String operators

  #include <string>
  bool operator==(const string& c1, const string& c2);
  bool operator!=(const string& c1, const string& c2);
  bool operator<(const string& c1, const string& c2);
  bool operator>(const string& c1, const string& c2);
  bool operator<=(const string& c1, const string& c2);
  bool operator>=(const string& c1, const string& c2);
  string operator+(const string& s1, const string& s2 );
  string operator+(const char* s, const string& s2 );
  string operator+( char c, const string& s2 );
  string operator+( const string& s1, const char* s );
  string operator+( const string& s1, char c );
  ostream& operator<<( ostream& os, const string& s );
  istream& operator>>( istream& is, string& s );
  string& operator=( const string& s );
  string& operator=( const char* s );
  string& operator=( char ch );
  char& operator[]( size_type index );

C++ strings can be compared and assigned with the standard comparison operators: ==, !=, <=, >=, <, >, and =. Performing a comparison or assigning one string to another takes linear time.

Two strings are equal if:

  1. Their size is the same, and
  2. Each member in location i in one string is equal to the the member in location i in the other string.              

Comparisons among strings are done lexicographically.

In addition to the normal container operators, strings can also be concatenated with the + operator and fed to the C++ I/O stream classes with the << and >> operators.

For example, the following code concatenates two strings and displays the result:

 string s1 = "Now is the time...";
 string s2 = "for all good men...";
 string s3 = s1 + s2;
 cout << "s3 is " << s3 << endl;            

Futhermore, strings can be assigned values that are other strings, character arrays, or even single characters. The following code is perfectly valid:

 char ch = 'N';
 string s;
 s = ch;         

Individual characters of a string can be examined with the [] operator, which runs in constant time.