// This code illustrates why we sometimes need the “explicit”
// declaration on a constructor, to avoid undesirable behavior.

class CheapVec {
  public:
    CheapVec() : data(nullptr), count(0) { }
    /* explicit */ CheapVec(int n) : data(new int[n]), count(n) { }
    ~CheapVec() { delete[] data; }

  private:
    int *data;
    int count;
};

int main() {
    CheapVec a;		// An empty vector
    CheapVec b(3);	// A vector of three items
    a = 3;		// This compiles!?
}