Equational properties of iterative monads

Abstract

Iterative monads of Calvin Elgot were introduced to treat the semantics of recursive equations purely algebraically. They are Lawvere theories with the property that all ideal systems of recursive equations have unique solutions. We prove that the unique solutions in iterative monads satisfy all the equational properties of iteration monads of Stephen Bloom and Zoltán Ésik, whenever the base category is hyper-extensive and locally finitely presentable. This result is a step towards proving that functorial iteration monads form a monadic category over sets in context. This shows that functoriality is an equational property when considered w.r.t. sets in context.