[HOpenGL] GLdouble/GLfloat vs. Double/Float

[Andre W B Furtado]

Hello. If I have

f :: a -> (Double, Double)
f x = g x

but g's signature is

g :: a -> (GLdouble,GLdouble)

Can I always assume that the result of f will be the same of g (I mean, no
truncations, rounding, etc.)? Do I have to use something like:

f :: a -> (Double, Double)
f x = (realToFrac g1, realToFrac g2)
      where (g1,g2) = g x

I'd like to ask the same question using GLfloat instead of GLdouble and
Float instead of Double.

Thanks a lot,
-- Andre