std::enable_nonlocking_formatter_optimization
Defined in header <format>
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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:
-
T
is one of the types where std::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 const bool.
Contents |
[edit] 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 |
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template<> constexpr bool enable_nonlocking_formatter_optimization<CharT> = true; |
(1) | |
Nonlocking flag for string formatters |
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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 |
(5) | |
template< class Traits > constexpr bool enable_nonlocking_formatter_optimization |
(6) | |
Nonlocking flag for arithmetic formatters |
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template<> constexpr bool enable_nonlocking_formatter_optimization<ArithmeticT> = true; |
(7) | |
Nonlocking flag for pointer formatters |
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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) | |
[edit] 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_time when its template parameter type
TimeZonePtr
is const std::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.
[edit] 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 |
[edit] 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) |