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In functional programming, an anamorphism is a kind of generic function which can (co)recursively construct a result of a certain type and which is parameterized by functions that determining what the next single step of the construction is. The term comes from Greek ἀνά (upwards) + morphism (from Greek μορφή, or form, shape) and the concept has its grounding in category theory.
The concept of anamorphism generalizes the list-producing unfold functions to arbitrary algebraic data types that can be described as final coalgebras. In fact, the terms 'anamorphism' and "unfold" (as a noun) are often used interchangeably. Anamorphisms, which are co-recursive, are dual to catamorphisms, which are recursive, just as unfolds are dual to folds.
The concept of anamorphism generalizes the list-producing unfold functions to arbitrary algebraic data types that can be described as final coalgebras. In fact, the terms 'anamorphism' and "unfold" (as a noun) are often used interchangeably. Anamorphisms, which are co-recursive, are dual to catamorphisms, which are recursive, just as unfolds are dual to folds.