On Tue, Aug 24, 2010 at 05:06:05AM +0200, Tobias Brandt wrote:
You don't need a type class, you can just define your functions with pattern matching: rad :: Angle a -> a rad (Radians x) = x rad (Degrees x) =*pi * (deg x) / 180 deg :: Angle a -> a deg (Radians x) =*180 * (rad x) / pi deg (Degrees x) = x
I may look like a nitpicker but the above function definitions lose their type information. I'd have written it this way: data Angle a = Radians a | Degrees a deriving (Eq, Show) rad :: Floating a => Angle a -> Angle a rad (Radians x) = Radians x rad (Degrees x) = Radians (pi * x / 180) deg :: Floating a => Angle a -> Angle a deg (Radians x) = Degrees (180 * x / pi) deg (Degrees x) = Degrees x On the other side, I am not particularly confident this approach is the best. Other people may give you better solutions … /‡ John