User-defined Literals

Note that a literal should start with an underscore _. We declare a new literal by this pattern:

[returnType] operator "" _[name]([parameters]) { [body] }

Note that parameters can be only one of these:

(const char *) (unsigned long long int) (long double) (char) (wchar_t) (char16_t) (char32_t) (const char *, size_t) (const wchar_t *, size_t) (const char16_t *, size_t) (const char32_t *, size_t)

Literals also can used with templates.

Example Code

std::vector<uint64_t> operator "" _v(unsigned long long int x) {
    return vector<uint64_t> {x};
} 

int main() {
    auto v = 36_v;
    std::cout << v.size() << ' ' << v[0] << std::endl;  // 1 36
}