#include <map>
#include <iostream>
using namespace std;

int main()
{
  map<const char*, double> m;
  pair key_value = pair("pi", 3.14);
  m.insert(key_value);

  cout << m["pi"];

  return 0;
}

#include <any>
#include <iostream>

int main()
{
  std::any ret1 = 1;
  std::any ret2 = "asdf";

  std::cout
    << std::any_cast<int>(ret1) << "\n"
    << std::any_cast<const char*>(ret2) 
        << std::endl;

  return 0;
}

#include <variant>
#include <string>
using namespace std;

int main()
{
  variant<int, string> ret = "asdf";

  string str = get<string>(ret);
  // int i = get<int>(ret); // Error

  string* pstr = get_if<string>(&ret);
  int* null_pointer = get_if<int>(&ret);

  bool equal_type_false = holds_alternative<int>(ret);
  bool equal_type_true  = holds_alternative<string>(ret);

  return 0;
}

#include <optional>
#include <iostream>

int main()
{
  std::optional<int> ret1 = 1;
  std::optional<int> ret2 = {};

  std::cout
    << ret1.value() << "\n"
    << ret1.value_or(100) << "\n"
    << ret2.value_or(100) << std::endl;

  return 0;
}