std::chrono:: operator<< (std::chrono::month)

Defined in header <chrono>
template < class CharT, class Traits > std:: basic_ostream < CharT, Traits > & operator << ( std:: basic_ostream < CharT, Traits > & os, const std:: chrono :: month & m ) ;		(since C++20)

If ! m. ok ( ) , inserts unsigned ( m ) followed by " is not a valid month" to os . Otherwise, forms a std:: basic_string < CharT > s consisting of the abbreviated month name for the month represented by m , determined using the locale associated with os , and inserts s into os .

Equivalent to

return os << ( m. ok ( ) ?
std:: format ( os. getloc ( ) , STATICALLY_WIDEN < CharT > ( "{:L%b}" ) , m ) :
std:: format ( os. getloc ( ) , STATICALLY_WIDEN < CharT > ( "{} is not a valid month" ) , unsigned ( m ) ) ) ;

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

Return value

os

Notes

This operator << is primarily intended for debugging use. For control over formatting, use std::format .

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
P2372R3	C++20	the given locale was used by default	L is needed to use the given locale

See also

format (C++20)	stores formatted representation of the arguments in a new string (function template)
std::formatter <std::chrono::month> (C++20)	formatting support for month (class template specialization)