std::time_get<CharT,InputIt>::get_weekday, std::time_get<CharT,InputIt>::do_get_weekday

Defined in header `<locale>`
public: iter_type get_weekday( iter_type beg, iter_type end, std::ios_base& str, std::ios_base::iostate& err, std::tm* t ) const;	(1)
protected: virtual iter_type do_get_weekday( iter_type beg, iter_type end, std::ios_base& str, std::ios_base::iostate& err, std::tm* t ) const;	(2)

1) Public member function, calls the protected virtual member function do_get_weekday of the most derived class.

2) Reads successive characters from the sequence [beg, end) and parses out the weekday name (possibly abbreviated), using the default format for weekdays expected by this locale, which is the same format as "%a" as used by the functions std::get_time, time_get::get, and the POSIX function strptime().

If it finds abbreviated name, followed by the characters that are valid for the full name, it continues reading until it consumes all the characters for the full name or finds a character that is not expected, in which case parsing fails even if the first few characters were a valid abbreviation.

The parsed weekday is stored in the std::tm field t->tm_wday.

If the end iterator is reached before a valid weekday name is read, the function sets std::ios_base::eofbit in err. If a parsing error is encountered, the function sets std::ios_base::failbit in err.

Parameters

beg	-	iterator designating the start of the sequence to parse
end	-	one past the end iterator for the sequence to parse
str	-	a stream object that this function uses to obtain locale facets when needed, e.g. std::ctype to skip whitespace or std::collate to compare strings
err	-	stream error flags object that is modified by this function to indicate errors
t	-	pointer to the std::tm object that will hold the result of this function call

Return value

Iterator pointing one past the last character in [beg, end) that was recognized as a part of a valid weekday name.

Notes

This function is usually case-insensitive.

If a parsing error is encountered, most implementations of this function leave *t unmodified.

Example

Run this code

#include <initializer_list>
#include <iostream>
#include <iterator>
#include <locale>
#include <sstream>
#include <string_view>
 
void try_get_wday(std::string_view s)
{
    std::cout << "Parsing the weekday out of '" << s
              << "' in the locale " << std::locale().name() << '\n';
    std::istringstream str {s.data()};
    std::ios_base::iostate err {std::ios_base::goodbit};
 
    std::tm t;
    std::time_get<char> const& facet = std::use_facet<std::time_get<char>>(str.getloc());
    std::istreambuf_iterator<char> ret = facet.get_weekday({str}, {}, str, err, &t);
    str.setstate(err);
    std::istreambuf_iterator<char> last{};
 
    if (str)
    {
        std::cout << "Successfully parsed, weekday number is " << t.tm_wday;
 
        if (ret != last)
        {
            std::cout << " Remaining content: ";
            std::copy(ret, last, std::ostreambuf_iterator<char>(std::cout));
        }
        else
            std::cout << " the input was fully consumed";
    }
    else
    {
        std::cout << "Parse failed. Unparsed string: ";
        std::copy(ret, last, std::ostreambuf_iterator<char>(std::cout));
    }
 
    std::cout << '\n';
}
 
void demo(std::string_view locale_name, std::initializer_list<std::string_view>&& data)
{
    try
    {
        std::locale::global(std::locale(locale_name.data()));
    }
    catch(std::runtime_error const& ex)
    {
        std::cout << "Cannot setup locale: " << locale_name << "\n"
                     "Exception: " << ex.what() << '\n';
        return;
    }
 
    for (std::string_view const weekday : data)
        try_get_wday(weekday);
}
 
int main()
{
    demo("lt_LT.utf8", { "Št", "Šeštadienis", });
    demo("en_US.utf8", { "SATELLITE", });
    demo("ja_JP.utf8", { "土曜日", });
}

Possible output:

Parsing the weekday out of 'Št' in the locale lt_LT.utf8
Successfully parsed, weekday number is 6 the input was fully consumed
Parsing the weekday out of 'Šeštadienis' in the locale lt_LT.utf8
Successfully parsed, weekday number is 6 the input was fully consumed
Parsing the weekday out of 'SATELLITE' in the locale en_US.utf8
Successfully parsed, weekday number is 6 Remaining content: ELLITE
Parsing the weekday out of '土曜日' in the locale ja_JP.utf8
Successfully parsed, weekday number is 6 the input was fully consumed

Defect reports

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

DR	Applied to	Behavior as published	Correct behavior
LWG 248	C++98	`eofbit` was not set upon reaching the end iterator	sets `eofbit` if a valid weekday name has not been read

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Metaprogramming library (C++11)
Diagnostics library
General utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Localizations library
Input/output library
Filesystem library (C++17)
Regular expressions library (C++11)
Concurrency support library (C++11)
Technical specifications
Symbols index
External libraries

Member functions
time_get::time_get
time_get::~time_get
time_get::date_ordertime_get::do_date_order
time_get::get_timetime_get::do_get_time
time_get::get_datetime_get::do_get_date
time_get::get_weekdaytime_get::do_get_weekday
time_get::get_monthnametime_get::do_get_monthname
time_get::get_yeartime_get::do_get_year
time_get::gettime_get::do_get