Hi, GLfloat haskell is instance of several number related typeclasses. A function like 'fromRational' could be used to create a GLfloat from another number that has a random instance. L On May 3, 2012 4:39 AM, "Mark Spezzano" wrote:

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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