Re: [Caml-list] Warnings opening modules (was: why is building ocaml hard?)

[Yotam Barnoy <yotambarnoy@gmail.com>]

Jeremy, how about taking a page from haskell, and having

type t = A.t(..)

This would import the same constructors locally. It also means we have
the full functionality covered, in terms of both opens and creating
limited local modules:

haskell:
import A(foo, bar, T(..))

ocaml:
let foo, bar = A.(foo, bar)
type t = A.t(..)

haskell:
import qualified LongA(foo, bar, T(..)) as A

ocaml:
module A = struct LongA.(let foo, bar = foo, bar type nonrec t = t(..)) end

It's still more verbose (especially the limited-qualified module) but
at least it's decent.



On Sat, Jul 16, 2016 at 5:58 AM, vrotaru.md@gmail.com
<vrotaru.md@gmail.com> wrote:
>
> About that missing type constructors problem. Seems doable:
>
> module A = struct
>   module T = struct
>     type t1 = ...
>     type t2 = ...
>   end
>   include T
>
>   let foo _ = ...
>   let bar : t2 -> t1  = ...
> end
>
> module B = struct
>
>   include A.T
>   let foo, bar = A.( foo, bar )
>
> end
>
> Obviously, not for already existing code.
>
> În sâm., 16 iul. 2016 la 10:41, Petter A. Urkedal <paurkedal@gmail.com> a
> scris:
>>
>> On 15 July 2016 at 18:13, Hendrik Boom <hendrik@topoi.pooq.com> wrote:
>> > And that's a real problem -- that fact that openning a module can fill
>> > the namespace with lots of stray identifiers, which the user does not
>> > control.
>>
>> Apart from the selective opens discussed, it would be good to tell
>> apart which modules are meant to be open and which are intrusive
>> without looking through them.  Most importantly the writer of the
>> library should be clear about it from the start when designing a
>> module, then the names will be consistent with the choice, and users
>> should be able to decide without evaluating the whole interface.
>>
>> A warning when opening an invasive module in a global scope could
>> help, as well.  One could maybe decide a module to be invasive from a
>> few heuristics with fall-back to a declaration:
>>
>> - A module interface defining a single-letter identifier, most
>> importantly a type "t" or a signature "S", is invasive.
>> - A module interface overriding any operator (or identifier?) defined
>> in Pervasives is invasive.
>> - A module interface declaring itself `[@@@ocaml.invasive]` is invasive.
>>
>> Conversely the user may silence the warning with `open M
>> [@@ocaml.invasive]`.
>>
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