C++ String Interning Code courtesy of Ruslan Abdikeev https://twitter.com/aruslan

intern-udl-aruslan.h

//Proposal N3599 by Richard Smith "Literal operator templates for strings". 
//Clang and GCC implement as an extension, MSVC doesnt imlement it
//more details are in the blog post http://alexpolt.github.io/intern.html

#include <cstddef>
#include <type_traits>
#include <utility>

template<char ...S> struct interned {
    static constexpr char value[] = { S..., 0 };
};
template<char ...S> constexpr char interned<S...>::value[];

template<typename charT, charT ...S> constexpr const char *operator""_intern() {
    static_assert(std::is_same<charT, char>(), "string char type mismatch");
    return interned<S...>::value;
}

template<typename charT, charT ...S> constexpr auto operator""_intern_t() {
    static_assert(std::is_same<charT, char>(), "string char type mismatch");
    return interned<S...>{};
}