[Haskell-cafe] Fwd: Ridiculously slow FFI, or cairo binding?

[wren ng thornton]

On 11/2/11 7:14 AM, Eugene Kirpichov wrote:
> I rewrote cFloatConv like this:
>
> import GHC.Float
> class (RealFloat a, RealFloat b) =>  CFloatConv a b where
>    cFloatConv :: a ->  b
>    cFloatConv = realToFrac
>
> instance CFloatConv Double Double where cFloatConv = id
> instance CFloatConv Double CDouble
> instance CFloatConv CDouble Double
> instance CFloatConv Float Float where cFloatConv = id
> instance CFloatConv Float Double where cFloatConv = float2Double
> instance CFloatConv Double Float where cFloatConv = double2Float

If you're going the MPTC route, I suggest you use 
logfloat:Data.Number.RealToFrac[1]. I don't have the CDouble and CFloat 
instances, but I could add them. The instances themselves are only 
moderately more clever than yours ---namely using CPP for portability to 
non-GHC compilers--- but I think it's good for people to rally around 
one implementation of the solution instead of having a bunch of copies 
of the same thing, each poorly maintained because of the distributedness.


[1] 
http://hackage.haskell.org/packages/archive/logfloat/0.12.1/doc/html/Data-Number-RealToFrac.html

-- 
Live well,
~wren