vprint_unicode(std::ostream)

Defined in header `<ostream>`
`void vprint_unicode( std::ostream& os, std::string_view fmt, std::format_args args );`		(since C++23)

Behaves as FormattedOutputFunction (except that some details of error reporting differ):

First, the function constructs and checks the sentry object.
Then, initializes an automatic variable as if by std::string out = std::vformat(os.getloc(), fmt, args);.
Finally, inserts the character sequence [out.begin(), out.end()) into os, that is, if os refers to a terminal capable of displaying Unicode, writes out to this terminal using the native Unicode API. Otherwise, writes unmodified out to the os.

Parameters

os - output stream to insert data into

fmt

an object that represents the format string. The format string consists of

ordinary characters (except { and }), which are copied unchanged to the output,
escape sequences {{ and }}, which are replaced with { and } respectively in the output, and
replacement fields.

Each replacement field has the following format:

`{` arg-id (optional) `}`	(1)
`{` arg-id (optional) `:` format-spec `}`	(2)

1) replacement field without a format specification 2) replacement field with a format specification

arg-id	-	specifies the index of the argument in `args` whose value is to be used for formatting; if it is omitted, the arguments are used in order. The arg-ids in a format string must all be present or all be omitted. Mixing manual and automatic indexing is an error.
format-spec	-	the format specification defined by the `std::formatter` specialization for the corresponding argument.

For basic types and standard string types, the format specification is interpreted as standard format specification.
For chrono types, the format specification is interpreted as chrono format specification.

For range types, the format specification is interpreted as range format specification.
For std::pair and std::tuple, the format specification is interpreted as tuple format specification.
For std::thread::id and std::stacktrace_entry, see thread id format specification and stacktrace entry format specification.
For std::basic_stacktrace, no format specifier is allowed.

(since C++23)

For other formattable types, the format specification is determined by user-defined formatter specializations.

args - arguments to be formatted

Return value

(none)

Exceptions

std::bad_alloc on allocation failure.
Propagate any exception thrown by any formatter, e.g. std::format_error, without regard to the value of os.exceptions() and without turning on ios_base::badbit in the error state of os.
May throw ios_base::failure caused by os.setstate(ios_base::badbit) which is called if an insertion into os fails.

Notes

If invoking the native Unicode API requires transcoding, the invalid code units are substituted with U+FFFD REPLACEMENT CHARACTER (see "The Unicode Standard Version 14.0 - Core Specification", Chapter 3.9).

Feature-test macro	Value	Std	Feature
`__cpp_lib_print`	202207L	(C++23)	Formatted output
`__cpp_lib_format`	202207L	(C++23)	Exposing `std::basic_format_string`

Example

External links

1.	Unicode
2.	The Unicode Standard Version 14.0 - Core Specification

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https://en.cppreference.com/w/cpp/io/basic_ostream/vprint_unicode

vprint_nonunicode(std::ostream) (C++23)	outputs character data using type-erased argument representation (function)
print(std::ostream) (C++23)	outputs formatted representation of the arguments (function template)
operator<<(std::basic_ostream)	inserts character data or insert into rvalue stream (function template)
vprint_unicode (C++23)	prints to Unicode capable `stdout` or a file stream using type-erased argument representation (function)
format (C++20)	stores formatted representation of the arguments in a new string (function template)

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