flexible contexts and context reduction

Sittampalam, Ganesh ganesh.sittampalam at credit-suisse.com
Thu Mar 27 05:06:52 EDT 2008

Well, Ord Foo doesn't hold, does it? So Ord (a, b) isn't equivalent to (Ord a, Ord b).


-----Original Message-----
From: Simon Peyton-Jones [mailto:simonpj at microsoft.com] 
Sent: 27 March 2008 09:05
To: Sittampalam, Ganesh; 'Tom Schrijvers'; Ganesh Sittampalam
Cc: glasgow-haskell-users at haskell.org; Martin Sulzmann
Subject: RE: flexible contexts and context reduction

Why "unfortunately"? Looks fine to me.


| Unfortunately, GHC accepts the following:
| {-# LANGUAGE FlexibleInstances #-}
| module Foo2 where
| data Foo = Foo
|   deriving Eq
| instance Ord (Foo, Foo) where
|   (Foo, Foo) < (Foo, Foo) = False

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