Anamorphism

In category theory, the concept of anamorphism ("ana" from the Greek ἀνά = upwards; "morphism" from the Greek μορφή = form, shape) denotes a morphism from a coalgebra to the final coalgebra for that endofunctor. These objects have been applied to functional programming as unfolds. The categorical dual of the anamorphism is the catamorphism.