hello_world.cpp

#include <algorithm>
#include <array>
#include <iostream>
#include <string>
#include <type_traits>

constexpr std::array<char, 27> ALPHABET = []() constexpr {
    std::remove_const<decltype(ALPHABET)>::type data{};
    data[0] = ' ';
    for (auto i = 0; i < data.size() - 1; ++i)
        data[i + 1] = 'A' + i;
    return data;
}
();

template <std::size_t size>
class Msg {
    std::array<decltype(ALPHABET)::const_iterator, size> text = []() constexpr {
        decltype(text) data{};
        std::fill(data.begin(), data.end(), ALPHABET.begin());
        return data;
    }
    ();
    typename decltype(text)::iterator ptr = text.begin();

public:
    Msg& operator++() {
        ++(*ptr);
        return *this;
    }
    Msg& operator++(int) {
        ++ptr;
        return *this;
    }
    operator std::string() {
        std::string out;
        out.reserve(size);
        for (auto it : text)
            out += *it;
        return out;
    }
};

int main() {
    std::cout << static_cast<std::string>(
        ++++++++(++++++++++++++++++++++++(++++++++++++++++++++++++++++++++++++(
            ++++++++++++++++++++++++++++++(++++++++++++++++++++++++++++++++++++++++++++++(
                ++++++++++++++++++++++++++++++(++++++++++++++++++++++++(++++++++++++++++++++++++(
                    ++++++++++(++++++++++++++++Msg<11>())++)++)++)++)++++)++)++)++)++);
}