In computer programming, particularly functional programming and type theory, an algebraic data type (sometimes also called a variant type[1]) is a datatype each of whose values is data from other datatypes wrapped in one of the constructo…

In computer programming languages, a recursive data type (also known as a recursively-defined, inductively-defined or inductive data type) is a data type for values that may contain other values of the same type. Data of recursive types ar…

Theorem: The Cartesian product of finitely many countable sets is countable.