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C++20 STL Cookbook

Copy from One Iterator to Another

Explore how to copy elements between containers using iterators in C++20 STL. Understand the use of std::copy, std::copy_n, copy_if, and move algorithms to manipulate container data effectively, including how to use back_inserter and ranges::copy for flexible data handling.

We'll cover the following...

The copy algorithms are generally used to copy from and to containers, but in fact, they work with iterators, which is far more flexible.

How to do it

In this recipe, we will experiment with std::copy and std::copy_n to get a good understanding of how they work:

  • Let's start with a function to print a container:

void printc(auto& c, string_view s = "") {
    if(s.size()) cout << format("{}: ", s);
    for(auto e : c) cout << format("[{}] ", e);
    cout << '\n';
}

  • In main(), we define a vector and print it with printc():

int main() {
    vector<string> v1
        { "alpha", "beta", "gamma", "delta",
            "epsilon" };
    printc(v1);
}

We get this output:

v1: [alpha] [beta] [gamma] [delta] [epsilon]

  • Now, let's create a second vector with enough space to copy the first vector:

vector<string> v2(v1.size());

  • We can copy v1 to ...