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      std::basic_string<CharT,Traits,Allocator>::npos

      From cppreference.com
      <cpp‎ |string‎ |basic string
       
       
       
      std::basic_string
       
      staticconst size_type npos=-1;

      This is a special value equal to the maximum value representable by the typesize_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.

      [edit]Note

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

      [edit]Example

      Run this code
      #include <bitset>#include <iostream>#include <string> int main(){// string search functions return npos if nothing is foundstd::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" indicatorstd::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'st00011

      [edit]See also

      [static]
      special value. The exact meaning depends on the context
      (public static member constant ofstd::basic_string_view<CharT,Traits>)[edit]
      Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/string/basic_string/npos&oldid=170917"

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