#include <algorithm>
#include <cstddef>
#include <iostream>
#include <iterator>
#include <string>

class string_literal
{
    char const* begin_;
    char const* end_;
    static constexpr std::size_t str_len(char const* begin, std::size_t len) {
        return *begin == 0? len: str_len(begin + 1, len + 1);
    }
public:
    constexpr string_literal(char const* b)
        : begin_(b), end_(b + str_len(b, 0)) {
    }
    constexpr string_literal(char const* b, char const* e)
        : begin_(b), end_(e) {
    }
    constexpr char const* begin() const { return this->begin_; }
    constexpr char const* end() const   { return this->end_; }
    bool operator== (std::string const& other) const {
        return other.size() == std::size_t(std::distance(begin_, end_))
            && std::equal(begin_, end_, other.begin());
    }
    bool operator!= (std::string const& other) const {
        return !(*this == other);
    }
};

std::ostream& operator<< (std::ostream& out, string_literal const& s) {
    std::ostream::sentry cerberos(out);
    if (cerberos) {
        out << '\'';
        std::copy(s.begin(), s.end(), std::ostreambuf_iterator<char>(out));
        out << '\'';
    }
    return out;
}

constexpr string_literal operator"" _sl(char const* begin, std::size_t)
{
    return string_literal(begin);
}

constexpr string_literal hello_1("hello"_sl);
constexpr string_literal hello_2("hello");

int main()
{
    std::cout << "hello\0world"_sl << '\n'; 
    std::cout << hello_1 << '\n'; 
}