From Jason Turner

[format.formatter.spec]

C++20 → C++23 3.4 KB 33 lines
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Archived: C++20 | C++23
Markdown: C++20 | C++23
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C++ Weekly: Ep 495

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  1. tmp/tmpcsqenl27/{from.md → to.md} +14 -14
tmp/tmpcsqenl27/{from.md → to.md} RENAMED
@@ -2,29 +2,29 @@
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  The functions defined in [[format.functions]] use specializations of the
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  class template `formatter` to format individual arguments.
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  Let `charT` be either `char` or `wchar_t`. Each specialization of
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- `formatter` is either enabled or disabled, as described below.
 
 
 
 
 
 
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- [*Note 1*: Enabled specializations meet the requirements, and disabled
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- specializations do not. — *end note*]
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-
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- Each header that declares the template `formatter` provides the
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- following enabled specializations:
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-
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- - The specializations
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  ``` cpp
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  template<> struct formatter<char, char>;
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  template<> struct formatter<char, wchar_t>;
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  template<> struct formatter<wchar_t, wchar_t>;
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  ```
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- - For each `charT`, the string type specializations
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  ``` cpp
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  template<> struct formatter<charT*, charT>;
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  template<> struct formatter<const charT*, charT>;
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- template<size_t N> struct formatter<const charT[N], charT>;
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  template<class traits, class Allocator>
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  struct formatter<basic_string<charT, traits, Allocator>, charT>;
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  template<class traits>
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  struct formatter<basic_string_view<charT, traits>, charT>;
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  ```
@@ -43,21 +43,21 @@ following enabled specializations:
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  The `parse` member functions of these formatters interpret the format
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  specification as a *std-format-spec* as described in
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  [[format.string.std]].
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- [*Note 2*: Specializations such as `formatter<wchar_t, char>` and
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  `formatter<const char*, wchar_t>` that would require implicit multibyte
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  / wide string or character conversion are disabled. — *end note*]
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  For any types `T` and `charT` for which neither the library nor the user
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  provides an explicit or partial specialization of the class template
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  `formatter`, `formatter<T, charT>` is disabled.
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  If the library provides an explicit or partial specialization of
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- `formatter<T, charT>`, that specialization is enabled except as noted
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- otherwise.
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  If `F` is a disabled specialization of `formatter`, these values are
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  `false`:
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  - `is_default_constructible_v<F>`,
@@ -76,11 +76,11 @@ An enabled specialization `formatter<T, charT>` meets the requirements
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  enum color { red, green, blue };
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  const char* color_names[] = { "red", "green", "blue" };
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  template<> struct std::formatter<color> : std::formatter<const char*> {
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- auto format(color c, format_context& ctx) {
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  return formatter<const char*>::format(color_names[c], ctx);
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  }
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  };
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  struct err {};
 
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  The functions defined in [[format.functions]] use specializations of the
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  class template `formatter` to format individual arguments.
5
 
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  Let `charT` be either `char` or `wchar_t`. Each specialization of
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+ `formatter` is either enabled or disabled, as described below. A
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+ *debug-enabled* specialization of `formatter` additionally provides a
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+ public, constexpr, non-static member function `set_debug_format()` which
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+ modifies the state of the `formatter` to be as if the type of the
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+ *std-format-spec* parsed by the last call to `parse` were `?`. Each
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+ header that declares the template `formatter` provides the following
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+ enabled specializations:
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+ - The debug-enabled specializations
 
 
 
 
 
 
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  ``` cpp
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  template<> struct formatter<char, char>;
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  template<> struct formatter<char, wchar_t>;
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  template<> struct formatter<wchar_t, wchar_t>;
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  ```
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+ - For each `charT`, the debug-enabled string type specializations
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  ``` cpp
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  template<> struct formatter<charT*, charT>;
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  template<> struct formatter<const charT*, charT>;
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+ template<size_t N> struct formatter<charT[N], charT>;
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  template<class traits, class Allocator>
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  struct formatter<basic_string<charT, traits, Allocator>, charT>;
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  template<class traits>
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  struct formatter<basic_string_view<charT, traits>, charT>;
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  ```
 
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  The `parse` member functions of these formatters interpret the format
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  specification as a *std-format-spec* as described in
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  [[format.string.std]].
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+ [*Note 1*: Specializations such as `formatter<wchar_t, char>` and
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  `formatter<const char*, wchar_t>` that would require implicit multibyte
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  / wide string or character conversion are disabled. — *end note*]
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  For any types `T` and `charT` for which neither the library nor the user
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  provides an explicit or partial specialization of the class template
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  `formatter`, `formatter<T, charT>` is disabled.
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  If the library provides an explicit or partial specialization of
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+ `formatter<T, charT>`, that specialization is enabled and meets the
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+ requirements except as noted otherwise.
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  If `F` is a disabled specialization of `formatter`, these values are
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  `false`:
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  - `is_default_constructible_v<F>`,
 
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  enum color { red, green, blue };
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  const char* color_names[] = { "red", "green", "blue" };
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  template<> struct std::formatter<color> : std::formatter<const char*> {
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+ auto format(color c, format_context& ctx) const {
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  return formatter<const char*>::format(color_names[c], ctx);
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  }
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  };
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  struct err {};