Re: [Haskell-beginners] Type constructors sharing a common field

On 4/29/2014 10:55 AM, Benjamin Edwards wrote:

|module Mainwhere

import Control.Applicative import Control.Lens

main ::IO () main =let p =Child 10 in print $ p ^. age

data Person =Child Int |Adult Int

age ::Lens' Person Int age k (Child x) =Child <$> k x age k (Adult x) =Adult <$> k x |

Hmm, what does the <$> mean here? I know it for functor application, but I don't understand how that works in this example.