[Haskell-cafe] double2Float is faster than (fromRational . toRational)

[Henning Thielemann]

On Fri, 21 May 2010, Daniel van den Eijkel wrote:

> Dear Haskellers,
>
> I just want to share an observation. I had to convert a Double to a Float 
> value in an inner loop of an application, and I used somethin like this:
>
> xf = (fromRational $ toRational xd) :: Float

I think realToFrac is the function to use here, and this might be replaced 
by double2Float by an optimizer rule. I think double2Float is from a GHC 
package and thus one should avoid to call double2Float directly.