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std::basic_string::npos(3)     C++ Standard Libary    std::basic_string::npos(3)

NAME
     std::basic_string::npos - std::basic_string::npos

Synopsis
	static const size_type npos = -1;

	This  is a special value equal to the maximum value representable by the
     type
	size_type. The exact meaning depends on context,  but  it  is  generally
     used either as
	end  of  string indicator by the functions that expect a string index or
     as the error
	indicator by the functions that return a string index.

Note
	Although the definition uses -1, size_type is an unsigned integer  type,
     and the
	value  of npos is the largest positive value it can hold, due to signed-
     to-unsigned
	implicit conversion. This is a portable way to specify the largest value
     of any
	unsigned type.

Example
     // Run this code

      #include <bitset>
      #include <iostream>
      #include <string>

      int main()
      {
	  // string search functions return npos if nothing is found
	  std::string s = "test";
	  if (s.find('a') == s.npos)
	      std::cout << "no 'a' in 'test'\n";

	  // functions that take string subsets as arguments
	  // use npos as the "all the way to the end" indicator
	  std::string s2(s, 2, std::string::npos);
	  std::cout << s2 << '\n';

	  std::bitset<5> b("aaabb", std::string::npos, 'a', 'b');
	  std::cout << b << '\n';
      }

Output:
      no 'a' in 'test'
      st
      00011

See also
	npos	 special value. The exact meaning depends on the context
	[static]    (public    static	 member     constant	 of	std::ba-
     sic_string_view<CharT,Traits>)

http://cppreference.com 	   2024.06.10	      std::basic_string::npos(3)
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