NAME¶

std::vprint_unicode(std::ostream) - std::vprint_unicode(std::ostream)

Synopsis¶

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

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

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

specifies the index of the argument in args whose value is to
be used for formatting; if it is omitted, the arguments are
arg-id - used in order.

The arg-id s in a format string must all be present or all be
fmt - omitted. Mixing manual and automatic indexing is an error.
the format specification defined by the std::formatter
format-spec - specialization for the corresponding argument. Cannot start
with }.

* 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. (since C++23)
* 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.

* For std::filesystem::path, see path format specification. (since C++26)

* 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¶

This section is incomplete
Reason: no example

See also¶

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

External links¶

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

Category:¶

* Todo no example