From Jason Turner

[range.istream]

C++17 → C++20 4.2 KB 153 lines
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Archived: C++17 | C++20
Markdown: C++17 | C++20
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  1. tmp/tmpakwl9_vc/{from.md → to.md} +150 -0
tmp/tmpakwl9_vc/{from.md → to.md} RENAMED
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+ ### Istream view <a id="range.istream">[[range.istream]]</a>
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+
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+ #### Overview <a id="range.istream.overview">[[range.istream.overview]]</a>
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+
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+ `basic_istream_view` models `input_range` and reads (using `operator>>`)
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+ successive elements from its corresponding input stream.
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+
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+ [*Example 1*:
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+
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+ ``` cpp
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+ auto ints = istringstream{"0 1 2 3 4"};
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+ ranges::copy(istream_view<int>(ints), ostream_iterator<int>{cout, "-"});
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+ // prints 0-1-2-3-4-
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+ ```
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+
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+ — *end example*]
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+
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+ #### Class template `basic_istream_view` <a id="range.istream.view">[[range.istream.view]]</a>
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+
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+ ``` cpp
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+ namespace std::ranges {
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+ template<class Val, class CharT, class Traits>
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+ concept stream-extractable = // exposition only
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+ requires(basic_istream<CharT, Traits>& is, Val& t) {
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+ is >> t;
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+ };
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+
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+ template<movable Val, class CharT, class Traits>
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+ requires default_initializable<Val> &&
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+ stream-extractable<Val, CharT, Traits>
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+ class basic_istream_view : public view_interface<basic_istream_view<Val, CharT, Traits>> {
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+ public:
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+ basic_istream_view() = default;
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+ constexpr explicit basic_istream_view(basic_istream<CharT, Traits>& stream);
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+
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+ constexpr auto begin()
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+ {
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+ if (stream_) {
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+ *stream_ >> object_;
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+ }
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+ return iterator{*this};
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+ }
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+
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+ constexpr default_sentinel_t end() const noexcept;
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+
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+ private:
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+ struct iterator; // exposition only
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+ basic_istream<CharT, Traits>* stream_ = nullptr; // exposition only
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+ Val object_ = Val(); // exposition only
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+ };
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+ }
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+ ```
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+
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+ ``` cpp
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+ constexpr explicit basic_istream_view(basic_istream<CharT, Traits>& stream);
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+ ```
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+
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+ *Effects:* Initializes *stream\_* with `addressof(stream)`.
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+
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+ ``` cpp
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+ constexpr default_sentinel_t end() const noexcept;
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+ ```
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+
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+ *Effects:* Equivalent to: `return default_sentinel;`
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+
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+ ``` cpp
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+ template<class Val, class CharT, class Traits>
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+ basic_istream_view<Val, CharT, Traits> istream_view(basic_istream<CharT, Traits>& s);
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+ ```
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+
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+ *Effects:* Equivalent to:
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+ `return basic_istream_view<Val, CharT, Traits>{s};`
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+
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+ #### Class template `basic_istream_view::iterator` <a id="range.istream.iterator">[[range.istream.iterator]]</a>
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+
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+ ``` cpp
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+ namespace std::ranges {
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+ template<movable Val, class CharT, class Traits>
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+ requires default_initializable<Val> &&
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+ stream-extractable<Val, CharT, Traits>
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+ class basic_istream_view<Val, CharT, Traits>::iterator { // exposition only
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+ public:
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+ using iterator_concept = input_iterator_tag;
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+ using difference_type = ptrdiff_t;
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+ using value_type = Val;
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+
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+ iterator() = default;
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+ constexpr explicit iterator(basic_istream_view& parent) noexcept;
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+
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+ iterator(const iterator&) = delete;
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+ iterator(iterator&&) = default;
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+
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+ iterator& operator=(const iterator&) = delete;
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+ iterator& operator=(iterator&&) = default;
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+
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+ iterator& operator++();
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+ void operator++(int);
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+
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+ Val& operator*() const;
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+
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+ friend bool operator==(const iterator& x, default_sentinel_t);
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+
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+ private:
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+ basic_istream_view* parent_ = nullptr; // exposition only
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+ };
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+ }
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+ ```
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+
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+ ``` cpp
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+ constexpr explicit iterator(basic_istream_view& parent) noexcept;
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+ ```
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+
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+ *Effects:* Initializes *parent\_* with `addressof(parent)`.
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+
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+ ``` cpp
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+ iterator& operator++();
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+ ```
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+
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+ *Preconditions:* *`parent_`*`->`*`stream_`*` != nullptr` is `true`.
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+
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+ *Effects:* Equivalent to:
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+
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+ ``` cpp
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+ *parent_->stream_>> parent_->object_;
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+ return *this;
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+ ```
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+
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+ ``` cpp
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+ void operator++(int);
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+ ```
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+
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+ *Preconditions:* *`parent_`*`->`*`stream_`*` != nullptr` is `true`.
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+
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+ *Effects:* Equivalent to `++*this`.
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+
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+ ``` cpp
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+ Val& operator*() const;
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+ ```
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+
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+ *Preconditions:* *`parent_`*`->`*`stream_`*` != nullptr` is `true`.
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+
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+ *Effects:* Equivalent to: `return `*`parent_`*`->`*`object_`*`;`
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+
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+ ``` cpp
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+ friend bool operator==(const iterator& x, default_sentinel_t);
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+ ```
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+
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+ *Effects:* Equivalent to:
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+ `return x.`*`parent_`*` == nullptr || !*x.`*`parent_`*`->`*`stream_`*`;`
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+