Symmetric difference: Difference between revisions

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@@ Line 1,247: / Line 1,247: @@
 <lang lua>SetPrototype = {
+    __index = {
-    union = function(self, other)
-        local res = Set{}
+        union = function(self, other)
-        for k in pairs(self) do res[k] = true end
+            local res = Set{}
-        for k in pairs(other) do res[k] = true end
+            for k in pairs(self) do res[k] = true end
-        return res
+            for k in pairs(other) do res[k] = true end
+            return res
-    end,
+        end,
-    intersection = function(self, other)
-        local res = Set{}
+        intersection = function(self, other)
-        for k in pairs(self) do res[k] = other[k] end
+            local res = Set{}
-        return res
+            for k in pairs(self) do res[k] = other[k] end
+            return res
-    end,
+        end,
-    difference = function(self, other)
-        local res = Set{}
+        difference = function(self, other)
-        for k in pairs(self) do
+            local res = Set{}
-            if not other[k] then res[k] = true end
+            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 res
+    },
-    end,
-    symmetric_difference = function(self, other)
-        return self:difference(other):union(other:difference(self))
-    end,
     -- return string representation of set
-    tostring = function(self)
+    __tostring = function(self)
+        -- list to collect all elements from the set
         local l = {}
-        for e in pairs(self) do l[#l+1] = e end
+        for k in pairs(self) do l[#l+1] = k end
         return "{" .. table.concat(l, ", ") .. "}"
     end,
+    -- allow concatenation with other types to yield string
-    -- print set
-    ["print"] = function(self)
+    __concat = function(a, b)
-        print(self:tostring())
+        return (type(a) == 'string' and a or tostring(a)) ..
+            (type(b) == 'string' and b or tostring(b))
     end
 }
@@ Line 1,282: / Line 1,286: @@
 function Set(items)
     local _set = {}
-    setmetatable(_set, {__index = SetPrototype})
+    setmetatable(_set, SetPrototype)
     for _, item in ipairs(items) do _set[item] = true end
     return _set
 end
-A = Set{"John", "Bob", "Mary", "Serena"}
+A = Set{"John", "Serena", "Bob", "Mary", "Serena"}
-B = Set{"Jim", "Mary", "John", "Bob"}
+B = Set{"Jim", "Mary", "John", "Jim", "Bob"}
-print "Set A:"
+print("Set A: " .. A)
-A:print()
+print("Set B: " .. B)
+print("\nSymm. difference (A\\B)∪(B\\A): " .. A:symmetric_difference(B))
-print "\nSet B:"
+print("Union            A∪B        : " .. A:union(B))
-A:print()
+print("Intersection     A∩B        : " .. A:intersection(B))
-print "\nSymmetric difference (A \\ B) ∪ (B \\ A):"
+print("Difference       A\\B        : " .. A:difference(B))
+print("Difference       B\\A        : " .. B:difference(A))</lang>
-A:symmetric_difference(B):print()
-print "\nUnion A ∪ B:"
-A:union(B):print()
-print "\nIntersection A ∩ B:"
-A:intersection(B):print()
-print "\nDifference A \\ B:"
-A:difference(B):print()
-print "\nDifference B \\ A:"
-B:difference(A):print()
-</lang>
 '''Output:'''
-    Set A:
+    Set A: {Serena, Mary, John, Bob}
-    {Mary, Serena, John, Bob}
+    Set B: {Mary, Jim, John, Bob}
-    Set B:
-    {Mary, Jim, John, Bob}
-    Symmetric difference (A \ B) ∪ (B \ A):
-    {Serena, Jim}
-    Union A ∪ B:
-    {John, Mary, Jim, Serena, Bob}
-    Intersection A ∩ B:
-    {Mary, John, Bob}
-    Difference A \ B:
-    {Serena}
+    Symm. difference (A\B)∪(B\A): {Serena, Jim}
-    Difference B \ A:
+    Union            A∪B        : {John, Serena, Jim, Mary, Bob}
-    {Jim}
+    Intersection     A∩B        : {Mary, John, Bob}
+    Difference       A\B        : {Serena}
+    Difference       B\A        : {Jim}
 =={{header|Mathematica}}==