cppdraft_translate/cppdraft/ostream/formatted/print.md

[ostream.formatted.print]

31 Input/output library [input.output]

31.7 Formatting and manipulators [iostream.format]

31.7.6 Output streams [output.streams]

31.7.6.3 Formatted output functions [ostream.formatted]

31.7.6.3.5 Print [ostream.formatted.print]

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template<class... Args> void print(ostream& os, format_string<Args...> fmt, Args&&... args);

1

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Effects: If the ordinary literal encoding ([lex.charset]) is UTF-8, equivalent to:vprint_unicode(os, fmt.str, make_format_args(args...));

Otherwise, equivalent to:vprint_nonunicode(os, fmt.str, make_format_args(args...));

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template<class... Args> void println(ostream& os, format_string<Args...> fmt, Args&&... args);

2

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Effects: Equivalent to:print(os, "{}\n", format(os.getloc(), fmt, std::forward(args)...));

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void println(ostream& os);

3

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Effects: Equivalent to:print(os, "\n");

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void vprint_unicode(ostream& os, string_view fmt, format_args args); void vprint_nonunicode(ostream& os, string_view fmt, format_args args);

4

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Effects: Behaves as a formatted output function ([ostream.formatted.reqmts]) of os, except that:

• (4.1)

failure to generate output is reported as specified below, and

• (4.2)

any exception thrown by the call to vformat is propagated without regard to the value of os.exceptions() and without turning on ios_base​::​badbit in the error state of os.

After constructing a sentry object, the function initializes a variable with automatic storage duration viastring out = vformat(os.getloc(), fmt, args);

• (4.3)

  If the function is vprint_unicode andos is a stream that refers to a terminal that is capable of displaying Unicode only via a native Unicode API, which is determined in an implementation-defined manner, flushes os and then writes out to the terminal using the native Unicode API; if out contains invalid code units,the behavior is undefined. Then establishes an observable checkpoint ([intro.abstract]).

• (4.4)

  Otherwise inserts the character sequence [out.begin(), out.end()) into os.

If writing to the terminal or inserting into os fails, calls os.setstate(ios_base​::​badbit) (which may throw ios_base​::​failure).

5

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Recommended practice: For vprint_unicode, if invoking the native Unicode API requires transcoding, implementations should substitute invalid code units with U+fffd replacement character per the Unicode Standard, Chapter 3.9 U+fffd Substitution in Conversion.