On 4/11/06, Simon Peyton-Jones <[EMAIL PROTECTED]> wrote:
> | > deriving (Show Foo)
>
> I'm all for that. A modest but useful gain. All we need is the syntax,
> and that is something that Haskell Prime might usefully define.
Speaking of which, how about simply qualifying a body-less instance
with
On Tue, Apr 11, 2006 at 02:19:22PM +0100, Simon Peyton-Jones wrote:
> | > newtype Id = Id Int
> | > data Term = ...
> | > newtype Subst = Subst (IM.IntMap Term)
> |
> | ideally, we'd like an MapLike instance, but we'd have to tediously
> write
> | it ourselves. if we allow the supergeneralized new
I like this idea. Needs fleshing out though.
| * you can only newtype derive the last argument to a MPTC.
| * you cannot co-derive an instance for multiple newtype renamings.
|
| it seems that both these can be solved when combined with the other
| proposed extension, allowing deriving clauses
ooops. sorry, I started with a 'Set' example and moved to a 'Map' one
and didn't fix all the code. here is a fixed version:
=
The newtype deriving extension is one of the most powerful tools for
writing robust, typesafe code. However it suffers from a couple
limitations.
* you can only newt
