Recursion is a Computational Effect

In a recent paper, Launchbury, Lewis, and Cook observe that some Haskellapplications could benefit from a combinator mfix for expressing recursion overmonadic types. We investigate three possible definitions of mfix and implementthem in Haskell.Like traditional fixpoint operators, there are two approaches to the definitionof mfix: an unfolding one based on mathematical semantics, and an updatingone based on operational semantics. The two definitions are equivalentin pure calculi...