CODEWITHSUNDEEP
c++stlistream-iterator
Chukwunonso Nwafor
Chukwunonso Nwafor

Reputation: 1

understanding equality from istream_iterator

Can someone please explain why this istream_iterator code.

// code extract from SGI STL istream_iterator class
bool _M_equal(const istream_iterator& __x) const {
   return (_M_ok == __x.M_ok) && (!_M_ok || _M_stream == __x._M_stream);
}

works and is not just written as

bool _M_equal(const istream_iterator& __x) const {
   return (_M_ok == __x.M_ok) && (_M_stream == __x._M_stream);
}

I don't understanding the reason for including !_M_ok. Thanks in advance.

Upvotes: 0

Views: 35

Answers (1)

Caleth
Caleth

Reputation: 63152

_M_stream == __x._M_stream has undefined behaviour if either _M_ok or __x._M_ok is false.

Upvotes: 1

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