- extList.ml ----
        include StdList.List

Nicolas Cannasse