/* This program demonstrates the confusing nature of string::npos. */

#include <iostream>
#include <string>
#include <cstdlib>
#include <cstdio>
using namespace std;

int main()
{
  string s;

  /* When find() fails, it return string::npos.  Therefore, when you want to see
     if a find() calls has succeeded or failed, you should test against string::npos, 
     as I do below: */

  s = "ABCDEFG";
  cout << (s.find("ABC") == string::npos) << endl;     // This should print 1 = true.
  cout << (s.find("CBA") == string::npos) << endl;     // This should print 0 = false.

  /* So, what exactly is string::npos?  If you look up the documentation, it's 
     of type std::string::size_type, which is an unsigned long.  If you use cout
     to print it, you get a giant integer.  As hex, it's 16 f's (all bits set to 
     one).  If you set it or typecast it to a signed long, it becomes -1.  What
     to make of all of this?  Just use "string::npos" when you want to test that
     a find() call has failed, and think smugly to yourself what a poor decision
     it was for find() to return a std::string::size_type... */

  cout << "When you use cout, string::npos is " << string::npos << endl;
  cout << "When you use hex,  string::npos is 0x" << hex << string::npos << endl;
  cout << "Using printf(\"%lu\"), you get:      ";
  printf("%lu\n", string::npos);
  cout << "Using printf(\"%ld\"), you get:      ";
  printf("%ld\n", string::npos);
  return 0;
}