[Haskell-beginners] ffi array and peekArray

[Sylvain Henry]

You can alias HklFactory:
type HklFactory = Ptr ()

Or if you want to avoid mixing HklFactory and other pointers, you can use:
newtype HklFactory = HklFactory (Ptr ()) deriving (Storable)

The latter requires the GeneralizedNewtypeDeriving extension, see:
https://wiki.haskell.org/Foreign_Function_Interface#Renaming_and_Storable_instances

Sylvain

2015-11-08 21:30 GMT+01:00 PICCA Frederic-Emmanuel <
frederic-emmanuel.picca at synchrotron-soleil.fr>:

> Ok, so now I get this error
>
>
> ghkl.hs:20:18:
>     No instance for (Foreign.Storable.Storable HklFactory)
>       arising from a use of ‘peekArray’
>     In a stmt of a 'do' block: peekArray n factories
>     In the expression:
>       do { factories <- c_hkl_factory_get_all ptr;
>            n <- peek ptr;
>            peekArray n factories }
>     In the second argument of ‘($)’, namely
>       ‘\ ptr
>          -> do { factories <- c_hkl_factory_get_all ptr;
>                  n <- peek ptr;
>                  .... }’
>
>
> What should I do to create a Storable for HklFactory which is a simple
> pointer.
>
> Thanks
>
> Frederic
> _______________________________________________
> Beginners mailing list
> Beginners at haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/beginners/attachments/20151108/8f93ff4f/attachment.html>