I would prefer if the compiler warns us if in expression `M.(x)` the value
`x` is not in the scope of `M`.

Clarification: usually when we say `M.(x + cross y)` we want to use only
values from module `M`
and problems arise when something is captured from outside the module. Such
kind of local opens
are usually use to open rich modules, that fully defines an algebra of a
type, i.e., a full suite of
common operations like, comparison operations, arithmetics, etc. So, using
local open is some kind
of local algebra switch operation. In other words switching to other domain
specific language.

A good style would be to explicitly qualify every external value that is
used inside the local opened scope:

M.(x * Vec.of_array [| 1; 2 |])


On Tue, Aug 4, 2015 at 8:26 AM, vrotaru.md@gmail.com <vrotaru.md@gmail.com>
wrote:

> After reading this thread, I'm starting to thinking about another option,
> namely: "local un-open", because I certainly dislike ambiguity.
>
> So, maybe, something like:
>
> Vec.( ^(3 * v) * vx + vy)
>
> where anything in ^(... ) is not subject local open.
>
> Regards
>
>
> În Mar, 4 aug. 2015 la 12:40, Daniel Bünzli <daniel.buenzli@erratique.ch>
> a scris:
>
>> Le mardi, 4 août 2015 à 10:26, Goswin von Brederlow a écrit :
>> > > let ox = V2.((dot v ox) * ox) in
>> > > V2.(3 * ox + oy)
>> >
>> > What is wrong with that code?
>> >
>> > I'm assuming V2 has:
>> >
>> > val (+): t -> t -> t
>> > val (*): int -> t -> t
>> > val dot: t -> t -> int
>>
>> It also has
>>
>> val ox : t
>>
>> Daniel
>>
>>
>>
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>