The double category of Hask functors and profunctors.

A library for working with natural transformations of type

forall a b. p a b -> q (f a) (g b)

See the Data.Square module for an introduction.

squares

squares is a library for working with natural transformations of type forall a b. p a b -> q (f a) (g b). These are squares in the double category of Haskell functors and profunctors.

See the Data.Square module for an introduction.