Re: [Caml-list] destructive local opens

[Goswin von Brederlow <goswin-v-b@web.de>]

On Tue, Aug 04, 2015 at 09:14:49AM -0400, Ivan Gotovchits wrote:
> 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 |])

You can't qualifylocal values or values of the surrounding module so
that is a no go.

I also often use local open to access records, as in:

let r = M.({ x = 1; y; z = depth; }) in

So I can't agree that M.() should only access values from M. Far from it.

 
> 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

MfG
	Goswin