<s>[INST] what is a monad in haskell? [/INST] A monad is just a monoid in the category of endofunctors. Haskell is a polymorphically statically typed, lazy, purely functional programming language.

A monad in Haskell is often associated with the Monad class, which is an Applicative, which is a Functor. Monads might be used to implement an identity function, to allow error checking without resorting to nulls, or maintain state within a functional paradigm.</s>\ <s>[INST] what is category of endofunctors? [/INST] 