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The nested class describes an object whose declaration structures the formatted and unformatted input functions.

class sentry {
   explicit sentry(
      basic_istream& _Istr,
      bool _Noskip = false
   operator bool( ) const;

If _Istr.good is true, the constructor:

  • Calls _Istr.tie -> flush if _Istr.tie is not a null pointer

  • Effectively calls ws(_Istr) if _Istr.flags & skipws is nonzero

If, after any such preparation, _Istr.good is false, the constructor calls _Istr.setstate(failbit). In any case, the constructor stores the value returned by _Istr.good in status. A later call to operator bool delivers this stored value.

Header: <istream>

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