[Caml-list] Tuples (covariant immutable arrays)

[Caml-list] Tuples (covariant immutable arrays)

[Lukasz Stafiniak]

Hi,

Does anyone have a Tuple module that exports arrays as immutable and covariant?

Thanks,
Łukasz

Re: [Caml-list] Tuples (covariant immutable arrays)

[Edgar Friendly]

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Batteries has a Cap submodule that provides type-level protection for
arrays so they can be Read-only/Write-only/Read-write.  The same idea with
a variance annotation and just read-only access seems to be what you're
looking for, no?

2012/3/14 Lukasz Stafiniak <lukstafi@gmail.com>

> Hi,
>
> Does anyone have a Tuple module that exports arrays as immutable and
> covariant?
>
> Thanks,
> Łukasz
>
>
> --
> Caml-list mailing list.  Subscription management and archives:
> https://sympa-roc.inria.fr/wws/info/caml-list
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>
>

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Re: [Caml-list] Tuples (covariant immutable arrays)

[Lukasz Stafiniak]

On Wed, Mar 14, 2012 at 10:03 PM, Edgar Friendly <thelema314@gmail.com> wrote:
> Batteries has a Cap submodule that provides type-level protection for arrays
> so they can be Read-only/Write-only/Read-write.  The same idea with a
> variance annotation and just read-only access seems to be what you're
> looking for, no?

It seems no, because Cap is invariant, and for a reason: for example,
Hashtbl.Cap.of_table says
"This operation involves no copying. In other words, in let cap =
of_table a in ..., any modification in a will also have effect on cap
and reciprocally."

What I'm thinking about is  type +'a Tuple.t with Tuple.of_list and
Tuple.of_array both performing a copy.

Re: [Caml-list] Tuples (covariant immutable arrays)

[Edgar Friendly]

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Ok, trivial enough a change.  You'll have to make a case for the usefulness
of this data structure being in batteries for us to make the change,
otherwise, feel free to use the batteries code as a basis for your Tuple
data structure.  LGPL2.1+linking exception should be sufficiently liberal
for most uses.

E.

btw, link to the docs I meant to include in my first email:
http://ocaml-batteries-team.github.com/batteries-included/hdoc/BatArray.Cap.html

On Wed, Mar 14, 2012 at 5:12 PM, Lukasz Stafiniak <lukstafi@gmail.com>wrote:

> On Wed, Mar 14, 2012 at 10:03 PM, Edgar Friendly <thelema314@gmail.com>
> wrote:
> > Batteries has a Cap submodule that provides type-level protection for
> arrays
> > so they can be Read-only/Write-only/Read-write.  The same idea with a
> > variance annotation and just read-only access seems to be what you're
> > looking for, no?
>
> It seems no, because Cap is invariant, and for a reason: for example,
> Hashtbl.Cap.of_table says
> "This operation involves no copying. In other words, in let cap =
> of_table a in ..., any modification in a will also have effect on cap
> and reciprocally."
>
> What I'm thinking about is  type +'a Tuple.t with Tuple.of_list and
> Tuple.of_array both performing a copy.
>

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Re: [Caml-list] Tuples (covariant immutable arrays)

[Alexandre Pilkiewicz]

type +'a t = (int -> 'a) * int

let get (a: 'a t) i = (fst a) i
let length (a: 'a t) = snd a

let of_array (a: 'a array) : 'a t =
  let a' = Array.copy a in
  (Array.get a', Array.length a')


should be enough