set operator= in C++ STL

The ‘=’ is an operator in C++ STL which copies (or moves) a set to another set and set::operator= is the corresponding operator function. There are three versions of this function:

  1. The first version takes reference of an set as an argument and copies it to an set.

    Syntax:

    ums1.operator=(set &set2)

    Parameters: The first version takes the reference of an set as argument.

  2. The second version performs a move assignment i.e it moves the content of an set to another set.

    Syntax:



    ums1.operator=(set &&set2)

    Parameters: The second version takes the r-value reference of an set as argument

  3. The third version assigns contents of an initializer list to an set.

    Syntax:

    ums1.operator=(initializer list)

    Parameters: The third version takes an initializer list as argument.

  4. Return Value: All of them return the value of this pointer(*this).

    The following programs illustrates set::operator= :

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    // C++ code to illustrate the method
    // set::operator=()
      
    #include <iostream>
    #include <set>
    using namespace std;
      
    // merge function
    template <class T>
    T merge(T a, T b)
    {
        T t(a);
        t.insert(b.begin(), b.end());
        return t;
    }
      
    int main()
    {
        set<int> sample1, sample2, sample3;
      
        // List initialization
        sample1 = { 1, 2, 3, 4, 5 };
        sample2 = { 6, 7, 8, 1 };
      
        // Merge both sets and
        // move the result to sample1
        sample3 = merge(sample1, sample2);
      
        // copy assignment
        sample1 = sample3;
      
        // Print the sets
        for (auto it = sample1.begin(); it != sample1.end(); ++it) {
            cout << *it << " ";
        }
      
        cout << endl;
      
        for (auto it = sample2.begin(); it != sample2.end(); ++it) {
            cout << *it << " ";
        }
      
        cout << endl;
      
        for (auto it = sample3.begin(); it != sample3.end(); ++it) {
            cout << *it << " ";
        }
      
        cout << endl;
      
        return 0;
    }

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    Output:

    1 2 3 4 5 6 7 8 
    1 6 7 8 
    1 2 3 4 5 6 7 8
    


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