NAME¶

std::vformat_to - std::vformat_to

Synopsis¶

Defined in header <format>
template< class OutputIt >
OutputIt vformat_to( OutputIt out, std::string_view fmt, (1) (since C++20)
std::format_args args );
template< class OutputIt >
OutputIt vformat_to( OutputIt out, std::wstring_view fmt, (2) (since C++20)
std::wformat_args args );
template< class OutputIt >

OutputIt vformat_to( OutputIt out, const std::locale& loc, (3) (since C++20)

std::string_view fmt, std::format_args args
);
template< class OutputIt >

OutputIt vformat_to( OutputIt out, const std::locale& loc, (4) (since C++20)

std::wstring_view fmt, std::wformat_args args
);

Format arguments held by args according to the format string fmt, and write the
result to the output iterator out. If present, loc is used for locale-specific
formatting.

Let CharT be decltype(fmt)::char_type (char for overloads (1,3), wchar_t for
overloads (2,4)).

These overloads participate in overload resolution only if OutputIt satisfies the
concept std::output_iterator<const CharT&>.

The behavior is undefined if OutputIt does not model (meet the semantic requirements
of) the concept std::output_iterator<const CharT&>, or if std::formatter<Ti, CharT>
does not meet the Formatter requirements for any Ti in the type of arguments.

Parameters¶

out - iterator to the output buffer
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
omitted. Mixing manual and automatic indexing is an error.
fmt - 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
loc - std::locale used for locale-specific formatting

Return value¶

Iterator past the end of the output range.

Exceptions¶

Throws std::format_error if fmt is not a valid format string for the provided
arguments. Also propagates any exception thrown by formatter or iterator operations.

Example¶

This section is incomplete
Reason: no example

Defect reports

The following behavior-changing defect reports were applied retroactively to
previously published C++ standards.

DR Applied to Behavior as published Correct behavior
P2216R3 C++20 type of args is parameterized on OutputIt not parameterized

See also¶

Category:¶

* Todo no example