Data commit

Task/Symmetric-difference/Lua/symmetric-difference-1.lua

@@ -0,0 +1,19 @@
+A = { ["John"] = true, ["Bob"] = true, ["Mary"] = true, ["Serena"] = true }
+B = { ["Jim"] = true, ["Mary"] = true, ["John"] = true, ["Bob"] = true }
+
+A_B = {}
+for a in pairs(A) do
+    if not B[a] then A_B[a] = true end
+end
+
+B_A = {}
+for b in pairs(B) do
+    if not A[b] then B_A[b] = true end
+end
+
+for a_b in pairs(A_B) do
+    print( a_b )
+end
+for b_a in pairs(B_A) do
+    print( b_a )
+end

Task/Symmetric-difference/Lua/symmetric-difference-2.lua

@@ -0,0 +1,56 @@
+SetPrototype = {
+    __index = {
+        union = function(self, other)
+            local res = Set{}
+            for k in pairs(self) do res[k] = true end
+            for k in pairs(other) do res[k] = true end
+            return res
+        end,
+        intersection = function(self, other)
+            local res = Set{}
+            for k in pairs(self) do res[k] = other[k] end
+            return res
+        end,
+        difference = function(self, other)
+            local res = Set{}
+            for k in pairs(self) do
+                if not other[k] then res[k] = true end
+            end
+            return res
+        end,
+        symmetric_difference = function(self, other)
+            return self:difference(other):union(other:difference(self))
+        end
+    },
+    -- return string representation of set
+    __tostring = function(self)
+        -- list to collect all elements from the set
+        local l = {}
+        for k in pairs(self) do l[#l+1] = k end
+        return "{" .. table.concat(l, ", ") .. "}"
+    end,
+    -- allow concatenation with other types to yield string
+    __concat = function(a, b)
+        return (type(a) == 'string' and a or tostring(a)) ..
+            (type(b) == 'string' and b or tostring(b))
+    end
+}
+
+function Set(items)
+    local _set = {}
+    setmetatable(_set, SetPrototype)
+    for _, item in ipairs(items) do _set[item] = true end
+    return _set
+end
+
+A = Set{"John", "Serena", "Bob", "Mary", "Serena"}
+B = Set{"Jim", "Mary", "John", "Jim", "Bob"}
+
+print("Set A: " .. A)
+print("Set B: " .. B)
+
+print("\nSymm. difference (A\\B)∪(B\\A): " .. A:symmetric_difference(B))
+print("Union            A∪B        : " .. A:union(B))
+print("Intersection     A∩B        : " .. A:intersection(B))
+print("Difference       A\\B        : " .. A:difference(B))
+print("Difference       B\\A        : " .. B:difference(A))