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-rw-r--r--util/set.lua27
1 files changed, 18 insertions, 9 deletions
diff --git a/util/set.lua b/util/set.lua
index 67f3dcaa..f550a721 100644
--- a/util/set.lua
+++ b/util/set.lua
@@ -5,7 +5,7 @@ module "set"
function new(list)
local items = {};
- local set = { items = items };
+ local set = { _items = items };
function set:add(item)
items[item] = true;
@@ -50,13 +50,13 @@ end
function union(set1, set2)
local set = new();
- local items = set.items;
+ local items = set._items;
- for item in pairs(set1.items) do
+ for item in pairs(set1._items) do
items[item] = true;
end
- for item in pairs(set2.items) do
+ for item in pairs(set2._items) do
items[item] = true;
end
@@ -65,14 +65,23 @@ end
function difference(set1, set2)
local set = new();
- local items = set.items;
+ local items = set._items;
- for item in pairs(set1.items) do
- items[item] = true;
+ for item in pairs(set1._items) do
+ items[item] = (not set2._items[item]) or nil;
end
- for item in pairs(set2.items) do
- items[item] = nil;
+ return set;
+end
+
+function intersection(set1, set2)
+ local set = new();
+ local items = set._items;
+
+ set1, set2 = set1._items, set2._items;
+
+ for item in pairs(set1) do
+ items[item] = (not not set2[item]) or nil;
end
return set;