[Haskell-cafe] convergence of functions of Complex variables

[Henning Thielemann]

On Wed, 15 Dec 2004, William Lee Irwin III wrote:

> On Wed, Dec 15, 2004 at 10:28:18AM +0000, Ross Paterson wrote:
> > abs :: Num a => a -> a, whereas you want something that returns a Double.
> > You could define
> > class Norm a where
> >         norm :: a -> Double
> > instance Norm Float where
> >         norm = realToFrac . abs
> > instance Norm Double where
> >         norm = abs
> > instance RealFloat a => Norm (Complex a) where
> >         norm = realToFrac . magnitude
> > and use norm instead of abs.
> 
> Thanks; this appears to do the trick for me. Something of this kind
> would be useful to have in the std. libraries, at least for me.

http://cvs.haskell.org/darcs/numericprelude/physunit/Normalization.hs