std::enable_nonlocking_formatter_optimization - cppreference.com (original) (raw)

| | | | | ----------------------------------------------------------------------------------------- | | ------------- | | 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

• 1 Basic standard specializations
• 2 Standard specializations for library types
• 3 Notes
• 4 See also

[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 | | | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ---- | | | 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) | |

[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:

• std::pair
• std::tuple
• std::chrono::duration

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

[edit] See also

| | defines formatting rules for a given type (class template) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | prints to stdout or a file stream using formatted representation of the arguments (function template) [edit] | | | same as std::print except that each print is terminated by additional new line (function template) [edit] |