[Haskell] Proposal: Allow "\=" for field update in record update syntax

Benjamin Franksen benjamin.franksen at bessy.de
Wed Mar 2 19:11:57 EST 2005

On Thursday 24 February 2005 23:27, Keean Schupke wrote:
> Benjamin Franksen wrote:
> > Automatic wrapping is easy. What is not so easy and I think not even
> > possible, is automatic _un_wrapping, so that the wrapping isn't exposed
> > at all to the programmer.
> One way to do this is to replace the type with a pair:
> data Wrap a = Wrap {unwrapA :: a}
> wrap a = (unwrapA,Wrap a)
> so to unwrap do:
> unwrap a = (fst a) (snd a)

This is extremely cool. The type of unwrap is indeed general enough. 
Unfortunately, it doesn't help, because the result type of wrap

Wrap (forall a. a -> a)

still isn't accepted in an instance declaration. Neither is the pair

(unwrap, Wrap (forall a. a -> a))

Or maybe I have not quite understood what you proposed to do with these 


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