C++ Iterators - Output Iterator

Output iterators in C++ are used to write data to a container or stream. They are used to iterate over a collection or a sequence of elements and write data to it.

Syntax

output_iterator iterator;

*iterator = value;

The value is written to the container at the location pointed by the iterator.

Example

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
    vector<int> v{1, 2, 3, 4, 5};
    ostream_iterator<int> out_it(cout, " ");
    copy(v.begin(), v.end(), out_it);
    return 0;
}

Output

1 2 3 4 5

Explanation

In the above example, we have created a vector "v" containing some integer values. We have then created an output iterator "out_it" that is used to write data to the output stream "cout". We have used the "copy" function to copy the elements of the vector to the output stream using the output iterator. The space between the elements is defined by the separator argument given to the ostream_iterator.

Use

Output iterators are used to write data to containers or streams. They are primarily used for output operations such as writing the data to a file or sending it to a network.

#include <fstream>
#include <iterator>
#include <algorithm>
using namespace std;

int main() {
    ofstream myfile("output.txt");
    ostream_iterator<int> out_it(myfile, "\n");
    copy_n(istream_iterator<int>(cin), 10, out_it);
}

In the above example, we have opened a file "output.txt" in write mode and created an output iterator "out_it" to write data to it. We have then used the "copy_n" function to read 10 integer values from the input stream using the input iterator "istream_iterator(cin)" and write them to the output stream using the output iterator.

Important Points

• Output iterators are used to write data to containers or streams.
• The value pointed to by the output iterator is written to the container.
• Output iterators are invalidated if incremented multiple times, as they may point to the previous value written.

Summary

In summary, output iterators in C++ are used to write data to containers or streams. They are primarily used for output operations and provide a way to write to a container or stream using a standard interface. Output iterators are invalidated if incremented multiple times, so care should be taken to avoid invalidating them.