15 Dec
2011
15 Dec
'11
10:19 a.m.
On Thu, Dec 15, 2011 at 06:49:13PM +1000, Gregory Crosswhite wrote:
So at the end of the day... what is the point of even making Maybe and [] instances of Alternative?
The Alternative and Monoid instances for [] are equivalent. However, the Alternative and Monoid instances for Maybe are not. To wit:
(Just (Sum 4)) <|> (Just (Sum 3)) Just (Sum {getSum = 4})
(Just (Sum 4)) `mappend` (Just (Sum 3)) Just (Sum {getSum = 7})
-Brent