A common example used to illustrate how monads arise from adjoint functors, State . One reason for such a good example is that the two adjoint functors (->) r and (,) r are both endofunctors on Hask. Other canonical monads include conjugate functors to and from Hask (for example, [] and Maybe ), which makes them more difficult for people who know Haskell but who have less background in category theory.
Are there any other common monads arising through conjugate endofentors on Husk? (Obviously, the Identity monad is one such case, but not very interesting.)
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