24 Ranges library [ranges]

24.6 Range factories [range.factories]

24.6.5 Istream view [range.istream]

24.6.5.1 Overview [range.istream.overview]

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basic_­istream_­view models input_­range and reads (using operator>>) successive elements from its corresponding input stream.
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[Example 1: auto ints = istringstream{"0 1 2 3 4"}; ranges::copy(ranges::istream_view<int>(ints), ostream_iterator<int>{cout, "-"}); // prints 0-1-2-3-4- — end example]

24.6.5.2 Class template basic_­istream_­view [range.istream.view]

namespace std::ranges { template<class Val, class CharT, class Traits> concept stream-extractable = // exposition only requires(basic_istream<CharT, Traits>& is, Val& t) { is >> t; }; template<movable Val, class CharT, class Traits> requires default_initializable<Val> && stream-extractable<Val, CharT, Traits> class basic_istream_view : public view_interface<basic_istream_view<Val, CharT, Traits>> { public: basic_istream_view() = default; constexpr explicit basic_istream_view(basic_istream<CharT, Traits>& stream); constexpr auto begin() { if (stream_) { *stream_ >> object_; } return iterator{*this}; } constexpr default_sentinel_t end() const noexcept; private: struct iterator; // exposition only basic_istream<CharT, Traits>* stream_ = nullptr; // exposition only Val object_ = Val(); // exposition only }; }
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constexpr explicit basic_istream_view(basic_istream<CharT, Traits>& stream);
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Effects: Initializes stream_­ with addressof(stream).
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constexpr default_sentinel_t end() const noexcept;
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Effects: Equivalent to: return default_­sentinel;
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template<class Val, class CharT, class Traits> basic_istream_view<Val, CharT, Traits> istream_view(basic_istream<CharT, Traits>& s);
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Effects: Equivalent to: return basic_­istream_­view<Val, CharT, Traits>{s};

24.6.5.3 Class template basic_­istream_­view​::​iterator [range.istream.iterator]

namespace std::ranges { template<movable Val, class CharT, class Traits> requires default_initializable<Val> && stream-extractable<Val, CharT, Traits> class basic_istream_view<Val, CharT, Traits>::iterator { // exposition only public: using iterator_concept = input_iterator_tag; using difference_type = ptrdiff_t; using value_type = Val; iterator() = default; constexpr explicit iterator(basic_istream_view& parent) noexcept; iterator(const iterator&) = delete; iterator(iterator&&) = default; iterator& operator=(const iterator&) = delete; iterator& operator=(iterator&&) = default; iterator& operator++(); void operator++(int); Val& operator*() const; friend bool operator==(const iterator& x, default_sentinel_t); private: basic_istream_view* parent_ = nullptr; // exposition only }; }
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constexpr explicit iterator(basic_istream_view& parent) noexcept;
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Effects: Initializes parent_­ with addressof(parent).
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iterator& operator++();
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Preconditions: parent_­->stream_­ != nullptr is true.
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Effects: Equivalent to: *parent_->stream_ >> parent_->object_; return *this;
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void operator++(int);
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Preconditions: parent_­->stream_­ != nullptr is true.
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Effects: Equivalent to ++*this.
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Val& operator*() const;
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Preconditions: parent_­->stream_­ != nullptr is true.
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Effects: Equivalent to: return parent_­->object_­;
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friend bool operator==(const iterator& x, default_sentinel_t);
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Effects: Equivalent to: return x.parent_­ == nullptr || !*x.parent_­->stream_­;