data ==== Various datatypes. Basic types: * [unit](unit.lean) : the singleton type * [bool](bool.lean) * [num](num.lean) : generic numerals * [string](string.lean) : ascii strings * [nat](nat/nat.md) : the natural numbers * [int](int/int.md) : the integers Constructors: * [option](option.lean) * [pair](pair.lean) * [list](list/list.md) * [set](set.lean)