Declaring

Sets are unordered collections of values of the same type, like lists are ordered collections. Like the mathematical sets and lists, sets can be empty and, if not, elements of sets in LIGO are unique, whereas they can be repeated in a list.

Like lists, the type of sets is parameterised over the type of its elements. Like list elements, set elements must all have the same type.

The empty set is denoted by the predefined value Set.empty. A non-empty set can be built by using the function Set.literal which takes a list of elements and returns a set containing them, and only them.

const empty_set: set<int> = Set.empty;

const my_set: set<int> = Set.literal(list([3, 2, 2, 1]));

Note: See the predefined namespace Set

Note: The element 2 is repeated in the list, but not in the set made from it.

Set elements are internally sorted by increasing values, so the type of the elements must be comparable, that is, they obey a total order (any two elements can be compared).