[Caml-list] Type That's Concrete From Within A Library Abstract From Without

[Caml-list] Type That's Concrete From Within A Library Abstract From Without

[Jun Inoue]

Dear list,

Is there a way to make a type concrete inside a library, yet opaque to
library users, preferably in a way that works with -pack?  This is a
nagging issue in our sundials package
(http://inria-parkas.github.io/sundialsml/).

Basically, we have a type declared in one module of the library that
is pattern-matched upon in other modules, like:

(* private.ml *)
type opaque_type = Foo | Bar

(* public.ml *)
let f : opaque_type -> int = function
  | Foo -> 0
  | Bar -> 1

There are a few constraints:
- We don't want users to be able to pattern-match on opaque_type.
- We need multiple modules in the library to pattern-match on
opaque-type (so moving opaque_typ e to public.ml is not an option).
- To avoid namespace pollution, we want to pack the whole library
(with ocamlc -pack) as a single Sundials module, so the user sees a
Sundials.Public module instead of just Public.

Is this possible?  Right now, we just collect public.cmo and
private.cmo into sundials.cma and throw away private.cmi.  But this
doesn't work with packing:

$ ocamlc -pack -o sundials.cmo private.cmo public.cmo

demands that there be a private.cmi.

-- 
Jun Inoue

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Re: [Caml-list] Type That's Concrete From Within A Library Abstract From Without

[Malcolm Matalka]

Jun Inoue <jun.lambda@gmail.com> writes:

> Dear list,
>
> Is there a way to make a type concrete inside a library, yet opaque to
> library users, preferably in a way that works with -pack?  This is a
> nagging issue in our sundials package
> (http://inria-parkas.github.io/sundialsml/).
>
> Basically, we have a type declared in one module of the library that
> is pattern-matched upon in other modules, like:
>
> (* private.ml *)
> type opaque_type = Foo | Bar
>
> (* public.ml *)
> let f : opaque_type -> int = function
>   | Foo -> 0
>   | Bar -> 1
>

Doesn't using .mli files do exactly what you want?

(* public.mli *)
type opaque_type
val f : opaque_type -> int

(* public.ml *)
type opaque_type = Foo | Bar

let f t = ....

> There are a few constraints:
> - We don't want users to be able to pattern-match on opaque_type.
> - We need multiple modules in the library to pattern-match on
> opaque-type (so moving opaque_typ e to public.ml is not an option).
> - To avoid namespace pollution, we want to pack the whole library
> (with ocamlc -pack) as a single Sundials module, so the user sees a
> Sundials.Public module instead of just Public.
>
> Is this possible?  Right now, we just collect public.cmo and
> private.cmo into sundials.cma and throw away private.cmi.  But this
> doesn't work with packing:
>
> $ ocamlc -pack -o sundials.cmo private.cmo public.cmo
>
> demands that there be a private.cmi.
>
> -- 
> Jun Inoue


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Re: [Caml-list] Type That's Concrete From Within A Library Abstract From Without

[Nicolás Ojeda Bär]

Dear Jun,

This is a limitation of module packs. However, there is a much better
alternative to module packs in the form of module aliases which will
allow you to do what you want.

You can head to
https://caml.inria.fr/pub/docs/manual-ocaml/extn.html#sec249 for a
more lengthy explanation, but briefly, in your example:

1. rename private.ml to sundials__private.ml and public.ml to
sundials__public.ml
2. create a file sundials.ml with contents:

  module Private = Sundials__private
  module Public = Sundials__public

3. compile sundials.ml with

  ocamlc -no-alias-deps -c sundials.ml

(you may want to disable warning 49 when doing this)

4. compile the individual files in the library with

  ocamlc -no-alias-deps -open Sundials -c sundials__private.ml
  ocamlc -no-alias-deps -open Sundials -c sundials__public.ml

5. You can now delete (or not install) sundials__private.cmi and ship
the other files

  sundials.cmo
  sundials.cmi
  sundials__public.cmo
  sundials__public.cmi
  sundials__private.cmo

to hide the private module from "outside" library users.

Note that if you use jbuilder/dune, then your library will be built
like this (steps 1-4) by default.

Hope it helps,

Best wishes,
Nicolás

On Thu, Apr 26, 2018 at 4:18 PM, Jun Inoue <jun.lambda@gmail.com> wrote:
> Dear list,
>
> Is there a way to make a type concrete inside a library, yet opaque to
> library users, preferably in a way that works with -pack?  This is a
> nagging issue in our sundials package
> (http://inria-parkas.github.io/sundialsml/).
>
> Basically, we have a type declared in one module of the library that
> is pattern-matched upon in other modules, like:
>
> (* private.ml *)
> type opaque_type = Foo | Bar
>
> (* public.ml *)
> let f : opaque_type -> int = function
>   | Foo -> 0
>   | Bar -> 1
>
> There are a few constraints:
> - We don't want users to be able to pattern-match on opaque_type.
> - We need multiple modules in the library to pattern-match on
> opaque-type (so moving opaque_typ e to public.ml is not an option).
> - To avoid namespace pollution, we want to pack the whole library
> (with ocamlc -pack) as a single Sundials module, so the user sees a
> Sundials.Public module instead of just Public.
>
> Is this possible?  Right now, we just collect public.cmo and
> private.cmo into sundials.cma and throw away private.cmi.  But this
> doesn't work with packing:
>
> $ ocamlc -pack -o sundials.cmo private.cmo public.cmo
>
> demands that there be a private.cmi.
>
> --
> Jun Inoue
>
> --
> 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] Type That's Concrete From Within A Library Abstract From Without

[Ivan Gotovchits]

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Hi Jun,

You can achieve this by implying an extra layer of indirection, i.e., by
having two levels of interfaces. For example,

   * A.ml - implementation of module A
   * A.mli - private interface of module A
   * B.ml  - implementation of module B that may rely on anything in A.mli
   * Std.ml - a set of modules that you would like to import, e.g., `module
A = A`, `module B = B`
   * Std.mli - public interface specification


Next, you deploy `std.cmxa` and `std.cmi` but keep `a.cmi` and `b.cmi` to
yourself. This will prevent users from accessing your private modules A and
B directly. (In oasis you can use PrivateModules stanza for this)

Now you will have `Std.A` and `Std.B` that exposes as much as you want. Not
sure whether it will work with the `-pack`, but you can use this approach
instead of it. This is how we address the same issue in [BAP][1]

Cheers,
Ivan

[1]: https://github.com/BinaryAnalysisPlatform/bap


On Thu, Apr 26, 2018 at 10:18 AM, Jun Inoue <jun.lambda@gmail.com> wrote:

> Dear list,
>
> Is there a way to make a type concrete inside a library, yet opaque to
> library users, preferably in a way that works with -pack?  This is a
> nagging issue in our sundials package
> (http://inria-parkas.github.io/sundialsml/).
>
> Basically, we have a type declared in one module of the library that
> is pattern-matched upon in other modules, like:
>
> (* private.ml *)
> type opaque_type = Foo | Bar
>
> (* public.ml *)
> let f : opaque_type -> int = function
>   | Foo -> 0
>   | Bar -> 1
>
> There are a few constraints:
> - We don't want users to be able to pattern-match on opaque_type.
> - We need multiple modules in the library to pattern-match on
> opaque-type (so moving opaque_typ e to public.ml is not an option).
> - To avoid namespace pollution, we want to pack the whole library
> (with ocamlc -pack) as a single Sundials module, so the user sees a
> Sundials.Public module instead of just Public.
>
> Is this possible?  Right now, we just collect public.cmo and
> private.cmo into sundials.cma and throw away private.cmi.  But this
> doesn't work with packing:
>
> $ ocamlc -pack -o sundials.cmo private.cmo public.cmo
>
> demands that there be a private.cmi.
>
> --
> Jun Inoue
>
> --
> 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] Type That's Concrete From Within A Library Abstract From Without

[Nicolás Ojeda Bär]

Sorry, I forgot the last step in my email, which is to create a cma
with all the compilation units:

  ocamlc -a sundials*.cmo -o sundials.cma

and install sundials.cma and the public *.cmi's as needed.

Best wishes,
Nicolás

On Thu, Apr 26, 2018 at 5:03 PM, Nicolás Ojeda Bär
<nicolas.ojeda.bar@lexifi.com> wrote:
> Dear Jun,
>
> This is a limitation of module packs. However, there is a much better
> alternative to module packs in the form of module aliases which will
> allow you to do what you want.
>
> You can head to
> https://caml.inria.fr/pub/docs/manual-ocaml/extn.html#sec249 for a
> more lengthy explanation, but briefly, in your example:
>
> 1. rename private.ml to sundials__private.ml and public.ml to
> sundials__public.ml
> 2. create a file sundials.ml with contents:
>
>   module Private = Sundials__private
>   module Public = Sundials__public
>
> 3. compile sundials.ml with
>
>   ocamlc -no-alias-deps -c sundials.ml
>
> (you may want to disable warning 49 when doing this)
>
> 4. compile the individual files in the library with
>
>   ocamlc -no-alias-deps -open Sundials -c sundials__private.ml
>   ocamlc -no-alias-deps -open Sundials -c sundials__public.ml
>
> 5. You can now delete (or not install) sundials__private.cmi and ship
> the other files
>
>   sundials.cmo
>   sundials.cmi
>   sundials__public.cmo
>   sundials__public.cmi
>   sundials__private.cmo
>
> to hide the private module from "outside" library users.
>
> Note that if you use jbuilder/dune, then your library will be built
> like this (steps 1-4) by default.
>
> Hope it helps,
>
> Best wishes,
> Nicolás
>
> On Thu, Apr 26, 2018 at 4:18 PM, Jun Inoue <jun.lambda@gmail.com> wrote:
>> Dear list,
>>
>> Is there a way to make a type concrete inside a library, yet opaque to
>> library users, preferably in a way that works with -pack?  This is a
>> nagging issue in our sundials package
>> (http://inria-parkas.github.io/sundialsml/).
>>
>> Basically, we have a type declared in one module of the library that
>> is pattern-matched upon in other modules, like:
>>
>> (* private.ml *)
>> type opaque_type = Foo | Bar
>>
>> (* public.ml *)
>> let f : opaque_type -> int = function
>>   | Foo -> 0
>>   | Bar -> 1
>>
>> There are a few constraints:
>> - We don't want users to be able to pattern-match on opaque_type.
>> - We need multiple modules in the library to pattern-match on
>> opaque-type (so moving opaque_typ e to public.ml is not an option).
>> - To avoid namespace pollution, we want to pack the whole library
>> (with ocamlc -pack) as a single Sundials module, so the user sees a
>> Sundials.Public module instead of just Public.
>>
>> Is this possible?  Right now, we just collect public.cmo and
>> private.cmo into sundials.cma and throw away private.cmi.  But this
>> doesn't work with packing:
>>
>> $ ocamlc -pack -o sundials.cmo private.cmo public.cmo
>>
>> demands that there be a private.cmi.
>>
>> --
>> Jun Inoue
>>
>> --
>> 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] Type That's Concrete From Within A Library Abstract From Without

[Jun Inoue]

Hi Ivan,

That's basically our current approach, but it doesn't solve the
namespace pollution problem.  In your example, when someone installs a
file named b.cmi (whose interface is unrelated to your b.ml), the name
conflict prevents loading the std.cma file at all:

$ ocaml
        OCaml version 4.04.0

# #show B;;
module B : sig val foo : int end
# #load "std.cma";;
The files std.cma and b.cmi disagree over interface B

So the technique makes B inaccessible but doesn't remove it from the
namespace.  This is why we want to -pack things, because our analogue
of b.ml is named matrix.ml, and there's no other sensible name for it.

This technique doesn't work with -pack because that option demands all
.cmi's, including b.cmi.  I guess we could rename matrix.ml to
matrix_internal_dont_touch.ml, but we wanted to know if there's a
cleaner approach.  I wish we could supply a .mli file to the product
of -pack, but that also doesn't work...

On Fri, Apr 27, 2018 at 12:06 AM, Ivan Gotovchits <ivg@ieee.org> wrote:
> Hi Jun,
>
> You can achieve this by implying an extra layer of indirection, i.e., by
> having two levels of interfaces. For example,
>
>    * A.ml - implementation of module A
>    * A.mli - private interface of module A
>    * B.ml  - implementation of module B that may rely on anything in A.mli
>    * Std.ml - a set of modules that you would like to import, e.g., `module
> A = A`, `module B = B`
>    * Std.mli - public interface specification
>
>
> Next, you deploy `std.cmxa` and `std.cmi` but keep `a.cmi` and `b.cmi` to
> yourself. This will prevent users from accessing your private modules A and
> B directly. (In oasis you can use PrivateModules stanza for this)
>
> Now you will have `Std.A` and `Std.B` that exposes as much as you want. Not
> sure whether it will work with the `-pack`, but you can use this approach
> instead of it. This is how we address the same issue in [BAP][1]
>
> Cheers,
> Ivan
>
> [1]: https://github.com/BinaryAnalysisPlatform/bap
>
>
> On Thu, Apr 26, 2018 at 10:18 AM, Jun Inoue <jun.lambda@gmail.com> wrote:
>>
>> Dear list,
>>
>> Is there a way to make a type concrete inside a library, yet opaque to
>> library users, preferably in a way that works with -pack?  This is a
>> nagging issue in our sundials package
>> (http://inria-parkas.github.io/sundialsml/).
>>
>> Basically, we have a type declared in one module of the library that
>> is pattern-matched upon in other modules, like:
>>
>> (* private.ml *)
>> type opaque_type = Foo | Bar
>>
>> (* public.ml *)
>> let f : opaque_type -> int = function
>>   | Foo -> 0
>>   | Bar -> 1
>>
>> There are a few constraints:
>> - We don't want users to be able to pattern-match on opaque_type.
>> - We need multiple modules in the library to pattern-match on
>> opaque-type (so moving opaque_typ e to public.ml is not an option).
>> - To avoid namespace pollution, we want to pack the whole library
>> (with ocamlc -pack) as a single Sundials module, so the user sees a
>> Sundials.Public module instead of just Public.
>>
>> Is this possible?  Right now, we just collect public.cmo and
>> private.cmo into sundials.cma and throw away private.cmi.  But this
>> doesn't work with packing:
>>
>> $ ocamlc -pack -o sundials.cmo private.cmo public.cmo
>>
>> demands that there be a private.cmi.
>>
>> --
>> Jun Inoue
>>
>> --
>> 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
>
>



-- 
Jun Inoue

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Re: [Caml-list] Type That's Concrete From Within A Library Abstract From Without

[Jacques Garrigue]

You can provide a mli for the -pack.
Just compile it before.

$ cat > a.ml
type t = int
let x : int = 3
$ cat > b.ml
let x2 = A.x * A.x
$ ocamlc -for-pack P a.ml b.ml
$ cat > p.mli
module A : sig type t val x : t end
module B : sig val x2 : int end
$ ocamlc -c p.mli 
$ ocamlc -pack -o p.cmo a.cmo b.cmo

Now, if you use your library with only p.cmo and p.cmi available, you will
only be able to access it through the interface you provided.

Also, the method using module aliases can work too: you just have
to use longer file names for the internal modules, to reduce the risk of
conflicts. But this is more involved than using -pack with a mli.

Jacques Garrigue

On 2018/04/27 14:48, Jun Inoue wrote:
> 
> Hi Ivan,
> 
> That's basically our current approach, but it doesn't solve the
> namespace pollution problem.  In your example, when someone installs a
> file named b.cmi (whose interface is unrelated to your b.ml), the name
> conflict prevents loading the std.cma file at all:
> 
> $ ocaml
>        OCaml version 4.04.0
> 
> # #show B;;
> module B : sig val foo : int end
> # #load "std.cma";;
> The files std.cma and b.cmi disagree over interface B
> 
> So the technique makes B inaccessible but doesn't remove it from the
> namespace.  This is why we want to -pack things, because our analogue
> of b.ml is named matrix.ml, and there's no other sensible name for it.
> 
> This technique doesn't work with -pack because that option demands all
> .cmi's, including b.cmi.  I guess we could rename matrix.ml to
> matrix_internal_dont_touch.ml, but we wanted to know if there's a
> cleaner approach.  I wish we could supply a .mli file to the product
> of -pack, but that also doesn't work...
> 
> On Fri, Apr 27, 2018 at 12:06 AM, Ivan Gotovchits <ivg@ieee.org> wrote:
>> Hi Jun,
>> 
>> You can achieve this by implying an extra layer of indirection, i.e., by
>> having two levels of interfaces. For example,
>> 
>>   * A.ml - implementation of module A
>>   * A.mli - private interface of module A
>>   * B.ml  - implementation of module B that may rely on anything in A.mli
>>   * Std.ml - a set of modules that you would like to import, e.g., `module
>> A = A`, `module B = B`
>>   * Std.mli - public interface specification
>> 
>> 
>> Next, you deploy `std.cmxa` and `std.cmi` but keep `a.cmi` and `b.cmi` to
>> yourself. This will prevent users from accessing your private modules A and
>> B directly. (In oasis you can use PrivateModules stanza for this)
>> 
>> Now you will have `Std.A` and `Std.B` that exposes as much as you want. Not
>> sure whether it will work with the `-pack`, but you can use this approach
>> instead of it. This is how we address the same issue in [BAP][1]
>> 
>> Cheers,
>> Ivan
>> 
>> [1]: https://github.com/BinaryAnalysisPlatform/bap
>> 
>> 
>> On Thu, Apr 26, 2018 at 10:18 AM, Jun Inoue <jun.lambda@gmail.com> wrote:
>>> 
>>> Dear list,
>>> 
>>> Is there a way to make a type concrete inside a library, yet opaque to
>>> library users, preferably in a way that works with -pack?  This is a
>>> nagging issue in our sundials package
>>> (http://inria-parkas.github.io/sundialsml/).
>>> 
>>> Basically, we have a type declared in one module of the library that
>>> is pattern-matched upon in other modules, like:
>>> 
>>> (* private.ml *)
>>> type opaque_type = Foo | Bar
>>> 
>>> (* public.ml *)
>>> let f : opaque_type -> int = function
>>>  | Foo -> 0
>>>  | Bar -> 1
>>> 
>>> There are a few constraints:
>>> - We don't want users to be able to pattern-match on opaque_type.
>>> - We need multiple modules in the library to pattern-match on
>>> opaque-type (so moving opaque_typ e to public.ml is not an option).
>>> - To avoid namespace pollution, we want to pack the whole library
>>> (with ocamlc -pack) as a single Sundials module, so the user sees a
>>> Sundials.Public module instead of just Public.
>>> 
>>> Is this possible?  Right now, we just collect public.cmo and
>>> private.cmo into sundials.cma and throw away private.cmi.  But this
>>> doesn't work with packing:
>>> 
>>> $ ocamlc -pack -o sundials.cmo private.cmo public.cmo
>>> 
>>> demands that there be a private.cmi.
>>> 
>>> --
>>> Jun Inoue
>>> 
>>> --
>>> 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] Type That's Concrete From Within A Library Abstract From Without

[Jun Inoue]

Hi Jacques,

OCaml gives a type error if a public type in b.ml references a
non-trivial type in a.ml.  Is there a way around this?

$ cat > a.ml
type t = Foo of int
let x : t = Foo 3
$ cat > b.ml
type t = A.t
let x2 = A.x
$ cat > p.mli
module B : sig type t = A.t val x2 : t end
$ ocamlc -for-pack P -c a.ml b.ml
$ ocamlc -c p.mli
$ ocamlc -pack -o p.cmo a.cmo b.cmo
File "_none_", line 1:
Error: The implementation (obtained by packing)
       does not match the interface p.mli:
       In module B:
       Modules do not match:
         sig type t = A.t val x2 : A.t end
       is not included in
         sig type t = A.t val x2 : t end
       In module B:
       Type declarations do not match:
         type t = A.t
       is not included in
         type t = A.t


On Fri, Apr 27, 2018 at 3:05 PM, Jacques Garrigue
<garrigue@math.nagoya-u.ac.jp> wrote:
> You can provide a mli for the -pack.
> Just compile it before.
>
> $ cat > a.ml
> type t = int
> let x : int = 3
> $ cat > b.ml
> let x2 = A.x * A.x
> $ ocamlc -for-pack P a.ml b.ml
> $ cat > p.mli
> module A : sig type t val x : t end
> module B : sig val x2 : int end
> $ ocamlc -c p.mli
> $ ocamlc -pack -o p.cmo a.cmo b.cmo
>
> Now, if you use your library with only p.cmo and p.cmi available, you will
> only be able to access it through the interface you provided.
>
> Also, the method using module aliases can work too: you just have
> to use longer file names for the internal modules, to reduce the risk of
> conflicts. But this is more involved than using -pack with a mli.
>
> Jacques Garrigue
>
> On 2018/04/27 14:48, Jun Inoue wrote:
>>
>> Hi Ivan,
>>
>> That's basically our current approach, but it doesn't solve the
>> namespace pollution problem.  In your example, when someone installs a
>> file named b.cmi (whose interface is unrelated to your b.ml), the name
>> conflict prevents loading the std.cma file at all:
>>
>> $ ocaml
>>        OCaml version 4.04.0
>>
>> # #show B;;
>> module B : sig val foo : int end
>> # #load "std.cma";;
>> The files std.cma and b.cmi disagree over interface B
>>
>> So the technique makes B inaccessible but doesn't remove it from the
>> namespace.  This is why we want to -pack things, because our analogue
>> of b.ml is named matrix.ml, and there's no other sensible name for it.
>>
>> This technique doesn't work with -pack because that option demands all
>> .cmi's, including b.cmi.  I guess we could rename matrix.ml to
>> matrix_internal_dont_touch.ml, but we wanted to know if there's a
>> cleaner approach.  I wish we could supply a .mli file to the product
>> of -pack, but that also doesn't work...
>>
>> On Fri, Apr 27, 2018 at 12:06 AM, Ivan Gotovchits <ivg@ieee.org> wrote:
>>> Hi Jun,
>>>
>>> You can achieve this by implying an extra layer of indirection, i.e., by
>>> having two levels of interfaces. For example,
>>>
>>>   * A.ml - implementation of module A
>>>   * A.mli - private interface of module A
>>>   * B.ml  - implementation of module B that may rely on anything in A.mli
>>>   * Std.ml - a set of modules that you would like to import, e.g., `module
>>> A = A`, `module B = B`
>>>   * Std.mli - public interface specification
>>>
>>>
>>> Next, you deploy `std.cmxa` and `std.cmi` but keep `a.cmi` and `b.cmi` to
>>> yourself. This will prevent users from accessing your private modules A and
>>> B directly. (In oasis you can use PrivateModules stanza for this)
>>>
>>> Now you will have `Std.A` and `Std.B` that exposes as much as you want. Not
>>> sure whether it will work with the `-pack`, but you can use this approach
>>> instead of it. This is how we address the same issue in [BAP][1]
>>>
>>> Cheers,
>>> Ivan
>>>
>>> [1]: https://github.com/BinaryAnalysisPlatform/bap
>>>
>>>
>>> On Thu, Apr 26, 2018 at 10:18 AM, Jun Inoue <jun.lambda@gmail.com> wrote:
>>>>
>>>> Dear list,
>>>>
>>>> Is there a way to make a type concrete inside a library, yet opaque to
>>>> library users, preferably in a way that works with -pack?  This is a
>>>> nagging issue in our sundials package
>>>> (http://inria-parkas.github.io/sundialsml/).
>>>>
>>>> Basically, we have a type declared in one module of the library that
>>>> is pattern-matched upon in other modules, like:
>>>>
>>>> (* private.ml *)
>>>> type opaque_type = Foo | Bar
>>>>
>>>> (* public.ml *)
>>>> let f : opaque_type -> int = function
>>>>  | Foo -> 0
>>>>  | Bar -> 1
>>>>
>>>> There are a few constraints:
>>>> - We don't want users to be able to pattern-match on opaque_type.
>>>> - We need multiple modules in the library to pattern-match on
>>>> opaque-type (so moving opaque_typ e to public.ml is not an option).
>>>> - To avoid namespace pollution, we want to pack the whole library
>>>> (with ocamlc -pack) as a single Sundials module, so the user sees a
>>>> Sundials.Public module instead of just Public.
>>>>
>>>> Is this possible?  Right now, we just collect public.cmo and
>>>> private.cmo into sundials.cma and throw away private.cmi.  But this
>>>> doesn't work with packing:
>>>>
>>>> $ ocamlc -pack -o sundials.cmo private.cmo public.cmo
>>>>
>>>> demands that there be a private.cmi.
>>>>
>>>> --
>>>> Jun Inoue
>>>>
>>>> --
>>>> 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
>
>
>



-- 
Jun Inoue

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Re: [Caml-list] Type That's Concrete From Within A Library Abstract From Without

[Mikhail Mandrykin]

Hello,

> $ cat > p.mli
> module B : sig type t = A.t val x2 : t end
It seems it's the ambiguity between the "outer" and "packed" module A. Shadowing the outer A in p.mli fixes it:

$ cat > p.mli
module A : sig type t end (* t is abstract *)
module B : sig type t = A.t val x2 : t end
$ ocamlc -c p.mli
$ ocamlc -pack -o p.cmo a.cmo b.cmo


On 27.04.2018 11:53, Jun Inoue wrote:
> Hi Jacques,
>
> OCaml gives a type error if a public type in b.ml references a
> non-trivial type in a.ml.  Is there a way around this?
>
> $ cat > a.ml
> type t = Foo of int
> let x : t = Foo 3
> $ cat > b.ml
> type t = A.t
> let x2 = A.x
> $ cat > p.mli
> module B : sig type t = A.t val x2 : t end
> $ ocamlc -for-pack P -c a.ml b.ml
> $ ocamlc -c p.mli
> $ ocamlc -pack -o p.cmo a.cmo b.cmo
> File "_none_", line 1:
> Error: The implementation (obtained by packing)
>         does not match the interface p.mli:
>         In module B:
>         Modules do not match:
>           sig type t = A.t val x2 : A.t end
>         is not included in
>           sig type t = A.t val x2 : t end
>         In module B:
>         Type declarations do not match:
>           type t = A.t
>         is not included in
>           type t = A.t
>
>
> On Fri, Apr 27, 2018 at 3:05 PM, Jacques Garrigue
> <garrigue@math.nagoya-u.ac.jp> wrote:
>> You can provide a mli for the -pack.
>> Just compile it before.
>>
>> $ cat > a.ml
>> type t = int
>> let x : int = 3
>> $ cat > b.ml
>> let x2 = A.x * A.x
>> $ ocamlc -for-pack P a.ml b.ml
>> $ cat > p.mli
>> module A : sig type t val x : t end
>> module B : sig val x2 : int end
>> $ ocamlc -c p.mli
>> $ ocamlc -pack -o p.cmo a.cmo b.cmo
>>
>> Now, if you use your library with only p.cmo and p.cmi available, you will
>> only be able to access it through the interface you provided.
>>
>> Also, the method using module aliases can work too: you just have
>> to use longer file names for the internal modules, to reduce the risk of
>> conflicts. But this is more involved than using -pack with a mli.
>>
>> Jacques Garrigue
>>
>> On 2018/04/27 14:48, Jun Inoue wrote:
>>> Hi Ivan,
>>>
>>> That's basically our current approach, but it doesn't solve the
>>> namespace pollution problem.  In your example, when someone installs a
>>> file named b.cmi (whose interface is unrelated to your b.ml), the name
>>> conflict prevents loading the std.cma file at all:
>>>
>>> $ ocaml
>>>         OCaml version 4.04.0
>>>
>>> # #show B;;
>>> module B : sig val foo : int end
>>> # #load "std.cma";;
>>> The files std.cma and b.cmi disagree over interface B
>>>
>>> So the technique makes B inaccessible but doesn't remove it from the
>>> namespace.  This is why we want to -pack things, because our analogue
>>> of b.ml is named matrix.ml, and there's no other sensible name for it.
>>>
>>> This technique doesn't work with -pack because that option demands all
>>> .cmi's, including b.cmi.  I guess we could rename matrix.ml to
>>> matrix_internal_dont_touch.ml, but we wanted to know if there's a
>>> cleaner approach.  I wish we could supply a .mli file to the product
>>> of -pack, but that also doesn't work...
>>>
>>> On Fri, Apr 27, 2018 at 12:06 AM, Ivan Gotovchits <ivg@ieee.org> wrote:
>>>> Hi Jun,
>>>>
>>>> You can achieve this by implying an extra layer of indirection, i.e., by
>>>> having two levels of interfaces. For example,
>>>>
>>>>    * A.ml - implementation of module A
>>>>    * A.mli - private interface of module A
>>>>    * B.ml  - implementation of module B that may rely on anything in A.mli
>>>>    * Std.ml - a set of modules that you would like to import, e.g., `module
>>>> A = A`, `module B = B`
>>>>    * Std.mli - public interface specification
>>>>
>>>>
>>>> Next, you deploy `std.cmxa` and `std.cmi` but keep `a.cmi` and `b.cmi` to
>>>> yourself. This will prevent users from accessing your private modules A and
>>>> B directly. (In oasis you can use PrivateModules stanza for this)
>>>>
>>>> Now you will have `Std.A` and `Std.B` that exposes as much as you want. Not
>>>> sure whether it will work with the `-pack`, but you can use this approach
>>>> instead of it. This is how we address the same issue in [BAP][1]
>>>>
>>>> Cheers,
>>>> Ivan
>>>>
>>>> [1]: https://github.com/BinaryAnalysisPlatform/bap
>>>>
>>>>
>>>> On Thu, Apr 26, 2018 at 10:18 AM, Jun Inoue <jun.lambda@gmail.com> wrote:
>>>>> Dear list,
>>>>>
>>>>> Is there a way to make a type concrete inside a library, yet opaque to
>>>>> library users, preferably in a way that works with -pack?  This is a
>>>>> nagging issue in our sundials package
>>>>> (http://inria-parkas.github.io/sundialsml/).
>>>>>
>>>>> Basically, we have a type declared in one module of the library that
>>>>> is pattern-matched upon in other modules, like:
>>>>>
>>>>> (* private.ml *)
>>>>> type opaque_type = Foo | Bar
>>>>>
>>>>> (* public.ml *)
>>>>> let f : opaque_type -> int = function
>>>>>   | Foo -> 0
>>>>>   | Bar -> 1
>>>>>
>>>>> There are a few constraints:
>>>>> - We don't want users to be able to pattern-match on opaque_type.
>>>>> - We need multiple modules in the library to pattern-match on
>>>>> opaque-type (so moving opaque_typ e to public.ml is not an option).
>>>>> - To avoid namespace pollution, we want to pack the whole library
>>>>> (with ocamlc -pack) as a single Sundials module, so the user sees a
>>>>> Sundials.Public module instead of just Public.
>>>>>
>>>>> Is this possible?  Right now, we just collect public.cmo and
>>>>> private.cmo into sundials.cma and throw away private.cmi.  But this
>>>>> doesn't work with packing:
>>>>>
>>>>> $ ocamlc -pack -o sundials.cmo private.cmo public.cmo
>>>>>
>>>>> demands that there be a private.cmi.
>>>>>
>>>>> --
>>>>> Jun Inoue
>>>>>
>>>>> --
>>>>> 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
>>
>>
>
>

-- 
Mikhail Mandrykin
Linux Verification Center, ISPRAS
web: http://linuxtesting.org
e-mail: mandrykin@ispras.ru


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Re: [Caml-list] Type That's Concrete From Within A Library Abstract From Without

[Elie Canonici Merle]

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Hi,

Do you need to expose that B.t and A.t are the same?

Because if you don't it works.

$ cat > a.ml
type t = Foo of int
let x : t = Foo 3
$ cat > b.ml
type t = A.t
let x2 = A.x
$ cat > p.mli
module B : sig type t val x2 : t end
$ ocamlc -for-pack P -c a.ml b.ml
$ ocamlc -c p.mli
$ ocamlc -pack -o p.cmo a.cmo b.cmo

If you need to expose the type equality you can make it work by adding the
signature of the module A while still keeping A.t abstract in p.mli (or
not, depending on your needs)

$ cat > a.ml
type t = Foo of int
let x : t = Foo 3
$ cat > b.ml
type t = A.t
let x2 = A.x
$ cat > p.mli
module A : sig type t end
module B : sig type t = A.t val x2 : t end
$ ocamlc -for-pack P -c a.ml b.ml
$ ocamlc -c p.mli
$ ocamlc -pack -o p.cmo a.cmo b.cmo

I hope it helps.


2018-04-27 10:53 GMT+02:00 Jun Inoue <jun.lambda@gmail.com>:

> Hi Jacques,
>
> OCaml gives a type error if a public type in b.ml references a
> non-trivial type in a.ml.  Is there a way around this?
>
> $ cat > a.ml
> type t = Foo of int
> let x : t = Foo 3
> $ cat > b.ml
> type t = A.t
> let x2 = A.x
> $ cat > p.mli
> module B : sig type t = A.t val x2 : t end
> $ ocamlc -for-pack P -c a.ml b.ml
> $ ocamlc -c p.mli
> $ ocamlc -pack -o p.cmo a.cmo b.cmo
> File "_none_", line 1:
> Error: The implementation (obtained by packing)
>        does not match the interface p.mli:
>        In module B:
>        Modules do not match:
>          sig type t = A.t val x2 : A.t end
>        is not included in
>          sig type t = A.t val x2 : t end
>        In module B:
>        Type declarations do not match:
>          type t = A.t
>        is not included in
>          type t = A.t
>
>
> On Fri, Apr 27, 2018 at 3:05 PM, Jacques Garrigue
> <garrigue@math.nagoya-u.ac.jp> wrote:
> > You can provide a mli for the -pack.
> > Just compile it before.
> >
> > $ cat > a.ml
> > type t = int
> > let x : int = 3
> > $ cat > b.ml
> > let x2 = A.x * A.x
> > $ ocamlc -for-pack P a.ml b.ml
> > $ cat > p.mli
> > module A : sig type t val x : t end
> > module B : sig val x2 : int end
> > $ ocamlc -c p.mli
> > $ ocamlc -pack -o p.cmo a.cmo b.cmo
> >
> > Now, if you use your library with only p.cmo and p.cmi available, you
> will
> > only be able to access it through the interface you provided.
> >
> > Also, the method using module aliases can work too: you just have
> > to use longer file names for the internal modules, to reduce the risk of
> > conflicts. But this is more involved than using -pack with a mli.
> >
> > Jacques Garrigue
> >
> > On 2018/04/27 14:48, Jun Inoue wrote:
> >>
> >> Hi Ivan,
> >>
> >> That's basically our current approach, but it doesn't solve the
> >> namespace pollution problem.  In your example, when someone installs a
> >> file named b.cmi (whose interface is unrelated to your b.ml), the name
> >> conflict prevents loading the std.cma file at all:
> >>
> >> $ ocaml
> >>        OCaml version 4.04.0
> >>
> >> # #show B;;
> >> module B : sig val foo : int end
> >> # #load "std.cma";;
> >> The files std.cma and b.cmi disagree over interface B
> >>
> >> So the technique makes B inaccessible but doesn't remove it from the
> >> namespace.  This is why we want to -pack things, because our analogue
> >> of b.ml is named matrix.ml, and there's no other sensible name for it.
> >>
> >> This technique doesn't work with -pack because that option demands all
> >> .cmi's, including b.cmi.  I guess we could rename matrix.ml to
> >> matrix_internal_dont_touch.ml, but we wanted to know if there's a
> >> cleaner approach.  I wish we could supply a .mli file to the product
> >> of -pack, but that also doesn't work...
> >>
> >> On Fri, Apr 27, 2018 at 12:06 AM, Ivan Gotovchits <ivg@ieee.org> wrote:
> >>> Hi Jun,
> >>>
> >>> You can achieve this by implying an extra layer of indirection, i.e.,
> by
> >>> having two levels of interfaces. For example,
> >>>
> >>>   * A.ml - implementation of module A
> >>>   * A.mli - private interface of module A
> >>>   * B.ml  - implementation of module B that may rely on anything in
> A.mli
> >>>   * Std.ml - a set of modules that you would like to import, e.g.,
> `module
> >>> A = A`, `module B = B`
> >>>   * Std.mli - public interface specification
> >>>
> >>>
> >>> Next, you deploy `std.cmxa` and `std.cmi` but keep `a.cmi` and `b.cmi`
> to
> >>> yourself. This will prevent users from accessing your private modules
> A and
> >>> B directly. (In oasis you can use PrivateModules stanza for this)
> >>>
> >>> Now you will have `Std.A` and `Std.B` that exposes as much as you
> want. Not
> >>> sure whether it will work with the `-pack`, but you can use this
> approach
> >>> instead of it. This is how we address the same issue in [BAP][1]
> >>>
> >>> Cheers,
> >>> Ivan
> >>>
> >>> [1]: https://github.com/BinaryAnalysisPlatform/bap
> >>>
> >>>
> >>> On Thu, Apr 26, 2018 at 10:18 AM, Jun Inoue <jun.lambda@gmail.com>
> wrote:
> >>>>
> >>>> Dear list,
> >>>>
> >>>> Is there a way to make a type concrete inside a library, yet opaque to
> >>>> library users, preferably in a way that works with -pack?  This is a
> >>>> nagging issue in our sundials package
> >>>> (http://inria-parkas.github.io/sundialsml/).
> >>>>
> >>>> Basically, we have a type declared in one module of the library that
> >>>> is pattern-matched upon in other modules, like:
> >>>>
> >>>> (* private.ml *)
> >>>> type opaque_type = Foo | Bar
> >>>>
> >>>> (* public.ml *)
> >>>> let f : opaque_type -> int = function
> >>>>  | Foo -> 0
> >>>>  | Bar -> 1
> >>>>
> >>>> There are a few constraints:
> >>>> - We don't want users to be able to pattern-match on opaque_type.
> >>>> - We need multiple modules in the library to pattern-match on
> >>>> opaque-type (so moving opaque_typ e to public.ml is not an option).
> >>>> - To avoid namespace pollution, we want to pack the whole library
> >>>> (with ocamlc -pack) as a single Sundials module, so the user sees a
> >>>> Sundials.Public module instead of just Public.
> >>>>
> >>>> Is this possible?  Right now, we just collect public.cmo and
> >>>> private.cmo into sundials.cma and throw away private.cmi.  But this
> >>>> doesn't work with packing:
> >>>>
> >>>> $ ocamlc -pack -o sundials.cmo private.cmo public.cmo
> >>>>
> >>>> demands that there be a private.cmi.
> >>>>
> >>>> --
> >>>> Jun Inoue
> >>>>
> >>>> --
> >>>> 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
> >
> >
> >
>
>
>
> --
> Jun Inoue
>
> --
> 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] Type That's Concrete From Within A Library Abstract From Without

[Timothy Bourke]

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* Nicolás Ojeda Bär [2018-04-26 17:03 +0200]:
>This is a limitation of module packs. However, there is a much better
>alternative to module packs in the form of module aliases which will
>allow you to do what you want.

Thank you for this suggestion. We have tried it on a development 
branch of the Sundials/ML library and it works quite well.

>4. compile the individual files in the library with
>
>  ocamlc -no-alias-deps -open Sundials -c sundials__private.ml
>  ocamlc -no-alias-deps -open Sundials -c sundials__public.ml

For the record, two details are worth noting regarding the "-open 
Sundials".

1. It works well with Merlin if one adds the line

      FLG -open Sundials

   to the .merlin file.

2. It does not work well with ocamldoc, which has no -open option.
   Maybe there is another way around this problem?

In any case, there currently seem to be some other limitations around 
ocamldoc and module aliases.

Tim.


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Re: [Caml-list] Type That's Concrete From Within A Library Abstract From Without

[Gabriel Scherer]

According to the OCaml changelog, ocamldoc support for -open was
contributed by Florian Angeletti for OCaml 4.04, so it should be
supported.
(But indeed there may be other limitations around module aliases.)
On Fri, Jul 6, 2018 at 10:08 AM Timothy Bourke <tim@tbrk.org> wrote:
>
> * Nicolás Ojeda Bär [2018-04-26 17:03 +0200]:
> >This is a limitation of module packs. However, there is a much better
> >alternative to module packs in the form of module aliases which will
> >allow you to do what you want.
>
> Thank you for this suggestion. We have tried it on a development
> branch of the Sundials/ML library and it works quite well.
>
> >4. compile the individual files in the library with
> >
> >  ocamlc -no-alias-deps -open Sundials -c sundials__private.ml
> >  ocamlc -no-alias-deps -open Sundials -c sundials__public.ml
>
> For the record, two details are worth noting regarding the "-open
> Sundials".
>
> 1. It works well with Merlin if one adds the line
>
>       FLG -open Sundials
>
>    to the .merlin file.
>
> 2. It does not work well with ocamldoc, which has no -open option.
>    Maybe there is another way around this problem?
>
> In any case, there currently seem to be some other limitations around
> ocamldoc and module aliases.
>
> Tim.
>

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Re: [Caml-list] Type That's Concrete From Within A Library Abstract From Without

[Timothy Bourke]

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* Gabriel Scherer [2018-07-06 10:52 +0200]:
>According to the OCaml changelog, ocamldoc support for -open was
>contributed by Florian Angeletti for OCaml 4.04, so it should be
>supported.

Thanks Gabriel (and Florian!).

Sorry for missing that: the option is indeed shown by ocamldoc -h, but 
I only checked the man page where it is missing
(Fix: https://github.com/ocaml/ocaml/pull/1887).

>(But indeed there may be other limitations around module aliases.)

We will use URLs for the time being, e.g.,
  {{!Sundials_config.version}Sundials.Config.version}.

Tim.


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