On 06/24/2013 08:44 AM, Adam Gundry wrote:
Hi everyone,
I am implementing an overloaded record fields extension for GHC as a GSoC project. Thanks to all those who gave their feedback on the original proposal! I've started to document the plan on the GHC wiki:
http://hackage.haskell.org/trac/ghc/wiki/Records/OverloadedRecordFields/Plan
If you have any comments on the proposed changes, or anything is unclear about the design, I'd like to hear from you.
Thanks,
Adam Gundry
_______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users The wiki page says:
The base design has the following distinct components: * A library class class Has (r :: *) (f :: String) (t :: *) where get :: r -> t * A record declaration generates an instance declaration for each field. For example data T a = T1 { x :: a, y :: Bool } | T2 { x :: a } would generate instance (t~a) => Has (T a) "x" t where get (T1 x _) = x get (T2 x) = x instance (t~Bool) => Has (T a) "y" t where get (T1 _ y) = y Is this instance for "y" not partial? If it is, is that a problem? Perhaps I missed something that makes that instance total. - Ollie