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.
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