Private classes

[Bas van Dijk]

Hi Joachim,

I used the following in the past:

module M (PublicClass(..)) where

class HiddenClass a

class HiddenClass a => PublicClass a where
  ...

instance HiddenClass SomeType

instance PublicClass SomeType where
  ...

Now users of M can't declare instances of PublicClass because they don't
have its superclass HiddenClass in scope.

Regards,

Bas
On Aug 17, 2013 8:10 PM, "Joachim Breitner" <mail at joachim-breitner.de>
wrote:

> Hi,
>
> for some reason I was under the impression that if I don’t export the
> methods of a class, then no user of my module can create instances. But
> I was wrong and in fact they can; the methods will just all be bound to
> "error ...".
>
> Is there really no way to create a class so that no-one else can create
> any instances?
>
> Greetings,
> Joachim
>
> --
> Joachim “nomeata” Breitner
>   mail at joachim-breitner.de • http://www.joachim-breitner.de/
>   Jabber: nomeata at joachim-breitner.de  • GPG-Key: 0x4743206C
>   Debian Developer: nomeata at debian.org
>
>
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