# (lispkit disjoint-set)
Library `(lispkit disjoint-set)` implements disjoint sets, a mutable union-find data structure that tracks a set of elements partitioned into disjoint subsets. Disjoint sets are based on hashtables and require the definition of an equality and a hash function.
**disjoint-set-type-tag** 
Symbol representing the `disjoint-set` type. The `type-for` procedure of library `(lispkit type)` returns this symbol for all disjoint set objects.
**(disjoint-set? \_obj**\_**)** 
Returns `#t` if *obj* is a disjoint set object; otherwise `#f` is returned.
**(make-eq-disjoint-set)**
Returns a new empty disjoint set using `eq` as equality and `eq-hash` as hash function.
**(make-eqv-disjoint-set)**
Returns a new empty disjoint set using `eqv` as equality and `eqv-hash` as hash function.
**(make-disjoint-set *****comparator)*** \
\&#xNAN;**(make-disjoint-set *****hash eql*****)**
Returns a new empty disjoint set using *eql* as equality and *hash* as hash function. Instead of providing two functions, a new disjoint set can also be created based on a *comparator*.
**(disjoint-set-make *****dset x*****)**
Adds a new singleton set *x* to *dset* if element *x* does not exist already in disjoint set *dset*.
**(disjoint-set-find *****dset x)*** \
\&#xNAN;**(disjoint-set-find *****dset x default*****)**
Looks up element *x* in *dset* and returns the set in which *x* is currently contained. Returns *default* if element *x* is not found. If *default* is not provided, `disjoint-set-find` uses `#f` instead.
**(disjoint-set-union *****dset x y*****)**
Unifies the sets containing *x* and *y* in disjoint set *dset*.
**(disjoint-set-size *****dset*****)**
Returns the number of sets in *dset*.