Modern C++ Features

#include <iostream>
#include <map>
#include <optional>
#include <string>
#include <tuple>
#include <variant>
using namespace std;

enum class Color { Red, Green, Blue };

optional<int> parse(const string &s) {
  try { return stoi(s); } catch (...) { return nullopt; }
}

int main() {
  Color c = Color::Green;
  cout << (c == Color::Green) << " " << static_cast<int>(c) << endl;

  auto r1 = parse("42");
  auto r2 = parse("abc");
  cout << r1.value_or(-1) << " " << r2.value_or(-1) << endl;

  tuple<string, int> person{"Ada", 36};
  auto [name, age] = person;
  cout << name << " " << age << endl;

  variant<int, string> v = "text";
  cout << holds_alternative<string>(v) << endl;

  map<string, int> m{{"a", 1}, {"b", 2}};
  if (auto it = m.find("b"); it != m.end()) cout << it->second << endl;

  constexpr int N = 5 * 5;
  static_assert(N == 25, "math works");
  cout << N << endl;
  return 0;
}

1 1
42 -1
Ada 36
1
2
25