C++ Quine

quine.cpp

#include <iostream>
int main() {
    std::string code1 = R"(
#include <iostream>
int main() {
)";
    std::string code2 = R"(
    std::cout << code1
              << "    std::string code1 = R\"(" << code1 << ")\";\n"
              << "    std::string code2 = R\"(" << code2 << ")\";\n"
              << code2;
}
)";

    std::cout << code1
              << "    std::string code1 = R\"(" << code1 << ")\";\n"
              << "    std::string code2 = R\"(" << code2 << ")\";\n"
              << code2;
}

std::cout << code1
error C2679: binary '<<': no operator found which takes a right-hand operand of type 'std::string' (or there is no acceptable conversion)

You forget to
#include < string >