#include <string>
  bool empty() const;

The empty() function returns true if the string has no elements, false otherwise.

For example:

  string s1;
  string s2("");
  string s3("This is a string");
  cout.setf(ios::boolalpha);
  cout << s1.empty() << endl;
  cout << s2.empty() << endl;
  cout << s3.empty() << endl;

When run, this code produces the following output:

  true
  true
  false