Efficient implementation of sets and multisets in R using hash tables

The package hset for the R language contains an implementation of a S4 class for sets and multisets of numbers. The implementation, based on the hash table data structure from the package hash (Brown, 2019), allows for quick operations when the set is a dynamic object. An important example is when a set or a multiset is part of the state of a Markov chain in which in each iteration various elements are moved in and out of the set.