Re: ``Orphan instances'' should be avoided anyway.

13 Aug 2008

      On Wed, 2008-08-13 at 09:29 +0100, Malcolm Wallace wrote:
...
...
We already have named instances:
data ShowDict alpha = ShowDict alpha {
   namedShows :: alpha -> String -> String
   }
This is not valid Haskell.
I must have been distracted.  I meant:

data ShowDict alpha = ShowDict {
  namedShows :: alpha -> String -> String
  }

obviously.
...
Either all components of the data  
structure are named fields, or none.  It is not possible to have a  
mixture of the two, as here.
In addition, there are many classes it is not currently possible to  
simulate using this technique, because the types go significantly  
beyond Haskell'98.
My proposal already required implicit parameters...

jcc

Re: ``Orphan instances'' should be avoided anyway.

Jonathan Cast