FreeBSD Manual Pages
std::format_to(3) C++ Standard Libary std::format_to(3) NAME std::format_to - std::format_to Synopsis Defined in header <format> template< class OutputIt, class... Args > OutputIt format_to( OutputIt out, /*format_string<Args...>*/ fmt, (1) (since C++20) Args&&... args ); template< class OutputIt, class... Args > OutputIt format_to( OutputIt out, /*wformat_string<Args...>*/ fmt, (2) (since C++20) Args&&... args ); template< class OutputIt, class... Args > OutputIt format_to( OutputIt out, const std::locale& loc, (3) (since C++20) /*format_string<Args...>*/ fmt, Args&&... args ); template< class OutputIt, class... Args > OutputIt format_to( OutputIt out, const std::locale& loc, (4) (since C++20) /*wformat_string<Args...>*/ fmt, Args&&... args ); Format args according to the format string fmt, and write the result to the output iterator out. If present, loc is used for locale-specific format- ting. 1) equivalent to return std::vformat_to(out, fmt.str, std::make_format_args(args...)); 2) equivalent to return std::vformat_to(std::move(out), fmt.str, std::make_wformat_args(args...)); 3) equivalent to return std::vformat_to(out, loc, fmt.str, std::make_format_args(args...)); 4) equivalent to return std::vformat_to(std::move(out), loc, fmt.str, std::make_wformat_args(args...)); Let CharT be 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 se- mantic requirements of) the concept std::output_iterator<const CharT&>, or if std::for- matter<Ti, CharT> does not meet the BasicFormatter requirements for any Ti in Args (as required by std::make_format_args and std::make_wformat_args). Parameters out - iterator to the output buffer parameter of unspecified type, whose initialization is valid only if the argument is convertible to std::string_view (for (1,3)) or std::wstring_view (for (2,4)), and the result of conver- sion is a constant expression and a valid format string for Args. 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) fmt - 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 arg-id - are used in order. The arg-ids in a format string must all be present or all be omitted. Mixing manual and automatic index- ing is an error. format-spec - the format specification defined by the std::formatter specialization for the corresponding argu- ment. * For basic types and standard string types, the format specification is interpreted as standard format specification. * For chrono types, the format specification is inter- preted 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 Return value Iterator past the end of the output range. Exceptions Propagates any exception thrown by formatter or iterator operations. Notes As of P2216R3, it is an error if the format string is not a constant expression. std::vformat_to can be used in this case. Example // Run this code #include <format> #include <iostream> #include <iterator> #include <string> auto main() -> int { std::string buffer; std::format_to( std::back_inserter(buffer), //< OutputIt "Hello, C++{}!\n", //< fmt "20"); //< arg std::cout << buffer; buffer.clear(); std::format_to( std::back_inserter(buffer), //< OutputIt "Hello, {0}::{1}!{2}", //< fmt "std", //< arg {0} "format_to()", //< arg {1} "\n", //< arg {2} "extra param(s)..."); //< unused std::cout << buffer; std::wstring wbuffer; std::format_to( std::back_inserter(wbuffer),//< OutputIt L"Hello, {2}::{1}!{0}", //< fmt L"\n", //< arg {0} L"format_to()", //< arg {1} L"std", //< arg {2} L"...is not..." //< unused L"...an error!"); //< unused std::wcout << wbuffer; } Output: Hello, C++20! Hello, std::format_to()! Hello, std::format_to()! Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Cor- rect behavior throws std::format_error for invalid invalid format string P2216R3 C++20 format string results in compile-time error objects that are neither const-usable nor P2418R2 C++20 copyable allow formatting these (such as generator-like objects) are not objects formattable See also format stores formatted representation of the arguments in a new string (C++20) (function template) format_to_n writes out formatted representation of its arguments through an output (C++20) iterator, not exceeding specified size (function template) http://cppreference.com 2022.07.31 std::format_to(3)
NAME | Synopsis | Parameters | Return value | Exceptions | Notes | Example | Output: | See also
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=std::format_to&sektion=3&manpath=FreeBSD+Ports+15.0>