Functorial Blog - Comonads and Day Convolution

The Day convolution of two functors is another functor, defined as follows: data Day f g a where Day :: (x -> y -> a) -> f x -> g y -> Day f g a There is an implementation of Day in Edward Kmett's kan-extensions package on Hackage. Day Convolution of Comonads While writing my last post, I was looking for a way to combine comonads, and found out some interesting things about Day convolution in the

[lotz84]

コモナド同士のDay Convolutionは自然にコモナドになって、さらにコモナドトランスフォーマーと同型になるのか！すごいなぁ