Monte has three builtin types of collections, each of which come in “const” (immutable) and “flex” (mutable) flavors.
Monte’s sets are ordered containers with the standard assortment of set-theoretic tools, like membership testing, iteration, union, and intersection. Members are stored based on the sameness test; two members overlap if, and only if, they are the same.
Sets support syntactic comparison using the <=> and related operators. The comparison takes the form of a subset test. Two sets s and t are equivalent, s <=> t, if, and only if, they contain the same members and are the same size.