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 literal elements and returns a set containing them, and only them.

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

const set1: set<int> = Set.literal([3, 2, 2, 1]);

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

Note: See the predefined namespace Set

If you want to build a big set from an arbitrary list of arbitrary values (not just literal values), then you must use Set.of_list instead of Set.literal:

const two = 2;

const set2 : set<int> = Set.of_list([3, two, two, 1]);

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).