Editing Data type (section)

=== Algebraic data types ===
{{Main|Algebraic data type}}

An [[algebraic data type]] (ADT) is a possibly recursive [[sum type]] of [[product type]]s. A value of an ADT consists of a constructor tag together with zero or more field values, with the number and type of the field values fixed by the constructor. The set of all possible values of an ADT is the set-theoretic disjoint union (sum), of the sets of all possible values of its variants (product of fields). Values of algebraic types are analyzed with pattern matching, which identifies a value's constructor and extracts the fields it contains.

If there is only one constructor, then the ADT corresponds to a product type similar to a tuple or record. A constructor with no fields corresponds to the empty product (unit type). If all constructors have no fields then the ADT corresponds to an [[enumerated type]].

One common ADT is the [[option type]], defined in Haskell as {{haskell|1=data Maybe a = Nothing {{!}} Just a}}.<ref>{{Cite web |title=6 Predefined Types and Classes |url=https://www.haskell.org/onlinereport/haskell2010/haskellch6.html#x13-1250006.1.8 |access-date=2022-06-15 |website=www.haskell.org}}</ref>