NAME¶

std::chrono::operator<<(std::chrono::day) - std::chrono::operator<<(std::chrono::day)

Synopsis¶

Defined in header <chrono>
template< class CharT, class Traits >

std::basic_ostream<CharT, Traits>& (since C++20)

operator<<( std::basic_ostream<CharT, Traits>& os, const
std::chrono::day& d );

Forms a std::basic_string<CharT> s consisting of the day value stored in d formatted
as a decimal number, with a leading zero if the result would otherwise be a single
decimal digit. Then, if !d.ok(), append " is not a valid day" to the formatted
string. Inserts that string into os.

Equivalent to

return os << (d.ok() ?
std::format(STATICALLY_WIDEN<CharT>("{:%d}"), d) :
std::format(STATICALLY_WIDEN<CharT>("{:%d} is not a valid day"), d));

where STATICALLY_WIDEN<CharT>("...") is "..." if CharT is char, and L"..." if CharT
is wchar_t.

Return value¶

os.

Example¶

// Run this code

#include <chrono>
#include <iostream>

int main()
{
constexpr std::chrono::day d1 {31}, d2 {7}, d3 {42}, d4 {};
std::cout << d1 << '\n'
<< d2 << '\n'
<< d3 << '\n'
<< d4 << '\n';
}

Possible output:¶

31
07
42 is not a valid day
00 is not a valid day

See also¶

format stores formatted representation of the arguments in
(C++20) a new string
(function template)
std::formatter<std::chrono::day> specialization of std::formatter that formats a day
(C++20) according to the provided format
(class template specialization)