(disj set) (disj set key) (disj set key & ks)
disj[oin]. Returns a new set of the same (hashed/sorted) type, that does not contain key(s).
user=> (disj #{1 2 3}) ; disjoin nothing
#{1 2 3}
user=> (disj #{1 2 3} 2) ; disjoin 2
#{1 3}
user=> (disj #{1 2 3} 4) ; disjoin non-existent item
#{1 2 3}
user=> (disj #{1 2 3} 1 3) ; disjoin several items at once
#{2}