17: Applicative Functors

LambdaCast

Building on the power of functors we examine a few scenarios where a normal Functor is problematic. Fortunately, there is a closely related structure known as an Applicative Functor that can provide the capabilities to solve a broader range of problems. Episode 17 patrons: Chad Wooley David Keathley Andre Carvalho Show Notes: Coconut programming language: http://coconut-lang.org/ Hack nights instead of presentations: http://tech.noredink.com/post/142283641812/designing-meetups-to-build-better-communities class Functor f => Applicative f where pure :: Applicative f => a -> f a ap :: Applicative f => f (a -> b) -> f a -> f b Example of applicative usage: pure (+) <*> Just 3 <*> Just 2 -- this results in Just 5 (+) <$> Just 3 <*> Just 2 -- this is the same as above liftA2 (+) (Just 3) (Just 2) -- alternate form using lift instead of infix operators