From Jason Turner

[format.parse.ctx]

C++17 → C++20 3.2 KB 103 lines
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Archived: C++17 | C++20
Markdown: C++17 | C++20
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tmp/tmpv026qn17/{from.md → to.md} RENAMED
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+ #### Class template `basic_format_parse_context` <a id="format.parse.ctx">[[format.parse.ctx]]</a>
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+
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+ ``` cpp
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+ namespace std {
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+ template<class charT>
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+ class basic_format_parse_context {
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+ public:
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+ using char_type = charT;
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+ using const_iterator = typename basic_string_view<charT>::const_iterator;
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+ using iterator = const_iterator;
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+
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+ private:
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+ iterator begin_; // exposition only
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+ iterator end_; // exposition only
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+ enum indexing { unknown, manual, automatic }; // exposition only
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+ indexing indexing_; // exposition only
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+ size_t next_arg_id_; // exposition only
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+ size_t num_args_; // exposition only
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+
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+ public:
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+ constexpr explicit basic_format_parse_context(basic_string_view<charT> fmt,
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+ size_t num_args = 0) noexcept;
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+ basic_format_parse_context(const basic_format_parse_context&) = delete;
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+ basic_format_parse_context& operator=(const basic_format_parse_context&) = delete;
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+
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+ constexpr const_iterator begin() const noexcept;
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+ constexpr const_iterator end() const noexcept;
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+ constexpr void advance_to(const_iterator it);
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+
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+ constexpr size_t next_arg_id();
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+ constexpr void check_arg_id(size_t id);
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+ };
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+ }
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+ ```
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+
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+ An instance of `basic_format_parse_context` holds the format string
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+ parsing state consisting of the format string range being parsed and the
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+ argument counter for automatic indexing.
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+
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+ ``` cpp
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+ constexpr explicit basic_format_parse_context(basic_string_view<charT> fmt,
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+ size_t num_args = 0) noexcept;
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+ ```
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+
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+ *Effects:* Initializes `begin_` with `fmt.begin()`, `end_` with
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+ `fmt.end()`, `indexing_` with `unknown`, `next_arg_id_` with `0`, and
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+ `num_args_` with `num_args`.
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+
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+ ``` cpp
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+ constexpr const_iterator begin() const noexcept;
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+ ```
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+
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+ *Returns:* `begin_`.
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+
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+ ``` cpp
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+ constexpr const_iterator end() const noexcept;
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+ ```
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+
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+ *Returns:* `end_`.
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+
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+ ``` cpp
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+ constexpr void advance_to(const_iterator it);
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+ ```
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+
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+ *Preconditions:* `end()` is reachable from `it`.
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+
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+ *Effects:* Equivalent to: `begin_ = it;`
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+
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+ ``` cpp
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+ constexpr size_t next_arg_id();
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+ ```
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+
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+ *Effects:* If `indexing_ != manual`, equivalent to:
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+
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+ ``` cpp
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+ if (indexing_ == unknown)
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+ indexing_ = automatic;
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+ return next_arg_id_++;
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+ ```
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+
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+ *Throws:* `format_error` if `indexing_ == manual` which indicates mixing
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+ of automatic and manual argument indexing.
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+
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+ ``` cpp
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+ constexpr void check_arg_id(size_t id);
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+ ```
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+
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+ *Effects:* If `indexing_ != automatic`, equivalent to:
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+
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+ ``` cpp
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+ if (indexing_ == unknown)
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+ indexing_ = manual;
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+ ```
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+
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+ *Throws:* `format_error` if `indexing_ == automatic` which indicates
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+ mixing of automatic and manual argument indexing.
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+
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+ *Remarks:* Call expressions where `id >= num_args_` are not core
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+ constant expressions [[expr.const]].
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+