chickadee » srfi-1 » lset-difference!

lset-union! = list_1 ...procedure
lset-intersection! = list_1 list_2 ...procedure
lset-difference! = list_1 list_2 ...procedure
lset-xor! = list_1 ...procedure
lset-diff+intersection! = list_1 list_2 ...procedure

These are linear-update variants. They are allowed, but not required, to use the cons cells in their first list parameter to construct their answer. lset-union! is permitted to recycle cons cells from any of its list arguments.