std::enable_nonlocking_formatter_optimization
Defined in header <format> | ||
|---|---|---|
template< class T > constexpr bool enable_nonlocking_formatter_optimization = false; | (since C++23) |
This template can be used by implementations to enable efficient implementations of std::print and std::println.
If std::enable_nonlocking_formatter_optimization<T> is true, printing an argument of type T can be performed in a more efficient way (see std::print for details). std::enable_nonlocking_formatter_optimization specializations can be true in the following cases:
-
Tis one of the types wherestd::formatter<T,CharT> is a basic standard specialization or standard specialization for a library type (see below). - A program may specialize this template for any cv-unqualified program-defined type
T. Such specializations must be usable in constant expressions and have type constbool.
Basic standard specializations
In the following list, CharT is either char or wchar_t, ArithmeticT is any cv-unqualified arithmetic type other than char, wchar_t, char8_t, char16_t, or char32_t:
| Nonlocking flag for character formatters | ||
template<> constexpr bool enable_nonlocking_formatter_optimization<CharT> = true; | (1) | |
| Nonlocking flag for string formatters | ||
template<> constexpr bool enable_nonlocking_formatter_optimization<CharT*> = true; | (2) | |
template<> constexpr bool enable_nonlocking_formatter_optimization<const CharT*> = true; | (3) | |
template< std::size_t N > constexpr bool enable_nonlocking_formatter_optimization<CharT[N]> = true; | (4) | |
template< class Traits, class Alloc >
constexpr bool enable_nonlocking_formatter_optimization
<std::basic_string<CharT, Traits, Alloc>> = true;
| (5) | |
template< class Traits >
constexpr bool enable_nonlocking_formatter_optimization
<std::basic_string_view<CharT, Traits>> = true;
| (6) | |
| Nonlocking flag for arithmetic formatters | ||
template<> constexpr bool enable_nonlocking_formatter_optimization<ArithmeticT> = true; | (7) | |
| Nonlocking flag for pointer formatters | ||
template<> constexpr bool enable_nonlocking_formatter_optimization<std::nullptr_t> = true; | (8) | |
template<> constexpr bool enable_nonlocking_formatter_optimization<void*> = true; | (9) | |
template<> constexpr bool enable_nonlocking_formatter_optimization<const void*> = true; | (10) |
Standard specializations for library types
Specializations of enable_nonlocking_formatter_optimization for all specializations of the following standard templates are defined as true:
-
std::chrono::zoned_timewhen its template parameter typeTimeZonePtris conststd::chrono::time_zone*
Specializations of enable_nonlocking_formatter_optimization for all specializations of the following standard templates are defined as conditionally true:
Specialization of enable_nonlocking_formatter_optimization for all formattable range types are always defined as false for which the range format kind is not std::range_format::disabled.
Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_print | 202403L |
(C++26) (DR23) | Formatted output with stream locking |
202406L |
(C++26) (DR23) | Enabling nonlocking formatter optimization for more formattable types |
See also
|
(C++20) | defines formatting rules for a given type (class template) |
|
(C++23) | prints to stdout or a file stream using formatted representation of the arguments (function template) |
|
(C++23) | same as std::print except that each print is terminated by additional new line (function template) |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/cpp/utility/format/enable_nonlocking_formatter_optimization
