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std::vformat_to

From cppreference.com
< cpp‎ | utility‎ | format
 
 
 
Formatting library
Formatting functions
(C++20)
(C++20)
(C++20)
vformat_to
(C++20)
Formatter
(C++20)
Formatting arguments
Format error
 
Defined in header <format>
template<class OutputIt>

OutputIt vformat_to(OutputIt out,
                    std::string_view fmt,

                    std::format_args_t<std::type_identity_t<OutputIt>, char> args);
(1) (since C++20)
template<class OutputIt, class... Args>

OutputIt vformat_to(OutputIt out,
                    std::wstring_view fmt,

                    std::format_args_t<std::type_identity_t<OutputIt>, wchar_t> args);
(2) (since C++20)
template<class OutputIt, class... Args>

OutputIt vformat_to(OutputIt out, const std::locale& loc,
                    std::string_view fmt,  

                    std::format_args_t<std::type_identity_t<OutputIt>, char> args);
(3) (since C++20)
template<class OutputIt, class... Args>

OutputIt vformat_to(OutputIt out, const std::locale& loc,
                    std::wstring_view fmt,  

                    std::format_args_t<std::type_identity_t<OutputIt>, wchar_t> args);
(4) (since C++20)

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 only participate in overload resolution 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 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.

Contents

[edit] Parameters

out - iterator to the output buffer
fmt - string view representing 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:

  • introductory { character;
  • (optional) arg-id, a non-negative number;
  • (optional) a colon (:) followed by a format specification;
  • final } character.

arg-id specifies the index of the argument in args whose value is to be used for formatting; if arg-id 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.

The format specification is 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 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

[edit] Return value

iterator past the end of the output range

[edit] 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.

[edit] Example

[edit] See also