Re: [Gtk2hs-users] Removing overhead in the class hierarchy

[Axel S. <A....@ke...>]

On 4 May 2004, at 00:16, Duncan Coutts wrote:
> So, you can see that the to* from* functions are just casting pointers,
> except that the pointers are wrapped in newtypes. The existing 
> mechanism
> uses class methods to cast away the newtype. My proposal is to cast
> directly (which is safe because newtypes do not change representation
> and casting pointer using unsafeCoerce is also safe). The external 
> types
> have not changed to the use of unsafeCoerce# is not exposed to the 
> user.

To actually get rid of class contexts, we would have to take the to* 
and from* functions out of the class:

toContainer :: ObjectClass o => o -> Container
toContainer = unsafeCoerce

I guess that GHC will remove the whole class context in this case 
(since it is not used). This would be a (small) gain if GHC cannot 
inline these functions when they are passed as a dictionary (I can 
imagine that GHC can never do that, but I never looked at the core 
produced).

If all the changes are restricted to Hierarchy.chs, then it's alright 
to commit since it's easily reverted.

Axel.