25 Iterators library [iterators]

25.6 Stream iterators [stream.iterators]

25.6.2 Class template istream_iterator [istream.iterator] General [istream.iterator.general]

The class template istream_iterator is an input iterator ([input.iterators]) that reads successive elements from the input stream for which it was constructed.
namespace std { template<class T, class charT = char, class traits = char_traits<charT>, class Distance = ptrdiff_t> class istream_iterator { public: using iterator_category = input_iterator_tag; using value_type = T; using difference_type = Distance; using pointer = const T*; using reference = const T&; using char_type = charT; using traits_type = traits; using istream_type = basic_istream<charT,traits>; constexpr istream_iterator(); constexpr istream_iterator(default_sentinel_t); istream_iterator(istream_type& s); constexpr istream_iterator(const istream_iterator& x) noexcept(see below); ~istream_iterator() = default; istream_iterator& operator=(const istream_iterator&) = default; const T& operator*() const; const T* operator->() const; istream_iterator& operator++(); istream_iterator operator++(int); friend bool operator==(const istream_iterator& i, default_sentinel_t); private: basic_istream<charT,traits>* in_stream; // exposition only T value; // exposition only }; }
The type T shall meet the Cpp17DefaultConstructible, Cpp17CopyConstructible, and Cpp17CopyAssignable requirements.