Practical Droste

Algebras

• Algebra: F[A] => A
• Coalgebra: A => F[A]
• AlgebraM: F[A] => M[A]
• CoalgebraM: A => M[F[A]]
• RAlgebra: F[(R, A)] => A
• RCoalgebra A => F[Either[R, A]]
• RAlgebraM: A => M[F[Either[R, A]]]
• RCoalgebraM: A => M[F[Either[R, A]]]

Recursion schemes

Fold(Recursion)	Unfold (Corecursion)	General
cata	ana	hylo
F[A] => A	A => F[A]
para	apo
F[(R,A)] => A	A => F[Either[R,A]

Open console

 > sh console.sh

References

• Practical Recursion Schemes
• Time traveling
• Functional Programming with Bananas Lenses Envelop es and Barb ed Wire
• AST playground: recursion schemes and recursive data
• Domain Modelling with Haskell: Factoring Out Recursion
• Recursion Schemes in Scala - An Absolutely Elementary Introduction
• F-Algebras
• Introduction to Recursion Schemes with Matryoshka
• Awesome Recursion schemes
• An Introduction to Recursion Schemes
• Those 10000 classes I never wrote
• Sorting slower
• Time Traveling Recursion Schemes
• Recursion Schemes