ユーザー定義リテラルで整数のRange-based for

iteraton_by_iota.cpp

#include <iostream>

namespace iota {
  class Iter {
    public:
      Iter(): iter(0) {}
      Iter(int x): iter(x) {}
      int operator*() {
        return iter;
      }
      const Iter& operator++() {
        iter++;
        return *this;
      }
      bool operator!=(const Iter &other) {
        return iter != other.iter;
      }
    private:
      int iter;
  };

  class Range {
    public:
      Range(int x): upper_bound(x) {}
      Iter begin() {
        return Iter();
      }
      Iter end() {
        return Iter(upper_bound);
      }
    private:
      const int upper_bound;
  };

  Range operator"" _times(unsigned long long x) {
    return Range(x);
  }
}

int main() {
  using iota::operator"" _times;
  for (int i : 10_times) {
    std::cout << i << std::endl;
  }
}