[Caml-list] Importing specific names

[Caml-list] Importing specific names

[José Romildo Malaquias]

Hello.

It seems that the expression ocaml "open module-path" exposes all names
exported by module-path.

Is there any way of exposing only a restrict set of names from a
module-path, instead of all names?

Romildo

Re: [Caml-list] Importing specific names

[David House]

If you want to list the things you want, rather than listing the
things you don't want, what's wrong with the following?

let x = Module.x
let y = Module.y
...

You could abbreviate that somewhat:

include (struct
  open Module
  let x = x
  let y = y
  ...
end)

On Fri, Oct 26, 2012 at 12:26 PM, José Romildo Malaquias
<j.romildo@gmail.com> wrote:
> Hello.
>
> It seems that the expression ocaml "open module-path" exposes all names
> exported by module-path.
>
> Is there any way of exposing only a restrict set of names from a
> module-path, instead of all names?
>
> Romildo
>
> --
> 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] Importing specific names

[David House]

I should add: although this is possible, I generally find it easier to
read code that has been written with as few opens as possible.

If you find you are using things from Module a lot, you might consider
creating a module alias:

module Mod = Very_long_module_name

You can then say Mod.foo, Mod.bar etc. This makes it obvious where foo
and bar come from, but you don't have to sacrifice readability by
typing such a long module name every time.

(Of course, there is an art to picking module abbreviations as well; I
find it best to pick a short abbreviation which holds at least some
meaning, rather than just "let module M = ...". E.g.:
  module Str = My_super_duper_string_module
Rather than:
  module S = My_super_duper_string_module
)

Yet another option is to do a local module alias ("let module Mod =
... in"), or a local open ("let open ... in"), in the function(s)
where you need access to things from Module. This keeps things as
localised as possible, which again increases readability. (You only
have to remember the meaning of a module alias for a very short time,
rather than for the scope of the whole module.)

On Fri, Oct 26, 2012 at 12:26 PM, David House <dhouse@janestreet.com> wrote:
> If you want to list the things you want, rather than listing the
> things you don't want, what's wrong with the following?
>
> let x = Module.x
> let y = Module.y
> ...
>
> You could abbreviate that somewhat:
>
> include (struct
>   open Module
>   let x = x
>   let y = y
>   ...
> end)
>
> On Fri, Oct 26, 2012 at 12:26 PM, José Romildo Malaquias
> <j.romildo@gmail.com> wrote:
>> Hello.
>>
>> It seems that the expression ocaml "open module-path" exposes all names
>> exported by module-path.
>>
>> Is there any way of exposing only a restrict set of names from a
>> module-path, instead of all names?
>>
>> Romildo
>>
>> --
>> 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] Importing specific names

[Matthieu Dubuget]

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Le 26/10/2012 13:26, José Romildo Malaquias a écrit :
>  Hello.
>
>  It seems that the expression ocaml "open module-path" exposes all names
>  exported by module-path.
>
>  Is there any way of exposing only a restrict set of names from a
>  module-path, instead of all names?
>
>  Romildo
>

Is this what you are looking for?

# module type RS = sig
    val length : string -> int
   end;;
module type RS = sig val length : string -> int end
# module ReducedString:RS = String;;
module ReducedString : RS
# ReducedString.length "coco";;
- : int = 4
# ReducedString.uppercase "coco";;
Error: Unbound value ReducedString.uppercase

Salutations

Matthieu


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Re: [Caml-list] Importing specific names

[Edgar Friendly]

On 10/26/2012 7:26 AM, José Romildo Malaquias wrote:
> Hello.
>
> It seems that the expression ocaml "open module-path" exposes all names
> exported by module-path.
>
> Is there any way of exposing only a restrict set of names from a
> module-path, instead of all names?
>
> Romildo
>
If I want to import only a few values from a module, I often use 
something like this:

   let (a,b,c) = Module.(a,b,c)

E.

Re: [Caml-list] Importing specific names

[Yaron Minsky]

Ah, that's great!  I wish I could do it for binding sub-modules too!

y

On Fri, Oct 26, 2012 at 10:48 AM, Edgar Friendly <thelema314@gmail.com> wrote:
> On 10/26/2012 7:26 AM, José Romildo Malaquias wrote:
>>
>> Hello.
>>
>> It seems that the expression ocaml "open module-path" exposes all names
>> exported by module-path.
>>
>> Is there any way of exposing only a restrict set of names from a
>> module-path, instead of all names?
>>
>> Romildo
>>
> If I want to import only a few values from a module, I often use something
> like this:
>
>   let (a,b,c) = Module.(a,b,c)
>
> E.
>
>
> --
> 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] Importing specific names

[Didier Cassirame]

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One way to do that is to define the signature you need, and restrict the
module with it.

module Restricted = (Module : sig val a ... end )

open Restricted

didier

2012/10/26 José Romildo Malaquias <j.romildo@gmail.com>

> Hello.
>
> It seems that the expression ocaml "open module-path" exposes all names
> exported by module-path.
>
> Is there any way of exposing only a restrict set of names from a
> module-path, instead of all names?
>
> Romildo
>
> --
> 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
>

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Re: [Caml-list] Importing specific names

[José Romildo Malaquias]

On Fri, Oct 26, 2012 at 12:26:02PM +0100, David House wrote:
> If you want to list the things you want, rather than listing the
> things you don't want, what's wrong with the following?
> 
> let x = Module.x
> let y = Module.y
> ...
> 
> You could abbreviate that somewhat:
> 
> include (struct
>   open Module
>   let x = x
>   let y = y
>   ...
> end)

That does not seem to work with types:

  (* test.ml *)
  include (struct
    open Lexing
    type position = position
  end)

# #use "test.ml";;
File "test.ml", line 4, characters 7-26:
Error: The type abbreviation position is cyclic

> On Fri, Oct 26, 2012 at 12:26 PM, José Romildo Malaquias
> <j.romildo@gmail.com> wrote:
> > Hello.
> >
> > It seems that the expression ocaml "open module-path" exposes all names
> > exported by module-path.
> >
> > Is there any way of exposing only a restrict set of names from a
> > module-path, instead of all names?

Re: [Caml-list] Importing specific names

[José Romildo Malaquias]

On Fri, Oct 26, 2012 at 03:55:43PM +0200, Matthieu Dubuget wrote:
> Le 26/10/2012 13:26, José Romildo Malaquias a écrit :
> >  Hello.
> >
> >  It seems that the expression ocaml "open module-path" exposes all names
> >  exported by module-path.
> >
> >  Is there any way of exposing only a restrict set of names from a
> >  module-path, instead of all names?
> 
> Is this what you are looking for?
> 
> # module type RS = sig
>     val length : string -> int
>    end;;
> module type RS = sig val length : string -> int end
> # module ReducedString:RS = String;;
> module ReducedString : RS
> # ReducedString.length "coco";;
> - : int = 4
> # ReducedString.uppercase "coco";;
> Error: Unbound value ReducedString.uppercase

This has the disadvantage to explicitly include the type signature of
values, and probably the type definition of types. There sould be easier
ways, where only the relevant names would have to be mentioned.

Romildo

Re: [Caml-list] Importing specific names

[José Romildo Malaquias]

On Fri, Oct 26, 2012 at 10:48:11AM -0400, Edgar Friendly wrote:
> On 10/26/2012 7:26 AM, José Romildo Malaquias wrote:
> > Hello.
> >
> > It seems that the expression ocaml "open module-path" exposes all names
> > exported by module-path.
> >
> > Is there any way of exposing only a restrict set of names from a
> > module-path, instead of all names?
> >
> > Romildo
> >
> If I want to import only a few values from a module, I often use 
> something like this:
> 
>    let (a,b,c) = Module.(a,b,c)

What about importing algebraic types with its constructors or record
types with its field names, without repeating the type definition? Would
that be possible?

For instance, I want to import the record type

  type position = {
       pos_fname :string;
       pos_lnum :int;
       pos_bol :int;
       pos_cnum :int;
  }

from the Lexing module.

Romildo