Le 30 oct. 08 à 21:18, David Allsopp a écrit :
Shouldn't I now be able to say:
string_of_int x;;
I don't think so. According to the manual [1] the only thing you can
do on private types is pattern match or project their fields. I
doesn't mean your type can be substituted by int.
Daniel
"David Allsopp" <[EMAIL PROTECTED]> writes:
> I thought that the point of private types was that you could
> deconstruct them... so values of type M.t are valid wherever an int
> is used but not the converse.
It should probably be ok for immutable data but not for mutable
ones. One example is usi
Daniel Bünzli wrote:
> Le 30 oct. 08 à 21:18, David Allsopp a écrit :
>
> > Shouldn't I now be able to say:
> >
> > string_of_int x;;
>
> I don't think so. According to the manual [1] the only thing you can
> do on private types is pattern match or project their fields. I
> doesn't mean your ty
From: "David Allsopp" <[EMAIL PROTECTED]>
> Thanks for this - although it's a link to an OCaml 3.10 manual so not
> applicable here it did point me to the correct chapter in the OCaml 3.11
> manual (I'd been looking in Part I of the manual and given up). What I
> should have written is
>
> string
Hi,
> Your intuition is correct that it would theoretically be possible to
> try subtyping in place of unification in some cases. The trouble is
> that thoses cases are not easy to specify (so that it would be hard
> for the programmer to known when he can remove a coercion), and that
> subtyping
Jacques Garrigue wrote:
> Your intuition is correct that it would theoretically be possible to
> try subtyping in place of unification in some cases. The trouble is
> that thoses cases are not easy to specify (so that it would be hard
> for the programmer to known when he can remove a coercion),
Edgar Friendly wrote:
> Jacques Garrigue wrote:
>
> > Your intuition is correct that it would theoretically be possible to
> > try subtyping in place of unification in some cases. The trouble is
> > that thoses cases are not easy to specify (so that it would be hard
> > for the programmer to known
Dear Dario,
Since you use a private abbreviation, extraction from the private type
must be explicit before you can do anything on its representation.
So the solution is simple enough:
module Mymod =
struct
let is_foo2 x =
match (x : _ Foobar.t :> [> ]) with `A -> true | `B -> false
From: Edgar Friendly <[EMAIL PROTECTED]>
> > So the current approach is to completely separate subtyping and type
> > inference, and require coercions everywhere subtyping is needed.
> >
> Would it be particularly difficult to, in the cases where type [x] is
> found but type [y] is expected, to t
David Allsopp wrote:
> Without the full coercion for x you'll get a type error because the type
> checker infers that the type of the [if] expression is [t] from the [then]
> branch and then fails to unify [> `B of int ] with [t] unless the type of
> [x] is first coerced to [> t ]. If the compiler
Jacques Garrigue wrote:
> If we limit ourselves to the case where both [x] and [y] contrain no
> type variables, this si not particularly difficult. However whether
> they will contain type variables or not depends heavily on how the
> type inference algorithm proceeds.
>
> If they contain type va
Edgar Friendly wrote:
> David Allsopp wrote:
>
> > Without the full coercion for x you'll get a type error because the type
> > checker infers that the type of the [if] expression is [t] from the
> > [then] branch and then fails to unify [> `B of int ] with [t] unless the
> > type of [x] is first c
David Allsopp wrote:
> I agree that the error will still show up somewhere if there is an error -
> but remember that a closed polymorphic variant type required an annotation
> in the first place (in this case, the type [t] and the explicit type
> annotation to use it)... so having made the explici
Hi,
> So my question is how can I make the Foobar code behave as if it were
> defined inside Node. Based on a previous thread [1], I'm guessing there
> is a solution, but I've been unable to hit on its exact formulation.
There have been no replies yet to my question, but I'm still stuck with
thi
Hi again,
I ditched the regular variants in favour of polymorphic variants, hoping
the coercion trick described by Jacques Garrigue would help [1]. I've also
simplified the formulation as much as possible. Anyway, I'm still stuck
with the same problem: while function 'sprint' works alright insid
Hmmm, a variant of your code may be exhibiting a bug in ocaml 3.11.0.
In your signature, change the +'a t signature to
type +'a t = private [< elem_t ]
and remove all annotations from the definition of sprint2. Then, as
defined, one gets the error message
File "bug2.ml", line 26, character
Hi,
> Hmmm, a variant of your code may be exhibiting a bug in ocaml 3.11.0.
Thanks for the reply. I'm kind of hoping it is indeed a bug, because
those are fixable and it would mean what I intend to do is feasible...
Best regards,
Dario Teixeira
Hi Jacques,
From: Jacques Carette
> Hmmm, a variant of your code may be exhibiting a bug in ocaml 3.11.0.
>
> In your signature, change the +'a t signature to
> type +'a t = private [< elem_t ]
> and remove all annotations from the definition of sprint2. Then, as
> defined, one gets the er
From: Dario Teixeira
> I ditched the regular variants in favour of polymorphic variants, hoping
> the coercion trick described by Jacques Garrigue would help [1]. I've also
> simplified the formulation as much as possible. Anyway, I'm still stuck
> with the same problem: while function 'sprint'
From: Dario Teixeira
> > So my question is how can I make the Foobar code behave as if it were
> > defined inside Node. Based on a previous thread [1], I'm guessing there
> > is a solution, but I've been unable to hit on its exact formulation.
>
> There have been no replies yet to my question, b
Hi,
Thank you very much for your help, Jacques! It's always enlightening to
see an Ocaml ninja in action, though I'm still digesting the finer points
of your message. Anyway, I have implemented all three solutions you suggested:
a) Using a private row and PV
b) Using a private abbreviation and
Hi,
On Wed, Jan 21, 2009 at 11:11:14AM -0800, Dario Teixeira wrote:
> So my question is whether it
> is at all possible to emulate GADTs using only PV + phantom types, or if on
> the
> contrary one needs to use the object system in these cases, as exemplified by
> solution c). In other words, is
From: Dario Teixeira
> Thank you very much for your help, Jacques! It's always enlightening to
> see an Ocaml ninja in action, though I'm still digesting the finer points
> of your message. Anyway, I have implemented all three solutions you
> suggested:
>
> a) Using a private row and PV
> b)
Hi,
And once more, thanks for your very informative reply. I spent the last
few days exploring these issues (there's quite some info on the Haskell
wiki) and weighting in the pros/cons of each solution.
I've decided for an approach similar to that taken by the Ocsigen guys.
That is, acknowledge
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