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 <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
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
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