[istream.iterator] (original) (raw)

24.6.2.1 General [istream.iterator.general]

The class template istream_iteratoris 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; T value; };}

The type T shall meet the Cpp17DefaultConstructible,Cpp17CopyConstructible, and Cpp17CopyAssignable requirements.

24.6.2.2 Constructors and destructor [istream.iterator.cons]

constexpr istream_iterator();constexpr istream_iterator(default_sentinel_t);

Effects: Constructs the end-of-stream iterator, value-initializing value.

Postconditions: in_stream == nullptr is true.

Remarks: If the initializer T() in the declaration auto x = T();is a constant initializer ([expr.const]), then these constructors are constexpr constructors.

istream_iterator(istream_type& s);

Effects: Initializes in_stream with addressof(s), value-initializes value, and then calls operator++().

constexpr istream_iterator(const istream_iterator& x) noexcept(_see below_);

Effects: Initializes in_stream with x.in_stream and initializes value with x.value.

Remarks: An invocation of this constructor may be used in a core constant expression if and only if the initialization of value from x.valueis a constant subexpression ([defns.const.subexpr]).

The exception specification is equivalent tois_nothrow_copy_constructible_v<T>.

~istream_iterator() = default;

Remarks: If is_trivially_destructible_v<T> is true, then this destructor is trivial.

24.6.2.3 Operations [istream.iterator.ops]

const T& operator*() const;

Preconditions: in_stream != nullptr is true.

const T* operator->() const;

Preconditions: in_stream != nullptr is true.

Returns: addressof(value).

istream_iterator& operator++();

Preconditions: in_stream != nullptr is true.

Effects: Equivalent to:if (!(*in_stream >> value)) in_stream = nullptr;

istream_iterator operator++(int);

Preconditions: in_stream != nullptr is true.

Effects: Equivalent to:istream_iterator tmp = *this;++*this;return tmp;

template<class T, class charT, class traits, class Distance> bool operator==(const istream_iterator<T,charT,traits,Distance>& x,const istream_iterator<T,charT,traits,Distance>& y);

Returns: x.in_stream == y.in_stream.

friend bool operator==(const istream_iterator& i, default_sentinel_t);