Ticket #3335 (closed proposal: fixed)
make some Applicative functions into methods, and split off Data.Functor
|Reported by:||ross||Owned by:|
|Type of failure:||Difficulty:||Unknown|
|Test Case:||Blocked By:|
The following functions
(<$) :: Functor f => a -> f b -> f a (*>) :: Applicative f => f a -> f b -> f b (<*) :: Applicative f => f a -> f b -> f a some :: Alternative f => f a -> f [a] many :: Alternative f => f a -> f [a]
are moved into the corresponding classes, with the existing implementations as default definitions. This gives people creating instances the option of defining specialized implementations of these functions, though they should be equivalent to the default definitions.
Although (<$) is now a method of the Functor class, it is hidden in the re-export by the Prelude, Control.Monad and Monad. The new module Data.Functor exposes the full class, plus the function (<$>). These are also re-exported by Control.Applicative.
Discussion on libraries@… to 20th July 2009.