On second-order iterative monads

Unifying Guarded and Unguarded Iteration

Models of iterated computation, such as (completely) iterative monads, often depend on a notion of guardedness, which guarantees unique solvability of recursive equations and requires roughly that recursive calls happen only under certain guarding operations. On the other hand, many models of iteration do admit unguarded iteration. Solutions are then no longer unique, and in general not even de...

Guarded and Unguarded Iteration for Generalized Processes

Models of iterated computation, such as (completely) iterative monads, often depend on a notion of guardedness, which guarantees unique solvability of recursive equations and requires roughly that recursive calls happen only under certain guarding operations. On the other hand, many models of iteration do admit unguarded iteration. Solutions are then no longer unique, and in general not even de...

On Iteratable Endofunctors

Completely iterative monads of Elgot et al. are the monads such that every guarded iterative equation has a unique solution. Free completely iterative monads are known to exist on every iteratable endofunctor H, i. e., one with final coalgebras of all functors H( ) + X. We show that conversely, if H generates a free completely iterative monad, then it is iteratable.

Iterative reflections of monads

Iterative monads, introduced by Calvin Elgot in the 1970’s, are those ideal monads in which every guarded system of recursive equations has a unique solution. For every ideal monad M we prove that an iterative reflection, i.e., an embedding M ↪−→ M̂ into an iterative monad with the expected universal property, exists. We also introduce the concept of iterativity for algebras for the monad M, fol...

Seventh-order iterative algorithm free from second derivative for solving algebraic nonlinear equations