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Difference between revisions of "cpp/utility/format/vformat to"

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< cpp‎ | utility‎ | format
m (+/es)
(P2216R3 std::format improvements)
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{{dcl header | format }}
 
{{dcl header | format }}
 
{{dcl | num=1 | since=c++20 |1=
 
{{dcl | num=1 | since=c++20 |1=
−
template<class OutputIt>
+
template< class OutputIt >
−
OutputIt vformat_to(OutputIt out,
+
OutputIt vformat_to( OutputIt out, std::string_view fmt, std::format_args args );
−
                    std::string_view fmt,  
+
−
                    std::format_args_t<std::type_identity_t<OutputIt>, char> args);
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}}
 
}}
 
{{dcl | num=2 | since=c++20 |1=
 
{{dcl | num=2 | since=c++20 |1=
−
template<class OutputIt, class... Args>
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template< class OutputIt >
−
OutputIt vformat_to(OutputIt out,
+
OutputIt vformat_to( OutputIt out, std::wstring_view fmt, std::wformat_args args );
−
                    std::wstring_view fmt,  
+
−
                    std::format_args_t<std::type_identity_t<OutputIt>, wchar_t> args);
+
 
}}
 
}}
 
{{dcl | num=3 | since=c++20 |1=
 
{{dcl | num=3 | since=c++20 |1=
−
template<class OutputIt, class... Args>
+
template< class OutputIt >
−
OutputIt vformat_to(OutputIt out, const std::locale& loc,
+
OutputIt vformat_to( OutputIt out, const std::locale& loc,
−
                    std::string_view fmt,
+
                    std::string_view fmt, std::format_args args );
−
                    std::format_args_t<std::type_identity_t<OutputIt>, char> args);
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}}
 
}}
 
{{dcl | num=4 | since=c++20 |1=
 
{{dcl | num=4 | since=c++20 |1=
−
template<class OutputIt, class... Args>
+
template< class OutputIt >
−
OutputIt vformat_to(OutputIt out, const std::locale& loc,
+
OutputIt vformat_to( OutputIt out, const std::locale& loc,
−
                    std::wstring_view fmt,
+
                    std::wstring_view fmt, std::wformat_args args );
−
                    std::format_args_t<std::type_identity_t<OutputIt>, wchar_t> args);
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}}
 
}}
 
{{dcl end}}
 
{{dcl end}}
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  |output=
 
  |output=
 
}}
 
}}
 +
 +
===Defect reports===
 +
{{dr list begin}}
 +
{{dr list item|paper=P2216R3|std=C++20|before=type of {{tt|args}} is parameterized on {{tt|OutputIt}}|after=not parameterized}}
 +
{{dr list end}}
  
 
===See also===
 
===See also===
  
 
{{langlinks|es|ja|zh}}
 
{{langlinks|es|ja|zh}}

Revision as of 03:26, 18 June 2021

 
C++
 
Utilities library
General utilities
Relational operators (deprecated in C++20)
 
Formatting library
Standard format specification
Formatting functions
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
vformat_to
(C++20)
Format strings
(C++20)(C++20)(C++20)
(C++26)
Formatting concepts
(C++23)
Formatter
(C++20)
(C++23)
(C++23)
(C++23)
(C++23)
(C++20)(C++20)(C++20)
(C++20)(C++20)(C++20)
(C++23)
(C++23)
Formatting arguments
(C++20)
(C++20)
(C++20)(C++20)(C++20)
(C++20) (deprecated in C++26)
(C++20)(C++20)
Format error
(C++20)
 
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, const std::locale& loc,

                     std::string_view fmt, std::format_args args );
 (3) (since C++20)
template< class OutputIt >

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

                     std::wstring_view fmt, std::wformat_args 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 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.

Contents

Parameters

out - iterator to the output buffer
fmt - string view representing the format string.

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-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 the std::formatter specialization for the corresponding argument. Cannot start with }.

(since C++23)
(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

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