const array

#include <iostream>
#include <array>
#include <algorithm>
#include <numeric>

typedef unsigned long long ULL;

// Delcare the litparser
template<ULL Sum, char... Chars> struct litparser;

// Specialize on the case where there's at least one character left:
template<ULL Sum, char Head, char... Rest>
struct litparser<Sum, Head, Rest...> {
// parse a digit. recurse with new sum and ramaining digits
  static const ULL value = litparser<
    (Head <'0' || Head >'9') ? throw std::exception() :
    Sum*10 + Head-'0' , Rest...>::value;
};

// When 'Rest' finally is empty, we reach this terminating case
template<ULL Sum>  struct litparser<Sum> {
  static const ULL value = Sum;
};

template<char... Chars>
auto operator"" _array(){
  return std::array<int, litparser<0,Chars...>::value>{};
}

int main() {
	auto a = 128_array;
	std::iota (a.begin(), a.end(), 1);
	for (const auto & v : a) {
		std::cout << v << ' ';
	}
	std::cout << std::endl;
}