std::print(std::ostream)

Formats args according to the format string fmt, and inserts the result into os

If the ordinary literal encoding is UTF-8, equivalent to:

• std::vprint_unicode (os, fmt.get ( ), std::make_format_args (args...) ) ;
• std::vprint_nonunicode (os, fmt.get ( ), std::make_format_args (args...) ) ;

The behavior is undefined if std::formatter <Ti, char > does not meet the BasicFormatter requirements for any Ti in Args (as required by std::make_format_args

Parameters

Return value

(none)

Exceptions

• std::bad_alloc on allocation failure.
• Propagate any exception thrown by any formatter, e.g. std::format_error, without regard to the value of os.exceptions() and without turning on ios_base::badbit in the error state of os
• May throw ios_base::failure caused by os.setstate(ios_base::badbit) which is called if an insertion into os

Notes

Example

#include <array>
#include <cctype>
#include <cstdio>
#include <format>
#include <numbers>
#include <ranges>
#include <sstream>
 
int main()
{
    std::array<char, 24> buf;
    std::format_to(buf.begin(), "{:.15f}", std::numbers::sqrt2);
 
    unsigned num{}, sum{};
 
    auto v = buf
           | std::views::filter(isdigit)
           | std::views::transform([](char x) { return x - '0'; })
           | std::views::take_while([&sum](char) { return sum < 42; });
 
    for (auto n : v)
        sum += n, ++num;
 
    std::stringstream stream;
 
#ifdef __cpp_lib_print
    std::print(stream,
#else
    stream << std::format(
#endif
        "√2 = {}...\n"
        "The sum of its first {} digits is {}{}",
        std::numbers::sqrt2, num, sum, '.'
    );
 
    std::puts(stream.str().data());
}

√2 = 1.4142135623730951...
The sum of its first 13 digits is 42.

See also