Task: Set
C++: #include <set>
#include <iostream>
#include <iterator>
#include <algorithm>

namespace set_display {
template <class T>
std::ostream& operator<<(std::ostream& os, const std::set<T>& set)
{
    os << '[';
    if (!set.empty()) {
        std::copy(set.begin(), --set.end(), std::ostream_iterator<T>(os, ", "));
        os << *--set.end();
    }
    return os << ']';
}
}

template <class T>
bool contains(const std::set<T>& set, const T& key)
{
    return set.count(key) != 0;
}

template <class T>
std::set<T> set_union(const std::set<T>& a, const std::set<T>& b)
{
    std::set<T> result;
    std::set_union(a.begin(), a.end(), b.begin(), b.end(), std::inserter(result, result.end()));
    return result;
}

template <class T>
std::set<T> set_intersection(const std::set<T>& a, const std::set<T>& b)
{
    std::set<T> result;
    std::set_intersection(a.begin(), a.end(), b.begin(), b.end(), std::inserter(result, result.end()));
    return result;
}

template <class T>
std::set<T> set_difference(const std::set<T>& a, const std::set<T>& b)
{
    std::set<T> result;
    std::set_difference(a.begin(), a.end(), b.begin(), b.end(), std::inserter(result, result.end()));
    return result;
}

template <class T>
bool is_subset(const std::set<T>& set, const std::set<T>& subset)
{
    return std::includes(set.begin(), set.end(), subset.begin(), subset.end());
}

int main()
{
    using namespace set_display;
    std::set<int> a{2, 5, 7, 5, 9, 2}; 
    std::set<int> b{1, 5, 9, 7, 4 };
    std::cout << "a = " << a << '\n';
    std::cout << "b = " << b << '\n';

    int value1 = 8, value2 = 5;
    std::cout << "Set a " << (contains(a, value1) ? "contains " : "does not contain ") << value1 << '\n';
    std::cout << "Set a " << (contains(a, value2) ? "contains " : "does not contain ") << value2 << '\n';

    std::cout << "Union of a and b: " << set_union(a, b) << '\n';
    std::cout << "Intersection of a and b: " << set_intersection(a, b) << '\n';
    std::cout << "Difference of a and b: " << set_difference(a, b) << '\n';

    std::set<int> sub{5, 9};
    std::cout << "Set b " << (is_subset(a, b) ? "is" : "is not") << " a subset of a\n";
    std::cout << "Set " << sub << ' ' << (is_subset(a, sub) ? "is" : "is not") << " a subset of a\n";

    std::set<int> copy = a;
    std::cout << "a " << (a == copy ? "equals " : "does not equal ") << copy << '\n';

    return 0;
}

VB: 





Private Function createSet(t As Variant) As Collection
    Dim x As New Collection
    For Each elem In t
        x.Add elem, elem
    Next elem
    Set createSet = x
End Function
Private Function isElement(s As Variant, x As Collection) As Boolean
    Dim errno As Integer, t As Variant
    On Error GoTo err
    t = x(s)
    isElement = True
    Exit Function
err:
    isElement = False
End Function
Private Function setUnion(A As Collection, B As Collection) As Collection
    Dim x As New Collection
    For Each elem In A
        x.Add elem, elem
    Next elem
    For Each elem In B
        On Error Resume Next 
        x.Add elem, elem
    Next elem
    Set setUnion = x
End Function
Private Function intersection(A As Collection, B As Collection) As Collection
    Dim x As New Collection
    For Each elem In A
        If isElement(elem, B) Then x.Add elem, elem
    Next elem
    For Each elem In B
        If isElement(elem, A) Then
            On Error Resume Next
            x.Add elem, elem
        End If
    Next elem
    Set intersection = x
End Function
Private Function difference(A As Collection, B As Collection) As Collection
    Dim x As New Collection
    For Each elem In A
        If Not isElement(elem, B) Then x.Add elem, elem
    Next elem
    Set difference = x
End Function
Private Function subset(A As Collection, B As Collection) As Boolean
    Dim flag As Boolean
    flag = True
    For Each elem In A
        If Not isElement(elem, B) Then
            flag = False
            Exit For
        End If
    Next elem
    subset = flag
End Function
Private Function equality(A As Collection, B As Collection) As Boolean
    Dim flag As Boolean
    flag = True
    If A.Count = B.Count Then
        For Each elem In A
            If Not isElement(elem, B) Then
                flag = False
                Exit For
            End If
        Next elem
    Else
        flag = False
    End If
    equality = flag
End Function
Private Function properSubset(A As Collection, B As Collection) As Boolean
    Dim flag As Boolean
    flag = True
    If A.Count < B.Count Then
        For Each elem In A
            If Not isElement(elem, B) Then
                flag = False
                Exit For
            End If
        Next elem
    Else
        flag = False
    End If
    properSubset = flag
End Function
Public Sub main()
    
    Dim s As Variant
    Dim A As Collection, B As Collection, C As Collection
    s = [{"Apple","Banana","Pear","Pineapple"}]
    Set A = createSet(s) 
    
    Debug.Print isElement("Apple", A) 
    Debug.Print isElement("Fruit", A) 
    
    s = [{"Fruit","Banana","Pear","Orange"}]
    Set B = createSet(s)
    Set C = setUnion(A, B)
    
    Set C = intersection(A, B)
    
    Set C = difference(A, B)
    
    Debug.Print subset(A, B)
    
    Debug.Print equality(A, B)
    
    Debug.Print properSubset(A, B)
    
    A.Remove "Apple"
    
    A.Remove 1
    
    A.Add "10", "10"
End Sub