What is "hylomorphism"

n. 1 (context philosophy English) The doctrine that every physical substance is the sum of its component matter and the form taken by that matter. 2 (context computer science English) composition of an anamorphism and a catamorphism

Hylomorphism (or hylemorphism) is a philosophical theory developed by Aristotle, which conceives being ( ousia) as a compound of matter and form.

The word is a 19th-century term for medical from the Greek words ὕλη hyle, "wood, matter" and μορφή, morphē, "form."

In computer science, and in particular functional programming, a hylomorphism is a recursive function, corresponding to the composition of an anamorphism (which first builds a set of results; also known as 'unfolding') followed by a catamorphism (which then folds these results into a final return value). Fusion of these two recursive computations into a single recursive pattern then avoids building the intermediate data structure. This is an example of deforestation, a program optimization strategy. A related type of function is a metamorphism, which is a catamorphism followed by an anamorphism.