Re: Unboxed Vectors of newtype'd values

5 Jun 2012


      Hi Bryan.
...
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
Yes, because these are superclasses of Unbox. So can't you simply say this:
...
newtype Foo = Foo Int
  deriving (Eq, Show, Unbox, M.MVector MVector, G.Vector Vector)
?

Cheers,
  Andres

-- 
Andres Löh, Haskell Consultant
Well-Typed LLP, http://www.well-typed.com