Compare sub string: string4.compare( 0, string2.length(), string2 ) : string compare « string « C++ Tutorial

#include <iostream>
using std::cout;
using std::endl;

#include <string>
using std::string;

int main()
{
   string string1( "AAAAAAAAAAAAAA" );
   string string2( "BBBBBBBBBBBBBB" ); 
   string string3( "CCCCCCCCCCCCCC" );
   string string4( string2 );
   
   cout << "string1: " << string1 << "\nstring2: " << string2
      << "\nstring3: " << string3 << "\nstring4: " << string4 << "\n\n";

   // comparing string2 and string4
   int result = string4.compare( 0, string2.length(), string2 );

   if ( result == 0 )
      cout << "string4.compare( 0, string2.length(), " << "string2 ) == 0" << endl;
   else {
      if ( result > 0 )
         cout << "string4.compare( 0, string2.length(), " << "string2 ) > 0" << endl;
      else
         cout << "string4.compare( 0, string2.length(), "
            << "string2 ) < 0" << endl;
   }
   return 0;
}

string1: AAAAAAAAAAAAAA
string2: BBBBBBBBBBBBBB
string3: CCCCCCCCCCCCCC
string4: BBBBBBBBBBBBBB

string4.compare( 0, string2.length(), string2 ) == 0

15.7.string compare
	15.7.1.	String: equals
	15.7.2.	string overloaded equality and relational operators
	15.7.3.	Compare string ignoring the case
	15.7.4.	Compare sub string: string4.compare( 0, string2.length(), string2 )
	15.7.5.	Use == > and < to compare strings
	15.7.6.	Use string.compare to compare two strings
	15.7.7.	Compare strings by index: string1.compare( 2, 5, string3, 0, 5)
	15.7.8.	Set with functor for string comparison
	15.7.9.	Case-Sensitive Substring Comparison: equivalent of strncmp()
	15.7.10.	Case-Sensitive Substring Comparison: generalization of strncmp()
	15.7.11.	Case-Sensitive String Comparisons
	15.7.12.	Use std::lexicographical_compare to compare two char arrays