std::vformat
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Feature test macros (C++20)
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Ranges library (C++20)
Filesystem library (C++17)
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Execution control library (C++26)
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Regular expressions library (C++11)
Formatting library (C++20)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
(C++26)
Formatting library
(C++20)
(C++20)
(C++20)
(C++20)
vformat
(C++20)
(C++20)
(C++20)(C++20)(C++20)
(C++26)
(C++23)
Formatter
(C++20)
(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)
(C++20)
Defined in header
<format>
std::string vformat( std::string_view fmt, std::format_args args );
(1)
(since C++20)
std::wstring vformat( std::wstring_view fmt, std::wformat_args args );
(2)
(since C++20)
std::string vformat( const std::locale & loc,
std::string_view fmt, std::format_args args );
(3)
(since C++20)
std::string_view fmt, std::format_args args );
std::wstring vformat( const std::locale & loc,
std::wstring_view fmt, std::wformat_args args );
(4)
(since C++20)
std::wstring_view fmt, std::wformat_args args );
Format arguments held by args according to the format string fmt, and return the result as a string. If present, loc is used for locale-specific formatting.
[edit] Parameters
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.
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 }.
- 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.
- 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.
(since C++26)
- For other formattable types, the format specification is determined by user-defined
formatterspecializations.
args
-
arguments to be formatted
loc
-
std::locale used for locale-specific formatting
[edit] Return value
A string object holding the formatted result.
[edit] Exceptions
Throws std::format_error if fmt is not a valid format string for the provided arguments, or std::bad_alloc on allocation failure. Also propagates any exception thrown by formatter or iterator operations.
[edit] Example
Run this code
#include <format> #include <iostream> template<typename... Args> inline void println(const std::format_string <Args...> fmt, Args&&... args) { std::cout << std::vformat(fmt.get(), std::make_format_args (args...)) << '\n'; } int main() { println("{}{} {}{}", "Hello", ',', "C++", -1 + 2 * 3 * 4); }
Output:
Hello, C++23