test of std::transform behavior when start and end are the same

test.cpp

#include <algorithm>
#include <vector>
#include <iostream>

int main() {
    std::vector<int> a = { 0, 1, 2, 3 };
    std::vector<int> b;

    std::transform(
        a.begin(), a.begin(),
        std::back_inserter(b),
        [](const auto& x) {
            return x;
        }
    );

    std::cout << "a.size() = " << a.size() << std::endl
        << "b.size() = " << b.size() << std::endl;

    return 0;
}