Oh, so you want the original behaviour of type declarations back. :) In Haskell 1.0, if you didn't specify any deriving, you got as much derived as possible. I quite liked it, but it was changed. -- Lennart On Tue, 22 May 2007, Alex Jacobson wrote:
Date: Tue, 22 May 2007 19:07:26 -0400 From: Alex Jacobson <alex@alexjacobson.com> To: haskell@CS.YALE.EDU Subject: [Haskell] boilerplate boilerplate
Consider this module for a blog entry that I will want to put in various generic collections that require Ord
{-# OPTIONS -fglasgow-exts #-} module Blog.Types where import Data.Typeable import Data.Generics
data BlogEntry = Entry EpochSeconds Name Email Title Body deriving (Eq,Ord,Read,Show,Typeable)
newtype Name = Name String deriving (Eq,Ord,Read,Show,Typeable) newtype Title = Title String deriving (Eq,Ord,Read,Show,Typeable) newtype Body = Body String deriving (Eq,Ord,Read,Show,Typeable)
It seems really unnecessarily verbose. Having to add the OPTION header AND import Data.Typeable and Data.Generics just to derive Typeable is a beat-down. It is even more of a beat-down to have to add a deriving clause for every newtype to make this all work nicely. Is there a way to make all types automatically derive everything unless there is an explicit instance declaration otherwise?
{-# OPTIONS -fglasgow-exts -fgenerics -fderiving#-} module Blog.Types where
data BlogEntry = Entry EpochSeconds Name Email Title Body newtype Name = Name String newtype Title = Title String newtype Body = Body String Isn't that much nicer?
-Alex-
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-- Lennart