[Caml-list] Functor signature "inheritance"

[Caml-list] Functor signature "inheritance"

[Shayne Fletcher]

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If one wants to include a functor signature in another...

module type EQ = sig
  type t
  val eq : t * t -> bool
end

module type EQ_PROD = functor (X : EQ) (Y : EQ) ->
sig
    type t = X.t * Y.t
    val eq : t * t -> bool
  end

module type ORD = sig
  include EQ
  val lt : t * t -> bool
end

module type LT_PROD = functor (X : EQ) (Y : EQ) ->
sig
  include EQ_PROD (*What do I say here?*)
end

​... How does one do that? Is there a syntax for this sort of thing?​

-- 
Shayne Fletcher

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Re: [Caml-list] Functor signature "inheritance"

[Nicolas Ojeda Bar]

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Hi Shayne,

One approach is to name the *output* signature of the functors:

module type EQ_PROD_S = sig
    module X : EQ
    module Y : EQ
    type t = X.t * Y.t
    val eq: t * t -> bool
end

module type EQ_PROD = functor (X : EQ) (Y : EQ) ->
    EQ_PROD_S with module X := X and module Y := Y

module type ORD_PROD_S = sig
    include EQ_PROD_S
    val lt : t * t -> bool
end

module type LT_PROD = functor (X : EQ) (Y : EQ) ->
    LT_PROD_S with module X := X and module Y := Y

etc.

Cheers,
Nicolas



On Fri, Oct 28, 2016 at 2:44 PM, Shayne Fletcher <
shayne.fletcher.50@gmail.com> wrote:

> If one wants to include a functor signature in another...
>
> module type EQ = sig
>   type t
>   val eq : t * t -> bool
> end
>
> module type EQ_PROD = functor (X : EQ) (Y : EQ) ->
> sig
>     type t = X.t * Y.t
>     val eq : t * t -> bool
>   end
>
> module type ORD = sig
>   include EQ
>   val lt : t * t -> bool
> end
>
> module type LT_PROD = functor (X : EQ) (Y : EQ) ->
> sig
>   include EQ_PROD (*What do I say here?*)
> end
>
> ​... How does one do that? Is there a syntax for this sort of thing?​
>
> --
> Shayne Fletcher
>

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Re: [Caml-list] Functor signature "inheritance"

[Shayne Fletcher]

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On Fri, Oct 28, 2016 at 9:01 AM, Nicolas Ojeda Bar <
nicolas.ojeda.bar@lexifi.com> wrote:

> One approach is to name the *output* signature of the functors:


​Ooh! Thanks!​

-- 
Shayne Fletcher

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Re: [Caml-list] Functor signature "inheritance"

[Shayne Fletcher]

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On Fri, Oct 28, 2016 at 9:01 AM, Nicolas Ojeda Bar <
nicolas.ojeda.bar@lexifi.com> wrote:

>
> One approach is to name the *output* signature of the functors:
>
> module type EQ_PROD_S = sig
>     module X : EQ
>     module Y : EQ
>     type t = X.t * Y.t
>     val eq: t * t -> bool
> end
>

​Sorry to be a bother. Got another one for you Nicolas​!

How do I achieve the intent of this:

module type EQ = sig
  type t
  val eq : t * t -> bool
end

module type NUM = sig
  type t
  val from_int : int -> t
  val ( + ) : t -> t -> t
end

module type MUL_S = sig
  module N : NUM
  module E : EQ  with type t := N.t

  type t = N.t
  val mul : t -> t -> t
end

module type MUL = functor (E : EQ) (N : NUM) -> MUL_S with module N := N
and module E := E

The idea is that the modules satisfying EQ and NUM must agree in their type
t and MUL brings them together and adds a 'mul' function.

-- 
Shayne Fletcher

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Re: [Caml-list] Functor signature "inheritance"

[Nicolas Ojeda Bar]

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Hi Shayne,

You can add a constrain to your functor arguments :

module type MUL = functor (E : EQ) (N : NUM with type t = E.t) ->
    MUL_S with module N := N and module E := E

Cheers,
Nicolas

On Fri, Oct 28, 2016 at 3:14 PM, Shayne Fletcher <
shayne.fletcher.50@gmail.com> wrote:

>
> On Fri, Oct 28, 2016 at 9:01 AM, Nicolas Ojeda Bar <
> nicolas.ojeda.bar@lexifi.com> wrote:
>
>>
>> One approach is to name the *output* signature of the functors:
>>
>> module type EQ_PROD_S = sig
>>     module X : EQ
>>     module Y : EQ
>>     type t = X.t * Y.t
>>     val eq: t * t -> bool
>> end
>>
>
> ​Sorry to be a bother. Got another one for you Nicolas​!
>
> How do I achieve the intent of this:
>
> module type EQ = sig
>   type t
>   val eq : t * t -> bool
> end
>
> module type NUM = sig
>   type t
>   val from_int : int -> t
>   val ( + ) : t -> t -> t
> end
>
> module type MUL_S = sig
>   module N : NUM
>   module E : EQ  with type t := N.t
>
>   type t = N.t
>   val mul : t -> t -> t
> end
>
> module type MUL = functor (E : EQ) (N : NUM) -> MUL_S with module N := N
> and module E := E
>
> The idea is that the modules satisfying EQ and NUM must agree in their
> type t and MUL brings them together and adds a 'mul' function.
>
> --
> Shayne Fletcher
>

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Re: [Caml-list] Functor signature "inheritance"

[Shayne Fletcher]

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On Fri, Oct 28, 2016 at 9:25 AM, Nicolas Ojeda Bar <
nicolas.ojeda.bar@lexifi.com> wrote:

> You can add a constrain to your functor arguments :
>
> module type MUL = functor (E : EQ) (N : NUM with type t = E.t) ->
>     MUL_S with module N := N and module E := E
>

​That does it! I tried so many different things :) You're a rock 'n roll
star.

We *really* need a comprehensive tutorial or reference on how to express
sharing constraints!​

-- 
Shayne Fletcher

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Re: [Caml-list] Functor signature "inheritance"

[rixed]

Best book I've seen about this is this one:
http://www.eyrolles.com/Informatique/Livre/programmation-fonctionnelle-generique-et-objet-9782711748433

unfortunately never translated, and out of print.
That's really a shame.

Re: [Caml-list] Functor signature "inheritance"

[Shayne Fletcher]

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On Fri, Oct 28, 2016 at 9:47 AM, <rixed@happyleptic.org> wrote:

> unfortunately never translated, and out of print.
> That's really a shame.
>

​Truly. I'd even try wading through it in French if it were available
somewhere but alas!​

-- 
Shayne Fletcher

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Re: [Caml-list] Functor signature "inheritance"

[Gabriel Scherer]

This book can be found in online repositories (do you know about the
Library Genesis project?), but I don't think it can be diffused
without a copyright violation. If the list is out of print, the author
should be able to ask for it to be either reprinted, or to recover
diffusion rights for it -- and thus make it available online if they
so desire. But that is a procedure that (as understood in French law)
only the author can perform, I believe.

On Fri, Oct 28, 2016 at 9:55 AM, Shayne Fletcher
<shayne.fletcher.50@gmail.com> wrote:
>
> On Fri, Oct 28, 2016 at 9:47 AM, <rixed@happyleptic.org> wrote:
>>
>> unfortunately never translated, and out of print.
>> That's really a shame.
>
>
> Truly. I'd even try wading through it in French if it were available
> somewhere but alas!
>
> --
> Shayne Fletcher

Re: [Caml-list] Functor signature "inheritance"

[Shayne Fletcher]

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On Fri, Oct 28, 2016 at 9:28 AM, Shayne Fletcher <
shayne.fletcher.50@gmail.com> wrote:

> On Fri, Oct 28, 2016 at 9:25 AM, Nicolas Ojeda Bar <
> nicolas.ojeda.bar@lexifi.com> wrote:
>
>> You can add a constrain to your functor arguments :
>>
>> module type MUL = functor (E : EQ) (N : NUM with type t = E.t) ->
>>     MUL_S with module N := N and module E := E
>>
>
> ​That does it! I tried so many different things :) You're a rock 'n roll
> star.
>

​Still stuck on how to achieve this I'm afraid.

module type EQ = sig
  type t
  val eq : t * t -> bool
end

module type NUM = sig
  type t
  val from_int : int -> t
  val ( + ) : t -> t -> t
end

module type MUL_S = sig
  include EQ
  include NUM with type t := t

  val mul : t -> t -> t
end

module type MUL = functor (E : EQ) (N : NUM with type t = E.t) -> MUL_S

module Mul_default (E : EQ) (N : NUM with type t = E.t) : MUL  = struct

  include E
  include (N : NUM with type t := E.t)

  let mul (x : t) (y : t) : t = failwith "foo"

end

Yields.

​Error: Signature mismatch:
       Modules do not match:
         sig
           type t = E.t
           val eq : t * t -> bool
           val from_int : int -> E.t
           val ( + ) : E.t -> E.t -> E.t
           val mul : t -> t -> t
         end
       is not included in
         MUL​

-- 
Shayne Fletcher

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Re: [Caml-list] Functor signature "inheritance"

[Shayne Fletcher]

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On Fri, Oct 28, 2016 at 12:12 PM, Shayne Fletcher <
shayne.fletcher.50@gmail.com> wrote:

> ​Still stuck on how to achieve this I'm afraid.
>

​Ah wait. I think I've got it.

module Mul_default (E : EQ) (N : NUM with type t = E.t) : MUL_S = struct

  type t = E.t
  include (E : EQ with type t := t)
  include (N : NUM with type t := t)

  let mul (x : t) (y : t) : t = failwith "foo"

end
​



-- 
Shayne Fletcher

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Re: [Caml-list] Functor signature "inheritance"

[Nicolas Ojeda Bar]

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Hi Shayne,

I did not try it, but I think you want

module Mul_default : MUL = functor (E : EQ) (N : NUM with type t = E.t)  ->
struct
    include E
    include (N : NUM with type t := E.t)

    let mul (x : t) (y : t) : t = failwith "foo"
end

Cheers,
Nicolas


On Fri, Oct 28, 2016 at 6:12 PM, Shayne Fletcher <
shayne.fletcher.50@gmail.com> wrote:

>
> On Fri, Oct 28, 2016 at 9:28 AM, Shayne Fletcher <
> shayne.fletcher.50@gmail.com> wrote:
>
>> On Fri, Oct 28, 2016 at 9:25 AM, Nicolas Ojeda Bar <
>> nicolas.ojeda.bar@lexifi.com> wrote:
>>
>>> You can add a constrain to your functor arguments :
>>>
>>> module type MUL = functor (E : EQ) (N : NUM with type t = E.t) ->
>>>     MUL_S with module N := N and module E := E
>>>
>>
>> ​That does it! I tried so many different things :) You're a rock 'n roll
>> star.
>>
>
> ​Still stuck on how to achieve this I'm afraid.
>
> module type EQ = sig
>   type t
>   val eq : t * t -> bool
> end
>
> module type NUM = sig
>   type t
>   val from_int : int -> t
>   val ( + ) : t -> t -> t
> end
>
> module type MUL_S = sig
>   include EQ
>   include NUM with type t := t
>
>   val mul : t -> t -> t
> end
>
> module type MUL = functor (E : EQ) (N : NUM with type t = E.t) -> MUL_S
>
> module Mul_default (E : EQ) (N : NUM with type t = E.t) : MUL  = struct
>
>   include E
>   include (N : NUM with type t := E.t)
>
>   let mul (x : t) (y : t) : t = failwith "foo"
>
> end
>
> Yields.
>
> ​Error: Signature mismatch:
>        Modules do not match:
>          sig
>            type t = E.t
>            val eq : t * t -> bool
>            val from_int : int -> E.t
>            val ( + ) : E.t -> E.t -> E.t
>            val mul : t -> t -> t
>          end
>        is not included in
>          MUL​
>
> --
> Shayne Fletcher
>

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Re: [Caml-list] Functor signature "inheritance"

[Shayne Fletcher]

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On Fri, Oct 28, 2016 at 12:16 PM, Shayne Fletcher <
shayne.fletcher.50@gmail.com> wrote:

> module Mul_default (E : EQ) (N : NUM with type t = E.t) : MUL_S = struct
>
>   type t = E.t
>   include (E : EQ with type t := t)
>   include (N : NUM with type t := t)
>

​Grrr. No. I mucked up and put MUL_S.
​



-- 
Shayne Fletcher

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Re: [Caml-list] Functor signature "inheritance"

[Shayne Fletcher]

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On Fri, Oct 28, 2016 at 12:17 PM, Nicolas Ojeda Bar <
nicolas.ojeda.bar@lexifi.com> wrote:

> I did not try it, but I think you want
>
> module Mul_default : MUL = functor (E : EQ) (N : NUM with type t = E.t)
>  -> struct
>     include E
>     include (N : NUM with type t := E.t)
>
>     let mul (x : t) (y : t) : t = failwith "foo"
> end
>

​​Phew!

module type EQ = sig
  type t
  val eq : t * t -> bool
end

module type NUM = sig
  type t
  val from_int : int -> t
  val ( + ) : t -> t -> t
end

module type MUL_basic = sig
  type t
  val mul : t -> t -> t
end

module type MUL = functor (E : EQ) (N : NUM with type t = E.t) -> MUL_basic

module Mul_default : MUL = functor (E : EQ) (N : NUM with type t = E.t)  ->
struct
    include E
    include (N : NUM with type t := E.t)

    let mul (x : t) (y : t) : t = failwith "foo"
end

​Thanks Nicolas. Lot to learn here!

-- 
Shayne Fletcher

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Re: [Caml-list] Functor signature "inheritance"

[Shayne Fletcher]

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On Oct 28, 2016 11:45 AM, "Gabriel Scherer" <gabriel.scherer@gmail.com>
wrote:
>
> This book can be found in online repositories (do you know about the
> Library Genesis project?), but I don't think it can be diffused
> without a copyright violation. If the list is out of print, the author
> should be able to ask for it to be either reprinted, or to recover
> diffusion rights for it -- and thus make it available online if they
> so desire. But that is a procedure that (as understood in French law)
> only the author can perform, I believe.

Copy. Thanks.

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Re: [Caml-list] Functor signature "inheritance"

[Shayne Fletcher]

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On Fri, Oct 28, 2016 at 9:25 AM, Nicolas Ojeda Bar <
nicolas.ojeda.bar@lexifi.com> wrote:

> You can add a constrain to your functor arguments :


​Thanks again for all your help, rixed, Gabriel, Nicolas! I wrote up all
that I learned in this exercise, here
<http://t.sidekickopen68.com/e1t/c/5/f18dQhb0S7lC8dDMPbW2n0x6l2B9nMJW7t5XZs7dSpxYMRJm4bRbwtnW2zhqcR56dRtXf5pnn5l02?t=http%3A%2F%2Fblog.shaynefletcher.org%2F2016%2F10%2Fimplementing-type-classes-as-ocaml.html&si=5384785918689280&pi=b7eb6b4a-9ca6-4f00-cb44-c90db32d717e>
.

-- 
Shayne Fletcher

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