All of Basic Category Theory

Featuring Mark Hopkins

Have you ever been puzzled by the suggestion that

data Lens s a = Lens { get :: s -> a, set :: a -> s -> s }

might be in some sense the same as

forall f. Functor f => (a -> f a) -> s -> f s/code>

or, more to the point, how on earth someone ever went about figuring this out...

Stop Paying for Free Monads

Featuring Mark Hopkins

Free monads, as used in the “Datatypes à la carte” pattern, are a useful way to structure code, separating of specification from implementation and enabling modularisation.

But they also come with a runtime performance penalty.

The complementary “typed tagless final...