Corecursive

The corecursive typeclass abstracts out the ability to corecursively unfold a structure. See Intro to Recursion Schemes for an introduction to how it works.

Main Combinators

Functor#embed

Given a Functor F, creates a Algebra which collapses a Kind<T, F> into a F (wrapped in an Eval for stack safety).

fun <F> Functor<F>.embed(): Algebra<F, Eval<Kind<T, F>>>

Functor#embedT

The implementation for embed; takes a Kind<F, Kind<T, F>> and returns a Kind<T, F> (wrapped in an Eval for stack safety).

fun <F> Functor<F>.embedT(tf: Kind<F, Eval<Kind<T, F>>>): Eval<Kind<T, F>>

Functor#ana

Unfold generalized over any Corecursive T for any Functor F.

fun <F, A> Functor<F>.ana(a: A, coalg: Coalgebra<F, A>): Kind<T, F>

Laws

Arrow provides CorecursiveLaws in the form of test cases for internal verification of lawful instances and third party apps creating their own Corecursive instances.

Data types

Arrow provides three datatypes that are instances of Corecursive, each modeling a different way of defining corecursion.

Type Class Hierarchy