8 local set = { items = items };
10 function set:add(item)
14 function set:contains(item)
22 function set:remove(item)
26 function set:add_list(list)
27 for _, item in ipairs(list) do
32 function set:include(otherset)
33 for item in pairs(otherset) do
38 function set:exclude(otherset)
39 for item in pairs(otherset) do
51 function union(set1, set2)
53 local items = set.items;
55 for item in pairs(set1.items) do
59 for item in pairs(set2.items) do
66 function difference(set1, set2)
68 local items = set.items;
70 for item in pairs(set1.items) do
74 for item in pairs(set2.items) do