Hi,

I tried this but now I get another error:

The data constructors of `GLfloat' are not all in scope

      so you cannot derive an instance for it

    In the stand-alone deriving instance for `Random GLfloat'

Mark

On 03/05/2012, at 10:39 AM, Patrick Palka wrote:

Because GLfloat is simply a newtype wrapper for CFloat, which has a Random instance, I would do:

{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
deriving instance Random GLFloat

On Wed, May 2, 2012 at 6:29 PM, Mark Spezzano <mark.spezzano@chariot.net.au> wrote:

Hi Haskellers,

I'm trying to generate a random vertex in OpenGL as follows.

genPosition :: IO (Vertex3 GLfloat)
genPosition = do x <- getStdRandom $ randomR (-1.6,1.6)
                              y <- getStdRandom $ randomR (-1.0,1.0)
                             return (Vertex3 x y (-1))

Unfortunately the compiler complains about me having to implement an instance of Random for  GLfloat.

How do I do this (or avoid having to do this)?

Cheers,

Mark


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