Demonstrate usage of noncopyable class in std containers

noncopyable.C

// http://stackoverflow.com/questions/17603666/copy-move-requirements-for-the-key-value-types-in-a-stdmap
#include <map>
#include <vector>

struct foo
{
  int i;

  foo(int j) : i(j) {}

  // make foo non-copyable
  foo(const foo &) = delete;             // copy ctor
  foo & operator=(const foo &) = delete; // assignment op

  // Use default move ctors.  You have to declare these, otherwise the
  // class will not have automatically generated move ctors.
  foo (foo && other) = default;
  foo & operator=(foo &&) = default;
};

// Required for foo to be used as a key in std::map
bool operator<(const foo & f1, const foo & f2)
{
  return f1.i < f2.i;
}

int main(int argc, char ** argv)
{
  // Test whether we can create a map where keys are non-copyable.  We
  // can, but the map itself cannot be copied (makes sense).
  {
    std::map<foo,int> f;
    // std::map<foo,int> f2 = f; // compile error - can't copy map with uncopyable items
    std::map<foo,int> f3 = std::move(f); // OK: when moving, nothing is copied
  }

  // Test whether we can create a map where values are non-copyable.
  {
    std::map<int, foo> f;
    std::map<int, foo> f3 = std::move(f); // OK: when moving, nothing is copied
  }

  // Test inserting noncopyable keys into the map.
  {
    std::map<foo, int> f;
    f.insert(std::make_pair(foo(1), 1));  // works if foo has move ctor
    f[foo(1)] = 1;                        // works if foo has move ctor
    f.emplace(std::make_pair(foo(1), 1)); // works if foo has move ctor
    f.emplace(foo(1), 1);                 // works if foo has move ctor
  }

  // Test non-copyable items in std::vector.
  {
    std::vector<foo> f;
    f.push_back(foo(1));     // works if foo has move ctor
    f.emplace_back(foo(1));  // works if foo has move ctor
    f.emplace_back(1);       // works by forwarding the arg to the foo ctor
  }

  return 0;
}