Johan Tibell wrote:
Bas van Dijk wrote:
Indeed, I would like to emphasize that my main reason for adding a flipped fmap is symmetry. I find it hard to explain why <$$> shouldn't be in this list:
(<$>) ∷ Functor f ⇒ (α → β) → (f α → f β) (<$$>) ∷ Functor f ⇒ f α → (α → β) → f β
(<*>) ∷ Applicative f ⇒ f (α → β) → (f α → f β) (<**>) ∷ Applicative f ⇒ f α → f (α → β) → f β
(>>=) ∷ Monad f ⇒ f α → (α → f β) → f β (=<<) ∷ Monad f ⇒ (α → f β) → (f α → f β)
I think the argument I would make is that (<**>) and (=<<) shouldn't have been added in the first place.
Concerning the addition of (=<<), I'm actually using it more often than the original (>>=). That's because it plays well with function composition, which is left to right. Here an example taken from some code I wrote: runMaker m = sequence_ . G.topsort' . rules2Graph . snd =<< runWriterT m (Arguably, I should should have used (<=<) and tacked a ($) at the end if want an explicit argument, but I'm unclear about the fixities of (<=<).) Regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com