std::vformat_to

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Text processing library

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to_chars (C++17)
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text_encoding

(C++26)

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Formatting library

Standard format specification
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format (C++20)
format_to (C++20)
format_to_n (C++20)
formatted_size (C++20)
vformat (C++20)
vformat_to (C++20)
Format strings
basic_format_stringformat_stringwformat_string (C++20)(C++20)(C++20)
runtime_format (C++26)
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formattable (C++23)
Formatter
formatter (C++20)
formatter<pair-or-tuple> (C++23)
formatter<range> (C++23)
range_formatter (C++23)
enable_nonlocking_formatter_optimization (C++23)
basic_format_parse_contextformat_parse_contextwformat_parse_context (C++20)(C++20)(C++20)
basic_format_contextformat_contextwformat_context (C++20)(C++20)(C++20)
range_format (C++23)
format_kind (C++23)
Formatting arguments
basic_format_arg (C++20)
basic_format_arg::handle (C++20)
basic_format_argsformat_argswformat_args (C++20)(C++20)(C++20)
visit_format_arg (C++20)(deprecated in C++26)
make_format_argsmake_wformat_args (C++20)(C++20)
Format error
format_error (C++20)

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Defined in header`<format>`
template<class OutputIt> OutputIt vformat_to( OutputIt out,std::string_view fmt,std::format_args args);	(1)	(since C++20)
template<class OutputIt> OutputIt vformat_to( OutputIt out,std::wstring_view fmt,std::wformat_args args);	(2)	(since C++20)
template<class OutputIt> OutputIt vformat_to( OutputIt out,conststd::locale& loc, std::string_view fmt,std::format_args args);	(3)	(since C++20)
template<class OutputIt> OutputIt vformat_to( OutputIt out,conststd::locale& loc, std::wstring_view fmt,std::wformat_args args);	(4)	(since C++20)

Format arguments held byargs according to the format stringfmt, and write the result to the output iteratorout. If present,loc is used for locale-specific formatting.

LetCharT bedecltype(fmt)::char_type (char for overloads(1,3),wchar_t for overloads(2,4)).

These overloads participate in overload resolution only ifOutputIt satisfies the conceptstd::output_iterator<const CharT&>.

OutputIt must model (meet the semantic requirements of) the conceptstd::output_iterator<const CharT&>, andstd::formatter<Ti, CharT> must meet theFormatter requirements for anyTi in the type of arguments. Otherwise, the behavior is undefined.

[edit]Parameters

out - iterator to the output buffer

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. Thearg-id s 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 thestd::formatter specialization for the corresponding argument. Cannot start with}.

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

For range types, the format specification is interpreted asrange format specification.
Forstd::pair andstd::tuple, the format specification is interpreted astuple format specification.
Forstd::thread::id andstd::stacktrace_entry, seethread id format specification andstacktrace entry format specification.
Forstd::basic_stacktrace, no format specifier is allowed.

(since C++23)

Forstd::filesystem::path, seepath format specification.

(since C++26)

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

args - arguments to be formatted

loc - std::locale used for locale-specific formatting

[edit]Return value

Iterator past the end of the output range.

[edit]Exceptions

Throwsstd::format_error iffmt is not a valid format string for the provided arguments. Also propagates any exception thrown by formatter or iterator operations.