lst-0681-book.cpp
// https://godbolt.org/z/5rdzn8YP4
namespace lits {
// allgemeines Template
template<char...> int operator"" _bin2();
// Spezialisierungen
template<> int operator"" _bin2<'0','0'>() { return 0; }
template<> int operator"" _bin2<'0','1'>() { return 1; }
template<> int operator"" _bin2<'1','0'>() { return 2; }
template<> int operator"" _bin2<'1','1'>() { return 3; }
}
int main() {
using namespace lits;
int one = 01_bin2;
int three = 11_bin2;
}