symmetric monoidal (∞,1)-category of spectra
In the study of recursion schemes, a catamorphism is the simple case of a fold over an inductive data type. In category theoretic terms, this is simply the unique homomorphism out of an initial algebra.
Given an endofunctor such that the category of -algebras has an initial object , the catamorphism for an -algebra is the unique homomorphism from the initial -algebra to . The unique morphism between the carriers is also denoted .
From the commuting square of the homomorphism, we have . By Lambek's theorem, has an inverse , so the catamorphism can be recursively defined by .
Let be a homomorphism between two -algebras and so that . Then .
If is an inductive type, then the catamorphism is a fold over the type. Some recursive functions can then be implemented in terms of a catamorphism.
Let be the functor so that the naturals are represented by the fixed point of (i.e. the carrier of the initial F-algebra). The recursor for the naturals can then be defined by a catamorphism.
HaskellWiki, Catamorphisms
Wikipedia, Catamorphism
Richard Bird, Oege de Moor (1997), Algebra of Programming, Prentice Hall
Maarten M. Fokkinga (1992), Law and Order in Algorithmics, PhD thesis, University of Twente
Roland C. Backhouse, Peter J. de Bruin, Ed Voermans, Jaap van der Woude (1991), Relational Catamorphisms, Computing Science Notes, Vol. 9111, Technische Universiteit Eindhoven
Last revised on December 15, 2022 at 23:35:07. See the history of this page for a list of all contributions to it.