PROPOSAL: classes for traversals
bulatz at HotPOP.com
Sat Nov 19 09:51:44 EST 2005
Friday, November 18, 2005, 2:05:37 PM, you wrote:
RP> Comments most welcome.
1) imho, it's better to change "Prelude." to "List." here:
instance Foldable  where
foldr = Prelude.foldr
foldl = Prelude.foldl
foldr1 = Prelude.foldr1
foldl1 = Prelude.foldl1
and in other places where you use list functions listed in Prelude
2) i can try to make Template Haskell machinery to automatically
derive instances of Foldable and Traversable, using your examples
for Tree as sample
-- If @f@ is also a 'Functor', define @('<$>') = 'fmap'@.
-- If it is also a 'Monad', define @'pure' = 'return'@ and @('<*>') = 'ap'@.
why you don't just define:
instance Monad m => Applicative m where
pure = return
(<*>) = ap
RP> They are proposed for the base package, and would replace FunctorM.
it is a beatiful contribution. but it doesn't work without definitions
for All, Any and so on :)
Bulat mailto:bulatz at HotPOP.com
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