5 Jun
2012
5 Jun
'12
5:56 p.m.
On Tue, Jun 5, 2012 at 12:02 AM, Simon Peyton-Jones
I see the boring code, but I don't see what you *want*! I'm guessing you want "generalised newtype deriving" but why does that not work?
Yes, I (and I assume Bas) want generalised newtype deriving to work, but it doesn't. I want to write something very simple: {-# LANGUAGE GeneralizedNewtypeDeriving #-} newtype Foo = Foo Int deriving (Eq, Show, *Unbox*) But with the above, GHC says: No instances for (M.MVector MVector Foo, G.Vector Vector Foo) arising from the 'deriving' clause of a data type declaration And then we begin the journey that eventually gets us to Bas's rather wordy code.