Am Samstag 21 November 2009 22:13:49 schrieb John Dorsey:
Chaddaï Fouché wrote:
second :: (b -> c) -> (d, b) -> (d, c) which corresponds exactly to the action of second you described (that's the only function that could have this type, except bottom of course).
Nonsense! There are several perfectly good Haskell functions with that type. I count seven:
second :: (b -> c) -> (d, b) -> (d, c) second = Control.Arrow.second second = undefined second = const undefined second = const (const undefined) second = const (const (undefined,undefined)) second f (d,b) = (undefined, f b) second f (d,b) = (d, undefined)
I don't see second f (d,b) = (undefined, f undefined) second f (d,b) = (d, f undefined) in there.
Why I'm stickling on that point on the beginners list, however, is a mystery. I'll go write a more useful response, in contrition.
John