Storable instance for Complex

[Henning Thielemann]

On Sun, 17 Feb 2008, Jed Brown wrote:

> On 15 Feb 2008, lemming at henning-thielemann.de wrote:
> > On Fri, 15 Feb 2008, Jed Brown wrote:
> >> I propose that the following instance be added to base:
> >>
> >> instance (RealFloat a, Storable a) => Storable (Complex a) where
> >> sizeOf z    = 2 * sizeOf (realPart z)
> >> alignment z = sizeOf (realPart z)
> >> peek p = do
> >> [r,i] <- peekArray 2 (castPtr p)
> >> return (r :+ i)
> >> poke p (r :+ i) = pokeArray (castPtr p) [r,i]
> >>
> >> This instance is binary compatible with C99, C++ and Fortran complex types.
> >>
> >> It is currently needed by at least two independent packages: hmatrix and
> >> fft. Since it is natural for user code to use both of these packages, we
> >> need to move the instance to a common location.
> >>
> >> http://hackage.haskell.org/trac/ghc/ticket/2099
> >
> > I also need it for signal processing.
>
> In light of the fact that several packages need this instance, I created
> a package storable-complex (on Hackage) which has the instance in
> Foreign.Storable.Complex.  In the interest of enabling our packages to
> play nicely *now*, I would like to encourage everyone needing this
> instance to get it from this common source.  When it (hopefully) makes
> it into base, we can use a flag in the .cabal file to get it from base
> instead of this package.

an instance for pairs would also be nice ... :-)