20 May
2009
20 May
'09
1:22 a.m.
On Tue, May 19, 2009 at 16:07, Jason Dusek
The former page also has a curious discussion of standalone deriving with a `for` keyword:
http://www.haskell.org/ghc/dist/current/docs/users_guide/type-extensions.htm...
Without this extension, adding an Eq implementation to a data type for which you do not have source requires an explicit class declaration, even if there is no reason the original data type author couldn't have written "deriving Eq". Standalone deriving allows you to get the convenience of deriving classes everywhere, not just on datatypes for which you can obtain, and use, the source. Denis