Binary Literals (C++11)

binary_literal.cc

#include <climits>

template <char c>
inline constexpr
unsigned long long int binary_digit ()
{
	static_assert (c == '0' || c == '1', "bad bit in binary literal");
	return (c - '0');
}

template <char...>
struct binary_literal;

template <char first, char... rest>
struct binary_literal <first, rest...>
{
	static inline constexpr
	unsigned long long int value ()
	{
		return (binary_digit <first> () << sizeof... (rest)) + binary_literal <rest...>::value ();
	}
};

template <>
struct binary_literal <>
{
	static inline constexpr
	unsigned long long int value ()
	{
		return 0;
	}
};

template <char... str>
inline constexpr
unsigned long long int operator "" _b ()
{
	static_assert (sizeof... (str) <= sizeof (unsigned long long int) * CHAR_BIT,
	               "binary literal too long");
	return binary_literal <str...>::value ();
}

#include <iostream>

int main ()
{
	std::cout << 1010_b << std::endl;
//	Will fail to compile:
//	std::cout << 2020_b << std::endl;
//	Will also fail to compile:
//	std::cout << 10101010101010101010101010101010101010101010101010101010101010101_b << std::endl;
}