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@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@joachim-breitner.de • http://www.joachim-breitner.de/
Jabber: nomeata@joachim-breitner.de • GPG-Key: 0x4743206C
Debian Developer: nomeata@debian.org

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